Characterisation of MHC Class I Genes in the Koala

Immunogenetics. 2018 Feb;70(2):125-133. doi: 10.1007/s00251-017-1018-2. Epub 2017 Jul 1.

Abstract

Koala (Phascolarctos cinereus) populations are on the decline across the majority of Australia's mainland. Two major diseases threatening the long-term survival of affected koala populations are caused by obligate intracellular pathogens: Chlamydia and koala retrovirus (KoRV). To improve our understanding of the koala immune system, we characterised their major histocompatibility complex (MHC) class I genes, which are centrally involved in presenting foreign peptides derived from intracellular pathogens to cytotoxic T cells. A total of 11 class I genes were identified in the koala genome. Three genes, Phci-UA, UB and UC, showed relatively high genetic variability and were expressed in all 12 examined tissues, whereas the other eight genes had tissue-specific expression and limited polymorphism. Evidence of diversifying selection was detected in Phci-UA and UC, while gene conversion may have played a role in creating new alleles at Phci-UB. We propose that Phci-UA, UB and UC are likely classical MHC genes of koalas, and further research is needed to understand their role in koala chlamydial and KoRV infections.

Keywords: Class I; Koala; MHC; Marsupial.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Australia
  • Genes, MHC Class I*
  • Genetic Variation
  • Genome
  • Phascolarctidae / genetics*
  • Transcriptome