title: MHC gene copy number variation in Tasmanian devils: implications for the spread of a contagious cancer.
abstract: Tasmanian devils face extinction owing to the emergence of a contagious cancer. Devil facial tumour disease (DFTD) is a clonal cancer spread owing to a lack of major histocompatibility complex (MHC) barriers in Tasmanian devil populations. We present a comprehensive screen of MHC diversity in devils and identify 25 MHC types and 53 novel sequences, but conclude that overall levels of MHC diversity at the sequence level are low. The majority of MHC Class I variation can be explained by allelic copy number variation with two to seven sequence variants identified per individual. MHC sequences are divided into two distinct groups based on sequence similarity. DFTD cells and most devils have sequences from both groups. Twenty per cent of individuals have a restricted MHC repertoire and contain only group I or only group II sequences. Counterintuitively, we postulate that the immune system of individuals with a restricted MHC repertoire may recognize foreign MHC antigens on the surface of the DFTD cell. The implication of these results for management of DFTD and this endangered species are discussed.
authors.affiliation: Faculty of Veterinary Science, University of Sydney, New South Wales, Australia.
authors.forename: Hannah V
authors.initials: HV
authors.lastname: Siddle
authors.forename: Jolanta
authors.initials: J
authors.lastname: Marzec
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Menna
authors.initials: M
authors.lastname: Jones
authors.forename: Katherine
authors.initials: K
authors.lastname: Belov
mesh_terms: D000820:Animal Diseases / Q000235:genetics / Q000276:immunology / Q000635:transmission*; D000818:Animals; D001733:Bites and Stings; D056727:Endangered Species; D005153:Facial Neoplasms / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D018628:Gene Dosage / Q000235:genetics*; D014644:Genetic Variation; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D008285:Major Histocompatibility Complex / Q000235:genetics*; D008394:Marsupialia / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II