Functional characterization of genetic variants associated with rare inherited renal disorders in the Sri Lankan population.

Rare inherited renal disorders (RIRD) are genetically heterogeneous conditions that contribute substantially to morbidity and mortality, particularly among pediatric and young adult populations. Although next-generation sequencing has improved diagnostic yield, functional interpretation of novel variants and variants of uncertain significance remains limited, especially in underrepresented populations such as Sri Lankans. This study aimed to functionally characterize genetic variants identified through whole-exome sequencing (WES) in Sri Lankan patients with clinically diagnosed RIRD. In RT-qPCR analysis, AVPR2 (Missense), DAAM2, OCRL, and CLCN5showed downregulation, while NPHS2 and COL4A5 showed upregulation in patient samples. Notably, DAAM2 expression was strongly downregulated, indicating potential functional relevance of its associated VUS. In silico protein modeling predicted significant structural disruption in several truncating variants, including COL4A5, OCRL, and AVPR2(frameshift), suggesting loss of functional domains or premature termination of protein synthesis. A missense variant in AVPR2 was predicted to affect the transmembrane region. RT-qPCR analysis supported the findings of protein modeling, demonstrating absent or reduced gene expression consistent with the protein modeling. Integrating protein modeling with gene expression analysis provides valuable functional insights into rare inherited renal disease-associated variants. This study supports the potential reclassification of selected variants and contributes to population-specific functional data, improving genetic interpretation and diagnostic precision for RIRD in Sri Lanka.