Almanac 2014: congenital heart disease

Advances in molecular genetics for pulmonary atresia

Genetic and environmental factors may be similar in certain CHD. It has been widely accepted that it is the cumulative effect of these risk factors that results in disease. Pulmonary atresia is a rare type of complex cyanotic CHD with a poor prognosis. Understanding the molecular mechanism of pulmonary atresia is essential for future diagnosis, prevention, and therapeutic approaches. In this article, we reviewed several related copy number variants and related genetic mutations, which were identified in patients with pulmonary atresia, including pulmonary atresia with ventricular septal defect and pulmonary atresia with intact ventricular septum.

Identification of candidate genes for congenital heart defects on proximal chromosome 8p

With the application of advanced molecular cytogenetic techniques, the number of patients identified as having abnormal chromosome 8p has increased progressively. Individuals with terminal 8p deletion have been extensively described in previous studies. The manifestations usually include cardiac anomalies, developmental delay/mental retardation, craniofacial abnormalities, and multiple other minor anomalies. However, some patients with proximal deletion also presented with similar phenotypic features. Here we describe a female child with an 18.5-Mb deletion at 8p11.23–p22 that include the cardiac-associated loci NKX2-6 and NRG1. Further mutation screening of these two candidate genes in 143 atrial septal defect patients, two heterozygous mutations NKX2-6 (c.1A > T) and NRG1 (c.1652G > A) were identified. The mutations were described for the first time in patients with congenital heart disease (CHD). The c.1A > T NKX2-6 generated a protein truncated by 45 amino acids with a decreased level of mRNA expression, whereas the NRG1 mutation had no significant effect on protein functions. Our findings suggest that 8p21-8p12 may be another critical region for 8p-associated CHD, and some cardiac malformations might be due to NKX2-6 haploinsufficiency. This study also links the NKX2-6 mutation to ASD for the first time, providing novel insight into the molecular underpinning of this common form of CHD.

3'UTR SNPs and Haplotypes in the GATA4 Gene Contribute to the Genetic Risk of Congenital Heart Disease

INTRODUCTION AND OBJECTIVES

Single-nucleotide polymorphisms within a microRNA binding site can have different effects on gene expression, influencing the risk of disease. This study aimed to evaluate the association between single-nucleotide polymorphisms and haplotypes in the 3'UTR of the GATA4 gene and congenital heart disease risk.

METHODS

Bioinformatics algorithms were used to analyze single-nucleotide polymorphisms in putative microRNA-binding sites of GATA4 3'UTR and to calculate the difference in free energy of hybridization (ΔFE, kcal/mol) for each wild-type vs the variant allele.

RESULTS

The study population comprised 146 Caucasian patients (73 males; 6.68 ± 7.79 years) and a 265 healthy newborn participants (147 males). The sum of all |ΔFE| was considered to predict the biological importance of single-nucleotide polymorphisms binding more microRNAs. Next, the 4 polymorphisms (+1158C > T, +1256 A > T, +1355 G > A, +1521C > G) with the highest predicted |ΔFEtot| (9.91, 14.85, 11.03, 21.66kcal/mol, respectively) were genotyped in a case-control study (146 patients and 250 controls). Applying a correction for multiple testing only the +1158 T allele was found to be associated with a reduced risk showing significant difference between patients and controls. Haplotype analysis showed that the T-T-G-C haplotype (more uncommon in congenital heart diseases than in controls) was associated with a significantly decreased risk (P = .03), while the rare C-A-A-C haplotype, which was very uncommon in controls (0.3%) compared with the disease (2.4%), was associated with a 4-fold increased risk of disease (P = .04).

CONCLUSIONS

Common variants in 3'UTR of the GATA4 gene jointly interact, affecting the congenital heart disease susceptibility, probably by altering microRNA posttranscriptional regulation.