transforming-growth-factor-beta and Cardiovascular-Abnormalities

Cardiovascular abnormalities are the major cause of morbidity and mortality in Marfan syndrome (MFS) and a few clinically related diseases that share, with MFS, the pathogenic contribution of dysregulated transforming growth factor β (TGFβ) signaling. They include Loeys-Dietz syndrome, Shprintzen-Goldberg syndrome, aneurysm-osteoarthritis syndrome and syndromic thoracic aortic aneurysms. Unlike the causal association of MFS with mutations in an extracellular matrix protein (ECM), the aforementioned conditions are due to defects in components of the TGFβ pathway. While TGFβ antagonism is being considered as a potential new therapy for these heritable syndromes, several points still need to be clarified in relevant animal models before this strategy could be safely applied to patients. Among others, unresolved issues include whether elevated TGFβ signaling is responsible for all MFS manifestations and is the common trigger of disease in MFS and related conditions. The scope of our review is to highlight the clinical and experimental findings that have forged our understanding of the natural history and molecular pathogenesis of cardiovascular manifestations in this group of syndromic conditions.

Topics: Animals; Aortic Aneurysm, Thoracic; Arachnodactyly; Cardiovascular Abnormalities; Craniosynostoses; Fibrillin-1; Fibrillins; Humans; Loeys-Dietz Syndrome; Marfan Syndrome; Mice; Microfilament Proteins; Signal Transduction; Transforming Growth Factor beta

Neural crest cells (NCCs) participate in the remodeling of the cardiac outflow tract and pharyngeal arch arteries during cardiovascular development. Integrin-linked kinase (ILK) is a serine/threonine kinase and a major regulator of integrin signaling. It links integrins to the actin cytoskeleton and recruits other adaptor molecules into a large complex to regulate actin dynamics and integrin function. Using the Cre-lox system, we deleted Ilk from NCCs of mice to investigate its role in NCC morphogenesis. The resulting mutants developed a severe aneurysmal arterial trunk that resulted in embryonic lethality during late gestation. Ilk mutants showed normal cardiac NCC migration but reduced differentiation into smooth muscle within the aortic arch arteries and the outflow tract. Within the conotruncal cushions, Ilk-deficient NCCs exhibited disorganization of F-actin stress fibers and a significantly rounder morphology, with shorter cellular projections. Additionally, absence of ILK resulted in reduced in vivo phosphorylation of Smad3 in NCCs, which correlated with reduced αSMA levels. Our findings resemble those seen in Pinch1 and β1 integrin conditional mutant mice, and therefore support that, in neural crest-derived cells, ILK and Pinch1 act as cytoplasmic effectors of β1 integrin in a pathway that protects against aneurysms. In addition, our conditional Ilk mutant mice might prove useful as a model to study aortic aneurysms caused by reduced Smad3 signaling, as occurs in the newly described aneurysms-osteoarthritis syndrome, for example.

Topics: Actin Cytoskeleton; Animals; Aorta, Thoracic; Aortic Aneurysm; Cardiovascular Abnormalities; Cell Differentiation; Cell Movement; Cell Proliferation; Craniofacial Abnormalities; Embryo Loss; Embryo, Mammalian; Gene Deletion; Integrases; Mice; Mice, Mutant Strains; Morphogenesis; Neural Crest; Organ Specificity; Phenotype; Protein Serine-Threonine Kinases; Signal Transduction; Smad3 Protein; Transforming Growth Factor beta; Wnt Proteins

Growth factor signaling results in dramatic phenotypic changes in cells, which require commensurate alterations in cellular metabolism. Mutations in SLC2A10/GLUT10, a member of the facilitative glucose transporter family, are associated with altered transforming growth factor-β (TGFβ) signaling in patients with arterial tortuosity syndrome (ATS). The objective of this work was to test whether SLC2A10/GLUT10 can serve as a link between TGFβ-related transcriptional regulation and metabolism during development. In zebrafish embryos, knockdown of slc2a10 using antisense morpholino oligonucleotide injection caused a wavy notochord and cardiovascular abnormalities with a reduced heart rate and blood flow, which was coupled with an incomplete and irregular vascular patterning. This was phenocopied by treatment with a small-molecule inhibitor of TGFβ receptor (tgfbr1/alk5). Array hybridization showed that the changes at the transcriptome level caused by the two treatments were highly correlated, revealing that a reduced tgfbr1 signaling is a key feature of ATS in early zebrafish development. Interestingly, a large proportion of the genes, which were specifically dysregulated after glut10 depletion gene and not by tgfbr1 inhibition, play a major role in mitochondrial function. Consistent with these results, slc2a10 morphants showed decreased respiration and reduced TGFβ reporter gene activity. Finally, co-injection of antisense morpholinos targeting slc2a10 and smad7 (a TGFβ inhibitor) resulted in a partial rescue of smad7 morphant phenotypes, suggesting scl2a10/glut10 functions downstream of smads. Taken together, glut10 is essential for cardiovascular development by facilitating both mitochondrial respiration and TGFβ signaling.

Topics: Amino Acid Sequence; Animals; Cardiovascular Abnormalities; Glucose Transport Proteins, Facilitative; Luciferases; Mitochondria; Molecular Sequence Data; Morpholinos; Mutation; Notochord; Phenotype; Receptors, Transforming Growth Factor beta; Sequence Homology, Amino Acid; Signal Transduction; Transcriptome; Transforming Growth Factor beta; Zebrafish

Pinch1, an adaptor protein composed of 5 LIM domains, has been suggested to play an important role in multiple cellular processes. We found that Pinch1 is highly expressed in neural crest cells and their derivatives. To examine the requirement for Pinch1 in neural crest development, we generated neural crest conditional Pinch1 knockout mice using the Wnt1-Cre/loxP system. Neural crest conditional Pinch1 mutant embryos die perinatally from severe cardiovascular defects with an unusual aneurysmal common arterial trunk. Pinch1 mutants also exhibit multiple deficiencies in cranial neural crest-derived structures. Fate mapping demonstrated that initial migration of neural crest cells to the pharyngeal arch region occurs normally in the mutant embryos. However, in the cardiac outflow tract of mutants, neural crest cells exhibited hyperplasia and failed to differentiate into smooth muscle. Markedly increased apoptosis is observed in outflow tract cushions of mutants between embryonic days 11.5 and 13.5, likely contributing to the observed defects in cushion/valve remodeling and ventricular septation. Expression of transforming growth factor-beta(2), which plays a crucial role in outflow tract development, was decreased or absent in the outflow tract of the mutants. The decrease in transforming growth factor-beta(2) expression preceded neural crest cell death. Together, our results demonstrate that Pinch1 plays an essential role in neural crest development, perhaps in part through transforming growth factor-beta signaling.

Topics: Adaptor Proteins, Signal Transducing; Animals; Cardiovascular Abnormalities; Cells, Cultured; Craniofacial Abnormalities; DNA-Binding Proteins; Female; Gene Expression Regulation, Developmental; LIM Domain Proteins; Membrane Proteins; Mice; Mice, Knockout; Mutation; Neural Crest; Signal Transduction; Transforming Growth Factor beta

Septation of the single tubular embryonic outflow tract into two outlet segments in the heart requires the precise integration of proliferation, differentiation and apoptosis during remodeling. Lack of proper coordination between these processes would result in a variety of congenital cardiac defects such as those seen in the retinoid X receptor alpha knockout (Rxra(-/-)) mouse. Rxra(-/-) embryos exhibit lethality between embryonic day (E) 13.5 and 15.5 and harbor a variety of conotruncal and aortic sac defects making it an excellent system to investigate the molecular and morphogenic causes of these cardiac malformations. At E12.5, before the embryonic lethality, we found no qualitative difference between wild type and Rxra(-/-) proliferation (BrdU incorporation) in outflow tract cushion tissue but a significant increase in apoptosis as assessed by both TUNEL labeling in paraffin sections and caspase activity in trypsin-dispersed hearts. Additionally, E12.5 embryos demonstrated elevated levels of transforming growth factor beta2 (TGFbeta2) protein in multiple cell lineages in the heart. Using a whole-mouse-embryo culture system, wild-type E11.5 embryos treated with TGFbeta2 protein for 24 hours displayed enhanced apoptosis in both the sinistroventralconal cushion and dextrodorsalconal cushion in a manner analogous to that observed in the Rxra(-/-). TGFbeta2 protein treatment also led to malformations in both the outflow tract and aortic sac. Importantly, Rxra(-/-) embryos that were heterozygous for a null mutation in the Tgfb2 allele exhibited a partial restoration of the elevated apoptosis and of the malformations. This was evident at both E12.5 and E13.5. The data suggests that elevated levels of TGFbeta2 can (1) contribute to abnormal outflow tract morphogenesis by enhancing apoptosis in the endocardial cushions and (2) promote aortic sac malformations by interfering with the normal development of the aorticopulmonary septum.

Topics: Animals; Aorta; Apoptosis; Cardiovascular Abnormalities; Heart; Heterozygote; Mice; Mice, Transgenic; Organ Culture Techniques; Receptors, Retinoic Acid; Retinoid X Receptors; Transcription Factors; Transforming Growth Factor beta; Transforming Growth Factor beta2