tretinoin and DiGeorge-Syndrome

Improved recognition of velocardiofacial syndrome (VCFS) has led to increasing awareness of VCFS by otolaryngologists. Understanding the developmental biologic processes affected in VCFS patients will help improve treatment and outcomes. Advanced application of molecular labeling techniques has better outlined the role of T-Box transcription factor 1 (TBX1) as the primary genetic anomaly leading to VCFS. TBX1 plays multiple roles during branchial, cardiac, and craniofacial development and increased understanding of how these systems are affected by TBX1 mutations will improve patient outcomes. Furthermore, additional modifiers of TBX1 expression have been identified that may explain the variability of VCFS phenotypes. The phenotypic spectrum of VCFS may include cardiac anomalies, velopharyngeal insufficiency, aberrant calcium metabolism, and immune dysfunction. Recent interest has focused on the cognitive and neuropsychiatric manifestations of VCFS. Improved understanding of the biology of VCFS associated mutations has the potential to improve therapeutic outcomes.. This article will discuss recent developmental biologic understanding of the role of TBX1 and genetic modifiers generating the phenotypic variability seen in VCFS patients. Special attention is given to advances in the realms of immunodeficiency, hypocalcemia, cardiac and arterial patterning anomalies, velopharyngeal insufficiency, as well as cognitive and psychiatric problems.. Enhanced understanding of the multiple systems affected by TBX1 mutations will result in improved patient outcomes and improved family education. Future research will lead to improved detection of potential targets for gene therapy and change the way physicians counsel families and treat patients.

Topics: Animals; Branchial Region; Calcium; DiGeorge Syndrome; Genetic Therapy; Homeostasis; Humans; Parathyroid Glands; Phenotype; T-Box Domain Proteins; T-Lymphocytes; Thymus Gland; Tretinoin

Tbx1 is a member of the Tbox family of binding domain transcription factors. TBX1 maps within the region of 22q11 deleted in humans with DiGeorge or velocardiofacial syndrome. Mice haploinsufficient for Tbx1 have phenotypes that recapitulate major features of the syndrome, notably abnormal growth and remodelling of the pharyngeal arch arteries. The Tbx1 haploinsufficiency phenotype is modified by genetic background and by mutations in putative downstream targets. Homozygous null mutations of Tbx1 have more severe defects including failure of outflow tract septation, and absence of the caudal pharyngeal arches. Tbx1 is a transcriptional activator, and loss of this activity has been linked to alterations in the expression of various genes involved in cardiovascular morphogenesis. In particular, Fgf and retinoic acid signalling are dysregulated in Tbx1 mutants. This article summarises the tissue specific and temporal requirements for Tbx1, and attempts to synthesis what is know about the developmental pathways under its control.

Topics: Animals; Branchial Region; DiGeorge Syndrome; Disease Models, Animal; Gene Deletion; Heart; Heart Defects, Congenital; Mice; Mutation; Phenotype; Signal Transduction; Syndrome; T-Box Domain Proteins; Tretinoin

DiGeorge syndrome (DGS) is a developmental defect which associates hypo- or aplasia of the thymus and parathyroids, facial dysmorphism and conotruncal cardiac malformations. The etiological factor in a great majority of DGS patients is monosomy for the 22q11.2 chromosomal region either through a large interstitial deletion of that region (inherited or de novo) or through an unbalanced translocation involving chromosome 22. In one instance, a balanced translocation of chromosome 22 was associated with a DGS phenotype. Extensive analyses of this region of chromosome 22 has led to the obtention of precise physical maps of the corresponding genomic region, to the cloning of the balanced translocation breakpoint and to the isolation of different genes from the minimal critical deleted region.

Topics: Abnormalities, Drug-Induced; Abnormalities, Multiple; Animals; Chromosome Aberrations; Chromosome Deletion; Chromosome Disorders; Chromosome Mapping; Chromosomes, Human, Pair 22; DiGeorge Syndrome; Female; Genes; Humans; Infant, Newborn; Male; Pregnancy; Pregnancy Complications; Rats; Syndrome; Translocation, Genetic; Tretinoin

Craniofacial dysmorphologies are common, ranging from simple facial disfigurement to complex malformations involving the whole head. With the advent of gene mapping and cloning techniques, the genetic element of both simple and complex human craniofacial dysmorphologies can be investigated. For many of the dysmorphic syndromes, it is possible to find families that display a particular phenotype in either an autosomal dominant, recessive, or X-linked manner. This article focuses on a subgroup of craniofacial dysmorphologies, covering these three main inheritance patterns, that are being studied using molecular biology techniques: DiGeorge syndrome, Treacher Collins syndrome, Greig cephalopolysyndactyly syndrome, acrocallosal syndrome, amelogenesis imperfecta, and X-linked cleft palate with ankyloglossia. Once the mutated or deleted gene or genes for each syndrome have been cloned, patterns of normal and abnormal craniofacial development should be elucidated. This should enhance both diagnosis and treatment of these common and disfiguring disorders.

Topics: Animals; Chromosome Aberrations; Chromosome Disorders; Cleft Palate; Cloning, Molecular; DiGeorge Syndrome; Facial Bones; Fetal Alcohol Spectrum Disorders; Forecasting; Genetic Linkage; Head; Humans; Mandibulofacial Dysostosis; Mice; Skull; Syndrome; Tongue; Tretinoin

The arterial and venous poles of the mammalian heart are hotspots of congenital heart defects (CHD) such as those observed in 22q11.2 deletion (or DiGeorge) and Holt-Oram syndromes. These regions of the heart are derived from late differentiating cardiac progenitor cells of the Second Heart Field (SHF) located in pharyngeal mesoderm contiguous with the elongating heart tube. The T-box transcription factor Tbx1, encoded by the major 22q11.2 deletion syndrome gene, regulates SHF addition to both cardiac poles from a common progenitor population. Despite the significance of this cellular addition the mechanisms regulating the deployment of common progenitor cells to alternate cardiac poles remain poorly understood. Here we demonstrate that Tbx5, mutated in Holt-Oram syndrome and essential for venous pole development, is activated in Tbx1 expressing cells in the posterior region of the SHF at early stages of heart tube elongation. A subset of the SHF transcriptional program, including Tbx1 expression, is subsequently downregulated in Tbx5 expressing cells, generating a transcriptional boundary between Tbx1-positive arterial pole and Tbx5-positive venous pole progenitor cell populations. We show that normal downregulation of the definitive arterial pole progenitor cell program in the posterior SHF is dependent on both Tbx1 and Tbx5. Furthermore, retinoic acid (RA) signaling is required for Tbx5 activation in Tbx1-positive cells and blocking RA signaling at the time of Tbx5 activation results in atrioventricular septal defects at fetal stages. Our results reveal sequential steps of cardiac progenitor cell patterning and provide mechanistic insights into the origin of common forms of CHD.

Topics: Abnormalities, Multiple; Animals; Coronary Vessels; DiGeorge Syndrome; Gene Expression Regulation, Developmental; Heart Defects, Congenital; Heart Septal Defects; Heart Septal Defects, Atrial; Lower Extremity Deformities, Congenital; Mice; Mice, Transgenic; Signal Transduction; Stem Cells; T-Box Domain Proteins; Tretinoin; Upper Extremity Deformities, Congenital

We assessed feeding-related developmental anomalies in the LgDel mouse model of chromosome 22q11 deletion syndrome (22q11DS), a common developmental disorder that frequently includes perinatal dysphagia--debilitating feeding, swallowing and nutrition difficulties from birth onward--within its phenotypic spectrum. LgDel pups gain significantly less weight during the first postnatal weeks, and have several signs of respiratory infections due to food aspiration. Most 22q11 genes are expressed in anlagen of craniofacial and brainstem regions critical for feeding and swallowing, and diminished expression in LgDel embryos apparently compromises development of these regions. Palate and jaw anomalies indicate divergent oro-facial morphogenesis. Altered expression and patterning of hindbrain transcriptional regulators, especially those related to retinoic acid (RA) signaling, prefigures these disruptions. Subsequently, gene expression, axon growth and sensory ganglion formation in the trigeminal (V), glossopharyngeal (IX) or vagus (X) cranial nerves (CNs) that innervate targets essential for feeding, swallowing and digestion are disrupted. Posterior CN IX and X ganglia anomalies primarily reflect diminished dosage of the 22q11DS candidate gene Tbx1. Genetic modification of RA signaling in LgDel embryos rescues the anterior CN V phenotype and returns expression levels or pattern of RA-sensitive genes to those in wild-type embryos. Thus, diminished 22q11 gene dosage, including but not limited to Tbx1, disrupts oro-facial and CN development by modifying RA-modulated anterior-posterior hindbrain differentiation. These disruptions likely contribute to dysphagia in infants and young children with 22q11DS.

Topics: Animals; Animals, Newborn; Body Patterning; Chromosome Deletion; Cranial Nerves; Craniofacial Abnormalities; Deglutition; Deglutition Disorders; DiGeorge Syndrome; Disease Models, Animal; Embryo, Mammalian; Feeding Behavior; Female; Gene Dosage; Gene Expression Regulation, Developmental; Male; Mice; Phenotype; Rhombencephalon; Signal Transduction; T-Box Domain Proteins; Tretinoin

We asked whether key morphogenetic signaling pathways interact with 22q11 gene dosage to modulate the severity of cranial or cardiac anomalies in DiGeorge/22q1 deletion syndrome (22q11DS). Sonic hedgehog (Shh) and retinoic acid (RA) signaling is altered in the brain and heart-clinically significant 22q11DS phenotypic sites-in LgDel mouse embryos, an established 22q11DS model. LgDel embryos treated with cyclopamine, an Shh inhibitor, or carrying mutations in Gli3(Xtj), an Shh-signaling effector, have morphogenetic anomalies that are either not seen, or seen at significantly lower frequencies in control or single-mutant embryos. Similarly, RA exposure or genetic loss of RA function via heterozygous mutation of the RA synthetic enzyme Raldh2 induces novel cranial anomalies and enhances cardiovascular phenotypes in LgDel but not other genotypes. These changes are not seen in heterozygous Tbx1 mutant embryos-a 22q11 gene thought to explain much of 22q11DS pathogenesis-in which Shh or RA signaling has been similarly modified. Our results suggest that full dosage of 22q11 genes beyond Tbx1 establish an adaptive range for morphogenetic signaling via Shh and RA. When this adaptive range is constricted by diminished dosage of 22q11 genes, embryos are sensitized to otherwise benign changes in Shh and RA signaling. Such sensitization, in the face of environmental or genetic factors that modify Shh or RA signaling, may explain variability in 22q11DS morphogenetic phenotypes.

Topics: Adaptation, Biological; Animals; Bone Morphogenetic Proteins; DiGeorge Syndrome; Female; Fibroblast Growth Factors; Gene Dosage; Gene Expression Regulation, Developmental; Hedgehog Proteins; Humans; Mice; Mice, Knockout; Morphogenesis; Neural Tube; Phenotype; Signal Transduction; Tretinoin

Topics: Animals; Chromatin; Chromosome Deletion; Chromosomes, Mammalian; DiGeorge Syndrome; Genetic Predisposition to Disease; Histone Acetyltransferases; Mice; Mutation; T-Box Domain Proteins; Tretinoin

Loss of Tbx1 and decrease of retinoic acid (RA) synthesis result in DiGeorge/velocardiofacial syndrome (DGS/VCFS)-like phenotypes in mouse models, including defects in septation of the outflow tract of the heart and anomalies of pharyngeal arch-derived structures including arteries of the head and neck, laryngeal-tracheal cartilage, and thymus/parathyroid. Wild-type levels of T-box transcription factor (Tbx)1 and RA signaling are required for normal pharyngeal arch artery development. Recent studies have shown that reduction of RA or loss of Tbx1 alters the contribution of second heart field (SHF) progenitor cells to the elongating heart tube.. Here we tested whether Tbx1 and the RA signaling pathway interact during the deployment of the SHF and formation of the mature aortic arch.. Molecular markers of the SHF, neural crest and smooth muscle cells, were analyzed in Raldh2;Tbx1 compound heterozygous mutants. Our results revealed that the SHF and outflow tract develop normally in Raldh2(+/-);Tbx1(+/-) embryos. However, we found that decreased levels of RA accelerate the recovery from arterial growth delay observed in Tbx1(+/-) mutant embryos. This compensation coincides with the differentiation of smooth muscle cells in the 4th pharyngeal arch arteries, and is associated with severity of neural crest cell migration defects observed in these mutants.. Our data suggest that differences in levels of embryonic RA may contribute to the variability in great artery anomalies observed in DGS/VCFS patients.

Topics: Aldehyde Oxidoreductases; Animals; Aorta, Thoracic; Branchial Region; Cell Differentiation; Crosses, Genetic; DiGeorge Syndrome; Disease Models, Animal; Down-Regulation; Embryo, Mammalian; Gene Expression Regulation, Developmental; Genotype; Gestational Age; Heart; Heterozygote; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Muscle, Smooth, Vascular; Mutation; Neural Crest; Phenotype; Signal Transduction; T-Box Domain Proteins; Tissue Culture Techniques; Tretinoin

Topics: Aldehyde Oxidoreductases; Animals; Aorta, Thoracic; Branchial Region; Cell Differentiation; DiGeorge Syndrome; Disease Models, Animal; Genotype; Heart; Humans; Mice; Mice, Mutant Strains; Muscle, Smooth, Vascular; Mutation; Neural Crest; Phenotype; Signal Transduction; T-Box Domain Proteins; Tretinoin

Both retinoic acid (RA) and Tbx1 are definitively indispensable for the development of the pharyngeal arches. The defects produced by a loss of Tbx1 highly resemble those induced by hyper- and hypo-RA. Based on these similarities, the effects of RA on Tbx1 expression pattern were explored during pharyngeal arch development in zebrafish. Whole-mount in situ hybridization and real-time quantitative PCR were used. Zebrafish embryos were treated with 5 x 10(-8)mol/L and 10(-7)mol/L RA at 12.5 hours post fertilization for 1.5 hours, respectively. Whole-mount in situ hybridization showed that Tbx1 was expressed in the cardiac region, pharyngeal arch and otic vesicle between 24 hpf and 72 hpf in zebrafish. Tbx1 expression was obviously reduced, even lost, in the pharyngeal arch and outflow tract in RA treated groups. Real-time quantitative PCR analysis showed that Tbx1 expression rose to a peak level at 36 hpf in wild type group. Repression of Tbx1 expression was most evident at 36 hpf, 24 hours after RA treatment. 10(-7 )mol/L RA caused a more severe effect on the Tbx1 expression level than 5 x 10(-8)mol/L RA. The results suggested that RA could produce an altered Tbx1 expression pattern in zebrafish. In addition, RA could repress Tbx1 expression in a dose-dependent manner.

Topics: Animals; Branchial Region; DiGeorge Syndrome; DNA-Binding Proteins; Down-Regulation; Embryo, Nonmammalian; Gene Expression Regulation, Developmental; In Situ Hybridization; Phenotype; Reverse Transcriptase Polymerase Chain Reaction; T-Box Domain Proteins; Tretinoin; Zebrafish; Zebrafish Proteins

22q11 deletion (del22q11) syndrome is characterized genetically by heterozygous deletions within chromosome 22q11 and clinically by a constellation of congenital malformations of the aortic arch, heart, thymus, and parathyroid glands described as DiGeorge syndrome (DGS). Here, we report that compound heterozygosity of mouse homologs of two 22q11 genes, CRKL and TBX1, results in a striking increase in the penetrance and expressivity of a DGS-like phenotype compared to heterozygosity at either locus. Furthermore, we show that these two genes have critical dose-dependent functions in pharyngeal segmentation, patterning of the pharyngeal apparatus along the anteroposterior axis, and local regulation of retinoic acid (RA) metabolism and signaling. We can partially rescue one salient feature of DGS in Crkl+/-;Tbx1+/- embryos by genetically reducing the amount of RA produced in the embryo. Thus, we suggest that del22q11 is a contiguous gene syndrome involving dose-sensitive interaction of CRKL and TBX1 and locally aberrant RA signaling.

Topics: Adaptor Proteins, Signal Transducing; Animals; Aorta; Branchial Region; Chromosomes, Human, Pair 22; Cytochrome P-450 Enzyme System; DiGeorge Syndrome; Disease Models, Animal; Embryo, Mammalian; Gene Deletion; Gene Expression; Gene Expression Regulation, Developmental; Genotype; Homeodomain Proteins; Humans; In Situ Hybridization; Mice; Mice, Inbred C57BL; Mice, Knockout; Nuclear Proteins; Retinoic Acid 4-Hydroxylase; Signal Transduction; T-Box Domain Proteins; Thymus Gland; Tretinoin

Cyp26a1, a gene required for retinoic acid (RA) inactivation during embryogenesis, was previously identified as a potential Tbx1 target from a microarray screen comparing wild-type and null Tbx1 mouse embryo pharyngeal arches (pa) at E9.5. Using real-time PCR and in situ hybridization analysis of Cyp26a1 and its two functionally related family members Cyp26b1 and c1, we demonstrate reduced and/or altered expression for all three genes in pharyngeal tissues of Tbx1 null embryos. Blockade of Cyp26 function in the chick embryo using R115866, a specific inhibitor of Cyp26 enzyme function, resulted in a dose-dependent phenocopy of the Tbx1 null mouse including loss of caudal pa and pharyngeal arch arteries (paa), small otic vesicles, loss of head mesenchyme and, at later stages, DiGeorge Syndrome-like heart defects, including common arterial trunk and perimembranous ventricular septal defects. Molecular markers revealed a serious disruption of pharyngeal pouch endoderm (ppe) morphogenesis and reduced staining for smooth muscle cells in paa. Expression of the RA synthesizing enzyme Raldh2 was also up-regulated and altered Hoxb1 expression indicated that RA levels are raised in R115866-treated embryos as reported for Tbx1 null mice. Down-regulation of Tbx1 itself was observed, in accordance with previous observations that RA represses Tbx1 expression. Thus, by specifically blocking the action of the Cyp26 enzymes we can recapitulate many elements of the Tbx1 mutant mouse, supporting the hypothesis that the dysregulation of RA-controlled morphogenesis contributes to the Tbx1 loss of function phenotype.

Topics: Abnormalities, Multiple; Animals; Benzothiazoles; Chick Embryo; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; DiGeorge Syndrome; Down-Regulation; Male; Mice; Mice, Knockout; Retinoic Acid 4-Hydroxylase; T-Box Domain Proteins; Tretinoin; Triazoles

Retinoic acid (RA), the active derivative of vitamin A, is involved in various developmental and homeostatic processes. To define whether certain developmental events are particularly sensitive to a decrease in embryonic RA levels, we generated mice bearing a hypomorphic allele of the RA-synthesizing enzyme Raldh2. The resulting mutant mice, which die perinatally, exhibit the features of the human DiGeorge syndrome (DGS) with heart outflow tract septation defects and anomalies of the aortic arch-derived head and neck arteries, laryngeal-tracheal cartilage defects, and thymus/parathyroid aplasia or hypoplasia. Analysis of Raldh2 hypomorph embryos reveal selective defects of the posterior (third to sixth) branchial arches, including absence or hypoplasia of the corresponding aortic arches and pharyngeal pouches, and local down-regulation of RA-target genes. Thus, a decreased level of embryonic RA (through genetic and/or nutritional causes) could represent a major modifier of the expressivity of human 22q11del-associated DiGeorge/velocardiofacial syndromes and, if severe enough, could on its own lead to the clinical features of the DiGeorge syndrome.

Topics: Aldehyde Oxidoreductases; Animals; Animals, Newborn; DiGeorge Syndrome; Embryo, Mammalian; Female; Gene Targeting; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Phenotype; Retinal Dehydrogenase; Tretinoin

Targeted inactivation of the mouse retinaldehyde dehydrogenase 2 (RALDH2/ALDH1a2), the enzyme responsible for early embryonic retinoic acid synthesis, is embryonic lethal because of defects in early heart morphogenesis. Transient maternal RA supplementation from E7.5 to (at least) E8.5 rescues most of these defects, but the supplemented Raldh2(-/-) mutants die prenatally, from a lack of septation of the heart outflow tract (Niederreither, K., Vermot, J., Messaddeq, N., Schuhbaur, B., Chambon, P. and Dollé, P. (2001). Development 128, 1019-1031). We have investigated the developmental basis for this defect, and found that the RA-supplemented Raldh2(-/-) embryos exhibit impaired development of their posterior (3rd-6th) branchial arch region. While the development of the first and second arches and their derivatives, as well as the formation of the first branchial pouch, appear to proceed normally, more posterior pharyngeal pouches fail to form and the pharyngeal endoderm develops a rudimentary, pouch-like structure. All derivatives of the posterior branchial arches are affected. These include the aortic arches, pouch-derived organs (thymus, parathyroid gland) and post-otic neural crest cells, which fail to establish segmental migratory pathways and are misrouted caudally. Patterning and axonal outgrowth of the posterior (9th-12th) cranial nerves is also altered. Vagal crest deficiency in Raldh2(-/-) mutants leads to agenesis of the enteric ganglia, a condition reminiscent of human Hirschprung's disease. In addition, we provide evidence that: (i) wildtype Raldh2 expression is restricted to the posteriormost pharyngeal mesoderm; (ii) endogenous RA response occurs in both the pharyngeal endoderm and mesoderm, and extends more rostrally than Raldh2 expression up to the 2nd arch; (iii) RA target genes (Hoxa1, Hoxb1) are downregulated in both the pharyngeal endoderm and mesoderm of mutant embryos. Thus, RALDH2 plays a crucial role in producing RA required for pharyngeal development, and RA is one of the diffusible mesodermal signals that pattern the pharyngeal endoderm.

Topics: Aldehyde Oxidoreductases; Animals; Branchial Region; Cell Movement; Cranial Nerves; DiGeorge Syndrome; Endoderm; Enteric Nervous System; Female; Gene Expression Regulation, Developmental; Hirschsprung Disease; Humans; Maternal-Fetal Exchange; Mesoderm; Mice; Mice, Knockout; Mice, Transgenic; Neural Crest; Phenotype; Pregnancy; Rhombencephalon; Signal Transduction; Tretinoin; Vagus Nerve

Topics: Animals; DiGeorge Syndrome; Disease Models, Animal; Fibroblast Growth Factor 8; Fibroblast Growth Factors; Humans; Pharynx; Tretinoin; Vascular Endothelial Growth Factor A