Identification of variants of ISL1 gene promoter and cellular functions in isolated ventricular septal defects.

Ventricular septal defects (VSDs) are the most common congenital heart defects (CHDs). Studies have documented that ISL1 has a crucial impact on cardiac growth, but the role of variants in the ISL1 gene promoter in patients with VSD has not been explored. In 400 subjects (200 patients with isolated and sporadic VSDs: 200 healthy controls), we investigated the ISL1 gene promoter variant and performed cellular functional experiments by using the dual-luciferase reporter assay to verify the impact on gene expression. In the ISL1 promoter, five variants were found only in patients with VSD by sequencing. Cellular functional experiments demonstrated that three variants decreased the transcriptional activity of the ISL1 promoter (P < 0.05). Further analysis with the online JASPAR database demonstrated that a cluster of putative binding sites for transcription factors may be altered by these variants, possibly resulting in change of ISL1 protein expression and VSD formation. Our study has, for the first time, identified novel variants in the ISL1 gene promoter region in the Han Chinese patients with isolated and sporadic VSD. In addition, the cellular functional experiments, electrophoretic mobility shift assay, and bioinformatic analysis have demonstrated that these variants significantly alter the expression of the ISL1 gene and affect the binding of transcription factors, likely resulting in VSD. Therefore, this study may provide new insights into the role of the gene promoter region for a better understanding of genetic basis of the formation of CHDs and may promote further investigations on mechanism of the formation of CHDs.

Association of DARS gene polymorphisms with the risk of isolated ventricular septal defects in the Chinese Han population.

BACKGROUND: Ventricular septal defects (VSD) are the most common subtype of congenital heart defects (CHD) and are estimated to account for 20 to 30% of all cases of CHD. The etiology of isolated VSD remains poorly understood. Eight core aminoacyl-tRNA synthetases (ARSs) (EPRS, MARS, QARS, RARS, IARS, LARS, KARS, and DARS) combine with three nonenzymatic components to form a complex known as the multisynthetase complex (MSC). Four single nucleotide polymorphisms (SNPs) in EPRS have been reported to be associated with risks of CHD in Chinese populations. METHODS: In this study, we hypothesize that SNPs of the DARS gene might influence susceptibility to sporadic isolated VSD. Therefore, we conducted a case-control study of 841 patients with isolated VSD and 2953 non-CHD controls from the Chinese Han population to evaluate how 4 potentially functional SNPs within the DARS gene were associated with the risk of VSD. RESULTS: We observed that the risk of VSD was significantly associated with rs2164331 [G/A; odds ratio (OR) = 0.78, 95% confidence interval (CI) = 0.69-0.91; P = 3.17 × 10-3], rs6738266 [G/A; OR = 1.17, 95% CI = 1.05-1.29, P = 1.83 × 10-3], and rs309143 [G/A; OR = 1.09, 95% CI = 1.01-1.17; P = 3.12 × 10-2]. Additionally, compared with individuals with 0-2 risk alleles, individuals carrying 3, 4, and 5 or more risk alleles had 1.01-, 1.22- and 1.46-fold greater risks of VSD, respectively. These findings revealed a significant dose-response effect for VSD risk among individuals carrying different numbers of risk alleles (Ptrend = 6.37 × 10-4). CONCLUSIONS: These findings indicate that genetic variants of the DARS gene may influence individual susceptibility to isolated VSD in the Chinese Han population.

A novel mutation of Hyaluronan synthase 2 gene in Chinese children with ventricular septal defect.

As a major product of extracellular matrix (ECM), Hyaluronic acid (HA) is involved in early cardiac development and mainly synthesized by Hyaluronan synthase 2 (HAS2) during embryogenesis. Targeted deletion of HAS2 gene in mice led to obvious cardiac and vascular defects. To clarify the potential association of the mutation in HAS2 with the development of congenital heart disease (CHD), in this study, we sequenced the coding region of HAS2 and identified a novel non-synonymous variant c.A1496T (p.Glu499Val) in one of 100 non-syndromic Ventricular Septal Defect (VSD) patients. The variant was not observed in 250 controls. In addition, to determine the contribution of HAS2 variant in VSD, we compared HA content in supernatant using HA quantitative analysis and found that the mutation obviously affected the HA synthetic activity of HAS2. To our knowledge, this is the first time that the mutation in HAS2 was found in Chinese VSD patients, which suggested that HAS2 may be involved in the etiology of non-syndromic VSD and have the vital function in the development of heart septum.

Novel and functional sequence variants within the TBX2 gene promoter in ventricular septal defects.

Congenital heart disease (CHD) is the most common birth defects in humans. To date, genetic causes for CHD remain largely unknown. T-box transcription factor 2 (TBX2) gene is expressed in the myocardium of atrioventricular canal, outflow tract and inflow tract and plays a critical role in heart chamber formation. Genomic deletion and duplication of TBX2 gene have been associated with cardiac defects. As TBX2 acts in a dose-dependent manner, we hypothesized that DNA sequence variants (DSVs) within TBX2 gene promoter may mediate CHD development by changing TBX2 levels. In this study, TBX2 gene promoter was genetically analyzed in large cohorts of patients with ventricular septal defect (VSD) (n = 324) and ethnic-matched healthy controls (n = 328). Four novel and heterozygous DSVs, g.59477201C > T, g.59477347G > A, g.59477353delG and g.59477371G > A were identified in VSD patients, but in none of controls. Functional analyses revealed that all of the four DSVs significantly decreased transcriptional activities of TBX2 gene promoter. Therefore, our data suggested that the DSVs within TBX2 gene promoter identified in VSD patients may contribute to VSD etiology.

Absence of association between length variation of an intronic region in the NFATC1 gene and congenital heart defects in a Han Chinese population.

Congenital heart defects are complicated birth defects due to the interaction of genetic and environmental factors. Previous research indicated the importance of transcription factors in heart development, which suggested that mutations of transcription factor genes could be genetic determinants of congenital heart defects. Recently, the length variation of an intronic region in the NFATC1 gene was linked to ventricular septal defect (VSD). In this study, we detected the length variation of the region in a Han Chinese population of patients with nonsyndromic VSD, atrial septal defect, patent ductus arteriosus, and control individuals. We found a new allele of the length variation with four repeats of a 44-bp region. At the same time, all the alleles were found in both patient and control groups and there were no significant differences in genotype distribution between the patients and controls. The results suggested no association of the length variation of the intronic region in NFATC1 gene with VSD, atrial septal defect, and patent ductus arteriosus.

Teratocarcinoma-derived growth factor 1 (TDGF1) sequence variants in patients with congenital heart defect.

The goal of our study was to identify potential pathogenic mutations in the TDGF1 gene in Chinese people with isolated CHD, particularly those with VSD, and to provide further insight into the etiology of CHD. A total of 500 CHD Chinese patients were investigated for mutations in the TDGF1 gene. Thirteen variants were found among the 500 isolated VSD patients and 250 controls, including one non-synonymous variant identified in patients but not in controls. This work firstly provides human genetic evidence of TDGF1 involved in the pathogenesis of VSD, expanding our knowledge of the causative mutations of congenital heart defects, in particular, the causative mutations of VSD.

Echocardiographic evaluation of the development of aortic valve prolapse in supracristal ventricular septal defect.

UNLABELLED: The development and timing of aortic valve prolapse (AoVP) and aortic regurgitation (AR) was studied by two-dimensional echocardiography in 99 consecutive patients with supracristal ventricular septal defect (VSD). Thirty patients (30%) had aortic valve prolapse (VSD + AoVP group), and 31 patients (31%) had AoVP with AR (VSD + AoVP + AR group). In the VSD + AoVP group, AoVP was detected first by echocardiography at the age of 6.8 +/- 4.2 years (mean +/- SD). In the VSD + AoVP + AR group, the interval from detection of AoVP to the appearance of AR was 3.4 +/- 2.0 years. The configuration of the prolapsed aortic valve was echocardiographically classified into two types: tear-drop type (small) prolapse and box type (large) prolapse. The frequency of tear-drop type prolapse was not significantly different between VSD + AoVP and VSD + AoVP + AR groups (43% versus 32%, respectively), indicating that even minor AoVP can result in AR. Four infants (4%) had AoVP at the ages of 1, 5, 7, and 11 months, respectively. All infants had tear-drop type prolapse. Two infants developed AR by colour flow mapping at the ages of 3 and 11 months, and the interval from prolapse to AR was only 2 and 4 months, respectively. CONCLUSION: Aortic valce involvement can develop under the age of 1 year in supracristal VSD. Regular evaluation by two-dimensional echocardiography with colour flow mapping is important in the follow-up of children with supracristal VSD.