Abstract
To examine the evolutionary diversities of the polymorphic repetitive region of the neurotransmitter-related genes, such as dopamine receptor D4 (DRD4), the serotonin transporter (5-HTT) and dopamine transporter (DAT1), we amplified and sequenced corresponding region in nonhuman primates.
Human DRD4 is polymorphic in repeat numbers of the 48-bp units located in the third cytoplasmic loop of the receptor. It has been indicated that individuals with long repeats (6 or more) display higher scores in a personality test for novelty seeking than those with shorter repeats. Four or more repeats have been reported in the DRD4 genes of simians. However, we found that most prosimians have 1 or 2 repeat unit(s). This indicates that 1) the ancestral primate may have had one 48-bp unit, 2) duplication occurred at the stage of prosimians, and 3) the repeat number increased after divergence into simian primates.
Tandem repeats consisting of 20-23 -bp units are located in the promoter region of human 5-HTT gene. It has been shown that individuals with 14 repeats in the promoter displayed higher scores in a personality test for anxiety/neuroticism than those with 16 repeats. Eight alleles including 15-23 repeats were observed in apes and polymorphism in repeat numbers was observed except chimpanzees. Allele including 14 repeats was observed only in humanand the frequency of allele with smaller number of repeats appears to increase during the process of hominization.
Tandem repeats consisting of 40-bp units are located in the 3' untranslated region of human DAT1 gene. Allele including 10 repeats is most common and the relationships between repeat numbers and personality (novelty seeking) or neuropsychiatry diseases have been reported. In this gene increase or decrease of the repeat number was not observed in the evolutionary context. Alleles including only 1 or 2 repeat unit(s) were observed in great apes, while DAT1 was highly polymorphic in gibbons with 8 alleles including 5-13 repeats. Tandem repeat structure of DAT1 gene was widely observed in simian primates.
