MHC class II variation in the endangered European mink Mustela lutreola (L. 1761)—consequences for species conservation

Abstract

The polymorphic major histocompatibility complex (MHC) has gained a specific relevance in pathogen resistance and mate choice. Particularly the antigen-binding site (ABS), encoded by exon 2 of the DRB class II gene, exhibits numerous alleles and extensive sequence variations between alleles. A lack of MHC variability has attributed to instances such as bottleneck effects or relaxed selection pressure and has a certain impact on the long-term viability of the species concerned. As a result of seriously decreased population density during the last century, the current population of the endangered European mink (Mustela lutreola, L. 1761) has suffered from geographic isolation. In this study, we amplified a partial sequence of the MHC class II DRB exon 2 (229 bp), assessed the degree of genetic variation and compared the variability with those of other Mustelidae. As a result, nine alleles were detected in 20 investigated individuals, which differ from each other by four to 25 nucleotide substitutions (two to 11 amino acid substitutions). Whilst an equal ratio for synonymous and non-synonymous substitutions was found inside the ABS, synonymous substitutions were significantly higher than non-synonymous substitutions in the non-ABS region. Results might indicate that no positive selection exists within the ex situ population of M. lutreola, at least in the analysed fragment. In addition, phylogenetic analyses support the trans-species model of evolution.

Extensive variation at MHC DRB in the New Zealand sea lion (Phocarctos hookeri) provides evidence for balancing selection

“…The detection of 28 nucleotide sequences that corresponded to 26 DRB peptides in 87 NZSL pups, three peptides of which account for the majority of observed alleles, is consistent with observations in terrestrial mammalian species (Schaschl et al, 2004;Becker et al, 2009;Srithayakumar et al, 2011). In fact, the detection of extensive variation at MHC DRB in mammalian species that are not of conservation concern is common; primates especially are highly variable at DRB (Otting et al, 2000;Schwensow et al, 2007).…”

“…In fact, the detection of extensive variation at MHC DRB in mammalian species that are not of conservation concern is common; primates especially are highly variable at DRB (Otting et al, 2000;Schwensow et al, 2007). However, it should be noted that the above species, apart from the European mink (Mustela lutreola, Becker et al, 2009), are of low conservation concern and have an expectation of overall moderate-tohigh genetic diversity, which would extend to genes of the MHC. Thus, given the recent population history of the NZSL, along with its restricted area of occupancy and declining population size, the level of MHC DRB diversity observed here was higher than expected.…”

Considerable MHC Diversity Suggests That the Functional Extinction of Baiji Is Not Related to Population Genetic Collapse

“…Further, the baiji showed a significant DRB allelic diversity with an average of 13.2% nucleotide (range 1–57) and 23.5% amino acid (range 0–30) differences between sequences, both of which were comparable to or higher than those found in some other endangered species (Table 5). For example, the average difference in amino acid sequence is 19.2% for the Arabian oryx ( Oryx leucoryx ) [31], 16.8% for the giant panda ( Ailuropoda melanoleuca ) [32], 13.2% for North American bison ( Bison bison ) [33], 12.7% for the San Nicolas Island fox [21], while only 5.4% for the European mink ( Mustela lutreola ) [34]. Actually, considerable MHC variation was also evidenced at the DQB and MHC-I loci in the baiji.…”

cDNA cloning and polymorphic domains of the major histocompatibility complex (MHC) class I in two Chinese native chicken breeds

“…Fax: 0086-551-5786013. and Yang, 2008;O'Leary et al, 2009), whales (Xu et al, 2009) wild animals (Koutsogiannouli et al, 2009;Becker et al, 2009) and avian (Ewald and Livant, 2004;Westerdahl et al, 2000).…”

“…Restriction fragment length polymorphism (RFLP) has been used to identify MHC allele diversity (Westerdahl et al, 2000), and cDNA-PCR was more often applied to sequencing MHC gene (Silva and Edwards, 2009;O'Leary et al, 2009;Becker et al, 2009). Domestic animals have been artificially selected and bred for a long time.…”