RESUMEN
ERBB family members and their ligands play an essential role in embryonic heart development and adult heart physiology. Among them, ERBB3 is a binding partner of ERBB2; the ERBB2/3 complex mediates downstream signaling for cell proliferation. ERBB3 has seven consensus binding sites to the p85 regulatory subunit of PI3K, which activates the downstream AKT pathway, leading to the proliferation of various cells. This study generated a human ERBB3 knock-in mouse expressing a mutant ERBB3 whose seven YXXM p85 binding sites were replaced with YXXA. Erbb3 knock-in embryos exhibited lethality between E12.5 to E13.5, and showed a decrease in mesenchymal cell numbers and density in AV cushions. We determined that the proliferation of mesenchymal cells in the atrioventricular (AV) cushion in Erbb3 knock-in mutant embryos was temporarily reduced due to the decrease of AKT and ERK1/2 phosphorylation. Overall, our results suggest that AKT/ERK activation by the ERBB3-dependent PI3K signaling is crucial for AV cushion morphogenesis during embryonic heart development.
Asunto(s)
Defectos de la Almohadilla Endocárdica/genética , Cojinetes Endocárdicos/metabolismo , Receptor ErbB-3/metabolismo , Animales , Sitios de Unión , Células CHO , Cricetinae , Cricetulus , Defectos de la Almohadilla Endocárdica/metabolismo , Cojinetes Endocárdicos/embriología , Humanos , Ratones , Ratones Endogámicos C57BL , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Unión Proteica , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptor ErbB-3/química , Receptor ErbB-3/genética , Transducción de SeñalRESUMEN
Atrioventricular valve development requires endothelial-to-mesenchymal transition (EndMT) that induces cushion endocardial cells to give rise to mesenchymal cells crucial to valve formation. In the adult endothelium, deletion of the docking protein FRS2α induces EndMT by activating TGFß signaling in a miRNA let-7-dependent manner. To study the role of endothelial FRS2α during embryonic development, we generated mice with an inducible endothelial-specific deletion of Frs2α (FRS2αiECKO). Analysis of the FRS2αiECKO embryos uncovered a combination of impaired EndMT in AV cushions and defective maturation of AV valves leading to development of thickened, abnormal valves when Frs2α was deleted early (E7.5) in development. At the same time, no AV valve developmental abnormalities were observed after late (E10.5) deletion. These observations identify FRS2α as a pivotal controller of cell fate transition during both EndMT and post-EndMT valvulogenesis.
Asunto(s)
Cojinetes Endocárdicos/embriología , Regulación del Desarrollo de la Expresión Génica , Proteínas de la Membrana/fisiología , Animales , Recuento de Células , Linaje de la Célula , Defectos de la Almohadilla Endocárdica/embriología , Defectos de la Almohadilla Endocárdica/genética , Cojinetes Endocárdicos/citología , Cojinetes Endocárdicos/patología , Células Endoteliales/citología , Eliminación de Gen , Proteínas de la Membrana/deficiencia , Proteínas de la Membrana/genética , Mesodermo/citología , Mesodermo/embriología , Ratones , Ratones Endogámicos C57BL , MicroARNs/fisiología , Válvula Mitral/anomalías , Válvula Mitral/embriología , Morfogénesis/genética , Fenotipo , Válvula Tricúspide/anomalías , Válvula Tricúspide/embriologíaRESUMEN
Background: Congenital heart defects (CHDs) are the most common type of birth defects and a major cause of infant mortality. Although knowledge of genetic risk variants for CHDs is scarce, most cases of CHDs are considered to be due to multifactorial inheritance. Objective: To analyze the association of 14 single nucleotide polymorphic variants previously associated with a risk of CHDs in a Mexican population with isolated CHDs. Materials and Methods: DNA samples obtained from healthy subjects and from subjects with isolated atrial, ventricular, or atrioventricular septal defects living in Northeastern Mexico were analyzed by real time-polymerase chain reaction for allelic discrimination of genetic variants of the genes TBX1, TBX20, ASTX-18-AS1, AXIN1, MTHFR, NKX2.5, BMP4, and NFATc1. The odds ratios (ORs) for allele and genotype frequencies and inheritance models were obtained. Results: Forty-two patients and 138 controls were included. Two variants were found to confer a risk of CHDs: variant rs4720169 of TBX20 in which the OR for the heterozygous state was 1.88 (95% confidence interval [CI]: 1.12-3.14, p = 0.010), whereas the OR for the homozygous state was 3.82 (95% CI: 1.18-12.3, p = 0.010); and variant rs12921862 of AXIN1 in which the OR for the heterozygous state was 4.15 (95% CI: 2.42-7.10; p ≤ 0.001), whereas the OR for the homozygous state was 9.2 (95% CI: 1.31-64.7, p = 0.008) for allele A. Conclusion: Genetic variants of the TBX20 and AXIN1 genes confer a significantly increased risk of congenital septal heart defects in a population from Northeastern Mexico.
Asunto(s)
Proteína Axina/genética , Defectos de la Almohadilla Endocárdica/genética , Defectos de los Tabiques Cardíacos/genética , Proteínas de Dominio T Box/genética , Alelos , Estudios de Casos y Controles , Niño , Preescolar , Femenino , Genotipo , Humanos , Lactante , Recién Nacido , Masculino , México , Proyectos Piloto , Polimorfismo de Nucleótido Simple , Estudios ProspectivosRESUMEN
OBJECTIVE: To perform prenatal diagnosis for a fetus with endocardial cushion defect and explore its mechanism. METHODS: The karotypes of the fetus and its parents were analyzed by routine G-banding. Their genomic DNA was also analyzed by array comparative genomic hybridization (aCGH). RESULTS: The fetus and its mother were found to have a karyotype of 46, XX, inv(8)(p21q24.1), while no karyotypic abnormality was detected for the father. aCGH has detected a 15.14 Mb deletion at 8p23.3-p22 and a 6.87 Mb duplication at 8q24.23-q24.3 in the fetus. CONCLUSION: The fetus was diagnosed with Rec8 syndrome. Its abnormal chromosomes have derived from the inv(8) carried by its mother. GATA4 and SOX7 may be the key genes for the endocardial cushion defect found in the fetus.
Asunto(s)
Defectos de la Almohadilla Endocárdica/embriología , Defectos de la Almohadilla Endocárdica/genética , Enfermedades Fetales/genética , Adulto , Aberraciones Cromosómicas , Bandeo Cromosómico , Defectos de la Almohadilla Endocárdica/diagnóstico , Femenino , Enfermedades Fetales/diagnóstico , Pruebas Genéticas , Humanos , Cariotipificación , Embarazo , Diagnóstico PrenatalRESUMEN
Congenital heart disease (CHD), the most common type of birth defect, is still the leading non-infectious cause of infant morbidity and mortality in humans. Aggregating evidence demonstrates that genetic defects are involved in the pathogenesis of CHD. However, CHD is genetically heterogeneous and the genetic components underpinning CHD in an overwhelming majority of patients remain unclear. In the present study, the coding exons and flanking introns of the PITX2 gene, which encodes a paired-like homeodomain transcription factor 2essential for cardiovascular morphogenesis as well as maxillary facial development, was sequenced in 196 unrelated patients with CHD and subsequently in the mutation carrier's family members available. As a result, a novel heterozygous PITX2 mutation, p.Q102X for PITX2a, or p.Q148X for PITX2b, or p.Q155X for PITX2c, was identified in a family with endocardial cushion defect (ECD) and Axenfeld-Rieger syndrome (ARS). Genetic analysis of the pedigree showed that the nonsense mutation co-segregated with ECD and ARS transmitted in an autosomal dominant pattern with complete penetrance. The mutation was absent in 800 control chromosomes from an ethnically matched population. Functional analysis by using a dual-luciferase reporter assay system revealed that the mutant PITX2 had no transcriptional activity and that the mutation eliminated synergistic transcriptional activation between PITX2 and NKX2.5, another transcription factor pivotal for cardiogenesis. To our knowledge, this is the first report on the association of PITX2 loss-of-function mutation with increased susceptibility to ECD and ARS. The findings provide novel insight into the molecular mechanisms underpinning ECD and ARS, suggesting the potential implications for the antenatal prophylaxis and personalized treatment of CHD and ARS.
Asunto(s)
Segmento Anterior del Ojo/anomalías , Defectos de la Almohadilla Endocárdica/genética , Anomalías del Ojo/genética , Proteínas de Homeodominio/genética , Mutación , Factores de Transcripción/genética , Secuencia de Aminoácidos , Animales , Células CHO , Niño , Preescolar , China , Mapeo Cromosómico , Estudios de Cohortes , Cricetulus , Enfermedades Hereditarias del Ojo , Femenino , Genotipo , Heterocigoto , Humanos , Masculino , Datos de Secuencia Molecular , Linaje , Penetrancia , Homología de Secuencia de Aminoácido , Activación Transcripcional , Proteína del Homeodomínio PITX2RESUMEN
Congenital heart defects (CHD) are found in ~50 % of Down syndrome (DS) patients. Genetic variants have been implicated, including CRELD1 mutations, but no previous study has examined the candidate genes, NKX2-5 and GATA4, in DS patients with secundum atrial defects (ASDII) and ventricular septal defects (VSD). Furthermore, CRELD1 mutations have not yet been studied in Mexican DS patients with atrioventricular septal defects (AVSD). Mexican DS patients (n = 148) with standard trisomy 21 were classified as follows: group I, normal heart; group II, VSD, ASDII, or both; and group III, AVSD. Mexican healthy controls (n = 113) were also included. Sequence analysis was performed on NKX2-5 and GATA4 in all three groups, and on CRELD1 in only group III. Statistical differences in the percentages of functional variants were analyzed by Fisher's exact test. Three non-synonymous variants in NKX2-5 were identified in the heterozygous state: a novel p.Pro5Ser was found in one DS patient without CHD; the p.Glu21Gln was found in one ASDII patient; and the p.Arg25Cys (R25C) was found in three patients (one from each DS study group). The p.Glu21Gln and R25C were also documented in 0.88 % of the controls. No significant difference was observed between the DS groups and healthy controls. Germline mutations in the NKX2-5, GATA4, and CRELD1 genes do not appear to be associated with CHD in Mexican DS patients. Our findings also support the notion that the R25C variant of NKX2-5 is a polymorphism, as it was not significantly different between our DS patients and controls.
Asunto(s)
Moléculas de Adhesión Celular/genética , Síndrome de Down/genética , Defectos de la Almohadilla Endocárdica/genética , Proteínas de la Matriz Extracelular/genética , Factor de Transcripción GATA4/genética , Mutación de Línea Germinal , Defectos de los Tabiques Cardíacos/genética , Proteínas de Homeodominio/genética , Factores de Transcripción/genética , Adolescente , Niño , Preescolar , Síndrome de Down/complicaciones , Femenino , Predisposición Genética a la Enfermedad , Proteína Homeótica Nkx-2.5 , Humanos , Lactante , Recién Nacido , Masculino , México , Polimorfismo GenéticoRESUMEN
AIMS: Valvular heart disease is responsible for considerable morbidity and mortality. Cardiac valves develop as the heart contracts, and they function throughout the lifetime of the organism to prevent retrograde blood flow. Their precise morphogenesis is crucial for cardiac function. Zebrafish is an ideal model to investigate cardiac valve development as it allows these studies to be carried out in vivo through non-invasive imaging. Accumulating evidence suggests a role for contractility and intracardiac flow dynamics in cardiac valve development. However, these two factors have proved difficult to uncouple, especially since altering myocardial function affects the intracardiac flow pattern. METHODS AND RESULTS: Here, we describe novel zebrafish models of developmental valve defects. We identified two mutant alleles of myosin heavy chain 6 that can be raised to adulthood despite having only one functional chamber-the ventricle. The adult mutant ventricle undergoes remodelling, and the atrioventricular (AV) valves fail to form four cuspids. In parallel, we characterized a novel mutant allele of southpaw, a nodal-related gene involved in the establishment of left-right asymmetry, which exhibits randomized heart and endoderm positioning. We first observed that in southpaw mutants the relative position of the two cardiac chambers is altered, affecting the geometry of the heart, while myocardial function appears unaffected. Mutant hearts that loop properly or exhibit situs inversus develop normally, whereas midline, unlooped hearts exhibit defects in their transvalvular flow pattern during AV valve development as well as defects in valve morphogenesis. CONCLUSION: Our data indicate that intracardiac flow dynamics regulate valve morphogenesis independently of myocardial contractility.
Asunto(s)
Circulación Coronaria , Defectos de la Almohadilla Endocárdica/embriología , Cojinetes Endocárdicos/embriología , Válvulas Cardíacas/anomalías , Hemodinámica , Mecanotransducción Celular , Animales , Animales Modificados Genéticamente , Función Atrial , Defectos de la Almohadilla Endocárdica/genética , Defectos de la Almohadilla Endocárdica/metabolismo , Defectos de la Almohadilla Endocárdica/fisiopatología , Cojinetes Endocárdicos/metabolismo , Cojinetes Endocárdicos/fisiopatología , Genotipo , Válvulas Cardíacas/metabolismo , Válvulas Cardíacas/fisiopatología , Morfogénesis , Mutación , Contracción Miocárdica , Cadenas Pesadas de Miosina/genética , Cadenas Pesadas de Miosina/metabolismo , Fenotipo , Pez Cebra/embriología , Pez Cebra/genética , Proteínas de Pez Cebra/genética , Proteínas de Pez Cebra/metabolismoRESUMEN
Holt-Oram syndrome (HOS) is a rare autosomal dominant disorder characterized by upper limb defects and congenital heart defects (CHD), which are often simple septal and conduction defects, less frequently complex CHDs. We report on a 9 year-old boy with clinical and radiologic features of HOS consisting of bilateral asymmetric hypoplastic thumbs, generalized brachydactyly, limited supination due to radioulnar synostosis, and sloping shoulders, and intermediate atrioventricular canal defect (AVCD) with aortic coarctation. A de novo, previously described mutation, (Arg279ter) was identified in the TBX5 gene. Molecular characterization of this mutation was carried out due to the atypical CHD. In order to investigate whether the mutated transcript of TBX5 was able to escape the post-transcriptional surveillance mechanism and to produce a truncated TBX5 protein, we analyzed the TBX5 transcript, and protein pattern in HOS, and WT cardiac tissues. Our results demonstrate that the mutant TBX5 transcript is cleared by the cellular mechanism of surveillance. This data provides some support for the hypothesis that a dominant negative mutation, which strongly impairs the WT allele, might be too hazardous to be maintained. The literature suggests that HOS is relatively common among syndromes associated with AVCD.
Asunto(s)
Anomalías Múltiples/genética , Coartación Aórtica/genética , Defectos de la Almohadilla Endocárdica/genética , Cardiopatías Congénitas/genética , Defectos del Tabique Interatrial/genética , Deformidades Congénitas de las Extremidades Inferiores/genética , Proteínas de Dominio T Box/genética , Deformidades Congénitas de las Extremidades Superiores/genética , Secuencia de Bases , Braquidactilia/genética , Niño , Defectos de los Tabiques Cardíacos , Humanos , Masculino , Mutación , Radio (Anatomía)/anomalías , Análisis de Secuencia de ADN , Sinostosis/genética , Cúbito/anomalíasRESUMEN
BACKGROUND: Heart morphogenesis involves sequential anatomical changes from a linear tube of a single channel peristaltic pump to a four-chamber structure with two channels controlled by one-way valves. The developing heart undergoes continuous remodeling, including septation. RESULTS: Pitx2-null mice are characterized by cardiac septational defects of the atria, ventricles, and outflow tract. Pitx2-null mice also exhibited a short outflow tract, including unseptated conus and deformed endocardial cushions. Cushions were characterized with a jelly-like structure, rather than the distinct membrane-looking leaflets, indicating that endothelial mesenchymal transition was impaired in Pitx2(-/-) embryos. Mesoderm cells from the branchial arches and neural crest cells from the otic region contribute to the development of the endocardial cushions, and both were reduced in number. Members of the Fgf and Bmp families exhibited altered expression levels in the mutants. CONCLUSIONS: We suggest that Pitx2 is involved in the cardiac outflow tract septation by promoting and/or maintaining the number and the remodeling process of the mesoderm progenitor cells. Pitx2 influences the expression of transcription factors and signaling molecules involved in the differentiation of the cushion mesenchyme during heart development.
Asunto(s)
Corazón/embriología , Proteínas de Homeodominio/fisiología , Organogénesis/genética , Factores de Transcripción/fisiología , Animales , Muerte Celular/genética , Linaje de la Célula/genética , Proliferación Celular , Embrión de Mamíferos , Defectos de la Almohadilla Endocárdica/genética , Cojinetes Endocárdicos/embriología , Cojinetes Endocárdicos/metabolismo , Endocardio/citología , Endocardio/embriología , Regulación del Desarrollo de la Expresión Génica , Corazón/fisiología , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Células Madre Mesenquimatosas/metabolismo , Células Madre Mesenquimatosas/fisiología , Ratones , Ratones Noqueados , Cresta Neural/embriología , Cresta Neural/metabolismo , Organogénesis/fisiología , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Proteína del Homeodomínio PITX2RESUMEN
Congenital heart defects affect 60-85% of patients with RASopathies. We analysed the clinical and molecular characteristics of atrioventricular canal defect in patients with mutations affecting genes coding for proteins with role in the RAS/MAPK pathway. Between 2002 and 2011, 101 patients with cardiac defect and a molecularly confirmed RASopathy were collected. Congenital heart defects within the spectrum of complete or partial (including cleft mitral valve) atrioventricular canal defect were diagnosed in 8/101 (8%) patients, including seven with a PTPN11 gene mutation, and one single subject with a RAF1 gene mutation. The only recurrent mutation was the missense PTPN11 c.124 A>G change (T42A) in PTPN11. Partial atrioventricular canal defect was found in six cases, complete in one, cleft mitral valve in one. In four subjects the defect was associated with other cardiac defects, including subvalvular aortic stenosis, mitral valve anomaly, pulmonary valve stenosis and hypertrophic cardiomyopathy. Maternal segregation of PTPN11 and RAF1 gene mutations occurred in two and one patients, respectively. Congenital heart defects in the affected relatives were discordant in the families with PTPN11 mutations, and concordant in that with RAF1 mutation. In conclusion, our data confirm previous reports indicating that atrioventricular canal defect represents a relatively common feature in Noonan syndrome. Among RASopathies, atrioventricular canal defect was observed to occur with higher prevalence among subjects with PTPN11 mutations, even though this association was not significant possibly because of low statistical power. Familial segregation of atrioventricular canal defect should be considered in the genetic counselling of families with RASopathies.
Asunto(s)
Defectos de la Almohadilla Endocárdica/genética , Síndrome de Noonan , Proteína Tirosina Fosfatasa no Receptora Tipo 11/genética , Proteínas Proto-Oncogénicas c-raf/genética , Defectos de la Almohadilla Endocárdica/fisiopatología , Femenino , Estudios de Asociación Genética , Cardiopatías Congénitas/epidemiología , Cardiopatías Congénitas/genética , Defectos de los Tabiques Cardíacos , Humanos , Masculino , Mutación , Síndrome de Noonan/genética , Síndrome de Noonan/metabolismo , Síndrome de Noonan/fisiopatología , Proteína SOS1/genéticaRESUMEN
During embryological development the heart develops from a simple tube into a complex fully developed heart with four chambers. Hence all congenital heart defects develop before the ninth week of gestation. Currently a steadily increasing number of genetic mutations have been found to be responsible for congenital heart defects. Nevertheless, up to now it has been impossible to diagnose a heart defect just on the basis of molecular pathology. Despite the current excellent prenatal and postnatal ultrasound diagnostics, the post-mortem examination is still the gold standard for the diagnosis of complex heart malformations. However, this requires knowledge of the pathomorphology of the heart malformation in question. Therefore, characteristic and distinguishing features of septal defects including atrioventricular septal defects are presented, especially as the latter are part of complex heart defects, such as conotruncal heart malformations.
Asunto(s)
Defectos de la Almohadilla Endocárdica/patología , Cardiopatías Congénitas/patología , Defectos de los Tabiques Cardíacos/patología , Análisis Mutacional de ADN , Diagnóstico Diferencial , Ecocardiografía , Defectos de la Almohadilla Endocárdica/genética , Femenino , Edad Gestacional , Atrios Cardíacos/patología , Cardiopatías Congénitas/genética , Tabiques Cardíacos/patología , Ventrículos Cardíacos/patología , Humanos , Recién Nacido , Embarazo , Arteria Pulmonar/patología , Síndrome , Transposición de los Grandes Vasos/patología , Tronco Arterial/patología , Ultrasonografía PrenatalRESUMEN
Members of the GATA family of transcription factors are critical regulators of heart development and mutations in 2 of them, GATA4 and GATA6 are associated with outflow tract and septal defects in human. The heart expresses 3 GATA factors, GATA4, 5 and 6 in a partially overlapping pattern. Here, we report that compound Gata4/Gata5 and Gata5/Gata6 mutants die embryonically or perinatally due to severe congenital heart defects. Almost all Gata4(+/-)Gata5(+/-) mutant embryos have double outlet right ventricles (DORV), large ventricular septal defects (VSD) as well as hypertrophied mitral and tricuspid valves. Only 25% of double compound Gata4/Gata5 heterozygotes survive to adulthood and these mice have aortic stenosis. Compound loss of a Gata5 and a Gata6 allele also leads to DORVs associated with subaortic VSDs. Expression of several transcription factors important for endocardial and myocardial cell differentiation, such as Tbx20, Mef2c, Hey1 and Hand2, was reduced in compound heterozygote embryos. These findings suggest the existence of important genetic interactions between Gata5 and the 2 other cardiac GATA factors in endocardial cushion formation and outflow tract morphogenesis. The data identify GATA5 as a potential genetic modifier of congenital heart disease and provide insight for elucidating the genetic basis of an important class of human birth defects.
Asunto(s)
Corazón Fetal/embriología , Corazón Fetal/metabolismo , Factor de Transcripción GATA4/metabolismo , Factor de Transcripción GATA5/metabolismo , Factor de Transcripción GATA6/metabolismo , Animales , Estenosis de la Válvula Aórtica/embriología , Estenosis de la Válvula Aórtica/genética , Estenosis de la Válvula Aórtica/metabolismo , Defectos de la Almohadilla Endocárdica/embriología , Defectos de la Almohadilla Endocárdica/genética , Defectos de la Almohadilla Endocárdica/metabolismo , Femenino , Factor de Transcripción GATA4/deficiencia , Factor de Transcripción GATA4/genética , Factor de Transcripción GATA5/deficiencia , Factor de Transcripción GATA5/genética , Factor de Transcripción GATA6/deficiencia , Factor de Transcripción GATA6/genética , Regulación del Desarrollo de la Expresión Génica , Cardiopatías Congénitas/embriología , Cardiopatías Congénitas/genética , Cardiopatías Congénitas/metabolismo , Defectos del Tabique Interventricular/embriología , Defectos del Tabique Interventricular/genética , Defectos del Tabique Interventricular/metabolismo , Heterocigoto , Humanos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fenotipo , Embarazo , ARN Mensajero/genética , ARN Mensajero/metabolismoAsunto(s)
Anomalías Múltiples , Síndrome de Down/embriología , Defectos de la Almohadilla Endocárdica/embriología , Corazón Fetal/anomalías , Defectos del Tabique Interatrial/embriología , Defectos del Tabique Interventricular/embriología , Animales , Cromosomas Humanos Par 21 , Modelos Animales de Enfermedad , Síndrome de Down/genética , Embrión de Mamíferos/anomalías , Defectos de la Almohadilla Endocárdica/genética , Genotipo , Edad Gestacional , Defectos del Tabique Interatrial/genética , Defectos del Tabique Interventricular/genética , Humanos , Imagenología Tridimensional , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Microscopía/métodos , Morfogénesis , FenotipoRESUMEN
RATIONALE: Heart valves develop from precursor structures called cardiac cushions, an endothelial-lined cardiac jelly that resides in the inner side of the heart tube. The cushions are then invaded by cells from different sources, undergo a series of complicated and poorly understood remodeling processes, and give rise to valves. Disruption of the fibroblast growth factor (FGF) signaling axis impairs morphogenesis of the outflow tract (OFT). Yet, whether FGF signaling regulates OFT valve formation is unknown. OBJECTIVE: To study how OFT valve formation is regulated and how aberrant cell signaling causes valve defects. METHODS AND RESULTS: By using mouse genetic manipulation, cell lineage tracing, ex vivo heart culture, and molecular biology approaches, we demonstrated that FGF signaling in the OFT myocardium upregulated Bmp4 expression, which then enhanced smooth muscle differentiation of neural crest cells (NCCs) in the cushion. FGF signaling also promoted OFT myocardial cell invasion to the cushion. Disrupting FGF signaling interrupted cushion remodeling with reduced NCCs differentiation into smooth muscle and less cardiomyocyte invasion and resulted in malformed OFT valves. CONCLUSIONS: The results demonstrate a novel mechanism by which the FGF-BMP signaling axis regulates formation of OFT valve primordia by controlling smooth muscle differentiation of cushion NCCs.
Asunto(s)
Proteína Morfogenética Ósea 4/metabolismo , Diferenciación Celular , Defectos de la Almohadilla Endocárdica/metabolismo , Cojinetes Endocárdicos/metabolismo , Válvulas Cardíacas/metabolismo , Corazón/embriología , Miocitos del Músculo Liso/metabolismo , Cresta Neural/metabolismo , Transducción de Señal , Animales , Sitios de Unión , Proteína Morfogenética Ósea 4/genética , Diferenciación Celular/genética , Linaje de la Célula , Células Cultivadas , Defectos de la Almohadilla Endocárdica/genética , Defectos de la Almohadilla Endocárdica/patología , Cojinetes Endocárdicos/patología , Factor 2 de Crecimiento de Fibroblastos/metabolismo , Genotipo , Válvulas Cardíacas/anomalías , Válvulas Cardíacas/patología , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Morfogénesis , Miocitos del Músculo Liso/patología , Cresta Neural/anomalías , Cresta Neural/patología , Técnicas de Cultivo de Órganos , Fenotipo , Regiones Promotoras Genéticas , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/genética , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/metabolismo , Receptor Tipo 2 de Factor de Crecimiento de Fibroblastos/genética , Receptor Tipo 2 de Factor de Crecimiento de Fibroblastos/metabolismo , Transducción de Señal/genética , Factor de Transcripción AP-1/metabolismo , TransfecciónRESUMEN
AIMS: Cardiac malformations are prevalent in trisomies of human chromosome 21 [Down's syndrome (DS)], affecting normal chamber separation in the developing heart. Efforts to understand the aetiology of these defects have been severely hampered by the absence of an accurate mouse model. Such models have proved challenging to establish because synteny with human chromosome Hsa21 is distributed across three mouse chromosomes. None of those engineered so far accurately models the full range of DS cardiac phenotypes, in particular the profound disruptions resulting from atrioventricular septal defects (AVSDs). Here, we present analysis of the cardiac malformations exhibited by embryos of the transchromosomic mouse line Tc(Hsa21)1TybEmcf (Tc1) which contains more than 90% of chromosome Hsa21 in addition to the normal diploid mouse genome. METHODS AND RESULTS: Using high-resolution episcopic microscopy and three-dimensional (3D) modelling, we show that Tc1 embryos exhibit many of the cardiac defects found in DS, including balanced AVSD with single and separate valvar orifices, membranous and muscular ventricular septal defects along with outflow tract and valve leaflet abnormalities. Frequencies of cardiac malformations (ranging from 38 to 55%) are dependent on strain background. In contrast, no comparable cardiac defects were detected in embryos of the more limited mouse trisomy model, Dp(16Cbr1-ORF9)1Rhr (Ts1Rhr), indicating that trisomy of the region syntenic to the Down's syndrome critical region, including the candidate genes DSCAM and DYRK1A, is insufficient to yield DS cardiac abnormalities. CONCLUSION: The Tc1 mouse line provides a suitable model for studying the underlying genetic causes of the DS AVSD cardiac phenotype.
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Anomalías Múltiples , Cromosomas Humanos Par 21 , Síndrome de Down/genética , Defectos de la Almohadilla Endocárdica/genética , Corazón Fetal/anomalías , Defectos del Tabique Interatrial/genética , Defectos del Tabique Interventricular/genética , Animales , Aorta/anomalías , Modelos Animales de Enfermedad , Síndrome de Down/embriología , Embrión de Mamíferos/anomalías , Defectos de la Almohadilla Endocárdica/embriología , Genotipo , Edad Gestacional , Defectos del Tabique Interatrial/embriología , Defectos del Tabique Interventricular/embriología , Humanos , Imagenología Tridimensional , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Microscopía/métodos , Morfogénesis , FenotipoRESUMEN
Defects in cardiac valvulogenesis are a common cause of congenital heart disease, and the study of this process promises to provide mechanistic insights and lead to novel therapeutics. Normal valve development involves multiple signaling pathways, and recently roles have been identified for extracellular matrix components, including glycosaminoglycans. We, therefore, explored the role of the glycosaminoglycan chondroitin sulfate during zebrafish cardiac development. Beginning at 33 hr, there is a distinct zone of chondroitin sulfate expression in the atrioventricular (AV) boundary, in the cardiac jelly between the endocardium and myocardium. This expression is both spatially and temporally restricted, and is undetectable after 48 hr. Chemical as well as genetic inhibition of chondroitin synthesis results in AV canal (AVC) defects, including loss of the atrioventricular constriction, blood regurgitation, and failure of circulation. Lack of chondroitin disrupts a marker of cell migration, results in a loss of myocardial and endothelial markers of valvulogenesis, and misregulates bone morphogenetic protein expression, supporting an early role in AVC development. In summary, we have defined a requirement for chondroitin sulfate expression in the normal patterning of the AV boundary, suggesting that this component of the cardiac jelly provides a necessary signal in this critical transition in vertebrate cardiogenesis.
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Sulfatos de Condroitina/metabolismo , Cojinetes Endocárdicos/embriología , Corazón/embriología , Animales , Animales Modificados Genéticamente , Tipificación del Cuerpo/efectos de los fármacos , Tipificación del Cuerpo/genética , Tipificación del Cuerpo/fisiología , Movimiento Celular/fisiología , Embrión no Mamífero , Desarrollo Embrionario/fisiología , Defectos de la Almohadilla Endocárdica/genética , Defectos de la Almohadilla Endocárdica/metabolismo , Cojinetes Endocárdicos/efectos de los fármacos , Cojinetes Endocárdicos/metabolismo , Endocardio/metabolismo , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Corazón/efectos de los fármacos , Miocardio/metabolismo , N-Acetilgalactosaminiltransferasas/antagonistas & inhibidores , N-Acetilgalactosaminiltransferasas/genética , ARN Interferente Pequeño/farmacología , Pez Cebra/embriología , Pez Cebra/genética , Pez Cebra/metabolismoRESUMEN
BACKGROUND: Atrioventricular canal defects account for 4% of all congenital heart anomalies. They arise from failure of endocardial cushion formation, a process dependent on transition of endothelial cells into clustered mesenchymal cells in the mid-atrioventricular septum. To date, the genetic signals necessary for atrioventricular canal defects are poorly understood. We hypothesized that bone morphogenetic protein signaling in cardiac endothelial cells may be crucial to this process. METHODS: To study the role of bone morphogenetic protein receptors (Bmpr) in the developing heart, we created knockout mice with inactivation of Bmpr1a selectively in endocardium. Two strains of null mice were created: one with constitutive endothelial-specific knockout of Bmpr1a and one with time-inducible, endothelial-specific knockout of Bmpr1a. Embryos and animals were analyzed by microscopy, RNA in situ hybridization, and microangiography. RESULTS: Animals with null mutation of Bmpr1a in endothelium were embryonic lethal at E11.5 to 12.0 and demonstrated absence of endocardial cushion formation. Embryos failed to form atrioventricular valves and adjacent septa. Endocardial knockout of Bmpr1a did not affect development of the outflow tract or aortic arches. Using time-inducible, cell-specific knockout mice, we show that Bmpr1a has two functions in the developing atrioventricular canal: to induce endocardial endothelial-mesenchymal transition, and to pattern the septal mesenchyme into endocardial cushions. We demonstrate that these processes are temporally linked to expression of the transcription factors Id1 and Id3. CONCLUSIONS: Endocardial cushion formation is dependent on cell-specific expression of Bmpr1a. Our results suggest that Bmpr1a-mediated signaling is a crucial pathway involved in pathogenesis of atrioventricular septal and valve malformations, which are among the most common congenital heart defects in humans.
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Receptores de Proteínas Morfogenéticas Óseas de Tipo 1/genética , Defectos de la Almohadilla Endocárdica/genética , Endocardio/embriología , Endotelio Vascular/embriología , Animales , Defectos de la Almohadilla Endocárdica/embriología , Defectos de la Almohadilla Endocárdica/patología , Cojinetes Endocárdicos/embriología , Cojinetes Endocárdicos/patología , Endocardio/patología , Endotelio Vascular/patología , Femenino , Genes Reporteros/genética , Operón Lac , Ratones , Ratones Noqueados , Proteínas del Complejo de Iniciación de Transcripción Pol1/genética , Embarazo , Transducción de Señal/genéticaAsunto(s)
Receptores de Proteínas Morfogenéticas Óseas de Tipo 1/genética , Defectos de la Almohadilla Endocárdica/genética , Endocardio/embriología , Endotelio Vascular/embriología , Animales , Defectos de la Almohadilla Endocárdica/embriología , Defectos de la Almohadilla Endocárdica/patología , Cojinetes Endocárdicos/embriología , Cojinetes Endocárdicos/patología , Endocardio/patología , Endotelio Vascular/patología , Femenino , Ratones , Ratones Noqueados , EmbarazoRESUMEN
Crouzon syndrome is an autosomal dominant disorder caused by mutation in the fibroblast growth factor receptor (FGFR)-2 gene. Recent findings from animal studies imply a critical role for FGFs in the regulation of cardiac development including cardiac cushion proliferation and valvulogenesis. We report on a 36-year-old woman, who required surgical closure for an atrial septal defect, a clinical feature that has not been previously reported in other patients with Crouzon syndrome. The findings suggest that cardiac investigations are warranted in patients with a diagnosis of Crouzon syndrome.