Genomic rare variant mechanisms for congenital cardiac laterality defect: A digenic model approach.

Laterality defects are defined by perturbations in the usual left-right asymmetry of organs. The genetic etiology that underlies congenital heart disease (CHD) is often unknown (less than 40%), so we used a digenic model approach for the identification of contributing variants in known laterality-defect-associated genes (n = 115) in the exome/genome sequencing (ES/GS) data from individuals with clinically diagnosed laterality defects. The unsolved ES/GS data were analyzed from three CHD cohorts: Baylor College of Medicine-Genomics Research to Elucidate the Genetics of Rare Diseases (BCM-GREGoR; n= 251 proband ES), Gabriella Miller Kids First Pediatric Research Program (Kids First; n = 158 trio GS), and Pediatric Cardiac Genomics Consortium (PCGC; n = 163 trio ES). trans-heterozygous digenic variants were identified in 2.8% (inherited digenic variants in 0.4%), 8.2%, and 13.5% of individuals, respectively; this was significantly higher than in 602 control trios provided by the 1000 Genomes Project (p = 0.001, 1.4e-07, and 8.9e-13, respectively). trans-heterozygous digenic variants were also identified in 0.4% and 1.4% of individuals with non-laterality CHD in Kids First and PCGC datasets, respectively, which was not statistically significant as compared to control trios (p = 1 and 0.059, respectively). Altogether, in laterality cohorts, 23% of digenic pairs were in the same structural complex of motile cilia. Out of 39 unique digenic pairs in laterality CHD, 29 are more likely to be potential digenic hits as predicted by the DiGePred tool. These findings provide further evidence that digenic epistatic interactions can contribute to the complex genetics of laterality defects.