Synergistic toxicity of compound heterozygous mutations in the COL4A3 gene causes end-stage renal disease in A large family of Alport syndrome.

Abstract

Alport syndrome (AS) is a genetic disorder characterized by kidney disease and hearing/vision abnormalities, resulting from mutations in the COL4A3, COL4A4, or COL4A5 genes. While numerous mutations have been identified in AS cases, the precise molecular mechanisms, particularly for compound mutations, remain under investigation. This study investigated the molecular mechanisms of AS in a proband with end-stage kidney disease (ESKD) using whole exome sequencing, which identified two compound heterozygous COL4A3 missense mutations: NM_000091.5:c.1354G > A (p.G452R) and NM_000091.5:c.4793 T > G (p.L1598R). Sixteen family members of the proband were genotyped, and further analyses, including in silico structural prediction, molecular docking, and in vitro co-immunoprecipitation assays, revealed that the p.G452R mutation disrupted the collagen triple helical structure, associated with hematuria in carriers, while the p.L1598R mutation interfered with the interaction between the NC1 domains of COL4A3 and COL4A4 proteins, crucial for collagen trimerization. These findings demonstrate a synergistic loss-of-function effect of the two mutations, contributing to the AS pathogenesis in the proband, and emphasize the importance of genetic screening and personalized treatment strategies for AS.