Three rare variants of SOX7 impairing its interaction with GATA4 may be a predisposing factor to complete AVSD

Abstract Background Atrioventricular septal defects (AVSD) are a complicated subtype of congenital heart defects for which the genetic basis is poorly understood. Many evidences have demonstrated that transcription factor SOX7 which can interact with GATA4 plays a pivotal role in the cardiovascular development. The critical role of GATA4 in the morphogenesis of atrioventricular septum implies SOX7 a potential involvement of AVSD. However, whether SOX7 variants are involved in the pathogenesis of AVSD needs to be explored. Methods 100 sporadic non-syndromic AVSD Chinese Han patients were recruited and the variants of SOX7 in 100 patients were screened by target sequencing. Functional assays were performed to testify the potential pathogenicity of nonsynonymous variants of SOX7 found in these AVSD patients. Results Through target sequencing, we identified three rare variants c.40C>G, c.542G>A, and c.743C>T of SOX7 in 100 sporadic non-syndromic AVSD Chinese Han patients. All mutant sites were highly conserved in mammals. Compared to the wildtype, these variants of SOX7 increased mRNA expression and decreased protein. In the developing murine hearts, SOX7 along with GATA4 expressed highly in the region of atrioventricular cushions. Moreover, SOX7 overexpression promoted the expression of GATA4 in human umbilical vein endothelial cells. Chromatin immunoprecipitation assay uncovered that SOX7 could directly bind to the region of GATA4 promoter. Luciferase assays demonstrated that SOX7 activated GATA4 promoter and the variants impaired the transcriptional activity of SOX7. Furthermore, the variants of SOX7 altered the regulation to the activity of GATA4 on its target genes. Conclusions Our studies provide evidence that deleterious variants in SOX7 are potential contributors to human AVSD and provide novel insights into the etiology of AVSD.