Evolution of ABO and Rh blood group genes in primates
Naruya Saitou, Laboratory of Evolutionary Genetics, National Institute of Genetics,
Mishima, Japan
We have been studying evolution of the ABO blood group gene of
primates. We recently determined intron 6 sequences for 10 alleles of common chimpanzee
and for 3 alleles of bonobo to estimate nucleotide diversities among them. Sequence length
polymorphisms are observed in this region due to differences of repeat numbers from 1 to
5. From a phylogenetic network of intron 6 sequences of ABO blood group genes for human,
common chimpanzee, and bonobo, effects of parallel substitutions and/or some kinds of
convergent events are predicted in the chimpanzee lineage. We also estimated nucleotide
diversities for common chimpanzee and bonobo ABO blood group genes, and these values were
0.219 and 0.208, respectively. This study is in press in Kitano and others (1999). We also
studied the Rh blood group gene. There are two tightly linked loci (D and CE) for the
human Rh blood group. Their gene products are membrane proteins having 12 trans-membrane
domains and form a complex with 50 kD glycoprotein on erythrocytes. We constructed
phylogenetic networks of human and nonhuman primate Rh genes, and they seemed to have
experienced gene conversions. We therefore used the site by site reconstruction method and
found seven converted regions. After eliminating the effect of gene conversion, we
reconstructed the phylogenetic tree for primate Rh blood group genes, and estimated rates
of nonsynonymous and synonymous substitutions for each branch of the tree. Many branches
showed higher rates of nonsynonymous substitutions than synonymous ones, and this suggests
that the Rh genes have experienced some kind of positive selection, probably through
interactions with other organisms. This study is in press in Kitano and Saitou (1999).
However, we did not find such evidence in rodent Rh genes (Kitano and others, 1998).
Kitano T., Sumiyama K., Noda R., Ferrell R., and Saitou N. (1999) Gene diversity of
chimpanzee ABO blood group genes elucidated from intron 6 sequences. Journal of Heredity
(in press).
Kitano T. and Saitou N. (1999) Evolution of Rh blood group genes has experienced gene
conversions and positive selection. Journal of Molecular Evolution (in press).
Kitano T., Sumiyama T., Shiroishi T., and Saitou N. (1998) Conserved evolution of the Rh50
gene compared to its homologous Rh blood group gene. Biochemical and Biophysical Research
Communications, vol. 249, No. 1, pp. 78