Project description:Atrioventricular septal defects (AVSD) are common cardiovascular malformations, occurring in 3.5/10,000 births. Although frequently associated with trisomy 21, autosomal dominant AVSD has also been described. Recently we identified and characterized the cell adhesion molecule CRELD1 (previously known as "cirrin") as a candidate gene for the AVSD2 locus mapping to chromosome 3p25. Analysis of the CRELD1 gene from individuals with non-trisomy 21-associated AVSD identified heterozygous missense mutations in nearly 6% of this population, including mutations in isolated AVSD and AVSD associated with heterotaxy syndrome. CRELD1 is the first human gene to be implicated in the pathogenesis of isolated AVSD and AVSD in the context of heterotaxy, which provides an important step in unraveling the pathogenesis of AVSD.
Project description:Atrioventricular septal defects (AVSD) are highly heritable, clinically significant congenital heart malformations. Genetic and environmental modifiers of risk are thought to work in unknown combinations to cause AVSD. Approximately 5-10% of simplex AVSD cases carry a missense mutation in CRELD1. However, CRELD1 mutations are not fully penetrant and require interactions with other risk factors to result in AVSD. Vascular endothelial growth factor-A (VEGFA) is a well-characterized modulator of heart valve development. A functional VEGFA polymorphism, VEGFA c.-634C, which causes constitutively increased VEGFA expression, has been associated with cardiac septal defects suggesting it may be a genetic risk factor. To determine if there is an allelic association with AVSD we genotyped the VEGFA c.-634 SNP in a simplex AVSD study cohort. Over-representation of the c.-634C allele in the AVSD group suggested that this genotype may increase risk. Correlation of CRELD1 and VEGFA genotypes revealed that potentially pathogenic missense mutations in CRELD1 were always accompanied by the VEGFA c.-634C allele in individuals with AVSD suggesting a potentially pathogenic allelic interaction. We used a Creld1 knockout mouse model to determine the effect of deficiency of Creld1 combined with increased VEGFA on atrioventricular canal development. Morphogenic response to VEGFA was abnormal in Creld1-deficient embryonic hearts, indicating that interaction between CRELD1 and VEGFA has the potential to alter atrioventricular canal morphogenesis. This supports our hypothesis that an additive effect between missense mutations in CRELD1 and a functional SNP in VEGFA contributes to the pathogenesis of AVSD.
Project description:Atrioventricular septal defects (AVSDs) are a common severe form of congenital heart disease (CHD). In this study we identified deleterious non-synonymous mutations in two cilia genes, Dnah11 and Mks1, in independent N-ethyl-N-nitrosourea-induced mouse mutant lines with heritable recessive AVSDs by whole-exome sequencing. Cilia are required for left/right body axis determination and second heart field (SHF) Hedgehog (Hh) signaling, and we find that cilia mutations affect these requirements differentially. Dnah11avc4 did not disrupt SHF Hh signaling and caused AVSDs only concurrently with heterotaxy, a left/right axis abnormality. In contrast, Mks1avc6 disrupted SHF Hh signaling and caused AVSDs without heterotaxy. We performed unbiased whole-genome SHF transcriptional profiling and found that cilia motility genes were not expressed in the SHF whereas cilia structural and signaling genes were highly expressed. SHF cilia gene expression predicted the phenotypic concordance between AVSDs and heterotaxy in mice and humans with cilia gene mutations. A two-step model of cilia action accurately predicted the AVSD/heterotaxyu phenotypic expression pattern caused by cilia gene mutations. We speculate that cilia gene mutations contribute to both syndromic and non-syndromic AVSDs in humans and provide a model that predicts the phenotypic consequences of specific cilia gene mutations.
Project description:The goal of this study was to identify the contribution of common genetic variants to Down syndrome-associated atrioventricular septal defect, a severe heart abnormality. Compared with the euploid population, infants with Down syndrome, or trisomy 21, have a 2000-fold increased risk of presenting with atrioventricular septal defects. The cause of this increased risk remains elusive. Here we present data from the largest heart study conducted to date on a trisomic background by using a carefully characterized collection of individuals from extreme ends of the phenotypic spectrum. We performed a genome-wide association study using logistic regression analysis on 452 individuals with Down syndrome, consisting of 210 cases with complete atrioventricular septal defects and 242 controls with structurally normal hearts. No individual variant achieved genome-wide significance. We identified four disomic regions (1p36.3, 5p15.31, 8q22.3, and 17q22) and two trisomic regions on chromosome 21 (around PDXK and KCNJ6 genes) that merit further investigation in large replication studies. Our data show that a few common genetic variants of large effect size (odds ratio >2.0) do not account for the elevated risk of Down syndrome-associated atrioventricular septal defects. Instead, multiple variants of low-to-moderate effect sizes may contribute to this elevated risk, highlighting the complex genetic architecture of atrioventricular septal defects even in the highly susceptible Down syndrome population.
Project description:PurposeThe goal of this study was to identify the contribution of large copy-number variants to Down syndrome-associated atrioventricular septal defects, the risk for which in the trisomic population is 2,000-fold more as compared with that of the general disomic population.MethodsGenome-wide copy-number variant analysis was performed on 452 individuals with Down syndrome (210 cases with complete atrioventricular septal defects; 242 controls with structurally normal hearts) using Affymetrix SNP 6.0 arrays, making this the largest heart study conducted to date on a trisomic background.ResultsLarge, common copy-number variants with substantial effect sizes (OR > 2.0) do not account for the increased risk observed in Down syndrome-associated atrioventricular septal defects. By contrast, cases had a greater burden of large, rare deletions (P < 0.01) and intersected more genes (P < 0.007) as compared with controls. We also observed a suggestive enrichment of deletions intersecting ciliome genes in cases as compared with controls.ConclusionOur data provide strong evidence that large, rare deletions increase the risk of Down syndrome-associated atrioventricular septal defects, whereas large, common copy-number variants do not appear to increase the risk of Down syndrome-associated atrioventricular septal defects. The genetic architecture of atrioventricular septal defects is complex and multifactorial in nature.
Project description:BackgroundThe most common type of congenital heart disease is the cardiac septal defects, which has reported to be caused by a missense mutation (G296S) in exon 3 of the GATA4 gene.AimsThe present study was undertaken to find out whether GATA4 gene is the prime cause of the septal defects in Mysore population.Materials and methodsGATA4 gene analyses were undertaken on 21 confirmed CHD cases by PCR and DNA sequencing.Results and conclusionAnalysis of this particular mutation in 21 septal defect patients revealed that none of the patients had the mutation, indicating that this mutation is population specific or septal defect in Mysore population is caused due to mutations in other regions of the GATA4 gene.
Project description:About half of people with trisomy 21 have a congenital heart defect (CHD), whereas the remainder have a structurally normal heart, demonstrating that trisomy 21 is a significant risk factor but is not causal for abnormal heart development. Atrioventricular septal defects (AVSD) are the most commonly occurring heart defects in Down syndrome (DS), and ∼65% of all AVSD is associated with DS. We used a candidate-gene approach among individuals with DS and complete AVSD (cases = 141) and DS with no CHD (controls = 141) to determine whether rare genetic variants in genes involved in atrioventricular valvuloseptal morphogenesis contribute to AVSD in this sensitized population. We found a significant excess (p < 0.0001) of variants predicted to be deleterious in cases compared to controls. At the most stringent level of filtering, we found potentially damaging variants in nearly 20% of cases but fewer than 3% of controls. The variants with the highest probability of being damaging in cases only were found in six genes: COL6A1, COL6A2, CRELD1, FBLN2, FRZB, and GATA5. Several of the case-specific variants were recurrent in unrelated individuals, occurring in 10% of cases studied. No variants with an equal probability of being damaging were found in controls, demonstrating a highly specific association with AVSD. Of note, all of these genes are in the VEGF-A pathway, even though the candidate genes analyzed in this study represented numerous biochemical and developmental pathways, suggesting that rare variants in the VEGF-A pathway might contribute to the genetic underpinnings of AVSD in humans.
Project description:Atrioventricular septal defects (AVSDs) are a frequent but not universal component of Down syndrome (DS), while AVSDs in otherwise normal individuals have no well-defined genetic basis. The contribution of copy number variation (CNV) to specific congenital heart disease (CHD) phenotypes including AVSD is unknown. We hypothesized that de novo CNVs on chromosome 21 might cause isolated sporadic AVSDs, and separately that CNVs throughout the genome might constitute an additional genetic risk factor for AVSD in patients with DS. We utilized a custom oligonucleotide arrays targeted to CNV hotspots that are flanked by large duplicated segments of high sequence identity. We assayed 29 euploid and 50 DS individuals with AVSD, and compared to general population controls. In patients with isolated-sporadic AVSD we identified two large unique deletions outside of chromosome 21 not seen in the expanded set of 8,635 controls, each overlapping with larger deletions associated with similar CHD reported in the DECIPHER database. There was a small duplication in one patient with DS and AVSD. We conclude that isolated sporadic AVSDs may be occasionally associated with large de novo genomic structural variation outside of chromosome 21. The absence of CNVs on chromosome 21 in patients with isolated sporadic AVSD suggests that sub-chromosomal duplications or deletions of greater than 150 kbp on chromosome 21 do not cause sporadic AVSDs. Large CNVs do not appear to be an additive risk factor for AVSD in the DS population.
Project description:ObjectivesThe study objectives were to analyze the outcomes of pediatric patients with heterotaxy syndrome undergoing cardiovascular surgery and to determine the predictors of mortality.MethodsA retrospective analysis of 82 patients diagnosed with heterotaxy syndrome who underwent cardiovascular surgery between January 2008 and December 2017 was performed. Univariate and multivariable Cox regression analyses to determine risk factors for mortality and Kaplan-Meier analysis for survival were performed.ResultsPatient mortality in the cohort was 34% (28/82), including 36% (20/55) for single ventricle palliation and 30% (8/27) for biventricular repair. At 5 years, the probability of survival did not differ between the groups by log-rank testing (P = .829). Multivariable analysis found extracorporeal membrane oxygenation support (hazard ratio, 10.4; 95% confidence interval, 4.3-25.4; P < .001), total anomalous pulmonary venous return (hazard ratio, 4.3; 95% confidence interval, 1.7-10.8; P = .002), and birth weight 2.5 kg or less (hazard ratio, 2.4; 95% confidence interval, 1.0-5.4; P = .041) to be independent risk factors for mortality in all-comers. Pulmonary vein stenosis was a univariate predictor of mortality among all patients with heterotaxy (hazard ratio, 3.0; 95% confidence interval, 1.4-6.4; P = .005) and in the subgroup of patients with single ventricles (hazard ratio, 4.0; 95% confidence interval, 1.7-9.7; P = .002). Overall survival was 66% (54/82) at a median follow-up time of 2.2 years (0.4-4.1) from the initial surgery.ConclusionsOutcomes of children with heterotaxy syndrome, irrespective of the operative pathway, remain suboptimal in the current era. Risk factors for mortality in this population include birth weight 2.5 kg or less, extracorporeal membrane oxygenation, pulmonary vein stenosis, and total anomalous pulmonary venous return, which may help to further optimize surgical decision making. Multiorgan system involvment is frequently encountered in these patients.