Single-cell transcriptomics trajectory and molecular convergence of clinically relevant mutations in Brugada syndrome

Brugada syndrome (BrS) is a rare, inherited arrhythmia with high risk of sudden cardiac death. To evaluate the molecular convergence of clinically relevant mutations and to identify developmental cardiac cell types that are associated with BrS etiology, we collected 733 mutations represented by 16 sodium, calcium, potassium channels, and regulatory and structural genes related to BrS. Among the clinically relevant mutations, 266 are unique singletons and 88 mutations are recurrent. We observed an overrepresentation of clinically relevant mutations (similar to 80%) in SCN5A gene and also identified several candidate genes, including GPD1L, TRPM4, and SCN10A. Furthermore, protein domain enrichment analysis revealed that a large proportion of the mutations impacted ion transport domains in multiple genes, including SCN5A, TRPM4, and SCN10A. A comparative protein domain analysis of SCN5A further established a significant (P = 0.04) enrichment of clinically relevant mutations within ion transport domain, including a significant (P = 0.02) mutation hotspot within 1321-1380 residue. The enrichment of clinically relevant mutations within SCN5A ion transport domain is stronger (P = 0.00003) among early onset of BrS. Our spatiotemporal cellular heart developmental (prenatal to adult) trajectory analysis applying single-cell transcriptome identified the most frequently BrS-mutated genes (SCN5A and GPD1L) are significantly upregulated in the prenatal cardiomyocytes. A more restrictive cellular expression trajectory is prominent in the adult heart ventricular cardiomyocytes compared to prenatal. Our study suggests that genomic and proteomic hotspots in BrS converge into ion transport pathway and cardiomyocyte as a major BrS-associated cell type that provides insight into the complex genetic etiology of BrS. NEW & NOTEWORTHY Brugada syndrome is a rare inherited arrhythmia with high risk of sudden cardiac death. We present the findings for a molecular convergence of clinically relevant mutations and identification of a single-cell transcriptome-derived cardiac cell types that are associated with the etiology of BrS. Our study suggests that genomic and proteomic hotspots in BrS converge into ion transport pathway and cardiomyocyte as a major BrS-associated cell type that provides insight into the complex genetic etiology of BrS.