Cross-Species Conservation and Function of ALDH6A1/Aldh6a1 Validate Zebrafish and Mouse as Complementary Experimental Systems for Methylmalonate Semialdehyde Dehydrogenase Deficiency

Methylmalonate semialdehyde dehydrogenase deficiency (MMSDD; OMIM #614265) is an ultra-rare autosomal recessive metabolic disorder caused by mutations in the ALDH6A1 gene, characterized by multi-system involvement including skeletal abnormalities, hypotonia, and visual impairment. To elucidate its pathogenic mechanisms, we characterized ALDH6A1/Aldh6a1 conservation and function using complementary zebrafish and mouse experimental systems. Bioinformatic and phylogenetic analyses revealed strong conservation of Aldh6a1/aldh6a1 gene structure, protein sequence, functional domains, and mitochondrial targeting across vertebrates. Spatiotemporal profiling also demonstrated dynamic embryonic expression in zebrafish neural tube, somites, liver, and intestine, as well as in metabolically active and developmentally relevant tissues of mice, with patterns that correspond to known MMSDD lesion sites in humans. Functional disruption of Aldh6a1 in zebrafish induced dose-dependent developmental defects, including spinal curvature, tail coiling, pericardial edema, and reduced survival, which were partially rescued by exogenous mRNA, confirming phenotype specificity effects. These findings support a role for ALDH6A1 in mitochondrial metabolism during neurogenesis, myogenesis, and organogenesis. Collectively, this cross-species framework highlights ALDH6A1/Aldh6a1 as essential for vertebrate development, provides mechanistic insight into the multi-system heterogeneity of MMSDD, and establishes a scalable platform for therapeutic discovery and precision intervention.