Interspecies and intraspecies variations in the serotonin transporter gene intron 3 VNTR in nonhuman primates

A variable number of tandem repeat (VNTR) polymorphism based on a 16 or 17-bp unit has been reported in the third intron of the human serotonin transporter gene (5-HTT). VNTRs have been shown to affect the transcriptional activity of genes, and VNTR polymorphisms possibly influence human personality and several psychoneurological disorders. To estimate the changes that occurred in the VNTRs during primate evolution, we amplified and sequenced the regions that corresponded to the human VNTRs in various primate species, including apes, Old World monkeys, and New World monkeys. The VNTR sequences were polymorphic in all the ape species examined, and alleles with repeat numbers of 18, 19, 23, and 24 in chimpanzees, 33, 35, 36, 38, and 40 in gorillas, 4 and 6 in orangutans, and 11, 13, 14, and 15 in gibbons were found. On the other hand, only a 5-repeat allele was detected in Old World monkeys such as the Japanese macaque and patas monkey. In this study we demonstrated for the first time that a repeat structure was not present in the corresponding regions in the New World monkeys examined, and only one unit sequence was found in them. These results suggested that the duplication of a unit in the VNTR region occurred in the Cercopithecidae species following the divergence of the Old World and New World monkeys, and various long repeated alleles were generated in humans and apes, except orangutans.