Class II multiformity generated by variable MHC-DRB region configurations in the California sea lion (Zalophus californianus)

Abstract

In light of the immunological importance of molecules encoded within the major histocompatibility complex ( MHC), there are numerous studies examining the variability of these genes in wildlife populations. An underlying assumption in many of these studies is that MHC diversity invariably arises from a high level of allelic variation at a single gene locus, leading to widespread descriptions of thriving species with apparently limited MHC polymorphism. Indeed, in a previous study we failed to find sequence features compatible with traditionally diverse peptide-binding functions in MHC class II ( DQA and DQB) genes in California sea lions and therefore expanded the search for polymorphism to the DRA and DRB genes. Our results show that, in contrast to Zaca-DQA, -DQB, and - DRA, Zaca-DRB has sequence features compatible with antigen binding and presentation. In fact Zaca-DRB constitutes a gene family, comprising at least seven loci, each of which exhibits limited variability, and which are present in variable configurations between individuals. This unusual mechanism for generating MHC DRB diversity is similar to that observed in the rhesus macaque, but has not been reported in any other species. The identification of a novel system of class II MHC variability in the California sea lion justifies new studies into the organizational basis of immunogenetic diversity in other marine species, and its role in infectious disease susceptibility.

Common cancer in a wild animal: the California sea lion ( Zalophus californianus ) as an emerging model for carcinogenesis

“…In the CSL, the presence of a specific MHC class II locus (Zaca-DRB.A) was associated with the presence of UGC [31]. The DRB family of genes in the CSL consists of eight loci designated Zaca-DRB.A to Zaca-DRB.H [31,32] and varying combinations of these have been identified. However, the presence of the Zaca-DRB.A locus in any combination was significantly associated with the presence of UGC [31].…”

Short Communication Sequence variation and gene duplication at the MHC DRB loci of the spotted seal Phoca largha

“…In MHC class II genes, the DRB regions exhibit the most elaborate polymorphisms, and these have been extensively characterized in marine mammals, due to their importance in immunological research (Bowen et al, 2004;Osborne et al, 2013). In this study, we examined the loci within the DRB region, with emphasis on the second exon of DRB.…”

Differential Expression of Immune Response Genes in Steller Sea Lions (Eumetopias jubatus): An Indicator of Ecosystem Health?

“…A primer pair recognizing the flanking regions of the putative peptide-binding site (based upon sequence data from the closely-related California sea lion (CSL; Zalophus californianus) DRBURN and DRBlociR) was used to amplify SSL (Euju)-DRB exon 2 and the preceding intron (Table 1). PCR amplifications using these class II primers were performed on 20 ng of each SSL DNA using protocols described in Bowen et al (2004). The PCR was performed on an MJ Research PTC-200 thermal cycler (MJ Research, Watertown, MA) and consisted of five cycles at 94°C for 30 seconds, 30 cycles at 60°C for 30 seconds, and 72°C for 2 minutes, ending with an extension step of 72°C for 10 minutes.…”

“…Caudal gluteal venous blood samples were collected into the anticoagulant, ethylenediaminetetraacetic acid (EDTA Vacutainer Ò CPTä; Becton Dickinson, Franklin, NJ) for isolation of peripheral blood leukocytes (PBLs) (Bowen et al, 2004). Extraction of DNA and RNA from PBLs was performed according to methods in Bowen et al (2004Bowen et al ( , 2005.…”

“…Caudal gluteal venous blood samples were collected into the anticoagulant, ethylenediaminetetraacetic acid (EDTA Vacutainer Ò CPTä; Becton Dickinson, Franklin, NJ) for isolation of peripheral blood leukocytes (PBLs) (Bowen et al, 2004). Extraction of DNA and RNA from PBLs was performed according to methods in Bowen et al (2004Bowen et al ( , 2005. A primer pair recognizing the flanking regions of the putative peptide-binding site (based upon sequence data from the closely-related California sea lion (CSL; Zalophus californianus) DRBURN and DRBlociR) was used to amplify SSL (Euju)-DRB exon 2 and the preceding intron (Table 1).…”