Congenital Heart Disease (CHD) is the most common congenital defect, but the genetic aetiology of a large proportion of CHD is unexplained. This project aimed to delineate novel genetic causes of CHD using Whole Exome Sequencing (WES) in a family-based approach.
Sixteen families were recruited to the study. WES data analysis followed a
standardized pipeline and candidate variants were prioritized on the basis of in silico pathogenicity prediction tools and review of the current literature.
Known and candidate genes in CHD were successfully identified using WES. In one family, a mutation in PIGV was identified, providing a diagnosis of Hyperphosphatasia and Mental Retardation syndrome and expanding the known phenotype of this condition. In a family with early-onset cardiomyopathy, a mutation in PPA2 was identified, encoding a mitochondria-specific pyrophosphatase enzyme. Through collaboration this gene was identified to be causative in three further families and
mutation pathogenicity was investigated by functional studies.
In a further family, a missense mutation in DNAAF1 was associated with heterotaxy, in the absence of clinical features of Primary Ciliary Dyskinesia, the phenotype usually associated with this gene. Zebrafish studies supported the pathogenicity of this variant and functional experiments identified novel interactants of DNAAF1 to include Pontin, Reptin and IFT88. Pontin was found to be expressed on the left side of the embryonic node in mice and zebrafish, a pattern which was abolished in dnaaf1-/- mutant fish,
suggesting DNAAF1 and Pontin to be involved in the development of early laterality. In two families with athelia, choanal atresia and CHD a candidate variant in KMT2D was identified. The phenotype was distinct from Kabuki syndrome and is likely to represent a novel KMT2D-related disorder.
WES was a successful tool in gene identification in CHD and, coupled with functional studies, has provided novel insights into the pathogenesis of CHD.
