Major Histocompatibility Complex Variation in the Arabian Oryx

Abstract

In the 1960s, the Arabian oryx was one of the most endangered species in the world, extinct in the wild and surviving in only a few captive herds. The present day population of over 2000 descends from a small number of founders and may have restricted genetic variation for important adaptive genes. We have examined the amount of genetic variation for a class II gene in the major histocompatibility complex thought to be the most important genetic basis for pathogen resistance in vertebrates. We found three very divergent alleles, which on average, differed by 24 nucleotides and 15 amino acids in the 236-bp fragment we examined. Using single-strand conformation polymorphism, we found that in a sample of 57 animals, the alleles were in Hardy-Weinberg proportions, although one allele was found only in four heterozygous individuals. The average heterozygosity for the 22 amino acid positions involved in antigen binding was 0.165, three times as high as that for the 56 amino acids not involved with antigen binding. Because the three alleles have such divergent sequences, it is likely that they may recognize peptides from quite different pathogens. As a result, maintenance of these variants should be considered as a goal in the captive breeding program of the Arabian oryx.

Allelic characterization of the second DRB locus of major histocompatibility complex class II in Ussuri sika deer (Cervus nippon hortulorum): highlighting the trans-species evolution of DRB alleles within Cervidae

“…The latter is due to common adaptive solutions to similar environmental pressures and is unlikely in non-sympatric deer species. The same evolutionary pattern has been observed in many other vertebrates (Hedrick et al 2000a(Hedrick et al , 2000bSeddon & Baverstock 2000;Otting et al 2002;Seddon & Ellegren 2002;Musolf et al 2004;Ottová et al 2005;Huchard et al 2006). We could not, however, estimate the impression of occasionally interspecific hybridization on DRB-2 allelic variations.…”

“…First, these allelic similarities were explained by the theories of "transspecies polymorphism" or "trans-species evolution": allelic lineages of common ancestors persist through speciation and are passed from species to species (Klein 1987). Several vertebrate species display trans-species polymorphism, including fish (Ottová et al 2005), rodents (Seddon & Baverstock 2000;Musolf et al 2004), carnivores (Hedrick et al 2000a;Seddon & Ellegren 2002), ungulates (Hedrick et al 2000b), and primates (Otting et al 2002;Huchard et al 2006).…”

Enhanced Selection for MHC Diversity in Social Tuco-Tucos

“…Selection can be difficult to detect using sample sizes that are realistic for many natural populations of vertebrates (Hedrick et al 2000), and thus we employed multiple tests to detect both population-and molecular-level departures from neutrality at the DQ␤ locus. For population level analyses, Hardy-Weinberg (Hardy 1908;Weinberg 1908) and EwensWatterson (Ewens 1972;Watterson 1978) tests were conducted using Arlequin Ver.…”

The evolutionary ecology of the major histocompatibility complex

“…Selection acting in contemporary populations is expected to have a detectable effect on genotypic frequencies within that population (Hedrick et al, 2000). Overdominance models of selection predict that heterozygote genotypes will be fitter than homozygote genotypes Evolutionary ecology of the MHC (Doherty and Zinkernagel, 1975) given that two variant alleles will identify a broader range of pathogens.…”