MGI:96090Pineal melatonin synthesis requires enzymes encoded by Asmt and Aanat. C57BL/6, BALB/c, AKR/J, NZB/Bl, IS/Cam, and CAST/Ei carry the a allele of Asmt and lack melatonin. SK/Cam, SF/Cam, PERU, and FDS carry the b allele and have normal melatonin levels.