Monomorphism and polymorphism at Mhc DRB loci in domestic and wild ruminants

Abstract

Genetic polymorphism at Mhc class II DRB loci was investigated in samples of musk-ox from Canada and Greenland; moose from Sweden, Norway, Canada, and Alaska; roe deer from Norway and Sweden; reindeer from Svalbard and Norway; fallow deer from Norway and Sweden; and red deer from Norway. The results were compared with published data on cattle, bison, goat, sheep, and red deer. Cattle-specific primers amplified a single DRB locus in all species except fallow deer and red deer, in which two loci were found. Single strand conformation polymorphism analysis and DNA sequence analysis were employed to detect genetic polymorphism. Complete monomorphism was found in musk-ox and fallow deer. Limited polymorphism was found in the moose, roe deer, and reindeer from Svalbard, whereas intermediate to extensive DRB diversity was present in reindeer from Norway and in bison, sheep, goat, cattle, and red deer. The restricted Mhc diversity in moose, roe deer, and fallow deer is notable in relation to the dramatic population expansion of moose and roe deer in Sweden during this century and since fallow deer is used for meat and game production with good results and without any marked disease problems. The results question the view that species or populations with restricted Mhc diversity have poor resistance to infectious diseases. A phylogenetic tree analysis revealed a clustering of DRB sequences within species rather than within allelic lineages across species. The results suggest trans-species persistence of polymorphic sequence motifs rather than of allelic lineages.

Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox ( Ovibos moschatus ) population dynamics

“…Modern musk ox harbor little genetic diversity at both the nuclear and mitochondrial levels (20)(21)(22). Our data indicate that total past genetic diversity (samples older than 100 14 C YBP), as measured by temporally unbiased π (23), was significantly higher than present (Table 1 and Fig.…”

Molecular characterization of expressed DQA and DQB genes in the California sea lion ( Zalophus californianus )

“…The identification of a polymorphic MHC gene m sea lions would be important, since there are several studies examining exon 2 of D^^ and DQB genes in other seal species that are used as evidence for a lack of MHC diversity in pinnipeds Slade 1992). The increasing recognition of thriving species with apparent limited MHC polymorphism has also been used to question the importance of MHC diversity in the vulnerability of a population to disease (Mikko et al 1999). If a yet undiscovered, more polymorphic class II MHC gene exists then these conclusions may be misleading.…”

Low diversity in the major histocompatibility complex class II DRB1 gene of the Spanish ibex, Capra pyrenaica

“…For example, population bottlenecks and genetic drift have been shown to play a major role in shaping MHC diversity of many wild species (Mikko et al, 1999). Natural populations of muskox (Ovibos moschatus), moose (Alces alces), fallow deer (Dama dama), beaver (Castor fiber), Asiatic lion (Panthera leo persica), cotton-top tamarin (Saguinus oedipus) and the cheetah (Acinonyx jubatus), among others, have shown reduced allelic variation or even monomorphism at the MHC loci, indicating that the presence of high genetic diversity is not a universal feature of this genetic system (O'Brien et al, 1987;Yuhki and O'Brien, 1990;Watkins et al, 1991;Ellegren et al, 1993, Mikko et al, 1999. Studying closely related species with different demographic histories (eg, endangered species that have suffered drastic reductions in population size vs populations that have not gone through genetic bottlenecks) may provide insights into the relative importance of selective and stochastic processes shaping the genetic diversity present at the MHC.…”