title: Patterns of MHC-G-Like and MHC-B Diversification in New World Monkeys.
abstract: The MHC class I (MHC-I) region in New World monkeys (Platyrrhini) has remained relatively understudied. To evaluate the diversification patterns and transcription behavior of MHC-I in Platyrrhini, we first analyzed public genomic sequences from the MHC-G-like subregion in Saimiri boliviensis, Ateles geoffroyi and Callicebus moloch, and from the MHC-B subregion in Saimiri boliviensis. While S. boliviensis showed multiple copies of both MHC-G-like (10) and -B (15) loci, A. geoffroyi and C. moloch had only three and four MHC-G-like genes, respectively, indicating that not all Platyrrhini species have expanded their MHC-I loci. We then sequenced MHC-G-like and -B cDNAs from nine Platyrrhini species, recovering two to five unique cDNAs per individual for both loci classes. In two Saguinus species, however, no MHC-B cDNAs were found. In phylogenetic trees, MHC-G-like cDNAs formed genus-specific clusters whereas the MHC-B cDNAs grouped by Platyrrhini families, suggesting a more rapid diversification of the former. Furthermore, cDNA sequencing in 12 capuchin monkeys showed that they transcribe at least four MHC-G-like and five MHC-B polymorphic genes, showing haplotypic diversity for gene copy number and signatures of positive natural selection at the peptide binding region. Finally, a quantitative index for MHC:KIR affinity was proposed and tested to predict putative interacting pairs. Altogether, our data indicate that i) MHC-I genes has expanded differentially among Platyrrhini species, ii) Callitrichinae (tamarins and marmosets) MHC-B loci have limited or tissue-specific expression, iii) MHC-G-like genes have diversified more rapidly than MHC-B genes, and iv) the MHC-I diversity is generated mainly by genetic polymorphism and gene copy number variation, likely promoted by natural selection for ligand binding.
authors.affiliation: Department of Biology and Institute of Genetics, Universidad Nacional de Colombia, Bogotá, Colombia.
authors.forename: Juan S
authors.initials: JS
authors.lastname: Lugo
authors.affiliation: Department of Biology and Institute of Genetics, Universidad Nacional de Colombia, Bogotá, Colombia.
authors.forename: Luis F
authors.initials: LF
authors.lastname: Cadavid
mesh_terms: D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D005805:Genes, MHC Class I; D056426:Genetic Loci; D014644:Genetic Variation; D016678:Genome; D006860:Hydrogen Bonding; D007438:Introns / Q000235:genetics; D010802:Phylogeny; D051078:Platyrrhini / Q000235:genetics*; D011110:Polymorphism, Genetic; D011544:Pseudogenes / Q000235:genetics; D012641:Selection, Genetic; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary