Identification of novel pathogenic mutations in ATP6V0A4 associated with distal renal tubular acidosis and analysis of wild-type expression in glomerular disease.

Distal renal tubular acidosis (dRTA) is a rare renal disorder caused by genetic mutations or secondary factors. If untreated, it can result in a significant electrolyte imbalance and progressive chronic kidney disease (CKD). This study investigated the key genes involved in renal tubular acid-base regulation (SLC4A1, ATP6V1B1 and ATP6V0A4) through whole exome sequencing (WES) in a clinical cohort. Notably, patients with ATP6V0A4 mutations were diagnosed at a younger age (mean 0.5 years) and exhibited more severe renal impairment, including reduced estimated glomerular filtration rate (eGFR), indicating heightened susceptibility to kidney damage. We identified novel ATP6V0A4 mutations (c.2219C > T, c.197-1G > C, and c.2293_c.2296del AGCG) and confirmed their pathogenicity using bioinformatics and in vitro experiments. We demonstrated that the c.197-1G > C mutation disrupted mRNA splicing, causing exon 5 skipping and introducing a premature termination codon, c.2293_c.2296del AGCG introduced a premature termination codon, while c.2219C > T impaired protein expression, intracellular pH regulation, and ATPase activity. Additionally, ATP6V0A4 expression decreases during diabetes progression, contributing to tubular dysfunction and the development of diabetic kidney disease (DKD). These findings underscore the crucial role of ATP6V0A4 in maintaining renal acid-base balance, its influence on CKD progression, and the importance of genetic analysis for the early diagnosis and personalized management of dRTA.