Retrospective analysis of a clinical exome sequencing cohort reveals the mutational spectrum and identifies candidate disease–associated loci for BAFopathies

PURPOSE: The BRG1/BRM-associated factor (BAF) complex is a chromatin remodeling complex playing a critical role in gene regulation. Defects in the genes encoding the BAF subunits lead to BAFopathies, a group of neurodevelopmental disorders with extensive locus and phenotypic heterogeneity. METHODS: We retrospectively analyzed data from 16,243 patients referred for clinical exome sequencing (ES) with a focus on the BAF complex. We applied a genotype-first approach combining predicted genic constraints to propose candidate BAFopathy genes. RESULTS: We identified 127 patients carrying pathogenic, likely pathogenic variants or de novo variants of unknown clinical significance (VUS) in 11 known BAFopathy genes. Those include 34 patients molecularly diagnosed through ES reanalysis with new gene-disease evidence (N= 21) or variant re-classifications in known BAFopathy genes (N=13). We also identified de novo or predicted loss-of-function variants in four candidate BAFopathy genes, ACTL6A, BICRA (implicated in BAFopathy during this study), PBRM1, and SMARCC1. CONCLUSION: We report the mutational spectrum of BAFopathies in an ES cohort. A genotype-driven and a pathway-based reanalysis of ES data identified new evidence for candidate genes for BAFopathies. Further mechanistic and phenotypic characterization of additional patients are warranted to confirm their roles in human disease and to delineate their associated phenotypic spectrums.