transforming-growth-factor-beta and Telangiectasia--Hereditary-Hemorrhagic

Endoglin, alias CD105, is a human membrane glycoprotein highly expressed in vascular endothelial cells. It is involved in angiogenesis and angiogenesis-related diseases, including the rare vascular pathology known as hereditary hemorrhagic telangiectasia type 1. Although endoglin acts as an accessory receptor for members of the transforming growth factor-β family, in recent years, emerging evidence has shown a novel functional role for this protein beyond the transforming growth factor-β system. In fact, endoglin has been found to be an integrin counterreceptor involved in endothelial cell adhesion processes during pathological inflammatory conditions and primary hemostasis. Furthermore, a circulating form of endoglin, also named as soluble endoglin, whose levels are abnormally increased in different pathological conditions, such as preeclampsia, seems to act as an antagonist of membrane-bound endoglin and as a competitor of the fibrinogen-integrin interaction in platelet-dependent thrombus formation. These studies suggest that membrane-bound endoglin and circulating endoglin are important components involved in vascular homeostasis and hemostasis.

Topics: Antigens, CD; Endoglin; Endothelial Cells; Female; Humans; Integrins; Pregnancy; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Transforming Growth Factors; Vascular Cell Adhesion Molecule-1

In this review, we discuss the role of transforming growth factor-beta (TGF-β) in the development of pulmonary vascular disease (PVD), both pulmonary arteriovenous malformations (AVM) and pulmonary hypertension (PH), in hereditary hemorrhagic telangiectasia (HHT). HHT or Rendu-Osler-Weber disease is an autosomal dominant genetic disorder with an estimated prevalence of 1 in 5000 persons and characterized by epistaxis, telangiectasia and AVMs in more than 80% of cases, HHT is caused by a mutation in the ENG gene on chromosome 9 encoding for the protein endoglin or activin receptor-like kinase 1 (ACVRL1) gene on chromosome 12 encoding for the protein ALK-1, resulting in HHT type 1 or HHT type 2, respectively. A third disease-causing mutation has been found in the SMAD-4 gene, causing a combination of HHT and juvenile polyposis coli. All three genes play a role in the TGF-β signaling pathway that is essential in angiogenesis where it plays a pivotal role in neoangiogenesis, vessel maturation and stabilization. PH is characterized by elevated mean pulmonary arterial pressure caused by a variety of different underlying pathologies. HHT carries an additional increased risk of PH because of high cardiac output as a result of anemia and shunting through hepatic AVMs, or development of pulmonary arterial hypertension due to interference of the TGF-β pathway. HHT in combination with PH is associated with a worse prognosis due to right-sided cardiac failure. The treatment of PVD in HHT includes medical or interventional therapy.

Topics: Activin Receptors, Type II; Animals; Arteriovenous Malformations; Endoglin; Humans; Hypertension, Pulmonary; Lung Diseases; Mutation; Risk; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Diseases

Hereditary hemorrhagic telangiectasia (HHT) can be clinically diagnosed, but children often lack characteristic features. We report a family with homozygous growth differentiation factor 2 (

Topics: Asian People; Child; Child, Preschool; Consanguinity; Endoglin; Epistaxis; Exome Sequencing; Female; Growth Differentiation Factor 2; Homozygote; Humans; Hypoxia; INDEL Mutation; Loss of Function Mutation; Male; Pedigree; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A

Genetic studies in animals and humans indicate that gene mutations that functionally perturb transforming growth factor β (TGF-β) signaling are linked to specific hereditary vascular syndromes, including Osler-Rendu-Weber disease or hereditary hemorrhagic telangiectasia and Marfan syndrome. Disturbed TGF-β signaling can also cause nonhereditary disorders like atherosclerosis and cardiac fibrosis. Accordingly, cell culture studies using endothelial cells or smooth muscle cells (SMCs), cultured alone or together in two- or three-dimensional cell culture assays, on plastic or embedded in matrix, have shown that TGF-β has a pivotal effect on endothelial and SMC proliferation, differentiation, migration, tube formation, and sprouting. Moreover, TGF-β can stimulate endothelial-to-mesenchymal transition, a process shown to be of key importance in heart valve cushion formation and in various pathological vascular processes. Here, we discuss the roles of TGF-β in vasculogenesis, angiogenesis, and lymphangiogenesis and the deregulation of TGF-β signaling in cardiovascular diseases.

Topics: Activin Receptors, Type II; Animals; Aortic Aneurysm; Atherosclerosis; Cardiovascular Diseases; Cell Communication; Endothelial Cells; Fibrosis; Humans; Hypertension, Pulmonary; Lymphangiogenesis; Myocardium; Neovascularization, Physiologic; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Patients who harbor brain arteriovenous malformations are at risk for intracranial hemorrhage. These malformations are often seen in inherited vascular diseases such as hereditary hemorrhagic telangiectasia. However, malformations within the brain also sporadically occur without a hereditary-coding component. Here, we review recent insights into the pathophysiology of arteriovenous malformations, in particular, certain signaling pathways that might underlie endothelial cell pathology. To better interpret the origins, determinants and consequences of brain arteriovenous malformations, we present a clinical case to illustrate the phenotypic landscape of the disease. We also propose that brain arteriovenous malformations might share certain signaling dimensions with those of anorectal hemorrhoids. This working hypothesis provides casual anchors from which to understand vascular diseases characterized by arteriovenous lesions with a hemorrhagic- or bleeding-risk component. Anat Rec, 2017. © The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists. Anat Rec, 300:1973-1980, 2017. © 2017 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Topics: Activin Receptors, Type II; Adult; Arteriovenous Fistula; Blood Pressure; Brain; Dietary Fiber; Endoglin; Endothelial Cells; Humans; Intracranial Arteriovenous Malformations; Magnetic Resonance Angiography; Male; Mutation; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Tomography, X-Ray Computed; Transforming Growth Factor beta

Hereditary Haemorrhagic Telangiectasia (HHT) is as an autosomal dominant trait characterized by frequent nose bleeds, mucocutaneous telangiectases, arteriovenous malformations (AVMs) of the lung, liver and brain, and gastrointestinal bleedings due to telangiectases. HHT is originated by mutations in genes whose encoded proteins are involved in the transforming growth factor β (TGF-β) family signalling of vascular endothelial cells. In spite of the great advances in the diagnosis as well as in the molecular, cellular and animal models of HHT, the current treatments remain just at the palliative level. Areas covered: Pathogenic mutations in genes coding for the TGF-β receptors endoglin (ENG) (HHT1) or the activin receptor-like kinase-1 (ACVRL1 or ALK1) (HHT2), are responsible for more than 80% of patients with HHT. Therefore, ENG and ALK1 are the main potential therapeutic targets for HHT and the focus of this review. The current status of the preclinical and clinical studies, including the anti-angiogenic strategy, have been addressed. Expert opinion: Endoglin and ALK1 are attractive therapeutic targets in HHT. Because haploinsufficiency is the pathogenic mechanism in HHT, several therapeutic approaches able to enhance protein expression and/or function of endoglin and ALK1 are keys to find novel and efficient treatments for the disease.

Topics: Activin Receptors, Type II; Angiogenesis Inhibitors; Animals; Drug Design; Endoglin; Endothelial Cells; Humans; Molecular Targeted Therapy; Mutation; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Correct organization of the vascular tree requires the balanced activities of several signaling pathways that regulate tubulogenesis and vascular branching, elongation, and pruning. When this balance is lost, the vessels can be malformed and fragile, and they can lose arteriovenous differentiation. In this review, we concentrate on the transforming growth factor (TGF)-β/bone morphogenetic protein (BMP) pathway, which is one of the most important and complex signaling systems in vascular development. Inactivation of these pathways can lead to altered vascular organization in the embryo. In addition, many vascular malformations are related to deregulation of TGF-β/BMP signaling. Here, we focus on two of the most studied vascular malformations that are induced by deregulation of TGF-β/BMP signaling: hereditary hemorrhagic telangiectasia (HHT) and cerebral cavernous malformation (CCM). The first of these is related to loss-of-function mutation of the TGF-β/BMP receptor complex and the second to increased signaling sensitivity to TGF-β/BMP. In this review, we discuss the potential therapeutic targets against these vascular malformations identified so far, as well as their basis in general mechanisms of vascular development and stability.

Topics: Animals; Blood Vessels; Bone Morphogenetic Proteins; Disease Models, Animal; Genetic Predisposition to Disease; Hemangioma, Cavernous, Central Nervous System; Humans; Mice, Transgenic; Mutation; Neovascularization, Physiologic; Phenotype; Risk Factors; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Malformations

Hereditary haemorrhagic telangiectasia is a rare systemic autosomal dominantly inherited disorder of the fibrovascular tissue with a wide variety of clinical manifestations. Diagnosis is based on the clinical Curaçao criteria or molecular genetic testing. Dilated vessels can develop into telangiectases or larger vascular malformations in various organs, calling for an interdisciplinary approach. Epistaxis and gastrointestinal bleeding can result from these vascular defects. Various conservative and interventional treatments have been described for these conditions. However, no optimal therapy exists. Treatment can become especially difficult due to progressive anaemia or when anticoagulant or anti-thrombotic therapy becomes necessary. Screening for pulmonary arteriovenous malformations (PAVM) should be performed in all confirmed and suspected patients. Treatment by percutaneous transcatheter embolotherapy and antibiotic prophylaxis is normally effective for PAVM. Cerebral or hepatic vascular malformations and rare manifestations need to be evaluated on a case-by-case basis to determine the best course of action for treatment.

Topics: Anemia, Iron-Deficiency; Antibiotic Prophylaxis; Anticoagulants; Arteriovenous Malformations; Disease Management; Embolization, Therapeutic; Epistaxis; Fibrinolytic Agents; Gastrointestinal Hemorrhage; Hemostatics; Humans; Hypertension, Pulmonary; Intracranial Arteriovenous Malformations; Liver; Lung; Neovascularization, Pathologic; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Thrombophilia; Transforming Growth Factor beta

Endoglin (CD105) is a type III auxiliary receptor for the transforming growth factor beta (TGFβ) superfamily. Several lines of evidence suggest that endoglin plays a critical role in maintaining cardiovascular homeostasis. Seemingly disparate disease conditions, including hereditary hemorrhagic telangiectasia, pre-eclampsia, and cardiac fibrosis, have now been associated with endoglin. Given the central role of the TGFβ superfamily in multiple disease conditions, this review provides a detailed update on endoglin as an evolving therapeutic target in the management of cardiovascular disease.

Topics: Animals; Antigens, CD; Cardiovascular Diseases; Cardiovascular System; Endoglin; Female; Homeostasis; Humans; Ligands; Male; Pre-Eclampsia; Pregnancy; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Ventricular Remodeling

Topics: Alleles; Anaplastic Lymphoma Kinase; Angiography; Antigens, CD; Chromosomes, Human, Pair 9; Cone-Beam Computed Tomography; Diagnosis, Differential; DNA Mutational Analysis; Endoglin; Esophageal and Gastric Varices; Genes, Dominant; Haploinsufficiency; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Liver; Prognosis; Receptor Protein-Tyrosine Kinases; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Tomography, X-Ray Computed; Transforming Growth Factor beta

The Rendu-Osler disease, also called Hereditary Hemorrhagic Telangiectasia (HHT) affects 1 in -5-8000 people. A french epidemiological study pointed out that it was particularly high in the Haut-Jura mountains in France. This pathology is characterized by frequent nosebleeds, mucocutaneous and visceral telangiectasia and hereditary autosomal-dominant trait. The mucocutaneous telangiectasia are hemorrhagic while the visceral telangiectasia, less frequent, lead to arteriovenous fistula in the lungs, the liver and the brain. HHT disease-causing genes (ENG, ACVRL1 and MADH4) encode proteins that modulate TGFβ superfamilly signaling in vascular endothelial cells. The recent discovery that BMP9 acts as the specific ligand of the receptor ALK1 and endoglin as its co-receptor shows that this signaling pathway is involved in the maturation phase of angiogenesis. Mice heterozygous for endoglin or ALK1 defects reproduce the HHT phenotype and further support the involvement of endothelial hyper proliferation in the pathogenesis of the disease. The medical management of patients remains mainly symptomatic, however the angiogenic trait of this disease should allow us to consider in the future new -therapeutic approaches using anti-angiogenic drugs.

Topics: Activin Receptors, Type II; Animals; Antigens, CD; Chromosome Aberrations; Disease Models, Animal; Endoglin; France; Genes, Dominant; Humans; Incidence; Mice; Receptors, Cell Surface; Signal Transduction; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Thoracic aortic aneurysms (TAAs) are potentially devastating, and due to their asymptomatic behavior, pose a serious health risk characterized by the lack of medical treatment options and high rates of surgical morbidity and mortality. Independent of the inciting stimuli (biochemical/mechanical), TAA development proceeds by a multifactorial process influenced by both cellular and extracellular mechanisms, resulting in alterations of the structure and composition of the vascular extracellular matrix (ECM). While the role of enhanced ECM proteolysis in TAA formation remains undisputed, little attention has been focused on the upstream signaling events that drive the remodeling process. Recent evidence highlighting the dysregulation of transforming growth factor-beta (TGF-beta) signaling in ascending TAAs from Marfan syndrome patients has stimulated an interest in this intracellular signaling pathway. However, paradoxical discoveries have implicated both enhanced TGF-beta signaling and loss of function TGF-beta receptor mutations, in aneurysm formation; obfuscating a clear functional role for TGF-beta in aneurysm development. In an effort to elucidate this subject, TGF-beta signaling and its role in vascular remodeling and pathology will be reviewed, with the aim of identifying potential mechanisms of how TGF-beta signaling may contribute to the formation and progression of TAA.

Topics: Animals; Aorta, Thoracic; Aortic Aneurysm, Thoracic; Aortic Dissection; Disease Progression; Ehlers-Danlos Syndrome; Extracellular Matrix; Genetic Predisposition to Disease; Humans; Marfan Syndrome; Mutation; Peptide Hydrolases; Receptors, Transforming Growth Factor beta; Signal Transduction; Smad Proteins; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Genetic mutations in members of the transforming growth factor-beta receptor superfamily are associated with two diseases characterised by changes in the structure of the lung vasculature, pulmonary arterial hypertension and hereditary haemorrhagic telangiectasia. Pulmonary arterial hypertension is characterised by increased vessel muscularisation, sharply contrasting with the reduction in smooth muscle that occurs in hereditary haemorrhagic telangiectasia. Intriguingly, both pathologies can exist in some patients with combined disease. In this review, we discuss the contributions of convergent and divergent ligand response profiles and differing tissue expression patterns of the affected receptors to the pathologies of these diseases. We address the possible contribution of inflammation in disease progression and focus on potential emerging therapeutic targets.

Topics: Animals; Bone Morphogenetic Protein Receptors, Type II; Disease Progression; Drug Delivery Systems; Humans; Hypertension, Pulmonary; Ligands; Protein Binding; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

The autosomal-dominant trait hereditary haemorrhagic telangiectasia (HHT) affects 1 in 5-8000 people. Genes mutated in HHT (most commonly for endoglin or activin receptor-like kinase (ALK1)) encode proteins that modulate transforming growth factor (TGF)-beta superfamily signalling in vascular endothelial cells; mutations lead to the development of fragile telangiectatic vessels and arteriovenous malformations. In this article, we review the underlying molecular, cellular and circulatory pathobiology; explore HHT clinical and genetic diagnostic strategies; present detailed considerations regarding screening for asymptomatic visceral involvement; and provide overviews of management strategies.

Topics: Activin Receptors, Type II; Antigens, CD; Endoglin; Hemorrhage; Humans; Mutation; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Endoglin is emerging as a pivotal component of the gateway for signaling by transforming growth factor-beta (TGF-beta) in vascular endothelial cells. Mutations in endoglin cause a rare vascular disorder in humans known as hereditary hemorrhagic telengiectasia (HHT). Although rare, in-depth analysis of mutant mice and mononuclear cells from the blood of patients with HHT have provided novel and exciting insights into how the vasculature is formed, maintained, and repaired during disease. Here, we review recent data on how endoglin is thought to function in endothelial cells and place it in the broader context of signaling by TGF-beta family members in vascular cells in general. We highlight where the controversies on underlying molecular mechanisms currently lie and indicate areas of present research focus.

Topics: Animals; Antigens, CD; Endoglin; Humans; Intracellular Signaling Peptides and Proteins; Mice; Muscle, Smooth, Vascular; Mutation; Neovascularization, Pathologic; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Brain arteriovenous malformations (BAVMs) are thought to be sporadic developmental vascular lesions, but familial occurrence has been described. We compared the characteristics of patients with familial BAVMs with those of patients with sporadic BAVMs.. We systematically reviewed the literature on patients with familial BAVMs. Three families that were found in our centre were added. Age, sex distribution and clinical presentation of the identified patients were compared with those in population based series of patients with sporadic BAVMs. Furthermore, we calculated the difference in mean age at diagnosis of parents and children to study possible anticipation.. We identified 53 patients in 25 families with BAVMs. Mean age at diagnosis of patients with familial BAVMs was 27 years (range 9 months to 58 years), which was younger than in the reference population (difference between means 8 years, 95% CI 3 to 13 years). Patients with familial BAVMs did not differ from the reference populations with respect to sex or mode of presentation. In families with BAVMs in successive generations, the age of the child at diagnosis was younger than the age of the parent (difference between means 22 years, 95% CI 13 to 30 years), which suggests clinical anticipation.. Few patients with familial BAVMs have been described. These patients were diagnosed at a younger age than sporadic BAVMs whereas their mode of presentation was similar. Although there are indications of anticipation, it remains as yet unclear whether the described families represent accidental aggregation or indicate true familial occurrence of BAVMs.

Topics: Adolescent; Adult; Anticipation, Genetic; Child; Child, Preschool; Female; Humans; Infant; Intracranial Arteriovenous Malformations; Male; Middle Aged; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by epistaxis, telangiectases, and multiorgan vascular dysplasia. The two major types of disease, HHT1 and HHT2, are caused by mutations in the ENG (endoglin) and ACVRL1 genes, respectively. The corresponding endoglin and ALK-1 proteins are specific endothelial receptors of the transforming growth factor beta superfamily essential for maintaining vascular integrity. Many mutations have been identified in ENG and ACVRL1 genes and support the haploinsufficiency model for HHT. Two more genes have recently been implicated in HHT: MADH4 mutated in a combined syndrome of juvenile polyposis and HHT (JPHT), and an unidentified HHT3 gene linked to chromosome 5. Current knowledge on the genetics of HHT is summarised, including the pathways that link the genes responsible for HHT and the potential mechanisms underlying the pathogenesis of the disease.

Topics: Activin Receptors, Type II; Antigens, CD; Endoglin; Humans; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT) is caused by mutations in endoglin (ENG; HHT1) or ACVRL1/ALK1 (HHT2) genes and is an autosomal dominant vascular dysplasia. Clinically, HHT is characterized by epistaxis, telangiectases and arteriovenous malformations in some internal organs such as the lung, brain or liver. Endoglin and ALK1 proteins are specific endothelial receptors of the transforming growth factor (TGF)-beta superfamily that are essential for vascular integrity. Genetic studies in mice and humans have revealed the pivotal role of TGF-beta signaling during angiogenesis. Through binding to the TGF-beta type II receptor, TGF-beta can activate two distinct type I receptors (ALK1 and ALK5) in endothelial cells, each one leading to opposite effects on endothelial cell proliferation and migration. The recent isolation and characterization of circulating endothelial cells from HHT patients has revealed a decreased endoglin expression, impaired ALK1- and ALK5-dependent TGF-beta signaling, disorganized cytoskeleton and the failure to form cord-like structures which may lead to the fragility of small vessels with bleeding characteristic of HHT vascular dysplasia or to disrupted and abnormal angiogenesis after injuries and may explain the clinical symptoms associated with this disease.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Animals; Antigens, CD; Cell Movement; Cell Proliferation; Cytoskeleton; Endoglin; Endothelium, Vascular; Humans; Mice; Mice, Knockout; Mutation; Neovascularization, Pathologic; Protein Serine-Threonine Kinases; Receptor, Transforming Growth Factor-beta Type I; Receptor, Transforming Growth Factor-beta Type II; Receptors, Cell Surface; Receptors, Transforming Growth Factor beta; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT) is characterized by vessel alterations such as dilatation of postcapillary venules and arterio-venous communications, which account for the major clinical manifestations of the disease. Two types of HHT have been characterized HHT-1 and HHT-2, respectively, depending the former on endoglin mutations and the latter on activin receptor-like kinase 1 (ALK-1) mutations. Both endoglin and ALK-1 bind to the transforming growth factor (TGF) superfamily which, physiologically, regulates the activities of endothelial cells and also those related to the extracellular matrix. In this review, the salient features of TGF-beta will be outlined with special reference to its activity on the immune system and on tumorigenesis. Furthermore, the involvement of TGF-beta in the pathogenesis of some gastrointestinal diseases will be discussed and, in particular, in the course of liver disease, Helicobacter pylori infection and inflammatory bowel disease. In the light of these data and of animal model of HHT, the potential risk of developing other diseases in HHT patients will be discussed.

Topics: Gastrointestinal Diseases; Humans; Liver Diseases; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Genetic studies in mice and humans have revealed the pivotal role of transforming growth factor-beta (TGF-beta) signaling during angiogenesis. Mice deficient for various TGF-beta signaling components present an embryonic lethality due to vascular defects. In patients, mutations in the TGF-beta type I receptor ALK1 or in the accessory TGF-beta receptor endoglin are linked to an autosomal dominant disorder of vascular dysplasia termed Hereditary Haemorrhagic Telangiectasia (HHT). It has puzzled researchers for years to explain the effects of TGF-beta being a stimulator and an inhibitor of angiogenesis in vitro and in vivo. Recently, a model has been proposed in which TGF-beta by binding to the TGF-beta type II receptor can activate two distinct type I receptors in endothelial cells (ECs), i.e., the EC-restricted ALK1 and the broadly expressed ALK-5, which have opposite effects on ECs behavior. ALK1 via Smad1/5 transcription factors stimulates EC proliferation and migration, whereas ALK5 via Smad2/3 inhibits EC proliferation and migration. Here, the new findings are presented concerning the molecular mechanisms that take place in ECs to precisely regulate and even switch between TGF-beta-induced biological responses. In particular, the role of the accessory TGF-beta receptor endoglin in the regulation of EC behavior is addressed and new insights are discussed concerning the possible mechanisms that are implicated in the development of HHT.

Topics: Animals; Endothelium, Vascular; Humans; Mice; Neovascularization, Physiologic; Receptors, Transforming Growth Factor beta; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Idiopathic pulmonary arterial hypertension (formerly primary pulmonary hypertension) can affect more than one member of the same family. In the past 25 years scientists have exposed the inheritance pattern and a major element of the molecular basis for inherited pulmonary arterial hypertension. Familial pulmonary arterial hypertension is inherited as an autosomal dominant trait with incomplete penetrance (i.e., several individuals inherit a predisposition to the disease, but never express it). Mutations in the gene that codes for bone morphogenetic protein receptor type II (BMPR-II) are a major predisposition for the development of pulmonary arterial hypertension. These mutations are present in at least half of familial cases of pulmonary arterial hypertension and 10 to 25% of idiopathic pulmonary arterial hypertension patients. Mutations in the gene that codes for activin receptor-like kinase (ALK 1), another transforming growth factor beta (TGF-beta) cell surface receptor, appear responsible for the rare occurrence of pulmonary arterial hypertension in patients with hereditary hemorrhagic telangiectasia. These discoveries coupled with other basic investigations offer opportunities for advances in the management of pulmonary arterial hypertension.

Topics: Activin Receptors; Bone Morphogenetic Protein Receptors, Type II; Forecasting; Genetic Predisposition to Disease; Humans; Hypertension, Pulmonary; Mutation; Pedigree; Polymorphism, Genetic; Risk Factors; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Transforming growth factor (TGF)-beta is a multifunctional protein that initiates its diverse cellular responses by binding to and activating specific type I and type II serine/threonine kinase receptors. TGF-beta can act as a regulator of proliferation, migration, survival, differentiation, and extracellular matrix synthesis in endothelial cells and vascular smooth muscle cells, as well as in the maintenance of vascular homeostasis. Importantly, genetic studies in humans have revealed the pivotal role of TGF-beta as well as its signaling components in angiogenesis. Mutations in two TGF-beta receptors (ie, the activin receptor-like kinase (ALK) 1 and the accessory TGF-beta receptor endoglin) have been linked to vascular disorders named hereditary hemorrhagic telangiectasia. In addition, knockout mice for the different components of the TGF-beta signaling pathway have shown that TGF-beta is indispensable for angiogenesis. Recent studies have revealed that TGF-beta can regulate vascular homeostasis by balancing the signaling between two distinct TGF-beta type I receptors (ie, the endothelial-restricted ALK1 and the broadly expressed ALK5 receptors). The activation of these receptors has been shown to induce opposite effects on endothelial cell behavior and angiogenesis. In this review, we will present recent advances in understanding the role of TGF-beta signaling in endothelial cells as well as the underlying molecular mechanisms by which perturbation of this pathway can lead to vascular disorders.

Topics: Animals; Humans; Mice; Mice, Knockout; Neovascularization, Physiologic; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Diseases

Hereditary hemorrhagic telangiectasia (HHT) is a vascular disorder in humans which has been mapped to two genes, endoglin and activin receptor-like kinase-1 (ALK-1) both of which mediate signaling by transforming growth factor beta ligands in vascular endothelial cells. Animal models have shown that these receptors are not only important for maintaining vascular integrity but also for angiogenesis both during embryonic development and during tumor growth. Here, we review the current status of reported mutations in the context of the clinical manifestations and the effects on the vessel wall both in patients and in animal models of the disease.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Animals; Antigens, CD; Chromosomes, Human, Pair 12; Chromosomes, Human, Pair 9; Endoglin; Humans; Hypertension, Pulmonary; Mice; Mice, Mutant Strains; Mutation; Neovascularization, Pathologic; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1; Zebrafish

Advances in our understanding of fundamental biological processes can be made by the analysis of defects manifested in inherited diseases. The genes responsible for these genetic syndromes often encode proteins that act at critical points of the pathways that control biological processes such as cell proliferation, cell-cell communication, cellular differentiation, and cell death. This approach has lead to the discovery of novel gene products and/or biochemical pathways involved in disease, genes that in turn play a fundamental role in normal biological processes. This forward genetic approach, focusing on Mendelian disorders of vascular anomalies, has been particularly fruitful for the study of genetic regulation of angiogenesis. This review summarizes the ongoing saga of two genetic syndromes involving disruption of normal vascular morphogenesis. Each inherited disorder involves the focal development of a distinct vascular anomaly. In hereditary hemorrhagic telangiectasia (HHT), the hallmark vascular lesion is termed an arteriovenous malformation, which involves the direct communication of an artery with a vein (arteriovenous shunt), without an intervening capillary bed. For cerebral cavernous malformations (CCM), the lesions are grossly-dilated, closely-packed, capillary-like sinusoidal chambers. The autosomal dominant mode of inheritance of each of these distinct syndromes suggested that the underlying genes might regulate critical aspects of vascular morphogenesis. Emerging but intriguing tales are being told by the genes (and their protein products) mutated in these disorders.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Amino Acid Motifs; Animals; Antigens, CD; Blood Vessels; Brain Diseases; Cell Adhesion; Cell Communication; Cell Division; Cytoskeleton; Endoglin; Genes, Dominant; Humans; Integrins; KRIT1 Protein; Mice; Mice, Knockout; Microtubule-Associated Proteins; Models, Biological; Mutation; Neovascularization, Pathologic; Protein Structure, Tertiary; Proto-Oncogene Proteins; Receptors, Cell Surface; Signal Transduction; Syndrome; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Primary pulmonary hypertension has been described as either sporadic or clustered in families. Familial primary pulmonary hypertension segregates as an autosomal dominant trait with markedly reduced disease gene penetrance. Defects within bone morphogenetic protein receptor type II gene, coding for a receptor member of the transforming growth factor-beta family, underlie familial primary pulmonary hypertension. Several lines of evidence point to the potential requirement of additional factors, either environmental or genetic, in the pathogenesis of the disease. In addition, a proportion of so-called sporadic primary pulmonary hypertension turns out to have an inherited basis, as demonstrated by germline bone morphogenetic protein receptor type II gene mutations. Analysis of cases in association with hereditary haemorrhagic telangiectasia led to the demonstration that pulmonary arterial hypertension can involve activin-receptor-like kinase 1 mutations, a type I transforming growth factor-beta receptor. These findings emphasise the critical role of the transforming growth factor-beta signalling pathway in pulmonary arterial hypertension. While this achievement has generated extreme interest, the pathobiology of severe pulmonary arterial hypertension remains unclear and genomic approaches to pulmonary hypertension research may identify additional molecular determinants for this disorder. Finally, there is an urgent need to develop relevant guidelines for genetic counselling to assist patients, their relatives and pulmonary vascular specialists to utilise these recent observations.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Bone Morphogenetic Protein Receptors, Type II; Genetic Testing; Germ-Line Mutation; Glycogen Storage Disease Type I; Humans; Hypertension, Pulmonary; Mutation; Protein Serine-Threonine Kinases; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Members of the transforming growth factor (TGF)-beta superfamily play critical roles in regulation of various cellular functions. Dysregulation of the signaling mechanisms of the TGF-beta superfamily proteins is associated with clinical diseases such as cancer, fibrotic diseases, and vascular disorders. Therefore, understanding these signaling mechanisms may provide us with novel ways to develop strategies for treating clinical diseases induced by these cytokines.. This review discusses our current understanding of the mechanisms of TGF-beta signaling, focusing on the roles of TGF-beta in regulation of vascular wall cells and on the regulation of TGF-beta superfamily signals by inhibitory Smads.

Topics: Bone Morphogenetic Proteins; DNA-Binding Proteins; Humans; Hypertension, Pulmonary; Ligases; Neovascularization, Pathologic; Signal Transduction; Smad Proteins; Telangiectasia, Hereditary Hemorrhagic; Trans-Activators; Transforming Growth Factor beta; Ubiquitin-Protein Ligases

Topics: Activin Receptors, Type I; Animals; Cell Division; Humans; Hypertension, Pulmonary; Osteochondrodysplasias; Protein Serine-Threonine Kinases; Receptor, Transforming Growth Factor-beta Type I; Receptor, Transforming Growth Factor-beta Type II; Receptors, Transforming Growth Factor beta; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Trans-Activators; Transforming Growth Factor beta

To date much of the recent work on pathological angiogenesis has focused on inflammatory diseases, diabetes and cancer in particular. Hereditary hemorrhagic telangiectasia or Rendu-Osler-Weber disease provides an example of the genetic disorder of angiogenesis in which a multisystemic angiodysplasia is responsible for severe hemorrhage. The disease pathogenesis is partially explained by a defect in the TGF-beta signaling system, although in more recent works a possible role of other vascular growth factors has been proposed. This paper provides a model of an aberrant angiogenesis in which multiple vascular growth factors could be involved in a diffuse angiodysplasia.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Animals; Antigens, CD; Endoglin; Endothelial Growth Factors; Growth Substances; Humans; Lymphokines; Neovascularization, Pathologic; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

This paper concentrates on the genetic aspects of pulmonary arterial hypertension (PAH), a diagnostically based subclass of pulmonary hypertension that includes primary pulmonary hypertension (PPH). During the past year, patients with familial and sporadic PPH were found to have germline heterozygous missense, nonsense and frameshift mutations in bone morphogenetic protein receptor II (BMPR2). Mutations in BMPR2, a member of the transforming growth factor-beta (TGF-beta) receptor superfamily, are predicted to interrupt the bone morphogenetic protein (BMP) signalling pathway, resulting in proliferation, rather than apoptosis of cells within small arterioles. Mechanistically, haploinsufficiency was found by using in vitro gene expression experiments, but a dominant-negative mechanism has not been excluded. The failure to find BMPR2 mutations in all families with familial PPH and in all patients with sporadic PPH suggests that other genes remain to be identified. Mutations in ALK1, a TGF-beta type 1 receptor, previously known to cause type 2 hereditary haemorrhagic telangiectasia (HHT), have also been reported in a few HHT families with clinical and histological features of PPH. The clinical development of PPH, as in neoplasia, appears to require 'two hits' The two hits can be provided either by genetic or environmental factors.

Topics: Animals; Bone Morphogenetic Protein Receptors, Type II; Frameshift Mutation; Humans; Hypertension, Pulmonary; Mutation, Missense; Protein Serine-Threonine Kinases; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Topics: Animals; Humans; Hypertension, Pulmonary; Mice; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Topics: Animals; Arteriosclerosis; Cell Cycle; Embryonic and Fetal Development; Fibrosis; Humans; Immune Tolerance; Neoplasm Metastasis; Neoplasms; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Topics: Antigens, CD; Arteriovenous Malformations; Embolization, Therapeutic; Endoglin; Genotype; Humans; Mutation; Phenotype; Protein Serine-Threonine Kinases; Pulmonary Artery; Pulmonary Veins; Receptors, Cell Surface; Receptors, Growth Factor; Receptors, Transforming Growth Factor beta; Telangiectasia, Hereditary Hemorrhagic; Tomography, X-Ray Computed; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

The soy isoflavone genistein attenuates growth factor- and cytokine-stimulated proliferation of both normal and cancer cells. This article reviews our current understanding of the potential mechanisms of action of genistein. In membrane preparations from mammalian cells, genistein is a potent and specific inhibitor of tyrosine autophosphorylation of the epidermal growth factor (EGF) receptor. However, in several cell systems in which it inhibits growth, genistein does not alter tyrosine phosphorylation of the EGF receptor or other tyrosine kinase substrates thought to be involved in signal transduction pathways, suggesting that other mechanisms may be responsible for its action. Alternatives include inhibition of DNA topoisomerase II activity, regulation of cell cycle checkpoints, and antiangiogenic and antioxidant activity. Experiments in our laboratory suggest a new concept, that genistein may inhibit cell growth by modulating transforming growth factor (TGF) beta1 signaling pathways. Such a link between genistein action and TGFbeta1 function is supported by preliminary results of studies in patients with hereditary hemorrhagic telangiectasia (a genetic disorder involving mutations in proteins that regulate TGFbeta receptor complex formation and signaling) in which several patients had dramatic attenuation of their symptoms after 1 wk of ingesting soy-based beverages. These preclinical studies in combination with our cell culture data suggest that the mechanism of genistein involves, if not requires, TGFbeta1-signaling.

Topics: Animals; Anticarcinogenic Agents; Breast Neoplasms; Cardiovascular Diseases; Cell Division; Female; Genistein; Humans; Male; Prostatic Neoplasms; Protein-Tyrosine Kinases; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Topics: Animals; Antigens, CD; Cell Cycle; Endoglin; Humans; Neoplasms; Protein Serine-Threonine Kinases; Receptors, Cell Surface; Receptors, Transforming Growth Factor beta; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

The transforming growth factor β (TGF-β)/ALK1/ENG signaling pathway maintains quiescent state of endothelial cells, but at the same time, it regulates neutrophil functions. Importantly, mutations of this pathway lead to a rare autosomal disorder called hereditary hemorrhagic telangiectasia (HHT), characterized with abnormal blood vessel formation (angiogenesis). As neutrophils are potent regulators of angiogenesis, we investigated how disturbed TGF-β/ALK1/ENG signaling influences angiogenic properties of these cells in HHT. We could show for the first time that not only endothelial cells, but also neutrophils isolated from such patients are ENG/ALK1 deficient. This deficiency obviously stimulates proangiogenic switch of such neutrophils. Elevated proangiogenic activity of HHT neutrophils is mediated by the increased spontaneous degranulation of gelatinase granules, resulting in high release of matrix-degrading matrix metalloproteinase 9 (MMP9). In agreement, therapeutic disturbance of this process using Src tyrosine kinase inhibitors impaired proangiogenic capacity of such neutrophils. Similarly, inhibition of MMP9 activity resulted in significant impairment of neutrophil-mediated angiogenesis. All in all, deficiency in TGF-β/ALK1/ENG signaling in HHT neutrophils results in their proangiogenic activation and disease progression. Therapeutic strategies targeting neutrophil degranulation and MMP9 release and activity may serve as a potential therapeutic option for HHT.

Topics: Activin Receptors, Type II; Endoglin; Endothelial Cells; Humans; Matrix Metalloproteinase 9; Neutrophils; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Patients with hereditary haemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, suffer from the consequences of abnormal vessel structures. These structures can lead to haemorrhages or shunt effects in liver, lungs and brain. This inherited and rare disease is characterized by mutations affecting the transforming growth factor-β (TGF-β)/Bone Morphogenetic Protein (BMP) pathway that results in arteriovenous malformations and studies indicate an impaired immune response. The mechanism underlying this altered immune response in HHT patients is still unknown. TGF-β interacts with hypoxia inducible factors (HIF), which both orchestrate inflammatory and angiogenic processes. Therefore, we analysed the expression of HIF and related genes in whole blood samples from HHT patients. We could show significantly decreased expression of HIF-1α on the mRNA and protein level. However, commonly known upstream regulators of HIF-1α in inflammatory responses were not affected, whereas HIF-1α target genes were significantly downregulated. There was no correlation between HIF1A or HIF2A gene expression and the severity of HHT detected. Our results represent a rare case of HIF-1α downregulation in a human disease, which underlines the relevance of HIFs in HHT. The study indicates an interaction of the known mutation in HHT and the dysregulation of HIF-1α in HHT patients, which might contribute to the clinical phenotype.

Topics: Arteriovenous Malformations; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Mutation; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT) is a rare, autosomal dominant genetic disorder characterized by life-threatening vascular dysplasia. Myeloid angiogenic cells (MACs), alternatively called early endothelial progenitor cells or circulating angiogenic cells, do not directly incorporate into developing blood vessels, but augment angiogenesis in a paracrine manner. MAC dysfunction has been reported in HHT. MicroRNAs (miRNAs) regulate cellular function by modulating gene expression post-transcriptionally. To date, the role of miRNAs in HHT MAC dysfunction has not been documented.. The goal of this study was to comparatively profile miRNAs in HHT patient and control MACs to identify dysregulated miRNAs that may be responsible for the observed MAC dysfunction in HHT.. MiRNA dysregulation, specifically reduced expression of miR-132-3p, in HHT MACs was identified. The dysregulated miRNAs are significantly enriched in the TGFβ, PI3K/AKT, and Hippo signalling pathways. These data suggest that alteration in miRNA expression may impair these pathways and contribute to MAC dysfunction in HHT.

Topics: Humans; MicroRNAs; p120 GTPase Activating Protein; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease caused by mutations in. We tested this hypothesis and investigated the therapeutic effects and potential risks of induced-ALK1 or -ENG overexpression (OE) for HHT.. We generated a novel mouse allele (ROSA26. These data support the notion that ENG and ALK1 form a linear signaling pathway for the formation of a proper arteriovenous network during angiogenesis. We suggest that ALK1 OE or activation can be an effective therapeutic strategy for HHT. Further research is required to study whether this therapy could be translated into treatment for humans.

Topics: Activin Receptors, Type II; Alleles; Animals; Apoptosis Regulatory Proteins; Arteriovenous Malformations; Disease Models, Animal; Endoglin; Endothelial Cells; Green Fluorescent Proteins; Growth Differentiation Factor 2; Mice; Mitochondrial Proteins; Receptors, Notch; Retinal Vessels; RNA, Untranslated; Signal Transduction; Skin; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia is an autosomal dominant vascular disorder caused by heterozygous, loss-of-function mutations in 4 transforming growth factor beta (TGFβ) pathway members, including the central transcriptional mediator of the TGFβ pathway, Smad4. Loss of Smad4 causes the formation of inappropriate, fragile connections between arteries and veins called arteriovenous malformations (AVMs), which can hemorrhage leading to stroke, aneurysm, or death. Unfortunately, the molecular mechanisms underlying AVM pathogenesis remain poorly understood, and the TGFβ downstream effectors responsible for hereditary hemorrhagic telangiectasia-associated AVM formation are currently unknown.. To identify potential biological targets of the TGFβ pathway involved in AVM formation, we performed RNA- and chromatin immunoprecipitation-sequencing experiments on BMP9 (bone morphogenetic protein 9)-stimulated endothelial cells (ECs) and isolated ECs from a Smad4-inducible, EC-specific knockout ( Smad4-iECKO) mouse model that develops retinal AVMs. These sequencing studies identified the angiopoietin-Tek signaling pathway as a downstream target of SMAD4. We used monoclonal blocking antibodies to target a specific component in this pathway and assess its effects on AVM development.. Sequencing studies uncovered 212 potential biological targets involved in AVM formation, including the EC surface receptor, TEK (TEK receptor tyrosine kinase) and its antagonistic ligand, ANGPT2 (angiopoietin-2). In Smad4-iECKO mice, Angpt2 expression is robustly increased, whereas Tek levels are decreased, resulting in an overall reduction in angiopoietin-Tek signaling. We provide evidence that SMAD4 directly represses Angpt2 transcription in ECs. Inhibition of ANGPT2 function in Smad4-deficient mice, either before or after AVMs form, prevents and alleviates AVM formation and normalizes vessel diameters. These rescue effects are attributed to a reversion in EC morphological changes, such as cell size and shape that are altered in the absence of Smad4.. Our studies provide a novel mechanism whereby the loss of Smad4 causes increased Angpt2 transcription in ECs leading to AVM formation, increased blood vessel calibers, and changes in EC morphology in the retina. Blockade of ANGPT2 function in an in vivo Smad4 model of hereditary hemorrhagic telangiectasia alleviated these vascular phenotypes, further implicating ANGPT2 as an important TGFβ downstream mediator of AVM formation. Therefore, alternative approaches that target ANGPT2 function may have therapeutic value for the alleviation of hereditary hemorrhagic telangiectasia symptoms, such as AVMs.

Topics: Angiopoietin-2; Animals; Arteriovenous Malformations; Cell Size; Disease Models, Animal; Endothelial Cells; Endothelium, Vascular; Gene Expression Regulation; Mice; Mice, Knockout; Receptor, TIE-2; Signal Transduction; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transcription, Genetic; Transforming Growth Factor beta

We characterized the NK cell phenotype and function in three family members with Hereditary Hemorrhagic Telangiectasia (HHT) due to heterozygous

Topics: Aged; Female; Humans; Killer Cells, Natural; Loss of Function Mutation; Male; Middle Aged; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder characterized by multi-systemic vascular dysplasia affecting 1 in 5000 people worldwide. Individuals with HHT suffer from many complications including nose and gastrointestinal bleeding, anemia, iron deficiency, stroke, abscess, and high-output heart failure. Identification of the causative gene mutations and the generation of animal models have revealed that decreased transforming growth factor-β (TGF-β)/bone morphogenetic protein (BMP) signaling and increased vascular endothelial growth factor (VEGF) signaling activity in endothelial cells are responsible for the development of the vascular malformations in HHT. Perturbations in these key pathways are thought to lead to endothelial cell activation resulting in mural cell disengagement from the endothelium. This initial instability state causes the blood vessels to response inadequately when they are exposed to angiogenic triggers resulting in excessive blood vessel growth and the formation of vascular abnormalities that are prone to bleeding. Drugs promoting blood vessel stability have been reported as effective in preclinical models and in clinical trials indicating possible interventional targets based on a normalization approach for treating HHT. Here, we will review how disturbed TGF-β and VEGF signaling relates to blood vessel destabilization and HHT development and will discuss therapeutic opportunities based on the concept of vessel normalization to treat HHT.

Topics: Animals; Endothelial Cells; Humans; Pericytes; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A

Hereditary hemorrhagic telangiectasia (HHT) is caused by mutations in TGFβ/BMP9 pathway genes and characterized by vascular malformations (VM) including arteriovenous malformations (AVM) in lung, liver, and brain, which lead to severe complications including intracranial hemorrhage (ICH) from brain VM. The clinical heterogeneity of HHT suggests a role for genetic modifier effects. Common variants in loci that modify phenotype severity in Tgfb knockout mice were previously reported as associated with lung AVM in HHT. Common variants in candidate genes were reported as associated with sporadic brain AVM and/or ICH. We investigated whether these variants are associated with HHT organ VM or with ICH from brain VM in 752 Caucasian HHT patients enrolled by the Brian Vascular Malformation Consortium.. We genotyped 11 candidate variants: four variants reported as associated with lung AVM in HHT (PTPN14 rs2936018, USH2A rs700024, ADAM17 rs12474540, rs10495565), and seven variants reported as associated with sporadic BAVM or ICH (APOE ε2, ANGPTL4 rs11672433, EPHB4 rs314308, IL6 rs1800795, IL1B rs1143627, ITGB8 rs10486391, TNFA rs361525). Association of genotype with any VM, lung AVM, liver VM, brain VM or brain VM ICH was evaluated by multivariate logistic regression adjusted for age, gender, and family clustering.. None of the 11 variants was significantly associated with any phenotype. There was a trend toward association of USH2A rs700024 with ICH (OR = 2.77, 95% CI = 1.13-6.80, p = .026).. We did not replicate previously reported associations with HHT lung AVM and variants in Tgfb modifier loci. We also did not find significant associations between variants reported in sporadic brain AVM and VM or ICH in HHT.

Topics: Adult; Aged; Brain; Central Nervous System Vascular Malformations; Female; Genetic Association Studies; Genotype; Humans; Intracranial Arteriovenous Malformations; Intracranial Hemorrhages; Liver; Lung; Male; Middle Aged; Mutation; Phenotype; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Malformations

Hereditary Hemorrhagic Telangiectasia type-1 (HHT1) is a genetic vascular disorder caused by haploinsufficiency of the TGFβ co-receptor endoglin. Dysfunctional homing of HHT1 mononuclear cells (MNCs) towards the infarcted myocardium hampers cardiac recovery. HHT1-MNCs have elevated expression of dipeptidyl peptidase-4 (DPP4/CD26), which inhibits recruitment of CXCR4-expressing MNCs by inactivation of stromal cell-derived factor 1 (SDF1). We hypothesize that inhibiting DPP4 will restore homing of HHT1-MNCs to the infarcted heart and improve cardiac recovery.. After inducing myocardial infarction (MI), wild type (WT) and endoglin heterozygous (Eng+/-) mice were treated for 5 days with the DPP4 inhibitor Diprotin A (DipA). DipA increased the number of CXCR4+ MNCs residing in the infarcted Eng+/- hearts (Eng+/- 73.17±12.67 vs. Eng+/- treated 157.00±11.61, P = 0.0003) and significantly reduced infarct size (Eng+/- 46.60±9.33% vs. Eng+/- treated 27.02±3.04%, P = 0.03). Echocardiography demonstrated that DipA treatment slightly deteriorated heart function in Eng+/- mice. An increased number of capillaries (Eng+/- 61.63±1.43 vs. Eng+/- treated 74.30±1.74, P = 0.001) were detected in the infarct border zone whereas the number of arteries was reduced (Eng+/- 11.88±0.63 vs. Eng+/- treated 6.38±0.97, P = 0.003). Interestingly, while less M2 regenerative macrophages were present in Eng+/- hearts prior to DipA treatment, (WT 29.88±1.52% vs. Eng+/- 12.34±1.64%, P<0.0001), DPP4 inhibition restored the number of M2 macrophages to wild type levels.. In this study, we demonstrate that systemic DPP4 inhibition restores the impaired MNC homing in Eng+/- animals post-MI, and enhances cardiac repair, which might be explained by restoring the balance between the inflammatory and regenerative macrophages present in the heart.

Topics: Animals; Chemokine CXCL12; Dipeptidyl Peptidase 4; Dipeptidyl-Peptidase IV Inhibitors; Disease Models, Animal; Endoglin; Fibrosis; Haploinsufficiency; Heart Ventricles; Heterozygote; Humans; Macrophages; Male; Mice; Mice, Transgenic; Myocardial Infarction; Myocardium; Regeneration; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Endoglin is an auxiliary receptor for members of the TGF-β superfamily and plays an important role in the homeostasis of the vessel wall. Mutations in endoglin gene (ENG) or in the closely related TGF-β receptor type I ACVRL1/ALK1 are responsible for a rare dominant vascular dysplasia, the Hereditary Hemorrhagic Telangiectasia (HHT), or Rendu-Osler-Weber syndrome. Endoglin is also expressed in human macrophages, but its role in macrophage function remains unknown. In this work, we show that endoglin expression is triggered during the monocyte-macrophage differentiation process, both in vitro and during the in vivo differentiation of blood monocytes recruited to foci of inflammation in wild-type C57BL/6 mice. To analyze the role of endoglin in macrophages in vivo, an endoglin myeloid lineage specific knock-out mouse line (Eng(fl/fl)LysMCre) was generated. These mice show a predisposition to develop spontaneous infections by opportunistic bacteria. Eng(fl/fl)LysMCre mice also display increased survival following LPS-induced peritonitis, suggesting a delayed immune response. Phagocytic activity is impaired in peritoneal macrophages, altering one of the main functions of macrophages which contributes to the initiation of the immune response. We also observed altered expression of TGF-β1 target genes in endoglin deficient peritoneal macrophages. Overall, the altered immune activity of endoglin deficient macrophages could help to explain the higher rate of infectious diseases seen in HHT1 patients.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Animals; Endoglin; Flow Cytometry; Gene Expression Regulation; Humans; Immunity, Innate; Inflammation; Intracellular Signaling Peptides and Proteins; Macrophages; Mice; Mice, Knockout; Opportunistic Infections; Phagocytosis; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT), the most common inherited vascular disorder, is predominantly caused by mutations in ENG and ACVRL1, which are part of the transforming growth factor beta (TGF-β) signaling pathway. HHT is characterized by the presence of mucocutaneous telangiectases and arteriovenous malformations in visceral organs, primarily the lungs, brain and liver. The most common symptom in HHT is epistaxis originating from nasal telangiectasia, which can be difficult to prevent and can lead to severe anemia. The clinical manifestations of HHT are extremely variable, even within family members, and the exact mechanism of how endoglin and ALK1 haploinsufficiency leads to HHT manifestations remains to be identified.. The purpose of this study was to detect significantly differentially regulated genes in HHT, and try to elucidate the pathways and regulatory mechanisms occurring in the affected tissue of HHT patients, in order to further characterize this disorder and hypothesize on how telangiectases develop. By microarray technology (Agilent G3 Human GE 8x60), we performed global gene expression profiling of mRNA transcripts from HHT nasal telangiectasial (n = 40) and non-telangiectasial (n = 40) tissue using a paired design. Comparing HHT telangiectasial and non-telangiectasial tissue, significantly differentially expressed genes were detected using a paired t-test. Gene set analysis was performed using GSA-SNP. In the group of ENG mutation carriers, we detected 67 differentially expressed mRNAs, of which 62 were down-regulated in the telangiectasial tissue. Gene set analysis identified the gene ontology (GO) terms vasculogenesis, TGF-β signaling, and Wnt signaling as differentially expressed in HHT1. Altered Wnt signaling might be related to HHT pathogenesis and a greater understanding of this may lead to the discovery of therapeutic targets in HHT.

Topics: Activin Receptors, Type II; Antigens, CD; Arteriovenous Malformations; Biopsy; Cluster Analysis; Endoglin; Family Health; Female; Gene Expression Profiling; Genotype; Humans; Male; Mutation; Nasal Mucosa; Nucleic Acid Hybridization; Principal Component Analysis; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Endoglin and activin receptor-like kinase 1 are specialized transforming growth factor-beta (TGF-β) superfamily receptors, primarily expressed in endothelial cells. Mutations in the corresponding ENG or ACVRL1 genes lead to hereditary hemorrhagic telangiectasia (HHT1 and HHT2 respectively). To discover proteins interacting with endoglin, ACVRL1 and TGF-β receptor type 2 and involved in TGF-β signaling, we applied LUMIER, a high-throughput mammalian interactome mapping technology. Using stringent criteria, we identified 181 novel unique and shared interactions with ACVRL1, TGF-β receptor type 2, and endoglin, defining potential novel important vascular networks. In particular, the regulatory subunit B-beta of the protein phosphatase PP2A (PPP2R2B) interacted with all three receptors. Interestingly, the PPP2R2B gene lies in an interval in linkage disequilibrium with HHT3, for which the gene remains unidentified. We show that PPP2R2B protein interacts with the ACVRL1/TGFBR2/endoglin complex and recruits PP2A to nitric oxide synthase 3 (NOS3). Endoglin overexpression in endothelial cells inhibits the association of PPP2R2B with NOS3, whereas endoglin-deficient cells show enhanced PP2A-NOS3 interaction and lower levels of endogenous NOS3 Serine 1177 phosphorylation. Our data suggest that endoglin regulates NOS3 activation status by regulating PPP2R2B access to NOS3, and that PPP2R2B might be the HHT3 gene. Furthermore, endoglin and ACVRL1 contribute to several novel networks, including TGF-β dependent and independent ones, critical for vascular function and potentially defective in HHT.

Topics: Activin Receptors, Type II; Animals; Antigens, CD; Blood Vessels; Embryo, Mammalian; Endoglin; Endothelium, Vascular; HEK293 Cells; Humans; Mice; Mice, Knockout; Protein Binding; Protein Interaction Maps; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Heterozygous loss-of-function SMAD4 mutations are associated with juvenile polyposis syndrome and hereditary hemorrhagic telangiectasia. Some carriers exhibit symptoms of both conditions, leading to juvenile polyposis-hereditary hemorrhagic telangiectasia syndrome. Three families have been reported with connective tissue abnormalities. To better understand the spectrum and extent of clinical findings in SMAD4 carriers, medical records of 34 patients (20 families) from five clinical practices were reviewed. Twenty-one percent of the patients (7/34) had features suggesting a connective tissue defect: enlarged aortic root (n = 3), aortic and mitral insufficiency (n = 2), aortic dissection (n = 1), retinal detachment (n = 1), brain aneurysms (n = 1), and lax skin and joints (n = 1). Juvenile polyposis-specific findings were almost uniformly present but variable. Ninety-seven percent of the patients had colon polyps that were generally pan-colonic and of variable histology and number. Forty-eight percent of the patients (15/31) had extensive gastric polyposis. Hereditary hemorrhagic telangiectasia features, including epistaxis (19/31, 61%), mucocutaneous telangiectases (15/31, 48%), liver arteriovenous malformation (6/16, 38%), brain arteriovenous malformation (1/26, 4%), pulmonary arteriovenous malformation (9/17, 53%), and intrapulmonary shunting (14/23, 61%), were documented in 76% of the patients. SMAD4 carriers should be managed for juvenile polyposis and hereditary hemorrhagic telangiectasia because symptoms of both conditions are likely yet unpredictable. Connective tissue abnormalities are an emerging component of juvenile polyposis-hereditary hemorrhagic telangiectasia syndrome, and larger studies are needed to understand these manifestations.

Topics: Adolescent; Adult; Aged; Child; Child, Preschool; Connective Tissue; Humans; Infant; Intestinal Polyposis; Middle Aged; Mutation; Neoplastic Syndromes, Hereditary; Retrospective Studies; Signal Transduction; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Young Adult

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by arteriovenous malformations and hemorrhages. This vascular disease results mainly from mutations in 2 genes involved in the TGF-β pathway (ENG and ALK1) that are exclusively expressed by endothelial cells. The present study identified miR-27a and miR-205 as two circulating miRNAs differentially expressed in HHT patients. The plasma levels of miR-27a are elevated while those of miR-205 are reduced in both HHT1 and HHT2 patients compared to healthy controls. The role of miR-205 in endothelial cells was further investigated. Our data indicates that miR-205 expression displaces the TGF-β balance towards the anti-angiogenic side by targeting Smad1 and Smad4. In line, overexpression of miR-205 in endothelial cells reduces proliferation, migration and tube formation while its inhibition shows opposite effects. This study not only suggests that detection of circulating miRNA (miR-27a and miR-205) could help for the screening of HHT patients but also provides a functional link between the deregulated expression of miR-205 and the HHT phenotype.

Topics: Cell Division; Cell Movement; Cells, Cultured; Down-Regulation; Endothelial Cells; Gene Expression Regulation; Gene Knockdown Techniques; Human Umbilical Vein Endothelial Cells; Humans; MicroRNAs; Neovascularization, Pathologic; Oligonucleotides, Antisense; Phenotype; Receptors, Transforming Growth Factor beta; ROC Curve; Signal Transduction; Smad1 Protein; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transcriptome; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT), the most common inherited vascular disorder, is caused by mutations in genes involved in the transforming growth factor beta (TGF-β) signaling pathway (ENG, ACVRL1, and SMAD4). Yet, approximately 15% of individuals with clinical features of HHT do not have mutations in these genes, suggesting that there are undiscovered mutations in other genes for HHT and possibly vascular disorders with overlapping phenotypes. The genetic etiology for 191 unrelated individuals clinically suspected to have HHT was investigated with the use of exome and Sanger sequencing; these individuals had no mutations in ENG, ACVRL1, and SMAD4. Mutations in BMP9 (also known as GDF2) were identified in three unrelated probands. These three individuals had epistaxis and dermal lesions that were described as telangiectases but whose location and appearance resembled lesions described in some individuals with RASA1-related disorders (capillary malformation-arteriovenous malformation syndrome). Analyses of the variant proteins suggested that mutations negatively affect protein processing and/or function, and a bmp9-deficient zebrafish model demonstrated that BMP9 is involved in angiogenesis. These data confirm a genetic cause of a vascular-anomaly syndrome that has phenotypic overlap with HHT.

Topics: Adolescent; Adult; Amino Acid Substitution; Animals; Blood Vessels; Female; Genetic Predisposition to Disease; Growth Differentiation Factor 2; Growth Differentiation Factors; Humans; Ligands; Male; Mice; Mutation; Mutation, Missense; Phenotype; Protein Binding; Protein Processing, Post-Translational; Signal Transduction; Syndrome; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Zebrafish

Dilation or aneurysm of the ascending aorta can progress to acute aortic dissection (Thoracic Aortic Aneurysms and Aortic Dissections, TAAD). Mutations in genes encoding TGF-β-related proteins (TGFBR1, TGFBR2, FBN1, and SMAD3) cause syndromic and inherited TAAD. SMAD4 mutations are associated with juvenile polyposis syndrome (JPS) and a combined JPS-hereditary hemorrhagic telangiectasia (HHT) known as JPS-HHT. A family with JPS-HHT was reported to have aortic root dilation and mitral valve abnormalities. We report on two patients with JPS-HHT with SMAD4 mutations associated with thoracic aortic disease. The first patient, an 11-year-old boy without Marfan syndrome features, had JPS and an apparently de novo SMAD4 mutation (c.1340_1367dup28). Echocardiography showed mild dilation of the aortic annulus and aortic root, and mild dilation of the sinotubular junction and ascending aorta. Computed tomography confirmed aortic dilation and showed small pulmonary arteriovenous malformations (PAVM). The second patient, a 34-year-old woman with colonic polyposis, HHT, and features of Marfan syndrome, had a SMAD4 mutation (c.1245_1248delCAGA). Echocardiography showed mild aortic root dilation. She also had PAVM and hepatic focal nodular hyperplasia. Her family history was significant for polyposis, HHT, thoracic aortic aneurysm, and dissection and skeletal features of Marfan syndrome in her father. These two cases confirm the association of thoracic aortic disease with JPS-HHT resulting from SMAD4 mutations. We propose that the thoracic aorta should be screened in patients with SMAD4 mutations to prevent untimely death from dissection. This report also confirms that SMAD4 mutations predispose to TAAD.

Topics: Adult; Aorta; Aortic Aneurysm, Thoracic; Child; Echocardiography; Female; Fibrillin-1; Fibrillins; Humans; Intestinal Polyposis; Male; Marfan Syndrome; Microfilament Proteins; Mutation; Protein Serine-Threonine Kinases; Receptor, Transforming Growth Factor-beta Type I; Receptor, Transforming Growth Factor-beta Type II; Receptors, Transforming Growth Factor beta; Signal Transduction; Smad3 Protein; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary haemorrhagic telangiectasia (HHT) [corrected] is a vascular dysplasia syndrome caused by mutations in transforming growth factor-β/bone morphogenetic protein pathway genes, ENG and ACVRL1. HHT [corrected] shows considerable variation in clinical manifestations, suggesting environmental and/or genetic modifier effects. Strain-specific penetrance of the vascular phenotypes of Eng(+/-) and Tgfb1(-/-) mice provides further support for genetic modification of transforming growth factor-β pathway deficits. We previously identified variant genomic loci, including Tgfbm2, which suppress prenatal vascular lethality of Tgfb1(-/-) mice. Here we show that human polymorphic variants of PTPN14 within the orthologous TGFBM2 locus influence clinical severity of HHT, [corrected] as assessed by development of pulmonary arteriovenous malformation. We also show that PTPN14, ACVRL1 and EFNB2, encoding EphrinB2, show interdependent expression in primary arterial endothelial cells in vitro. This suggests an involvement of PTPN14 in angiogenesis and/or arteriovenous fate, acting via EphrinB2 and ACVRL1/activin receptor-like kinase 1. These findings contribute to a deeper understanding of the molecular pathology of HHT [corrected] in particular and to angiogenesis in general.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Animals; Chromosome Mapping; Ephrin-B2; Exons; Female; Genetic Variation; Haplotypes; Humans; Male; Mice; Mice, Congenic; Mice, Inbred C57BL; Mice, Transgenic; Models, Genetic; Mutation; Phenotype; Protein Tyrosine Phosphatases, Non-Receptor; Species Specificity; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Topics: Activin Receptors, Type II; Antigens, CD; Endoglin; Humans; Mutation; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Loss-of-function mutations in genes coding for transforming growth factor-beta/bone morphogenetic protein receptors and changes in nitric oxide(*) (NO(*)) bioavailability are associated with hereditary hemorrhagic telangiectasia and some forms of pulmonary arterial hypertension. How these abnormalities lead to seemingly disparate pulmonary pathologies remains unknown. Endoglin (Eng), a transforming growth factor-beta coreceptor, is mutated in hereditary hemorrhagic telangiectasia and involved in regulating endothelial NO(*) synthase (eNOS)-derived NO(*) production and oxidative stress. Because some patients with pulmonary arterial hypertension harbor ENG mutations leading to haplo insufficiency, we investigated the pulmonary vasculature of Eng(+/-) mice and the potential contribution of abnormal eNOS activation to pulmonary arterial hypertension.. Hemodynamic, histological, and biochemical assessments and x-ray micro-CT imaging of adult Eng(+/-) mice indicated signs of pulmonary arterial hypertension including increased right ventricular systolic pressure, degeneration of the distal pulmonary vasculature, and muscularization of small arteries. These findings were absent in 3-week-old Eng(+/-) mice and were attributable to constitutively uncoupled eNOS activity in the pulmonary circulation, as evidenced by reduced eNOS/heat shock protein 90 association and increased eNOS-derived superoxide ((*)O(2)(-)) production in a BH(4)-independent manner. These changes render eNOS unresponsive to regulation by transforming growth factor-beta/bone morphogenetic protein and underlie the signs of pulmonary arterial hypertension that were prevented by Tempol.. Adult Eng(+/-) mice acquire signs of pulmonary arterial hypertension that are attributable to uncoupled eNOS activity and increased (*)O(2)(-) production, which can be prevented by antioxidant treatment. Eng links transforming growth factor/bone morphogenetic protein receptors to the eNOS activation complex, and its reduction in the pulmonary vasculature leads to increased oxidative stress and pulmonary arterial hypertension.

Topics: Animals; Antioxidants; Bone Morphogenetic Protein Receptors; Cyclic N-Oxides; Disease Models, Animal; Endoglin; Endothelium, Vascular; Hypertension, Pulmonary; Intracellular Signaling Peptides and Proteins; Mice; Mice, Inbred C57BL; Mutation; Nitric Oxide Synthase Type III; Oxidative Stress; Reactive Oxygen Species; Spin Labels; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT; OMIM 187300) is an autosomal dominant vascular disorder characterized by telangiectases and internal arteriovenous malformations caused by mutations in certain elements of the TGF-beta receptor complex. In the case of HHT1 mutations in the endoglin gene are responsible, whereas mutations in the ALK1 gene (an activin receptor-like kinase 1), lead to HHT2. Another two loci found at chromosome 5 and chromosome 7, whose target genes remain unidentified, lead to types 3 and 4 of the disease, respectively. Mutations in the MADH4/SMAD4 gene, another member of the TGF-beta signalling pathway, lead to a combined syndrome of familial juvenile polyposis associated with HHT.. In an attempt to identify some soluble components differentially expressed in the plasma of HHT patients, angiopoietin-2 and soluble endoglin concentrations were analyzed with standard quantitative sandwich ELISA.. Angiopoietin-2 and soluble endoglin levels are reduced in plasma of HHT patients compared to control individuals, and a diagnostic algorithm for HHT based on these protein levels is proposed.. Down-regulated protein levels of angiopoietin-2 and soluble endoglin in plasma represent novel HHT biomarkers that could be useful in the biochemical diagnosis of HHT facilitating the rapid identification of potential HHT patients.

Topics: Adult; Aged; Angiopoietin-2; Antigens, CD; Biomarkers; Discriminant Analysis; Endoglin; Enzyme-Linked Immunosorbent Assay; Humans; Middle Aged; Mutation; Receptors, Cell Surface; Signal Transduction; Solubility; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Young Adult

Recurrent epistaxis is the most frequent clinical manifestation of hereditary haemorrhagic telangiectasia (HHT). Its treatment is difficult. Our objective was to assess the use of tranexamic acid (TA), an antifibrinolytic drug, for the treatment of epistaxis in HHT patients and to investigate in vitro the effects of TA over endoglin and ALK-1 expression and activity in endothelial cells. A prospective study was carried out on patients with epistaxis treated with oral TA in the HHT Unit of Sierrallana Hospital (Cantabria, Spain). Primary cultures of endothelial cells were treated with TA to measure the levels of endoglin and ALK-1 at the cell surface by flow cytometry. RNA levels were also measured by real-time PCR, and the transcriptional effects of TA on reporters for endoglin, ALK-1 and the endoglin/ALK-1 TGF-beta pathway were assessed. The results showed that the fourteen HHT patients treated orally with TA improved, and the frequency and severity of their epistaxis were decreased. No complications derived from the treatment were observed. Cultured endothelial cells incubated with TA exhibited increased levels of endoglin and ALK-1 at the protein and mRNA levels, enhanced TGF-beta signaling, and improved endothelial cell functions like tubulogenesis and migration. In summary, oral administration of TA proved beneficial for epistaxis treatment in selected patients with HHT. In addition to its already reported antifibrinolytic effects, TA stimulates the expression ofALK-1 and endoglin, as well as the activity of the ALK-1/endoglin pathway.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Administration, Oral; Adult; Aged; Aged, 80 and over; Antifibrinolytic Agents; Antigens, CD; Cell Movement; Cells, Cultured; Dose-Response Relationship, Drug; Endoglin; Endothelial Cells; Epistaxis; Female; Humans; Male; Middle Aged; Neovascularization, Physiologic; Plasminogen; Prospective Studies; Protein Serine-Threonine Kinases; Receptor, Transforming Growth Factor-beta Type I; Receptors, Cell Surface; Receptors, Transforming Growth Factor beta; Recurrence; RNA, Messenger; Signal Transduction; Spain; Telangiectasia, Hereditary Hemorrhagic; Time Factors; Tranexamic Acid; Transcription, Genetic; Transforming Growth Factor beta; Treatment Outcome

Hereditary hemorrhagic telangiectasia (HHT) or Osler-Weber-Rendu syndrome is an autosomal dominant vascular disorder characterized by telangiectases and internal arteriovenous malformations. It is caused by mutations in elements of the transforming growth factor-beta (TGF-beta) receptor complex: endoglin, a co-receptor, responsible for HHT1, or ALK1 (activin receptor-like kinase 1), a type I receptor leading to HHT2. Recently, we have established cultures of HHT endothelial cells, primary targets of the disease. These cells showed deficient TGF-beta signaling and angiogenesis, representing a useful human model to study the molecular mechanism of this disease. To understand the pathogenic mechanism underlying HHT, we have used total RNA probes to compare HHT versus non-HHT cells by expression microarrays. This work represents a systematic study to identify target genes affected in HHT cells. Given the similarity of symptoms in HHT1 and HHT2, special interest has been put on the identification of common targets for both HHT types. As a result, 277 downregulated and 63 upregulated genes were identified in HHT versus control cells. These genes are involved in biological processes relevant to the HHT pathology, such as angiogenesis, cytoskeleton, cell migration, proliferation and NO synthesis. The type of misregulated genes found in HHT endothelial cells lead us to propose a model of HHT pathogenesis, opening new perspectives to understand this disorder. Moreover, as the disease is originated by mutations in proteins of the TGF-beta receptor complex, these results may be useful to find out targets of the TGF-beta pathway in endothelium.

Topics: Animals; Cell Adhesion; Cell Movement; Cell Proliferation; Endothelium, Vascular; Gene Expression Profiling; Genetic Predisposition to Disease; Humans; Mice; Neovascularization, Pathologic; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Wound Healing

Germ-line mutations in bone morphogenic protein type II receptor (Bmpr2) confer susceptibility to pulmonary arterial hypertension (PAH), which is characterized by obstructive vascular lesions in small arteries. The molecular and cellular mechanisms that account for the etiology of this disorder remain elusive, as does the role of Bmpr2 in postnatal tissue homeostasis. Here we show that in adult mice, stably silencing Bmpr2 expression by RNA interference does not increase pulmonary arterial resistance but results in severe mucosal hemorrhage, incomplete mural cell coverage on vessel walls, and gastrointestinal hyperplasia. We present evidence that BMP receptor signaling regulates vascular remodeling during angiogenesis by maintaining the expression of endothelial guidance molecules that promote vessel patterning and maturation and by counteracting growth factor-induced AKT activation. Attenuation of this function may cause vascular dysmorphogenesis and predisposition to angioproliferative diseases. Our findings provide a mechanistic link between PAH and other diseases associated with the BMP/TGF-beta pathways, such as hereditary hemorrhagic telangiectasia and juvenile polyposis syndrome.

Topics: Adenomatous Polyposis Coli; Animals; Bone Morphogenetic Protein Receptors, Type II; Gene Dosage; Germ-Line Mutation; Hemorrhage; Homeostasis; Hypertension, Pulmonary; Mice; Mice, Knockout; Neovascularization, Pathologic; Proto-Oncogene Proteins c-akt; RNA Interference; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

The endoglin heterozygous (Eng(+/-)) mouse, which serves as a model of hereditary hemorrhagic telangiectasia (HHT), was shown to express reduced levels of endothelial NO synthase (eNOS) with impaired activity. Because of intricate changes in vasomotor function in the Eng(+/-) mice and the potential interactions between the NO- and prostaglandin-producing pathways, we assessed the expression and function of cyclooxygenase (COX) isoforms. A specific upregulation of COX-2 in the vascular endothelium and increased urinary excretion of prostaglandin E(2) were observed in the Eng(+/-) mice. Specific COX-2 inhibition with parecoxib transiently increased arterial pressure in Eng(+/-) but not in Eng(+/+) mice. Transfection of endoglin in L6E9 myoblasts, shown previously to stimulate eNOS expression, led to downregulation of COX-2 with no change in COX-1. In addition, COX-2 promoter activity and protein levels were inversely correlated with endoglin levels, in doxycyclin-inducible endothelial cells. Chronic NO synthesis inhibition with N(omega)-nitro-l-arginine methyl ester induced a marked increase in COX-2 only in the normal Eng(+/+) mice. N(omega)-nitro-l-arginine methyl ester also increased COX-2 expression and promoter activity in doxycyclin-inducible endoglin expressing endothelial cells, but not in control cells. The level of COX-2 expression following transforming growth factor-beta1 treatment was less in endoglin than in mock transfected L6E9 myoblasts and was higher in human endothelial cells silenced for endoglin expression. Our results indicate that endoglin is involved in the regulation of COX-2 activity. Furthermore, reduced endoglin levels and associated impaired NO production may be responsible, at least in part, for augmented COX-2 expression and activity in the Eng(+/-) mice.

Topics: Animals; Antigens, CD; Cyclooxygenase 2; Dinoprostone; Endoglin; Endothelium, Vascular; Gene Expression Regulation, Enzymologic; Heterozygote; Humans; Intracellular Signaling Peptides and Proteins; Mice; Mice, Knockout; Nitric Oxide; Promoter Regions, Genetic; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Transforming Growth Factor beta1

To detect the level of transforming growth factor-beta1 (TGF-beta1), TGF-beta2, vascular endothelial growth factor (VEGF) and platelet-derived growth factor receptor-alpha (PDGFRalpha) in plasma and peripheral blood leukocytes in a hereditary hemorrhagic telangiectasia type 2 (HHT-2) family, and explore the implication of angiogenesis related proteins in HHT-2 pathogenesis.. The diagnosis of the HHT-2 patient was based on clinical features and further confirmed by determining a C1231T mutation of activin receptor-like kinase 1 (ALK1) gene. Five other new members in this family were evaluated with ALK1 gene screening and clinical manifestation. Plasma level of TGF-beta1, TGF-beta2 or VEGF was measured by ELISA, and the expression of PDGFRalpha,TGF-beta1, and VEGF in peripheral blood leukocytes by flow cytometry combined with direct or indirect immunofluorescence.. No C1231T mutation was detected in exon 8 of ALK1 gene in the 5 new members. Plasma TGF-beta1 and TGF-beta2 concentration in 3 affected HHT case was (16 954 +/- 3 709) ng/L and (11 548 +/- 2 611) ng/L, respectively, compared with that of normal control, the difference was not significant (P > 0.05). VEGF concentration in the 3 HHT patients, 6 unaffected family members and 6 normal controls was (179.2 +/- 22.0) microg/L, (149.8 +/- 22.7) microg/L and (132.9 +/- 21.0) microg/ L, respectively. Plasma VEGF level in HHT patients was significantly higher than that in normal subjects (P < 0.025). Peripheral leukocyte PDGFRalpha and VEGF in HHT patients and unaffected family members were markedly higher than that of normal control (P < 0.05 and P < 0.02), while TGF-beta1 distribution was similar in HHT patients and normal subjects.. Compared with normal controls there is no difference in plasma TGF-beta1 concentration on peripheral leukocytes of HHT patients. Plasma VEGF concentration or leukocytes VEGF expression in HHT is significantly higher than that of normal subjects. Leukocytes PDGFRalpha expression in HHT is significantly higher than that of normal control. These changes may be associated with a compensable mechanism in HHT.

Topics: Adolescent; Adult; Aged; Child, Preschool; Female; Granulocytes; Humans; Leukocytes, Mononuclear; Male; Middle Aged; Pedigree; Receptor, Platelet-Derived Growth Factor alpha; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A

Pulmonary arterial hypertension (PAH) is a potentially fatal vasculopathy that can develop at any age. Adult-onset disease has previously been associated with mutations in BMPR2 and ALK-1. Presentation in early life may be associated with congenital heart disease but frequently is idiopathic.. We performed mutation analysis in genes encoding receptor members of the transforming growth factor-beta cell-signaling pathway in 18 children (age at presentation <6 years) with PAH. Sixteen children were initially diagnosed with idiopathic PAH and 2 with PAH in association with congenital heart defects. Germ-line mutations were observed in 4 patients (22%) (age at disease onset, 1 month to 6 years), all of whom presented with idiopathic PAH. The BMPR2 mutations (n=2, 11%) included a partial gene deletion and a nonsense mutation, both arising de novo in the proband. Importantly, a missense mutation of ALK-1 and a branch-site mutation of endoglin were also detected. Presenting clinical features or progression of pulmonary hypertension did not distinguish between patients with mutations in the different genes or between those without mutations.. The cause of PAH presenting in childhood is heterogeneous in nature, with genetic defects of transforming growth factor-beta receptors playing a critical role.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Amino Acid Motifs; Amino Acid Substitution; Antigens, CD; Bone Morphogenetic Protein Receptors, Type II; Child; Child, Preschool; Codon, Nonsense; DNA Mutational Analysis; Endoglin; Exons; Female; Genetic Predisposition to Disease; Genotype; Germ-Line Mutation; Heart Defects, Congenital; Humans; Hypertension, Pulmonary; Infant; Infant, Newborn; Male; Mutation, Missense; Protein Serine-Threonine Kinases; Receptors, Cell Surface; Receptors, Transforming Growth Factor beta; RNA Splicing; Sequence Deletion; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Endoglin (CD105) is a proliferation-associated protein that is strongly expressed in endothelial tissue and has a role in tumor angiogenesis. Mutations in endoglin are also linked to Hereditary Hemorrhagic Telangiectasia type 1 (HHT1), an autosomal dominant disease associated with aberrant angiogenesis. We report an unusual association of HHT1 and Hereditary Nonpolyposis Colorectal Cancer (HNPCC) in the same kindred. Genetic analysis indicates that these 2 syndromes are genetically unrelated and separately segregated within the family. The mutation in the endoglin gene leads to a truncated protein. The mutation in the mismatch repair gene MLH1 causes a splicing defect, giving synthesis to an unstable mRNA from this mutated allele. The potential protective role of an endoglin mutation in patients with HNPCC is discussed.

Topics: Adaptor Proteins, Signal Transducing; Adult; Alleles; Antigens, CD; Base Pair Mismatch; Carrier Proteins; Colorectal Neoplasms, Hereditary Nonpolyposis; DNA Repair; Endoglin; Exons; Female; Genetic Linkage; Humans; Male; Middle Aged; Mutation; MutL Protein Homolog 1; Neoplasm Proteins; Nuclear Proteins; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

To determine if patients with hereditary hemorrhagic telangiectasia (HHT) show alterations in transforming growth factor (TGF)-beta and its pathways.. Blood samples were obtained from HHT patients and controls, while endothelial cells were derived from umbilical veins of newborns (HUVEC) from HHT families. TGF-beta1 in plasma, or secreted by HUVEC, and plasma endoglin levels were measured by ELISA. Cellular levels of endoglin and receptor Smad proteins were tested by metabolic labeling and immunoprecipitation, mRNA levels for endoglin and TGF-beta1 by real-time PCR, and receptor Smad phosphorylation by Western blotting.. TGF-beta1 and endoglin plasma levels analyzed in 197 individuals showed an inverse correlation with age. Circulating levels of TGF-beta1 were reduced in HHT1 patients (with Endoglin mutations) compared to control, but not in HHT2 patients (with ALK1 mutations). Endoglin levels were unchanged in plasma but decreased in activated monocytes and HUVEC with an HHT1 genotype. These HUVEC also expressed reduced levels of endoglin and TGF-beta1 mRNA, secreted less TGF-beta1, and showed normal receptor Smad expression and phosphorylation.. Decreased plasma TGF-beta1 levels in HHT1 patients correlate with reduced production by endothelial cells. The lower endoglin expression in these cells may alter the regulation of TGF-beta1 via Smad-independent pathways.

Topics: Antigens, CD; Case-Control Studies; Cells, Cultured; Endoglin; Endothelium, Vascular; Humans; Immunoprecipitation; Infant, Newborn; Mutation; Receptors, Cell Surface; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Smad Proteins, Receptor-Regulated; Statistics, Nonparametric; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Umbilical Veins; Vascular Cell Adhesion Molecule-1

Hereditary hemorrhagic telangiectasia (HHT), an inherited vascular dysplasia, is caused by mutations in endoglin or activin receptor-like kinase (ALK)-1. Haploinsufficiency for these genes is thought to result in an imbalanced angiogenic activity. The aim of this study was to evaluate the plasma levels and the expression profiles of angiogenic and angiogenesis-related factors in the context of HHT.. Vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-beta1 plasma concentrations were determined in 31 HHT patients and 40 healthy controls by ELISA. VEGF and TGF-beta1 plasma concentrations were correlated with the patients' clinicopathological features. Tissue expression of angiogenic and angiogenesis related proteins was determined by immunostaining on nasal cryostat sections from 13 HHT patients and 5 healthy controls.. Of the 31 patients, 29 had statistically significantly raised plasma concentrations of VEGF and TGF-beta1 but there was no correlation with specific clinicopathological features. Increased VEGF, TGF-beta1 and ALK1 immunostaining was seen in all 13 investigated patients. beta-smooth muscle actinin immunostaining was increased in 12 patients. Increased endoglin immunostaining was seen in only 9 patients.. This study provides evidence of the role of VEGF and TGF-beta1 in the pathogenesis of HHT. Plasma concentrations of these two factors may serve as further diagnostic criteria for HHT. For the first time, we report increased TGF-beta1 plasma concentrations and increased TGF-beta1 and ALK1 tissue expression in HHT, which appear not to be specifically associated with either endoglin or ALK1 mutations. The data suggest that HHT is an angiogenic disorder characterized by an over-expression of VEGF, TGF-beta1 and ALK1.

Topics: Activin Receptors; Adult; Aged; Aged, 80 and over; Female; Gene Expression Regulation; Humans; Male; Middle Aged; Muscle, Smooth; Neovascularization, Pathologic; Telangiectasia, Hereditary Hemorrhagic; Tissue Distribution; Transforming Growth Factor beta; Transforming Growth Factor beta1; Vascular Endothelial Growth Factor A

Hereditary haemorrhagic telangiectasia (HHT) is originated by mutations in endoglin (HHT1) and ALK1 (HHT2) genes. The purpose of this work was to isolate and characterize circulating endothelial cells from HHT patients.. Pure primary cultures of blood outgrowth endothelial cells (BOECs) were obtained from 50 ml of peripheral blood by selection on collagen plates with endothelial medium.. The amount of endoglin in HHT1-BOECs is half the controls, but HHT2-BOECs are also endoglin-deficient. Since the TGF-beta/ALK1 pathway activates the endoglin promoter activity, these results suggest the involvement of ALK1 in endoglin gene expression. Endothelial TGF-beta pathways, mediated by ALK1 and ALK5, are impaired in HHT cells. HHT-BOECs show disorganized and depolymerized actin fibers, as compared to the organized stress fibers of healthy-BOECs. Functionally, HHT-BOECs have impaired tube formation, in contrast with the cord-like structures derived from normal donors.. Decreased endoglin expression, impaired TGF-beta signalling, disorganized cytoskeleton, and failure to form cord-like structures are common characteristics of endothelial cells from HHT patients. These features may lead to fragility of small vessels and bleeding characteristic of the HHT vascular dysplasia and to a disrupted and abnormal angiogenesis, which may explain the clinical symptoms associated with this disease.

Topics: Activin Receptors, Type I; Antigens, CD; Blotting, Western; Case-Control Studies; Cell Culture Techniques; Cell Separation; Cells, Cultured; Cytoskeleton; Endoglin; Endothelial Cells; Flow Cytometry; Humans; Microscopy, Fluorescence; Mutagenesis, Site-Directed; Mutation; Neovascularization, Physiologic; Protein Serine-Threonine Kinases; Receptor, Transforming Growth Factor-beta Type I; Receptors, Cell Surface; Receptors, Transforming Growth Factor beta; Reverse Transcriptase Polymerase Chain Reaction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Antigens, CD; Arteriovenous Malformations; Blood Coagulation; Endoglin; Epistaxis; Head; Humans; Membrane Proteins; Mutation; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Antigens, CD; Endoglin; Humans; Mutation; Neovascularization, Pathologic; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

We determined the diagnosis of hereditary hemorrhagic telangiectasis (HHT) in a suspected HHT family, identified ALK1 gene mutation and established a gene diagnosis method of HHT. The level of related plasma proteins (transforming growth factor beta and thrombomodulin) were also analyzed.. Bleeding history and family history were collected; Dilatant nasal mucosal capillaries in proband were observed under nasal cavity endoscope; exons 3, 7, 8 of ALK1 gene in proband and her family members were amplified with polymerase chain reaction (PCR), and the PCR products were analyzed. Using enzyme-linked immunosorbent assay (ELISA), plasma TGF-beta1 and TGF-beta2 concentrations were measured. Plasma thrombomodulin (TM) level was detected by Western blotting.. Of all family members, four had epstaxis, two had evident telangiectases on skin or mucosa. Gene screening results showed that C to T substitution at position 1231 in exon 8 of ALK1 gene (CGG-->TGG) existed in proband, her affected brother and their father. The mutation did not exist in proband's sister-in-law and nephew. Plasma TGF-beta1 concentrations in the affected HHT was 20,538, 17,194, 13,131 pg/ml, while that of normal control and unaffected family members was 15,950, 20,297, 12,836 pg/ml, respectively. Plasma TGF-beta2 in HHT patients was 14,502, 9550, 10,592 and that of normal controls 8579, 20,297, 7680 pg/ml respectively. Level of plasma TM was in HHT subjects significantly lower than in normal subjects.. Chinese HHT individuals have mutant ALK1 gene, a C1231T variation on exon 8 of ALK1 is responsible for HHT clinical phenotypes in this family. ALK1 gene analysis, together with special clinical phenotypes and family history, provides a reliable method in diagnosing HHT. In affected HHT subjects, plasma TGFbeta levels were not obviously different from those of normal subject; while plasma TM concentration was significantly lower than that in normal subjects. The significance and mechanism remain to be elucidated.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Aged; Asian People; China; Female; Humans; Male; Middle Aged; Mutation; Telangiectasia, Hereditary Hemorrhagic; Thrombomodulin; Transforming Growth Factor beta

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder in humans that is characterised by multisystemic vascular dyplasia and recurrent haemorrhage. Germline mutations in one of two different genes, endoglin or ALK1 can cause HHT. Both are members of the transforming growth factor (TGF) beta receptor family of proteins, and are expressed primarily on the surface of endothelial cells (ECs). Mice that lack endoglin or activin receptor like kinase (ALK) 1 die at mid-gestation as a result of defects in the yolk sac vasculature. Here, we have analyzed TGFbeta signalling in yolk sacs from endoglin knockout mice and from mice with endothelial-specific deletion of the TGFbeta type II receptor (TbetaRII) or ALK5. We show that TGFbeta/ALK5 signalling from endothelial cells to adjacent mesothelial cells is defective in these mice, as evidenced by reduced phosphorylation of Smad2. This results in the failure of vascular smooth muscle cells to differentiate and associate with endothelial cells so that blood vessels remain fragile and become dilated. Phosphorylation of Smad2 and differentiation of smooth muscle can be rescued by culture of the yolk sac with exogenous TGFbeta1. Our data show that disruption of TGFbeta signalling in vascular endothelial cells results in reduced availability of TGFbeta1 protein to promote recruitment and differentiation of smooth muscle cells, and provide a possible explanation for weak vessel walls associated with HHT.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Animals; Cell Differentiation; DNA-Binding Proteins; Endothelial Cells; Mice; Mice, Knockout; Myocytes, Smooth Muscle; Paracrine Communication; Phosphorylation; Protein Serine-Threonine Kinases; Receptor, Transforming Growth Factor-beta Type I; Receptor, Transforming Growth Factor-beta Type II; Receptors, Transforming Growth Factor beta; Smad2 Protein; Telangiectasia, Hereditary Hemorrhagic; Trans-Activators; Transforming Growth Factor beta; Yolk Sac

Topics: Angiopoietins; Central Nervous System Vascular Malformations; Fibroblast Growth Factor 2; Gene Expression; Genetic Counseling; Genetic Therapy; Genotype; Hemangioma, Cavernous, Central Nervous System; Hepatocyte Growth Factor; Humans; Phenotype; Platelet-Derived Growth Factor; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder because of mutations in the genes coding for endoglin (HHT1) or ALK-1 (HHT2). The disease is associated with haploinsufficiency and a murine model was obtained by engineering mice that express a single Endoglin allele. Of a total of 171 mice that were observed for 1 year, 50 developed clinical signs of HHT. Disease prevalence was high in 129/Ola strain (72%), intermediate in the intercrosses (36%), and low in C57BL/6 backcrosses (7%). Most mice first presented with an ear telangiectasia and/or recurrent external hemorrhage. One-third of mice with HHT showed severe vascular abnormalities such as dilated vessels, hemorrhages, liver and lung congestion, and/or brain and heart ischemia. Disease sequelae included stroke, hydrocephalus, fatal hemorrhage, and congestive heart failure. Thus the murine model reproduces the multiorgan manifestations of the human disease. Levels of circulating latent transforming growth factor (TGF)-beta1 were significantly lower in the 129/Ola than in the C57BL/6 strain. Intercrosses and 129/Ola mice expressing reduced endoglin also showed lower plasma TGF-beta1 levels than control. These data suggest that modifier genes involved in the regulation of TGF-beta1 expression act in combination with a single functional copy of endoglin in the development of HHT.

Topics: Abnormalities, Multiple; Animals; Antigens, CD; Blood Vessels; Brain; Cerebral Hemorrhage; Disease Models, Animal; Endoglin; Gastrointestinal Hemorrhage; Genes; Heart Defects, Congenital; Heart Failure; Hemorrhage; Heterozygote; Liver; Lung; Lung Diseases; Mice; Mice, Inbred C57BL; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Transforming Growth Factor beta1; Vascular Cell Adhesion Molecule-1

Most patients with familial primary pulmonary hypertension have defects in the gene for bone morphogenetic protein receptor II (BMPR2), a member of the transforming growth factor beta (TGF-beta) superfamily of receptors. Because patients with hereditary hemorrhagic telangiectasia may have lung disease that is indistinguishable from primary pulmonary hypertension, we investigated the genetic basis of lung disease in these patients.. We evaluated members of five kindreds plus one individual patient with hereditary hemorrhagic telangiectasia and identified 10 cases of pulmonary hypertension. In the two largest families, we used microsatellite markers to test for linkage to genes encoding TGF-beta-receptor proteins, including endoglin and activin-receptor-like kinase 1 (ALK1), and BMPR2. In subjects with hereditary hemorrhagic telangiectasia and pulmonary hypertension, we also scanned ALK1 and BMPR2 for mutations.. We identified suggestive linkage of pulmonary hypertension with hereditary hemorrhagic telangiectasia on chromosome 12q13, a region that includes ALK1. We identified amino acid changes in activin-receptor-like kinase 1 that were inherited in subjects who had a disorder with clinical and histologic features indistinguishable from those of primary pulmonary hypertension. Immunohistochemical analysis in four subjects and one control showed pulmonary vascular endothelial expression of activin-receptor-like kinase 1 in normal and diseased pulmonary arteries.. Pulmonary hypertension in association with hereditary hemorrhagic telangiectasia can involve mutations in ALK1. These mutations are associated with diverse effects, including the vascular dilatation characteristic of hereditary hemorrhagic telangiectasia and the occlusion of small pulmonary arteries that is typical of primary pulmonary hypertension.

Topics: Activin Receptors; Adult; Bone Morphogenetic Protein Receptors, Type II; Child; Child, Preschool; Chromosome Mapping; Chromosomes, Human, Pair 12; Female; Humans; Hypertension, Pulmonary; Lung; Male; Microsatellite Repeats; Middle Aged; Mutation; Mutation, Missense; Pedigree; Protein Serine-Threonine Kinases; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Topics: Activin Receptors; Bone Morphogenetic Protein Receptors, Type II; Genetic Markers; Humans; Hypertension, Pulmonary; Mutation; Protein Serine-Threonine Kinases; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Pulmonary arteriovenous malformations (PAVMs) occur in over 25% of patients with the autosomal dominant disorder hereditary haemorrhagic telangiectasia (HHT). Mutations in two genes, endoglin and ALK-1, are known to cause HHT. Each encodes a protein expressed on vascular endothelial cells and involved in signalling by members of the transforming growth factor (TGF)-beta superfamily. To date, PAVMs have not been detected in ALK-1 families. There is evidence from a single HHT family without pulmonary involvement that a third HHT gene may exist. To establish the existence of a further HHT gene responsible for PAVMs, linkage analyses were performed on an expanded PAVM-HHT family in which HHT did not result from endoglin mutations.. Family members were assessed clinically to assign HHT disease status and were screened for PAVMs. DNA was extracted from blood obtained from 20 individuals of known disease status. Short tandem repeat polymorphic markers spanning the intervals containing the endoglin and ALK-1 genes were amplified by the polymerase chain reaction using (33)P-labelled oligonucleotide primers, separated by denaturing polyacrylamide gel electrophoresis (PAGE), and the resultant autoradiographs were examined for allele sizes. Linkage analyses were performed using MLINK and GENEHUNTER.. Twelve members spanning four generations were affected with HHT. Two had proven PAVMs, one with a classical appearance, the other exhibiting microscopic PAVMs exacerbated by pregnancy. Two point lod and multipoint lod scores significantly excluded linkage to endoglin and ALK-1 in this pedigree.. This study confirms the existence of a third HHT locus that accounts for disease in some HHT patients with pulmonary involvement.

Topics: Activin Receptors; Adolescent; Adult; Aged; Aged, 80 and over; Antigens, CD; Child; Dystonic Disorders; Endoglin; Female; Genetic Linkage; Genotype; Humans; Male; Middle Aged; Pedigree; Protein Serine-Threonine Kinases; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Germ line mutations in one of two distinct genes, endoglin or ALK-1, cause hereditary hemorrhagic telangiectasia (HHT), an autosomal dominant disorder of localized angiodysplasia. Both genes encode endothelial cell receptors for the transforming growth factor beta (TGF-beta) ligand superfamily. Endoglin has homology to the type III receptor, betaglycan, although its exact role in TGF-beta signaling is unclear. Activin receptor-like kinase 1 (ALK-1) has homology to the type I receptor family, but its ligand and corresponding type II receptor are unknown. In order to identify the ligand and type II receptor for ALK-1 and to investigate the role of endoglin in ALK-1 signaling, we devised a chimeric receptor signaling assay by exchanging the kinase domain of ALK-1 with either the TGF-beta type I receptor or the activin type IB receptor, both of which can activate an inducible PAI-1 promoter. We show that TGF-beta1 and TGF-beta3, as well as a third unknown ligand present in serum, can activate chimeric ALK-1. HHT-associated missense mutations in the ALK-1 extracellular domain abrogate signaling. The ALK-1/ligand interaction is mediated by the type II TGF-beta receptor for TGF-beta and most likely through the activin type II or type IIB receptors for the serum ligand. Endoglin is a bifunctional receptor partner since it can bind to ALK-1 as well as to type I TGF-beta receptor. These data suggest that HHT pathogenesis involves disruption of a complex network of positive and negative angiogenic factors, involving TGF-beta, a new unknown ligand, and their corresponding receptors.

Topics: Activin Receptors; Activins; Animals; Antigens, CD; Bone Morphogenetic Proteins; Cell Line; COS Cells; Endoglin; Inhibins; Ligands; Protein Serine-Threonine Kinases; Proteoglycans; Rabbits; Receptors, Cell Surface; Receptors, Transforming Growth Factor beta; Recombinant Fusion Proteins; Sequence Homology, Amino Acid; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Endoglin is a transmembrane glycoprotein 633 residues in length expressed at the surface of endothelial cells as a disulphide-linked homodimer; the specific cysteine residues involved in endoglin dimerization are unknown. Mutations in the coding region of the endoglin gene are responsible for hereditary haemorrhagic telangiectasia type 1 (HHT1), a dominantly inherited vascular disorder. Many of these mutations, if translated, would lead to truncated forms of the protein. It is therefore of interest to assess the protein expression of different truncated forms of endoglin. Infections in vitro or in vivo with recombinant vaccinia virus, as well as transient transfections with expression vectors, were used to express normal and truncated forms of endoglin. Truncated mutants could be classified into three different groups: (1) those that did not produce stable transcripts; (2) those that produced stable transcripts but did not secrete the protein; and (3) those that secreted a soluble dimeric protein. This is the first time that a recombinant truncated form of endoglin has been found to be expressed in a soluble form. Because a chimaeric construct encoding the N-terminal sequence of platelet/endothelial cell adhesion molecule (PECAM-1) antigen fused to residues Ile281-Ala658 of endoglin also yielded a dimeric surface protein, these results suggest that cysteine residues contained within the fragment Cys330-Cys412 are involved in disulphide bond formation. Infection with vaccinia recombinants encoding an HHT1 mutation did not affect the expression of the normal endoglin, and did not reveal an association of the recombinant soluble form with the transmembrane endoglin, supporting a haploinsufficiency model for HHT1.

Topics: Animals; Antigens, CD; Cell Line; Cell Membrane; Cysteine; Dimerization; Disulfides; Endoglin; Endothelium, Vascular; Gene Expression; Humans; Peptide Fragments; Protein Binding; Protein Isoforms; Receptors, Cell Surface; Recombinant Fusion Proteins; Reducing Agents; RNA, Messenger; Sequence Deletion; Solubility; Telangiectasia, Hereditary Hemorrhagic; Transfection; Transforming Growth Factor beta; Vaccinia virus; Vascular Cell Adhesion Molecule-1

Endoglin (CD105) is a cell surface component of the transforming growth factor-beta (TGF-beta) receptor complex highly expressed by endothelial cells. Mutations in the endoglin gene are responsible for the hereditary hemorrhagic telangiectasia type 1 (HHT1), also known as Osler-Weber-Rendu syndrome (OMIM 187300). This is an autosomal dominant vascular disorder probably caused by a haploinsufficiency mechanism displaying low levels of the normal protein. To understand the mechanisms underlying the regulated expression of endoglin, a genomic DNA clone containing 3.3 kb of the 5'-flanking sequence of the human endoglin gene has been isolated. The 5'-flanking region of the endoglin gene lacks consensus TATA and CAAT boxes, but contains two GC-rich regions and consensus motifs for Sp1, ets, GATA, AP-2, NFkappaB, and Mad, as well as TGF-beta-, glucocorticoid-, vitamin D-, and estrogen-responsive elements. As determined by primer extension and 5' RACE experiments, a cluster of transcriptional start sites was found to be located 350 bp upstream from the translation initiation codon. To analyze the endoglin promoter activity, the upstream -400/+341 fragment was fused to the luciferase gene and transient transfections were conducted in several cell types. This construct displayed a tissue-specific activity in human and bovine endothelial cells. Analysis of various deletion constructs showed the existence of a basal promoter region within the -81/+350 fragment as well as major transcriptional regulatory elements within the -400/-141 fragment. Electrophoretic mobility shift assays demonstrated the specific interaction of a member of the ets family with a consensus motif located at position -68. A promoter construct mutated at this ets sequence showed a much reduced activity as compared with the wild-type construct, supporting the involvement of this ets motif in the basal activity of the promoter. The endoglin promoter exhibited inducibility in the presence of TGF-beta1, suggesting possible therapeutic treatments in HHT1 patients, in which the expression level of the normal endoglin allele might not reach the threshold required for its function. Isolation and characterization of the human endoglin promoter represents an initial step in elucidating the controlled expression of the endoglin gene.

Topics: Amino Acid Sequence; Animals; Antigens, CD; Base Sequence; Cattle; Cloning, Molecular; Endoglin; Endothelium, Vascular; Gene Expression Regulation; Humans; Molecular Sequence Data; Mutagenesis, Site-Directed; Organ Specificity; Promoter Regions, Genetic; Receptors, Cell Surface; Regulatory Sequences, Nucleic Acid; Sequence Analysis, DNA; Telangiectasia, Hereditary Hemorrhagic; Transcription, Genetic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Hereditary haemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is an autosomal dominant vascular disorder which associates epistaxis, mucocutaneous and visceral telangiectases, and recurrent haemorrhage with chronic anaemia and visceral shuntings. Recently, the tumour growth factor (TGF)-beta binding protein endoglin localized to 9q33-34 was identified as responsible for HHT in several large kindreds with pulmonary arteriovenous malformations (PAVMs). Additional linkage studies demonstrated that HHT is a genetically heterogeneous disorder with families unlinked to this region of 9q. In the families in which HHT was not linked to chromosome 9, less PAVMs were present. Furthermore, in one of these families, HHT was found linked to 3p22, where the TGF-beta II receptor is located. In this linkage study, we have analysed DNA from two families, in which HHT was unlinked to chromosome 9q and 3p, and PAVMs were absent, with a series of genetic markers on the centromeric region of chromosome 12. Using two-point linkage analysis, a significant lod score of Zmax = 7.86 at theta = 0.05 was obtained with the D12S85 microsatellite marker.

Topics: Antigens, CD; Chromosome Mapping; Chromosomes, Human, Pair 12; Endoglin; Female; Genetic Linkage; Genetic Markers; Humans; Lod Score; Male; Membrane Glycoproteins; Pedigree; Polymerase Chain Reaction; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by multisystemic vascular dysplasia and recurrent haemorrhage. Linkage for some families has been established to chromosome 9q33-q34. In the present study, endoglin, a transforming growth factor beta (TGF-beta) binding protein, was analysed as a candidate gene for the disorder based on chromosomal location, expression pattern and function. We have identified mutations in three affected individuals: a C to G substitution converting a tyrosine to a termination codon, a 39 base pair deletion and a 2 basepair deletion which creates a premature termination codon. We have identified endoglin as the HHT gene mapping to 9q3 and have established HHT as the first human disease defined by a mutation in a member of the TGF-beta receptor complex.

Topics: Amino Acid Sequence; Antigens, CD; Base Sequence; Chromosome Mapping; Chromosomes, Human, Pair 9; Codon; DNA, Complementary; Endoglin; Female; Humans; Male; Membrane Glycoproteins; Molecular Sequence Data; Pedigree; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Terminator Regions, Genetic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1