ALDH1A1 and Parkinson disease: Among the most under-expressed genes in PD patients DA neurons there are several genes that show a fold decrease from 3 to almost 5, including the known genes ALDH1A1 (chr9), encoding for a member of aldehyde dehydrogenase family, the cysteinyl-tRNA synthetase gene CARS (chr11), GLDN (chr15), encoding for gliomedin and BEX5 (Brain Expressed, X-Linked 5).