title: Evolution of the opossum major histocompatibility complex: evidence for diverse alternative splice patterns and low polymorphism among class I genes.
abstract: The opossum major histocompatibility complex (MHC) shares a similar organization with that of non-mammals while containing a diverse set of class I genes more like that of eutherian (placental) mammals. There are 11 class I loci in the opossum MHC region, seven of which are known to be transcribed. The previously described Monodelphis domestica (Modo)-UA1 and Modo-UG display characteristics consistent with their being classical and non-classical class I genes, respectively. Here we describe the characteristics of the remaining five transcribed class I loci (Modo-UE, -UK, -UI, -UJ and -UM). All five genes have peptide-binding grooves with low or no polymorphism, contain unpaired cysteines with the potential to produce homodimer formation and display genomic organizational features that would be unusual for classical class I loci. In addition, Modo-UJ and -UM were expressed in alternatively spliced mRNA forms, including a potentially soluble isoform of Modo-UJ. Thus, the MHC region of the opossum contains a single class I gene that is clearly classical and six other class I genes each with its own unique characteristics that probably perform roles other than or in addition to antigen presentation.
authors.affiliation: Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, NM, USA. mlbaker@unm.edu
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Baker
authors.forename: Sandra D
authors.initials: SD
authors.lastname: Melman
authors.forename: James
authors.initials: J
authors.lastname: Huntley
authors.forename: Robert D
authors.initials: RD
authors.lastname: Miller
mesh_terms: D000483:Alleles; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D048309:Monodelphis / Q000235:genetics / Q000276:immunology*; D011110:Polymorphism, Genetic; D016415:Sequence Alignment
chemical_list: D015395:Histocompatibility Antigens Class I