title: Class I genes have split from the MHC in the tammar wallaby.
abstract: Genes within the Major Histocompatibility Complex (MHC) are critical to the immune response and immunoregulation. Comparative studies have revealed that the MHC has undergone many changes throughout evolution yet in tetrapods the three different classes of MHC genes have maintained linkage, suggesting that there may be some functional advantage obtained by maintaining this clustering of MHC genes. Here we present data showing that class II and III genes, the antigen processing gene TAP2, and MHC framework genes are found together in the tammar wallaby on chromosome 2. Surprisingly class I loci were not found on chromosome 2 but were mapped to ten different locations spread across six chromosomes. This distribution of class I loci in the wallaby on nearly all autosomes is not a characteristic of all marsupials and may be a relatively recent phenomenon. It highlights the need for the inclusion of more than one marsupial species in comparative studies and raises questions regarding the functional significance of the clustering of MHC genes.
authors.affiliation: ARC Centre for Kangaroo Genomics, Research School of Biological Sciences, The Australian National University, Canberra, Australia. Janine.Deakin@anu.edu.au
authors.forename: J E
authors.initials: JE
authors.lastname: Deakin
authors.forename: H V
authors.initials: HV
authors.lastname: Siddle
authors.forename: J G R
authors.initials: JG
authors.lastname: Cross
authors.forename: K
authors.initials: K
authors.lastname: Belov
authors.forename: J A M
authors.initials: JA
authors.lastname: Graves
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial; D033481:Chromosomes, Mammalian / Q000235:genetics; D002999:Clone Cells; D005805:Genes, MHC Class I / Q000235:genetics*; D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007614:Macropodidae / Q000235:genetics*; D008297:Male; D008677:Metaphase; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D015395:Histocompatibility Antigens Class I