Abstract
BackgroundBats are an extremely successful group of mammals and possess a variety of unique characteristics, including their ability to co-exist with a diverse range of pathogens. The major histocompatibility complex (MHC) is the most gene dense and polymorphic region of the genome and MHC class II (MHC-II) molecules play a vital role in the presentation of antigens derived from extracellular pathogens and activation of the adaptive immune response. Characterisation of the MHC-II region of bats is crucial for understanding the evolution of the MHC and of the role of pathogens in shaping the immune system.ResultsHere we describe the relatively contracted MHC-II region of the Australian black flying-fox (Pteropus alecto), providing the first detailed insight into the MHC-II region of any species of bat. Twelve MHC-II genes, including one locus (DRB2) located outside the class II region, were identified on a single scaffold in the bat genome. The presence of a class II locus outside the MHC-II region is atypical and provides evidence for an ancient class II duplication block. Two non-classical loci, DO and DM and two classical, DQ and DR loci, were identified in P. alecto. A putative classical, DPB pseudogene was also identified. The bat’s antigen processing cluster, though contracted, remains highly conserved, thus supporting its importance in antigen presentation and disease resistance.ConclusionsThis detailed characterisation of the bat MHC-II region helps to fill a phylogenetic gap in the evolution of the mammalian class II region and is a stepping stone towards better understanding of the immune responses in bats to viral, bacterial, fungal and parasitic infections.
Highlights
Bats are an extremely successful group of mammals and possess a variety of unique characteristics, including their ability to co-exist with a diverse range of pathogens
To further build on this work and obtain deeper insights into the evolution of the major histocompatibility complex (MHC) region, we describe the organisation of the MHC class II (MHC-II) region of P. alecto, with the aid of its whole genome sequence [56]
Bat genome data and annotation The recently completed P. alecto genome was interrogated for MHC-II, AP and conserved class II flanking genes using the BLAST algorithm [57]
Summary
We describe the relatively contracted MHC-II region of the Australian black flying-fox (Pteropus alecto), providing the first detailed insight into the MHC-II region of any species of bat. Twelve MHC-II genes, including one locus (DRB2) located outside the class II region, were identified on a single scaffold in the bat genome. The presence of a class II locus outside the MHC-II region is atypical and provides evidence for an ancient class II duplication block. Two non-classical loci, DO and DM and two classical, DQ and DR loci, were identified in P. alecto. A putative classical, DPB pseudogene was identified. The bat’s antigen processing cluster, though contracted, remains highly conserved, supporting its importance in antigen presentation and disease resistance
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