CHROMOSOMAL MAPPING OF THE GENE ENCODING SEROTONIN N-ACETYLTRANSFERASE TO RAT-CHROMOSOME 10Q32.3 AND MOUSE-CHROMOSOME 11E2

Pineal melatonin is produced during the night. Its nocturnal increase regulates circadian rhythms and the photoperiodic reproductive respons e. Serotonin is acetylated to N-acetylserotonin by serotonin N-acetylt ransferase (SNAT) and then methylated to form melatonin by hydroxyindo le-O-methyltransferase (HIOMT). The rhythmicity of melatonin synthesis is regulated by the rhythmic activity of SNAT. Most laboratory mice d o not have melatonin because of a genetic defect in the activity of SN AT and/or HIOMT. In a previous study using a recombinant inbred strain , we have found that the locus controlling pineal SNAT activity (Nat4) is located on mouse Chromosome 11. Recently, SNAT has been cloned in the rat. In the present study, the gene encoding SNAT was localized, u sing a rat cDNA fragment, on rat and mouse chromosomes by direct R-ban ding fluorescence in situ hybridization (FISH). In addition, using mol ecular linkage analysis with interspecific backcross mice, a gene enco ding SNAT was mapped on a mouse chromosome. The gene encoding SNAT was localized to rat chromosome 10q32.3 and mouse Chromosome 11E2 by FISH . The molecular linkage analysis demonstrated that the gene encoding S NAT maps 1.5 cM distal to D11Mit11. The data suggest that Natl encodes SNAT. These chromosomal locations are in a region of conserved linkag e homology between the two species.