title: Characterisation of major histocompatibility complex class I genes at the fetal-maternal interface of marsupials.
abstract: Major histocompatibility complex class I molecules (MHC-I) are expressed at the cell surface and are responsible for the presentation of self and non-self antigen repertoires to the immune system. Eutherian mammals express both classical and non-classical MHC-I molecules in the placenta, the latter of which are thought to modulate the maternal immune response during pregnancy. Marsupials last shared a common ancestor with eutherian mammals such as humans and mice over 160 million years ago. Since, like eutherians, they have an intra-uterine development dependent on a placenta, albeit a short-lived and less invasive one, they provide an opportunity to investigate the evolution of MHC-I expression at the fetal-maternal interface. We have characterised MHC-I mRNA expression in reproductive tissues of the tammar wallaby (Macropus eugenii) from the time of placental attachment to day 25 of the 26.5 day pregnancy. Putative classical MHC-I genes were expressed in the choriovitelline placenta, fetus, and gravid endometrium throughout the whole of this period. The MHC-I classical sequences were phylogenetically most similar to the Maeu-UC (50/100 clones) and Maeu-UA genes (7/100 clones). Expression of three non-classical MHC-I genes (Maeu-UD, Maeu-UK and Maeu-UM) were also present in placental samples. The results suggest that expression of classical and non-classical MHC-I genes in extant marsupial and eutherian mammals may have been necessary for the evolution of the ancestral therian placenta and survival of the mammalian fetus at the maternal-fetal interface.
authors.affiliation: Department of Reproduction Management, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke Strasse 17, Berlin, Germany, ina.buentjen@gmail.com.
authors.forename: Ina
authors.initials: I
authors.lastname: Buentjen
authors.forename: Barbara
authors.initials: B
authors.lastname: Drews
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Frankenberg
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Hildebrandt
authors.forename: Marilyn B
authors.initials: MB
authors.lastname: Renfree
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Menzies
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019143:Evolution, Molecular; D005260:Female; D005805:Genes, MHC Class I / Q000235:genetics*; D015395:Histocompatibility Antigens Class I / Q000235:genetics* / Q000276:immunology*; D007614:Macropodidae / Q000235:genetics / Q000276:immunology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology; D010802:Phylogeny; D010920:Placenta / Q000276:immunology*; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis; D017422:Sequence Analysis, DNA
chemical_list: D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D012333:RNA, Messenger