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Parasite-mediated selection of major histocompatibility complex variability in wild brandt's voles (Lasiopodomys brandtii) from Inner Mongolia, China.

ABSTRACT: BACKGROUND:Genes of the major histocompatibility complex (MHC) exhibit high levels of variability, which is believed to have arisen through pathogen-mediated selection. We investigated the relationship between parasite load and genetic diversity at selectively neutral, non-coding markers (microsatellites) and adaptive genetic variation at a functionally important part of the MHC in six independent natural populations of Brandt's voles (Lasiopodomys brandtii) from two regions of the Xilingol Grassland area of Inner Mongolia. RESULTS:Two-hundred and fifty-two voles were screened for gastrointestinal parasites, and were assessed for genetic variation. Parasite screening was done through non-invasive fecal egg counts, while allelic diversity was determined via single-stranded conformation polymorphism and DNA sequencing. We detected eight distinct helminth egg morphotypes. A total of 10 microsatellite loci were genotyped and 19 unique MHC class II B alleles were isolated. The rate of nonsynonymous substitutions (dN) exceeded the rate of synonymous substitutions (dS) at putative antigen binding sites of DRB. Neutral and adaptive genetic diversity differed between the six vole populations. To test the main pathogen-driven selection hypotheses for the maintenance of host MHC diversity and parasite species-specific co-evolutionary effects, multivariate approaches (generalized linear mixed models) were used to test for associations between the MHC class II DRB genotype and infections with nematodes. We found no evidence for heterozygote advantage, and overall heterozygosity was lower than expected in the MHC alleles. We identified an association between the parasite load and specific MHC alleles in the voles, and this pattern varied between geographic regions. CONCLUSIONS:The results suggest that MHC variability in Brandt's voles is maintained by rare allele advantage and fluctuating selection, but the data failed to show any heterozygote advantage effect. Our results add to a growing body of evidence showing that the mode and relative strength of pathogen-driven selection acting on MHC diversity varies within specific wild populations. In addition, our study contributes to the understanding of what maintains MHC diversity, of host-pathogen coevolution and of how genetic diversity is maintained in voles.

SUBMITTER: Zhang M

PROVIDER: S-EPMC3720540 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Parasite-mediated selection of major histocompatibility complex variability in wild brandt's voles (Lasiopodomys brandtii) from Inner Mongolia, China.

Zhang Min M He Hongxuan H

BMC evolutionary biology 20130712

<h4>Background</h4>Genes of the major histocompatibility complex (MHC) exhibit high levels of variability, which is believed to have arisen through pathogen-mediated selection. We investigated the relationship between parasite load and genetic diversity at selectively neutral, non-coding markers (microsatellites) and adaptive genetic variation at a functionally important part of the MHC in six independent natural populations of Brandt's voles (Lasiopodomys brandtii) from two regions of the Xilin ...[more]

PMID: 23848494

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Project description:BACKGROUND:Subterranean rodents have evolved many features to adapt to their hypoxic environment. The brain is an organ that is particularly vulnerable to damage caused by exposure to hypoxic conditions. To investigate the mechanisms of adaption to a hypoxic underground environment, we carried out a cross-species brain transcriptome analysis by RNA sequencing and identified genes that are differentially expressed between the subterranean vole Lasiopodomys mandarinus and the closely related above-ground species Lasiopodomys brandtii under chronic hypoxia [10.0% oxygen (O2)] and normoxia (20.9% O2). RESULTS:A total of 355 million clean reads were obtained, including 69,611 unigenes in L. mandarinus and 69,360 in L. brandtii. A total of 235 and 92 differentially expressed genes (DEGs) were identified by comparing the hypoxic and control groups of L. mandarinus and L. brandtii, respectively. A Gene Ontology (GO) analysis showed that upregulated DEGs in both species had similar functions in response to hypoxia, whereas downregulated DEGs in L. mandarinus were enriched GO terms related to enzymes involved in aerobic reactions. In the Kyoto Encyclopedia of Genes and Genomes pathway analysis, upregulated DEGs in L. mandarinus were associated with angiogenesis and the increased O2 transport capacity of red blood cells, whereas downregulated DEGs were associated with immune responses. On the other hand, upregulated DEGs in L. brandtii were associated with cell survival, vascular endothelial cell proliferation, and neuroprotection, while downregulated genes were related to the synaptic transmission by neurons. CONCLUSIONS:L. mandarinus actively adapts its physiological functions to hypoxic conditions, for instance by increasing O2 transport capacity and modulating O2 consumption. In contrast, L. brandtii reacts passively to hypoxia by decreasing overall activity in order to reduce O2 consumption. These results provide insight into hypoxia adaptation mechanisms in subterranean rodents that may be applicable to humans living at high altitudes or operating in other O2-poor environments.

Dataset Information

Parasite-mediated selection of major histocompatibility complex variability in wild brandt's voles (Lasiopodomys brandtii) from Inner Mongolia, China.

Publications

Parasite-mediated selection of major histocompatibility complex variability in wild brandt's voles (Lasiopodomys brandtii) from Inner Mongolia, China.

Similar Datasets

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