Comparative analysis of monoamine oxidase intronic polymorphisms in primates

Monoamine oxidases (MAOs) are involved in the degradation of various biogenic amines such as dopamine and serotonin. Two isozymic genes, MAOA and MAOB, have been identified, both of which are located on the X chromosome. In humans, intron 2 of both MAOs contains dinucleotide repeats, MAin2 and MBin2, that have been suggested as candidate genes for mood disorders and Parkinson’s disease. In this study, we surveyed the corresponding regions in nonhuman primates. The MAin2 and MBin2 regions were amplified in a total of 37 species from all primate lineages, including samples from 6 simian and 7 prosimian species. MAin2 and MBin2 were successfully amplified for all the simian species but failed to amplify in the prosimians. A series of alleles of MAin2 and MBin2 ranging from 222 bp to 254 bp and from 224 bp to 284 bp, respectively, were identified. Chimpanzees, gorillas, orangutans, and gibbons were polymorphic for both MAin2 and MBin2. Common marmosets and tamarins were polymorphic for MAin2 only. In the genus Macaca, MBin2 was polymorphic in 15 of the 18 species examined and 2–11 alleles were observed. Conversely, MAin2 was not diverse, exhibiting only 1–2 alleles. Since the MAin2 and MBin2 regions are associated with mental disorders, they might serve as useful markers for surveying the association with behavioral traits in the abovementioned primate species.