An Excess of Deleterious Variants in VEGF-A Pathway Genes in Down-Syndrome-Associated Atrioventricular Septal Defects

Division of Cardiovascular Medicine and the Heart Research Center, Oregon Health & Science University, Portland, OR 97239, USA.
The American Journal of Human Genetics (Impact Factor: 10.93). 10/2012; 91(4):646-59. DOI: 10.1016/j.ajhg.2012.08.017
Source: PubMed


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.

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    • "In addition, we examined Frzb mRNA, which encodes a secreted antagonist of WNT signalling that is required for atrioventricular cardiac cushion development in the chicken (Person et al., 2005). Furthermore, mutation of FRZB has been associated with one case of atrioventricular septal defect in humans (Ackerman et al., 2012). Interestingly , murine Frzb expression decreases in the absence of Tbx1 in vivo (Liao et al., 2008) and is upregulated when Tbx5 is overexpressed in mouse cardio fibroblasts (Zhou et al., 2012). "
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    ABSTRACT: Ventricular septal defects (VSDs) are the most commonly occurring congenital heart defect. They are regularly associated with complex syndromes, including DiGeorge syndrome and Holt-Oram syndrome, which are characterised by haploinsufficiency for the T-box transcription factors TBX1 and TBX5, respectively. The histone acetyltransferase monocytic leukaemia zinc finger protein, MOZ (MYST3/KAT6A), is required for the expression of the Tbx1 and Tbx5 genes. Homozygous loss of MOZ results in DiGeorge syndrome-like defects including VSD. The Moz gene is expressed in the ectodermal, mesodermal and endodermal aspects of the developing pharyngeal apparatus and heart, however it is unclear in which of these tissues MOZ is required for heart development. The role of MOZ in the activation of Tbx1 would suggest a requirement for MOZ in the mesoderm, because deletion of Tbx1 in the mesoderm causes VSDs. Here, we investigated the tissue-specific requirements for MOZ in the mesoderm. We demonstrate that Mesp1-cre-mediated deletion of Moz results in high penetrance of VSDs and overriding aorta and a significant decrease in MOZ-dependent Tbx1 and Tbx5 expression. Together, our data suggest that the molecular pathogenesis of VSDs in Moz germline mutant mice is due to loss of MOZ-dependent activation of mesodermal Tbx1 and Tbx5 expression. Copyright © 2015. Published by Elsevier Inc.
    Developmental Biology 04/2015; 403(1). DOI:10.1016/j.ydbio.2015.04.011 · 3.55 Impact Factor
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    • "However similar to previous studies, Vegf-a mRNA levels were increased in diabetic fetal hearts [35]. Elevated expression levels of VEGF-A are associated with congenital heart defects [46,47]. High VEGF-A levels in fetal hearts inhibit epithelial-to-mesenchymal transition (EMT) in the endocardial cushion, which contributes to formation of atrioventricular septum [48,49]. "
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    ABSTRACT: Pregestational diabetes is a major risk factor of congenital heart defects (CHDs). Glutathione is depleted and reactive oxygen species (ROS) production is elevated in diabetes. In the present study, we aimed to examine whether treatment with N-acetylcysteine (NAC), which increases glutathione synthesis and inhibits ROS production, prevents CHDs induced by pregestational diabetes. Female mice were treated with streptozotocin (STZ) to induce pregestational diabetes prior to breeding with normal males to produce offspring. Some diabetic mice were treated with N-acetylcysteine (NAC) in drinking water from E0.5 to the end of gestation or harvesting of the embryos. CHDs were identified by histology. ROS levels, cell proliferation and gene expression in the fetal heart were analyzed. Our data show that pregestational diabetes resulted in CHDs in 58% of the offspring, including ventricular septal defect (VSD), atrial septal defect (ASD), atrioventricular septal defects (AVSD), transposition of great arteries (TGA), double outlet right ventricle (DORV) and tetralogy of Fallot (TOF). Treatment with NAC in drinking water in pregestational diabetic mice completely eliminated the incidence of AVSD, TGA, TOF and significantly diminished the incidence of ASD and VSD. Furthermore, pregestational diabetes increased ROS, impaired cell proliferation, and altered Gata4, Gata5 and Vegf-a expression in the fetal heart of diabetic offspring, which were all prevented by NAC treatment. Treatment with NAC increases GSH levels, decreases ROS levels in the fetal heart and prevents the development of CHDs in the offspring of pregestational diabetes. Our study suggests that NAC may have therapeutic potential in the prevention of CHDs induced by pregestational diabetes.
    Cardiovascular Diabetology 02/2014; 13(1):46. DOI:10.1186/1475-2840-13-46 · 4.02 Impact Factor
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    • "substrate adhesion in the H9C2 cell line. Recent studies also suggest the potential contribution of VEGFA (Ackerman et al. 2012), ciliome and Hedgehog (Ripoll et al. 2012), and folate (Locke et al. 2010) pathways to the pathogenicity of CHD in DS. There are also several mouse models for partial or complete trisomy syntenic to human chromosome 21 (Sago et al. 1998; Shinohara et al. 2001; Dunlevy et al. 2010; Yu et al. 2010). "
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    ABSTRACT: Congenital heart defect (CHD) occurs in 40% of Down syndrome (DS) cases. While carrying three copies of chromosome 21 increases the risk for CHD, trisomy 21 itself is not sufficient to cause CHD. Thus additional genetic variation and/or environmental factors could contribute to the CHD risk. Here we report genomic variations that in concert with trisomy 21, determine the risk for CHD in DS. This case-control GWAS includes 187 DS with CHD (AVSD=69, ASD=53, VSD=65) as cases, and 151 DS without CHD as controls. Chromosome 21 specific association study revealed rs2832616 and rs1943950 as CHD risk alleles (adjusted genotypic P-values < 0.05). These signals were confirmed in a replication cohort of 92 DS-CHD cases and 80 DS-without CHD (nominal P-value 0.0022). Furthermore, CNV analyses using a customized chromosome 21 aCGH of 135K probes in 55 DS-AVSD and 53 DS-without CHD revealed three CNV regions associated with AVSD risk (FDR ≤ 0.05). Two of these regions which are located within the previously identified CHD region on chromosome 21 were further confirmed in a replication study of 49 DS-AVSD and 45 DS- without CHD (FDR ≤ 0.05). One of these CNVs maps near the RIPK4 gene, and the second includes the ZNF295 gene, highlighting the potential role of these genes in the pathogenesis of CHD in DS. We propose that the genetic architecture of the CHD risk of DS is complex, and includes trisomy 21, SNP and CNV variations in chromosome 21. In addition, a yet unidentified genetic variation in the rest of the genome may contribute to this complex genetic architecture.
    Genome Research 06/2013; 23(9). DOI:10.1101/gr.147991.112 · 14.63 Impact Factor
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