Aldehyde dehydrogenase 6, a cytosolic retinaldehyde dehydrogenase prominently expressed in sensory neuroepithelia during development

We have isolated the chick and mouse homologs of human aldehyde dehydrogena se 6 (ALDH6) that encode a third cytosolic retinaldehyde-specific aldehyde dehydrogenase, In both chick and mouse embryos, strong expression is observ ed in the sensory neuroepithelia of the head. In situ hybridization analysi s in chick, shows compartmentalized expression primarily in the ventral ret ina, olfactory epithelium, and otic vesicle; additional sites of expression include the isthmus, Rathke's pouch, posterior spinal cord interneurons, a nd developing limbs. Recombinant chick ALDH6 has a K-0.5 = 0.26 muM, V-max = 48.4 nmol/min/mg and exhibits strong positive cooperativity (H = 1.9) tow ard all-trans-retinaldehyde; mouse ALDH6 has similar kinetic parameters. Ex pression constructs can confer 1000-fold increased sensitivity to retinoic acid receptor-dependent signaling from retinol in transient transfections e xperiments. The localization of ALDH6 to the developing sensory neuroepithe lia of the eye, nose, and ear and discreet sites within the CNS suggests a role for RA signaling during primary neurogenesis at these sites.