New species-specific alleles at the primate MHC-G locus.

Six different ape MHC-G DNA sequences (four in humans: HLA-G01011, HLA-GII, HLA-G0103, and HLA-GIV; one in chimpanzees: Patr-GI; and one in gorillas: Gogo-G1) have been obtained. Only synonymous or conservative ("Thr"-to-"Ser") substitutions are allowed between the four human alleles. One allele of MHC-G exon-2 sequences has been found both in gorilla (Gorilla gorilla) and chimpanzee (Pan troglodytes). The Patr-GI DNA sequence shows two nonsynonymous substitutions when compared with the human HLA-G01011 sequence: "CGG"-to-"TGG" ("Arg"-to-"Trp") at codon 35 and "ATG"-to-"ATA" ("Met"-to-"Ile") at codon 76. One nonsynonymous "GAG"-to-"GGG" ("Glu"-to-"Gly") substitution is observed in the Gogo-GI exon-2 DNA sequence, when compared with the human 01011 allele. None of these three different substitutions have been observed in humans and are, thus, considered species specific. Also, evidence is provided that the human HLA-GII and G0103 may have been originated after human speciation. Finally, phylogenetic relationships among the six MHC-G alleles, tamarins G-"like" alleles, and other human class I genes (both "classical" and "nonclassic") are discussed.