Major Histocompatibility Complex Variation in the Arabian Oryx

Abstract

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.

Low MHC DRB class II diversity in the mountain goat: past bottlenecks and possible role of pathogens and parasites

“…The number of MHC DRB class II alleles in the three populations of mountain goats studied is low and comparable to those reported amongst species known to have gone through population bottlenecks (Hedrick et al 1999(Hedrick et al , 2000aSommer et al 2002;Blankenburg et al 2003;Drake et al 2004;Babik et al 2005;Wan et al 2006). The low genetic diversity in mountain goats could be largely attributable to Pleistocene glaciations as has been suggested in other ungulates (Mikko et al 1999;Loehr et al 2006), where depletion of the gene pool would have occurred via the combined actions of inbreeding and genetic drift.…”

“…Many other endangered species exhibit low MHC polymorphism and are known to have gone through severe population bottlenecks (Hedrick et al 1999(Hedrick et al , 2000aBlankenburg et al 2003). However, some species persist and do well despite low MHC polymorphism or even monomorphism caused by past population bottlenecks (Mikko and Andersson 1995;Mikko et al 1999), including some of anthropic origin (Ellegren et al 1993;Weber et al 2004).…”

Genetic variation at MHC, mitochondrial and microsatellite loci in isolated populations of Brown trout (Salmo trutta)

“…Diversity at MHC is supposed to have adaptive significance (O'Brien et al 1985;Paterson et al 1998;Langefors et al 2001a;Arkush et al 2002), and in fact its preservation has been proposed as a major objective in conservation programmes (Hughes 1991;Aguilar et al 2004; but see Vrijenhoek and Leberg 1991;Miller and Hedrick 1991). However, cases exist where very low MHC diversity has been found in viable populations (Slade 1992;Ellegren et al 1993;Seddon and Baverstock 1999;Hedrick et al 2000;Smulders et al 2003;Miller and Lambert 2004a;Weber et al 2004), or where there is a high correlation between neutral and MHC variation Landry and Bernatchez 2001). Indeed, the importance of the MHC for population survival in the wild will depend on several factors, like local conditions (e.g., pathogen load) or the particular characteristics of the species studied.…”

“…Indeed, several studies have shown that populations exhibiting low levels of variability at the MHC or with certain haplotypes are more susceptible to diseases (O'Brien et al 1985;Paterson et al 1998;Langefors et al 2001a;Arkush et al 2002). However, there is also evidence of populations with no or a low variability at the MHC that however have remained viable (Slade 1992;Ellegren et al 1993;Seddon and Baverstock 1999;Hedrick et al 2000;Miller and Lambert 2004a;Weber et al 2004). …”

Major Histocompatibility Complex Variation in the Endangered Crested Ibis Nipponia nippon and Implications for Reintroduction

“…Moreover, documented evidence has been presented that a pattern of a low number of MHC alleles, with a high degree of divergence between alleles, was observed in bottlenecked species such as the Seychelles warbler (Richardson and Westerdahl, 2003), the Arabian oryx (Hedrick et al, 2000b), and the American bison (Mikko et al, 1997). A comparatively low level of divergence, however, between the crested ibis MHC alleles (e.g., the nucleotide differences and amino acid variations) was observed in this study, which indicates the high degree of overlap between the repertoires of peptides that the respective alleles can present.…”