ALDH1A1 (Aldehyde dehydrogenase family 1 member A1) is an aldehyde dehydrogenase. It is oxidizing a wide variety of aliphatic aldehydes (retinaldehyde, acetaldehyde, etc.) to the corresponding carboxylic acids (retinoic acid, acetic acid, etc.). ALDH1A1 is involved in retinoic acid (RA) synthesis during vertebrate embryogenesis. It is  known mesencephalic dopaminergic marker. Therefore it is studied in Parkinson's Disease (PD) since it is being expressed in the the A9 dopaminergic (DA) neuronal group projecting to the dorsal striatum; this is the most vulnerable site in PD. ALDH1A1 is expressed in the epithelium of many organs, including brain, liver, testis, eye lens and cornea. The retinoic acid produced by ALDH1A1 is also important for the differentiation of hematopoietic stem cells.