The UT family of MHC class I loci unique to non-eutherian mammals has limited polymorphism and tissue specific patterns of expression in the opossum.
The Major Histocompatibility Complex (MHC) class I family of genes encode for molecules that have well-conserved structures, but have evolved to perform diverse functions. The availability of the gray, short-tailed opossum, Monodelphis domestica whole genome sequence has allowed for analysis of MHC class I gene content in this marsupial. Utilization of a novel method to search for MHC related domain structures revealed a previously unknown family of MHC class I-related genes. These genes, named UT1-17, are clustered on chromosome 1 in the opossum, unlinked to the MHC region. UT genes are only found in marsupial and monotreme genomes, consistent with being ancient in mammals yet lost in eutherian mammals. This study investigates the expression and polymorphism of the UT loci in the opossum to gain insight into their possible function.



Of the 17 opossum UT genes, most have restricted tissue transcription patterns, with the thymus and skin being the most common sites. Full-length structure of 11 UT transcripts revealed genes varying between five and eight exons, typical for class I family members. There were only two alternative splice variants found. The UT genes also have limited polymorphism and little evidence of positive selection. One locus, UT8, was chosen for further analysis due to its conservation amongst marsupials and generic characteristics. UT8 transcription is limited to developing αβ thymocytes, and is absent from mature αβ T cells in peripheral lymphoid tissues.



The overall characteristics and features of UT genes including low polymorphism and restricted tissue expression make it likely that the molecules encoded by UT genes perform roles other than antigenic peptide presentation.
Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM, 87131, USA.
Katina V
KV
Krasnec
Bioinformatics Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Pde, Parkville, 3052, Australia.|Department of Medical Biology, University of Melbourne, Melbourne, Australia.|Peter MacCallum Cancer Centre, East Melbourne, 3002, Australia.|Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Australia.
Anthony T
AT
Papenfuss
Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM, 87131, USA. rdmiller@unm.edu.
Robert D
RD
Miller
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D016000:Cluster Analysis; D005786:Gene Expression Regulation; D053263:Gene Regulatory Networks; D005805:Genes, MHC Class I / Q000235:genetics*; D016678:Genome; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008394:Marsupialia / Q000276:immunology; D008969:Molecular Sequence Data; D009893:Opossums / Q000235:genetics / Q000276:immunology*; D009928:Organ Specificity; D010802:Phylogeny; D011110:Polymorphism, Genetic; D051381:Rats
D015395:Histocompatibility Antigens Class I
Class I; Genomics; MHC; Marsupials