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Positive Selection on MHC Class II DRB and DQB Genes in the Bank Vole (Myodes glareolus).

Author:
  • Kristin Scherman
  • Lars Råberg
  • Helena Westerdahl
Publishing year: 2014
Language: English
Pages: 293-305
Publication/Series: Journal of Molecular Evolution
Volume: 78
Issue: 5
Document type: Journal article
Publisher: Springer

Abstract english

The major histocompatibility complex (MHC) class IIB genes show considerable sequence similarity between loci. The MHC class II DQB and DRB genes are known to exhibit a high level of polymorphism, most likely maintained by parasite-mediated selection. Studies of the MHC in wild rodents have focused on DRB, whilst DQB has been given much less attention. Here, we characterised DQB genes in Swedish bank voles Myodes glareolus, using full-length transcripts. We then designed primers that specifically amplify exon 2 from DRB (202 bp) and DQB (205 bp) and investigated molecular signatures of natural selection on DRB and DQB alleles. The presence of two separate gene clusters was confirmed using BLASTN and phylogenetic analysis, where our seven transcripts clustered according to either DQB or DRB homologues. These gene clusters were again confirmed on exon 2 data from 454-amplicon sequencing. Our DRB primers amplify a similar number of alleles per individual as previously published DRB primers, though our reads are longer. Traditional d N/d S analyses of DRB sequences in the bank vole have not found a conclusive signal of positive selection. Using a more advanced substitution model (the Kumar method) we found positive selection in the peptide binding region (PBR) of both DRB and DQB genes. Maximum likelihood models of codon substitutions detected positively selected sites located in the PBR of both DQB and DRB. Interestingly, these analyses detected at least twice as many positively selected sites in DQB than DRB, suggesting that DQB has been under stronger positive selection than DRB over evolutionary time.

Keywords

  • Biological Sciences
  • Zoology

Other

Published
  • CAnMove
  • ISSN: 0022-2844
Helena Westerdahl
E-mail: helena [dot] westerdahl [at] biol [dot] lu [dot] se

Senior lecturer

MEMEG

+46 46 222 36 69

E-C250

50

Research group

Molecular Ecology and Evolution Lab

Projects

Doctoral students and postdocs

Research fellows

Postdocs

Luz Garcia-Longoria

PhD students, main supervisor

Samantha Mellinger

PhD students, assistant supervisor

Gustaf Ekelund Ugge

Helena Westerdahl w house sparrow