Rapid Evolution of the MH Class I Locus Results in Different Allelic Compositions in Recently Diverged Populations of Atlantic Salmon

Consuegra, Sofía; Megens, Hendrik‐Jan; Schaschl, Helmut; Leon, Kathleen; Stet, R.J.M.; Jordan, William Chester

doi:10.1093/molbev/msi096

Cited by 57 publications

(41 citation statements)

References 48 publications

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“…As a ubiquitous evolutionary force, recombination has been shown to contribute substantially to MHC diversity, creating new alleles in isolated populations (Consuegra et al, 2005). However, in the present study, we have not detected signal of recombination in the MHC-I exon 4 sequences.…”

Section: Effects Of Recombination and Purifying Selectioncontrasting

confidence: 82%

MHC Class I Exon 4 in the Multiocellated Racerunners (Eremias multiocellata): Polymorphism, Duplication and Selection

Yuan¹,

Zeng²,

Guo³

2014

AHR

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The major histocompatibility complex (MHC) is a dynamic genetic region with an essential role in the adaptive immunity of jawed vertebrates. The MHC polymorphism is affected by many processes such as birth-anddeath evolution, gene conversion, and concerted evolution. Studies investigating the evolution of MHC class I genes have been biased toward a few particular taxa and model species. However, the investigation of this region in nonavian reptiles is still in its infancy. We present the first characterization of MHC class I genes in a species from the family Lacertidae. We assessed genetic diversity and a role of selection in shaping the diversity of MHC class I exon 4 among 37 individuals of Eremias multiocellata from a population in Lanzhou, China. We generated 67 distinct DNA sequences using cloning and sequencing methods, and identified 36 putative functional variants as well as two putative pseudogene-variants. We found the number of variants within an individual varying between two and seven, indicating that there are at least four MHC class I loci in this species. Gene duplication plays a role in increasing copy numbers of MHC genes and allelic diversity in this species. The class I exon 4 sequences are characteristic of low nucleotide diversity. No signal of recombination is detected, but purifying selection is detected in β2-microglobulin interaction sites and some other silent sites outside of the function-constraint regions. Certain identical alleles are shared by Eremias multiocellata and E. przewalskii and E. brenchleyi, suggesting trans-species polymorphism. The data are compatible with a birth-and-death model of evolution.class II genes, have been the subjects of the majority of research in the fields of ecology and evolution (reviewed in Sommer, 2005; Milinski, 2006;Piertney and Oliver, 2006;Ujvari and Belov, 2011). This is because MHC includes the most polymorphic genes in vertebrate populations. Given the extraordinary richness and diversity of continuously evolving pathogens in the environment, it is not surprising that the MHC harbors the most polymorphic genes described thus far, with some loci, such as the human HLA-B locus, possessing more than 2000 alleles (de Bakker and Raychaudhuri, 2012). The number of genes in the MHC varies enormously between species, even between individuals of the same species (Malaga-Trillo et al., 1998;Figueroa et al., 2001). It has been noted that balancing selection is an evolutionary force that can maintain many haplotypes over long periods of evolutionary time. Genes that

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Section: Effects Of Recombination and Purifying Selectioncontrasting

confidence: 82%

MHC Class I Exon 4 in the Multiocellated Racerunners (Eremias multiocellata): Polymorphism, Duplication and Selection

Yuan¹,

Zeng²,

Guo³

2014

AHR

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“…Kundu and Faulkes (2004) were able to identify PSS in four species of African mole-rats (Bathyergidae: Heliophobius argenteocinereus, Heterocephalus glaber, Cryptomys hottentotus hottentotus, Cryptomys damarensis). As in our study in Malagasy fattailed dwarf lemurs, the comparisons of PSS in Atlantic salmon (Salmo salar) (Consuegra et al, 2005) and in two chamois subspecies (Rupicapra spp.) revealed high but not complete coincidence with the human ABS.…”

Section: Discussionmentioning

confidence: 65%

Neutral versus adaptive genetic variation in parasite resistance: importance of major histocompatibility complex supertypes in a free-ranging primate

et al. 2007

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Current discussions in evolutionary ecology and conservation genetics focus on the relative importance of using selective neutral markers or markers of coding genes to identify adaptive and evolutionary relevant processes. Genetic diversity might be particularly important in immune genes (e.g., in genes of the major histocompatibility complex, MHC), which are influencing pathogen and parasite resistance. We investigated the effects of neutral versus adaptive genetic variation in parasite resistance in a natural population of fat-tailed dwarf lemurs (Cheirogaleus medius). No association between neutral overall individual genetic diversity and parasite load could be detected. In 149 individuals, we identified 50 MHC class II alleles of the functionally important duplicated DRB locus. The investigation of the functional importance of immune gene (MHC) diversity and parasite selection in natural populations is often problematic due to extensive polymorphism in the MHC genes and restrictions in available sample sizes. Here, for the first time we applied an approach that has been developed in human medical studies. Eleven MHC class II supertypes were identified based on shared antigen-binding similarities. The number of individual MHC supertypes had no influence on the nematode burden. However, we found evidence for a specific MHC supertype (supertype 1) that was linked to infected individuals, a higher number of different nematode infections and high intensity of infection per individual. Moreover, one rare MHC supertype (supertype 7) was revealed to be advantageous with respect to parasite burden. Thus, our results add evidence to the small body of studies that show significant associations between specific MHC constitutions and naturally occurring parasites in the complexity of natural populations.

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“…Therefore, simulations were initiated with a single allele and new alleles were introduced at one of two per-locus rates (m L ¼ 2m, where m is the per-gene mutation rate): 10 À5 and 10 À6 . Here we consider these allele-introduction rates to represent the combined effects of point mutation and recombination, both of which are important to the generation of MHC diversity (Martinsohn et al 1999;Ohta 1999;Richman et al 2003;Consuegra et al 2005;Reusch and Langefors 2005;Schaschl et al 2006). We ran simulations with three different effective population sizes (N e ) of 10 3 , 10 4 , and 10…”

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confidence: 99%

An Asymmetric Model of Heterozygote Advantage at Major Histocompatibility Complex Genes: Degenerate Pathogen Recognition and Intersection Advantage

Stoffels

Spencer

2008

Genetics

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We characterize the function of MHC molecules by the sets of pathogens that they recognize, which we call their ''recognition sets.'' Two features of the MHC-pathogen interaction may be important to the theory of polymorphism construction at MHC loci: First, there may be a large degree of overlap, or degeneracy, among the recognition sets of MHC molecules. Second, when infected with a pathogen, an MHC genotype may have a higher fitness if that pathogen belongs to the overlapping portion, or intersection, of the two recognition sets of the host, when compared with a genotype that contains that pathogen in only one of its recognition sets. We call this benefit ''intersection advantage,'' g, and incorporate it, as well as the degree of recognition degeneracy, m, into a model of heterozygote advantage that utilizes a set-theoretic definition of fitness. Counterintuitively, we show that levels of polymorphism are positively related to m and that a high level of recognition degeneracy is necessary for polymorphism at MHC loci under heterozygote advantage. Increasing g reduces levels of polymorphism considerably. Hence, if intersection advantage is significant for MHC genotypes, then heterozygote advantage may not explain the very high levels of polymorphism observed at MHC genes.

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Rapid Evolution of the MH Class I Locus Results in Different Allelic Compositions in Recently Diverged Populations of Atlantic Salmon

Cited by 57 publications

References 48 publications

MHC Class I Exon 4 in the Multiocellated Racerunners (Eremias multiocellata): Polymorphism, Duplication and Selection

MHC Class I Exon 4 in the Multiocellated Racerunners (Eremias multiocellata): Polymorphism, Duplication and Selection

Neutral versus adaptive genetic variation in parasite resistance: importance of major histocompatibility complex supertypes in a free-ranging primate

An Asymmetric Model of Heterozygote Advantage at Major Histocompatibility Complex Genes: Degenerate Pathogen Recognition and Intersection Advantage

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