ALDH1A2 is a NAD-dependent aldehyde dehydrogenase that catalyzes oxidation of retinal substrates to retinoic acid (RA), a critical signaling molecule 1. This enzyme is essential for initiating meiosis and controlling transcriptional regulation of developmental genes 2. ALDH1A2 functions primarily in the cytosol and demonstrates substrate specificity, efficiently metabolizing retinal and medium-chain aldehydes while showing minimal activity with other aldehyde substrates 3. Mechanistically, ALDH1A2-mediated RA biosynthesis operates through cooperative pathways. In intestinal epithelial cells, cometabolism with bacterial ALDH1A2 generates elevated RA levels that suppress Th17-mediated colitis via RAR-α signaling 4. In kidney glomerular parietal epithelial cells, ALDH1A2 expression is selectively enriched and dysregulated in various kidney pathologies, suggesting roles in both normal physiology and disease 5. Clinically, ALDH1A2 variants associate with multiple conditions. Common variants (rs7169289) increase newborn kidney volume and umbilical cord RA levels, potentially protective against vitamin A deficiency 6. Hand osteoarthritis associates with ALDH1A2 variants at 15q22 (OR=1.46, P=1.1×10⁻¹¹) 7. ALDH1A2 upregulation appears therapeutically relevant in amyotrophic lateral sclerosis, where apigenin-mediated ALDH1A2 elevation reduces oxidative stress and apoptosis 8. Additionally, ALDH1A2 promoter methylation silencing occurs in bladder cancer, with therapeutic potential through demethylation strategies inducing apoptosis 9.