A premature ovarian insufficiency-associated LMD-3 point mutation impairs protein stability and causes autophagic-lysosomal dysfunction in Caenorhabditis elegans

Reproductive longevity decline characterizes both natural aging and premature ovarian insufficiency (POI). While our previous work established C. elegans LMD-3 as a critical regulator of reproductive capacity, the in vivo consequences of specific clinical mutations remain unclear. Here, we modeled the POI-associated human NCOA7 W804C mutation by engineering the orthologous W690C substitution into the C. elegans lmd-3 locus. We demonstrate that this single-nucleotide substitution severely compromises LMD-3 protein stability and reduces transcript levels. This mutational destabilization is associated with profound systemic autophagic-lysosomal dysfunction, which impairs macromolecular degradation and leads to widespread proteotoxic accumulation of misfolded proteins. Coincident with these organismal defects, mutant animals exhibit an early-onset collapse in reproductive capacity driven by elevated germline apoptosis. Crucially, this pathology is consistent with reduced vitamin B12 availability; mecobalamin supplementation can mitigate the lysosomal block, restoring autophagic flux, proteostasis, and fecundity. These findings elucidate how a clinical mutation drives systemic lysosomal failure and reproductive decline, suggesting vitamin B12 supplementation as a promising metabolic intervention worth further translational exploration.