POSTER NO: 565

AIM1 polymorphism among human populations with diverged skin color

¹Kazuhiro Nakayama, ²Shoji Fukamachi, ³Hiroshi Kimura, ³Yoshiro Koda, ⁴Augustinus Soemantri, ¹Takafumi Ishida
¹Department of Biological Science, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo, Japan, ²Graduate School of Frontier Science, University of Tokyo, Chiba, Japan, ³Department of Forensic Medicine, Kurume University School of Medicine, Fukuoka, Japan, ⁴Department of Child Health, Faculty of Medicine, Diponegoro University, Semarang, Indonesia

The genetic background for human skin color has been a major topic in human genetics. Many genes associated with the skin pigment system have been identified; however, there are no reports about the genes accountable for inter-population skin color diversity. The gene for AIM-1 protein (AIM1) was recently found to be responsible for the body color of medaka fish, the coat color of mouse and the human oculocutaneous albinism type 4. In the search for genes controlling human skin color variations, we have investigated genetic polymorphisms of AIM1 among representatives of major human populations with varying degrees of skin pigmentation including white South Africans (n = 54), Ghanaians (n = 50), Japanese (n = 49) and New Guinea Islanders (n = 52). From the evolutionary point of view, AIM1 of a chimpanzee (Pan troglodytes), a bonobo (Pan paniscus), a gorilla (Gorilla gorilla), an orangutan (Pongo pygmaeus) and a Japanese macaque (Macaca fuscata) were also studied. We found two nonsynonymous single nucleotide polymorphisms in the initial PCR-direct sequencing study. These two nucleotide polymorphisms were screened against the subjected populations by using PCR-RFLP method and allele specific PCR method. One of the nucleotide polymorphisms causing the Glu272Lys showed variable frequencies in Japanese and New Guinea Islanders, whereas monomorphism of the Glu allele in other populations. Another nucleotide polymorphism causing Leu374Phe, which showed a distinctive population distribution, existed exclusively in white South Africans but not in the other populations. Comparison with AIM1 sequence of other primate species, mouse and medaka fish showed that the Leu allele was a human prototype allele. High conservation of leucine residue at the position throughout all species indicates that the presence of the leucine residue may be critical for the function of AIM-1. These results indicate that the loss of leucine in amino acid position 374 of AIM-1 may play a role in hypopigmentation in the Caucasian population.