Evolution of New World Primate MHC Class I Genes

Abstract

We cloned, sequenced and transfected the MHC class I genes from three other species of bone-chimeric primates (the saddle-backed tamarin, S. fuscicollis; the common marmoset, Callithrix jacehus; and the golden-headed lion tamarin, Leontopithecus rosalia) and a single species of a non-bone marrow-chimeric New World primate (the owl monkey, Aotus trivirqatus). The MHC class I genes of the bone marrow-chimeric species all displayed low levels of MHC class I variation; the MHC class I genes of the non-bone marrow-chimeric A.trivirqatus were highly variable. This finding suggests that bone marrow-chimerism may indeed be related to a reduction in MHC class I variation in New World primates. To investigate the relatedness of these New World primate MHC class I genes, gene trees were constructed. All of the New World primate classical MHC class I genes, including those of A.trivirqatus, were related to the human non-clasical HLA-G gene. The S.fuscicollis MHC class I genes were indistinguishable from those of S.oedipus. Surprisingly, the MHC class I genes of C.jacchus were only distantly related to the MHC class I genes of S.oedipus and S.fuscicollis. Interestingly, the functional MHC class I genes of C.jacchus were closely related to two pseudo genes of S.oedipus. These data suggest that MHC class I evolution in New World primates may take place by duplication and subsequent inactivation or expansion of certain genes.