MHC screening for marsupial conservation: extremely low levels of class II diversity indicate population vulnerability for an endangered Australian marsupial

Abstract

Variation at genetic regions of functional significance is a new focus in conservation genetics. One of the prime candidates for such studies is the major histocompatibility complex (MHC). This gene region, with its critical role in immune response in vertebrates, is thought to have a significant impact on population fitness. The screening of diversity at MHC regions in non-model organisms presents a number of challenges that need to be overcome before its widespread incorporation into conservation programs. Here we present an approach and data for the screening of diversity at a class II MHC locus in wild and captive populations of the western barred bandicoot (Perameles bougainville). Primers developed to amplify the DAB gene in the tammar wallaby were modified to amplify the same gene in western barred bandicoots. Alleles were identified by cloning and sequencing of PCR products. Screening of all populations was carried out via high resolution melt analysis (HRM) and revealed just two sequence copies for this gene present in every individual from all populations. Alignment of translated amino acid sequences show that these variants contain many conserved elements indicative of functional MHC class II genes and suggest that they represent separate duplicated loci. Such a low level of MHC diversity is surprising for wild mammalian populations and exposes this species to increased vulnerability to novel disease pathogens.