Evolution of class I major histocompatibility complex genes and molecules in humans and apes

Six different ape MHC-G DNA sequences and HLA-G∗IV; one in chimpanzees: Patr-G∗I; and one in gorillas: Gogo-G∗1) 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-G∗I DNA sequence shows two nonsynonymous substitutions when compared with the human HLA-G∗01011 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-G∗I 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-G∗II and G∗0103 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.