Genetic analysis of an enhancer of the NKX2-5 gene in ventricular septal defects

Abstract

Congenital heart disease (CHD) is one of the most common birth defects in humans. Mutations in cardiac transcription factor genes, such as GATA4, NKX2-5 and TBX5 genes, have been associated to a small portion of familial and isolated CHD cases. NKX2-5, a highly conserved homeobox gene, is expressed in the developing heart. During embryonic development, NKX2-5 plays pivotal roles in specifying cardiac progenitors, cardiac morphogenesis, cardiomyocyte differentiation and conduction system development. Numerous mutations in NKX2-5 gene have been reported in CHD patients, including atrial septal defect, ventricular septal defect (VSD) and tetrology of Fallot. We have previously identified the sequence variants within the NKX2-5 gene promoter in VSD patients. As several studies have revealed that the NKX2-5 gene is regulated by a complex module involving promoter and multiple independent cardiac enhancers, one of which is located between −3500bp and −2500bp upstream to the transcription start site, we hypothesized that the variants within the cardiac enhancer may contribute to CHD. In this study, we genetically analyzed the enhancer of NKX2-5 gene in large cohorts of VSD patients (n=322) and controls (n=336). The results showed that three novel variants, g.1467G>A, g.1487Ins with a 13bp insertion and g.1515Ins with a 6bp insertion, were identified within the enhancer element in both VSD patients and controls with similar frequencies (P>0.05). Therefore, our data suggested that the enhancer of NKX2-5 gene may not be a contributor to the VSD etiology. Other regulatory elements of the NKX2-5 gene will be further analyzed in CHD patients.