Major Histocompatibility Complex Diversity Research Articles

Genetic Diversity of MHC B-F/B-L Region in 21 Chicken Populations.

The chicken major histocompatibility complex (MHC) on chromosome 16 is the most polymorphic region across the whole genome, and also an ideal model for genetic diversity investigation. The MHC B-F/B-L region is 92 kb in length with high GC content consisting of 18 genes and one pseudogene (Blec4), which plays important roles in immune response. To evaluate polymorphism of the Chinese indigenous chickens as well as to analyze the effect of selection to genetic diversity, we used WaferGen platform to identify sequence variants of the B-F/B-L region in 21 chicken populations, including the Red Jungle Fowl (RJF), Cornish (CS), White Leghorns (WLs), 16 Chinese domestic breeds, and two well-known inbred lines 63 and 72. A total of 3,319 single nucleotide polymorphism (SNPs) and 181 INDELs in the B-F/B-L region were identified among 21 populations, of which 2,057 SNPs (62%) and 159 INDELs (88%) were novel. Most of the variants were within the intron and the flanking regions. The average variation density was 36 SNPs and 2 INDELs per kb, indicating dramatical high diversity of this region. Furthermore, BF2 was identified as the hypervariable genes with 67 SNPs per kb. Chinese domestic populations showed higher diversity than the WLs and CS. The indigenous breeds, Nandan Yao (NY), Xishuangbanna Game (XG), Gushi (GS), and Xiayan (XY) chickens, were the top four with the highest density of SNPs and INDELs. The highly inbred lines 63 and 72 have the lowest diversity, which might be resulted from a long-term intense selection for decades. Collectively, we refined the genetic map of chicken MHC B-F/B-L region, and illustrated genetic diversity of 21 chicken populations. Abundant genetic variants were identified, which not only strikingly expanded the current Ensembl SNP database, but also provided comprehensive data for researchers to further investigate association between variants in MHC and immune traits.

Major histocompatibility complex class II DR and DQ evolution and variation in wild capuchin monkey species (Cebinae).

The major histocompatibility complex (MHC) is an important gene complex contributing to adaptive immunity. Studies of platyrrhine MHC have focused on identifying experimental models of immune system function in the equivalent Human Leukocyte Antigen (HLA). These genes have thus been explored primarily in captive platyrrhine individuals from research colonies. However, investigations of standing MHC variation and evolution in wild populations are essential to understanding its role in immunity, sociality and ecology. Capuchins are a promising model group exhibiting the greatest habitat diversity, widest diet breadth and arguably the most social complexity among platyrrhines, together likely resulting in varied immunological challenges. We use high-throughput sequencing to characterize polymorphism in four Class II DR and DQ exons for the first time in seven capuchin species. We find evidence for at least three copies for DQ genes and at least five for DRB, with possible additional unrecovered diversity. Our data also reveal common genotypes that are inherited across our most widely sampled population, Cebus imitator in Sector Santa Rosa, Costa Rica. Notably, phylogenetic analyses reveal that platyrrhine DQA sequences form a monophyletic group to the exclusion of all Catarrhini sequences examined. This result is inconsistent with the trans-species hypothesis for MHC evolution across infraorders in Primates and provides further evidence for the independent origin of current MHC genetic diversity in Platyrrhini. Identical allele sharing across cebid species, and more rarely genera, however, does underscore the complexity of MHC gene evolution and the need for more comprehensive assessments of allelic diversity and genome structure.

Avian blood parasite richness decreases with major histocompatibility complex class I loci number.

Major histocompatibility complex (MHC) genes are among the most polymorphic in the vertebrate genome. The high allele diversity is believed to be maintained primarily by sexual and pathogen-mediated balancing selection. The number of MHC loci also varies greatly across vertebrates, most notably across birds. MHC proteins play key roles in presenting antigens on the cell surface for recognition by T cells, with class I proteins specifically targeting intracellular pathogens. Here, we explore the hypothesis that MHC class I diversity (measured as loci number) coevolves with haemosporidian parasite burden of the host. Using data on 54 bird species, we demonstrate that high-MHC class I diversity is associated with significantly lower richness of Plasmodium, Haemoproteus as well as overall haemosporidian parasite lineages, the former thus indicating more efficient protection against intracellular pathogens. Nonetheless, the latter associations were only detected when MHC diversity was assessed using cloning and not 454 pyrosequencing-based studies, nor across all genotyping methods combined. Our results indicate that high-MHC class I diversity might play a key role in providing qualitative resistance against diverse haemosporidian parasites in birds, but further clarification is needed for the origin of contrasting results when using different genotyping methods for MHC loci quantification.

Balancing selection, genetic drift, and human-mediated introgression interplay to shape MHC (functional) diversity in Mediterranean brown trout.

The extraordinary polymorphism of major histocompatibility complex (MHC) genes is considered a paradigm of pathogen‐mediated balancing selection, although empirical evidence is still scarce. Furthermore, the relative contribution of balancing selection to shape MHC population structure and diversity, compared to that of neutral forces, as well as its interaction with other evolutionary processes such as hybridization, remains largely unclear. To investigate these issues, we analyzed adaptive (MHC‐DAB gene) and neutral (11 microsatellite loci) variation in 156 brown trout (Salmo trutta complex) from six wild populations in central Italy exposed to introgression from domestic hatchery lineages (assessed with the LDH gene). MHC diversity and structuring correlated with those at microsatellites, indicating the substantial role of neutral forces. However, individuals carrying locally rare MHC alleles/supertypes were in better body condition (a proxy of individual fitness/parasite load) regardless of the zygosity status and degree of sequence dissimilarity of MHC, hence supporting balancing selection under rare allele advantage, but not heterozygote advantage or divergent allele advantage. The association between specific MHC supertypes and body condition confirmed in part this finding. Across populations, MHC allelic richness increased with increasing admixture between native and domestic lineages, indicating introgression as a source of MHC variation. Furthermore, introgression across populations appeared more pronounced for MHC than microsatellites, possibly because initially rare MHC variants are expected to introgress more readily under rare allele advantage. Providing evidence for the complex interplay among neutral evolutionary forces, balancing selection, and human‐mediated introgression in shaping the pattern of MHC (functional) variation, our findings contribute to a deeper understanding of the evolution of MHC genes in wild populations exposed to anthropogenic disturbance.

High throughput analysis of MHC-I and MHC-DR diversity of Brazilian cattle populations.

The major histocompatibility complex (MHC) contains many genes that play key roles in initiating and regulating immune responses. This includes the polymorphic MHCI and MHCII genes that present epitopes to CD8+ and CD4+ T-cells, respectively. Consequently, the characterisation of the repertoire of MHC genes is an important component of improving our understanding of the genetic variation that determines the outcomes of immune responses. In cattle, MHC (BoLA) research has predominantly focused on Holstein-Friesian animals (as the most economically important breed globally), although the development of high-throughput approaches has allowed the BoLA-DRB3 repertoire to be studied in a greater variety of breeds. In a previous study we reported on the development of a MiSeq-based method to enable high-throughput and high-resolution analysis of bovine MHCI repertoires. Herein, we report on the expansion of this methodology to incorporate analysis of the BoLA-DRB3 and its application to analyse MHC diversity in a large cohort of cattle from Brazil (>500 animals), including representatives from the three major Bos indicus breeds present in Brazil - Guzerat, Gir and Nelore. This large-scale description of paired MHCI-DRB3 repertoires in Bos indicus cattle has identified a small number of novel DRB3 alleles, a large number of novel MHCI alleles and haplotypes, and provided novel insights into MHCI-MHCII association - further expanding our knowledge of bovine MHC diversity.

Genetic diversity of the endangered Japanese golden eagle at neutral and functional loci

AbstractThe Japanese golden eagle (Aquila chrysaetos japonica) is an endangered subspecies with declining reproductive success. Previous research on this subspecies reported genetic diversity in northern Japan and in captivity using neutral genetic markers, but the situation in other areas of Japan and diversity at functional genetic loci are understudied. Here, we increased wild samples from western Japan and captive samples from zoos and analyzed genetic diversity of mitochondrial DNA, nuclear microsatellite loci, and the major histocompatibility complex (MHC) DRB exon 2 region. In addition, wild Scottish samples were analyzed and literature from European subspecies and other raptor species was surveyed to compare with the Japanese golden eagle. Overall, levels of mtDNA haplotype and microsatellite diversity observed in western Japan were similar to previously studied northern regions. However, microsatellite allelic diversity was lower compared to other golden eagle subspecies. MHC diversity indices, especially in captive Japanese golden eagles, were also low relative to raptors classified as Least Concern by the IUCN. This pattern could be explained by the loss of rare alleles due to genetic drift—a consequence of a declining population—suggesting the possibility of an early population bottleneck. Moreover, genetic structure analyses suggested that the Japanese population likely consists of one gene pool, so the bottleneck may affect the entire population. From these results, we suggest maintaining gene flow between local populations to prevent inbreeding and further loss of alleles, increasing the number of breeding pairs in captivity, and releasing captive individuals to reinforce the wild population.

Mate choice for major histocompatibility complex (MHC) complementarity in the Yellow-rumped Flycatcher (Ficedula zanthopygia)

BackgroundGenes of the major histocompatibility complex (MHC) are an important component of the vertebrate immune system and play a significant role in mate choice in animal populations. However, the MHC genetic targets of female mate choice have not been clearly identified, and whether female mate choice is based on neutral genetic characteristics remains an open question. Here, we focus on the effects of morphological traits and genetic similarity among individuals in MHC class IIB (MHC IIB) exon 2 on mating in a sexually dimorphic songbird that exhibits social monogamy with extra-pair paternity (EPP).MethodsWe sequenced 64 parent–offspring triads sampled over a 3-year period using two MHC class II loci to detect disassortative mating in the Yellow-rumped Flycatcher (Ficedula zanthopygia).ResultsWe found that MHC similarity in social pairs was lower than that in random pairs. Extra-pair mate choice according to MHC IIB was observed, in which females’ extra-pair mates had fewer MHC alleles than their within-pair mates, but there was no significant band-sharing between extra-pair sires and potential extra-pair mates. However, the interaction between the MHC diversity of females and that of the social males affected the occurrence of EPP.ConclusionsOur results support the “optimality hypothesis” of MHC-based social and extra-pair choice. Female choice probably maintains a certain level of MHC diversity in offspring in the Yellow-rumped Flycatcher.

MHC Reflects Fine-Scale Habitat Structure in White-Tailed Eagles, Haliaeetus albicilla.

The major histocompatibility complex (MHC) genes code for key immune receptors responsible for recognition of intra- and extracellular pathogens (MHC class I and class II, respectively). It was hypothesized that MHC polymorphism can be maintained via fluctuating selection resulting from between-habitat variation in pathogen regimes. We examined associations between MHC class I and class II genes and habitat structure in an apex avian predator, the white-tailed eagle, Haliaeetus albicilla. We genotyped MHC class I and class II genes in ca. 150 white-tailed eagle chicks from nearly 100 nesting territories distributed across 3 distinct populations in Poland. Habitat structure was quantified at the level of foraging territories and directly at the nest sites. We found strong support for associations of habitat traits with diversity and allelic composition at the MHC class II. Forest area within territory and forest productivity were identified as the major habitat predictors of MHC class II polymorphism, whereas other habitat traits (distance to nearest open water, grassland, and water area within territory or understory presence) showed fewer associations with class II alleles. In contrast, there was little support for associations between MHC class I genes and habitat structure. All significant associations were apparent at the within-population level rather than between populations. Our results suggest that extracellular (rather than intracellular) pathogens may exert much stronger selective pressure on the white-tailed eagle. Associations of habitat structure with MHC class II may reflect fluctuating (balancing) selection, which maintains MHC diversity within populations.

Trade‐offs in expressed major histocompatibility complex diversity seen on a macroevolutionary scale among songbirds

To survive organisms must defend themselves against pathogens. Classical Major Histocompatibility Complex (MHC) genes play a key role in pathogen defense by encoding molecules involved in pathogen recognition. MHC diversity influences the variety of pathogens individuals can recognize and respond to and has consequently been a popular genetic marker for disease resistance in ecology and evolution. However, MHC diversity is predominantly estimated using genomic DNA (gDNA) with little knowledge of expressed diversity. This limits our ability to interpret the adaptive significance of variation in MHC diversity, especially in species with very many MHC genes, such as songbirds. Here we address this issue using phylogenetic comparative analyses of the number of MHC class I alleles (MHC-I diversity) in gDNA and complementary DNA (cDNA), i.e. expressed alleles, across thirteen songbird species. We propose three theoretical relationships that could be expected between genomic and expressed MHC-I diversity on a macro-evolutionary scale and test which of these are best supported. In doing so, we show that significantly fewer MHC-I alleles than the number available are expressed, suggesting that optimal MHC-I diversity could be achieved by modulating gene expression. Understanding the relationship between genomic and expressed MHC-I diversity is essential for interpreting variation in MHC diversity in an evolutionary context. This article is protected by copyright. All rights reserved.

Association between sexually selected traits and allelic distance in two unlinked MHC II loci in white-tailed deer (Odocoileus virginianus)

Body size and secondary sexual characteristics are drivers of male reproductive success among polygynous species. A gene complex found to be associated with morphology in several species is the major histocompatibility complex (MHC). However, while several studies have found that greater MHC diversity is associated with larger body size and secondary sexual characteristics, other studies have demonstrated that maximal MHC diversity is not always optimal for the individual’s fitness. This study tested if MHC diversity, measured as pairwise allelic distances at each of two unlinked MHC II loci (exon 2 for the classical antigen-binding protein MHC-DRB and exon 2 for the accessory protein MHC-DOB), was associated with body size (male and female) or antler size in a semi-wild enclosed population of white-tailed deer (Odocoileus virginianus). After accounting for the effect of age on body and antler size, we used residual analysis to assess whether MHC allelic distances explained any of the remaining variation in body and antler size. While we found no associations between physical characteristics and MHC-DRB, we found that both male body and antler size were associated with MHC-DOB nucleotide allelic distances. Specifically, we found a quadratic relationship between MHC-DOB and male body size, where body size peaked at moderate MHC-DOB nucleotide allelic distance. However, we found a positive linear association between MHC-DOB nucleotide allelic distances and antler size. Neither MHC-DRB nor MHC-DOB influenced female body size, even though the average allelic distances of males and females were not significantly different. Our results suggest that MHC-DOB, or a gene genetically linked to this locus, may influence male morphological characteristics in white-tailed deer.

MHC II α polymorphism of Nile tilapia, Oreochromis niloticus, and its association with the susceptibility to Gyrodactylus cichlidarum (Monogenea) infection

Nile tilapia, Oreochromis niloticus, is among the most preeminent aquaculture species in the world. In aquaculture systems, this species is vulnerable to various pathogens including Gyrodactylus cichlidarum (Monogenea). The major histocompatibility complex (MHC) genes, a highly polymorphic gene superfamily, have vital roles in adaptive immunity and are closely associated with disease resistance. In the present study, the relationship between MHC II α polymorphism of Oreochromis niloticus and the susceptibility to G. cichlidarum infection were analyzed. A total of 50 alleles of MHC II α were identified, which demonstrated a high level of polymorphism representing a variability of 89.6% amino acid sites. In the peptide-binding region (PBR) and entire region, the values of dN to dS were 1.155 and 1.180, respectively. Infection experiments revealed that hosts with moderate polymorphism of MHC II α (2 to 3 alleles) had relatively higher resistance to G. cichlidarum infection. In addition, the alleles Orni-DAA*0201 and Orni-DAA*0701 were found to be significantly associated with susceptibility (P < 0.05), while Orni-DAA*3601 was highly associated with resistance (P < 0.05). The results suggested that the diversity of MHC II α allele was associated with the susceptibility of tilapia to this monogenean, which would contribute to the study on MHC diversity maintenance and molecular-assisted selection of O. niloticus to enhance disease resistance. Of course, small scale of productive tests is required to further confirm these results.

What evolutionary processes maintain MHC IIꞵ diversity within and among populations of stickleback?

Major Histocompatibility Complex (MHC) genes code for proteins that recognize foreign protein antigens to initiate T‐cell‐mediated adaptive immune responses. They are often the most polymorphic genes in vertebrate genomes. How evolution maintains this diversity remains of debate. Three main hypotheses seek to explain the maintenance of MHC diversity by invoking pathogen‐mediated selection: heterozygote advantage, frequency‐dependent selection, and fluctuating selection across landscapes or through time. Here, we use a large‐scale field parasite survey in a stickleback metapopulation to test predictions derived from each of these hypotheses. We identify over 1000 MHC IIβ variants (alleles spanning paralogous genes) and find that many of them covary positively or negatively with parasite load, suggesting that these genes contribute to resistance or susceptibility. However, despite our large sample‐size, we find no evidence for the widely cited stabilizing selection on MHC heterozygosity, in which individuals with an intermediate number of MHC variants have the lowest parasite burden. Nor do we observe a rare‐variant advantage, or widespread fluctuating selection across populations. In contrast, we find that MHC diversity is best predicted by neutral genome‐wide heterozygosity and between‐population genomic divergence, suggesting neutral processes are important in shaping the pattern of metapopulation MHC diversity. Thus, although MHC IIβ is highly diverse and relevant to the type and intensity of macroparasite infection in these populations of stickleback, the main models of MHC evolution still provide little explanatory power in this system.

Within-trio tests provide little support for post-copulatory selection on major histocompatibility complex haplotypes in a free-living population.

Sexual selection has been proposed as a force that could help maintain the diversity of major histocompatibility complex (MHC) genes in vertebrates. Potential selective mechanisms can be divided into pre-copulatory and post-copulatory, and in both cases, the evidence for occurrence is mixed, especially in natural populations. In this study, we used a large number of parent-offspring trios that were diplotyped for MHC class II genes in a wild population of Soay sheep (Ovis aries) to examine whether there was within-trio post-copulatory selection on MHC class II genes at both the haplotype and diplotype levels. We found there was transmission ratio distortion of one of the eight MHC class II haplotypes (E) which was transmitted less than expected by fathers, and transmission ratio distortion of another haplotype (A) which was transmitted more than expected by chance to male offspring. However, in both cases, these deviations were not significant after correction for multiple tests. In addition, we did not find any evidence of post-copulatory selection at the diplotype level. These results imply that, given known parents, there is no strong post-copulatory selection on MHC class II genes in this population.

First Evidence of a Relationship Between Female Major Histocompatibility Complex Diversity and Eggshell Bacteria in House Sparrows (Passer domesticus)

Bacteria are known to exert positive and negative influences on animals’ health and fitness. Bacteria, in particular those inhabiting the skin and inner organs of vertebrates, are horizontally or vertically transmitted. Specifically, mothers of bird species can transfer bacterial strains to their offspring when the egg is passing the reproductive tract, as the eggshell rubs against the wall of the uterus. In this context, the female immune system might play an important role in influencing the vertical transmission of bacteria. Here, we investigate the relationship between the major histocompatibility complex (MHC) and cultivable eggshell bacteria originating putatively from the female urogenital tract in a captive population of house sparrows (Passer domesticus). We predict that females with a more variable MHC will transfer fewer bacteria onto the eggshells. Our results show a negative relationship between the number of functional MHC class I alleles and bacteria originating in the urinary tract and growing on a selective medium. This is the first study to find a correlation between female MHC diversity and eggshell bacteria.

High Levels of Genetic Variation in MHC-Linked Microsatellite Markers from Native Chicken Breeds.

The major histocompatibility complex (MHC) is a highly polymorphic gene region that regulates cellular communication in all specific immune responses. In this study, we investigated 11 microsatellite (MS) markers in the MHC-B region of chicken populations from four countries: Sri Lanka, Bangladesh, South Korea, and Nigeria. The MS markers were divided into two sets. Set 1 included five novel MS markers, which we assessed using 192 samples from 21 populations. Set 2 included six previously reported markers, which we assessed using 881 samples from 29 populations. The Set 1 MS markers had lower polymorphism (polymorphic information content (PIC) < 0.5) than the Set 2 markers (PIC = 0.4–0.9). In all populations, the LEI0258 marker was the most polymorphic, with a total of 38 alleles (PIC = 0.912, expected heterozygosity (He) = 0.918). Local populations from Sri Lanka, Bangladesh, and Nigeria had higher allele diversity and more haplotypes for Set 2 MS markers than Korean and commercial populations. The Sri Lankan Karuwalagaswewa village population had the highest MHC diversity (mean allele number = 8.17, He = 0.657), whereas the white leghorn population had the lowest (mean allele number = 2.33, He = 0.342). A total of 409 haplotypes (89 shared and 320 unique), with a range of 4 (Rhode Island red) to 46 (Karuwalagaswewa village (TA)), were identified. Among the shared haplotypes, the B21-like haplotype was identified in 15 populations. The genetic relationship observed in a neighbour-joining tree based on the DA distance agreed with the breeding histories and geographic separations. The results indicated high MHC diversity in the local chicken populations. The difference in the allelic pattern among populations presumably reflects the effects of different genotypes, environments, geographic variation, and breeding policies in each country. The selection of MHC allele in domestic poultry can vary due to intensification of poultry production. Preserved MHC diversity in local chicken provides a great opportunity for future studies that address the relationships between MHC polymorphisms and differential immune responses.

Spatiotemporal adaptive evolution of an MHC immune gene in a frog-fungus disease system.

Genetic diversity of major histocompatibility complex (MHC) genes is linked to reduced pathogen susceptibility in amphibians, but few studies also examine broad spatial and temporal patterns of MHC and neutral genetic diversity. Here, we characterized range-wide MHC diversity in the Northern leopard frog, Rana pipiens, a species found throughout North America that is experiencing disease-related declines. We used previously sequenced neutral markers (mitochondrial DNA and microsatellites), sequenced an expressed MHC class IIß gene fragment, and measured infection prevalence and intensity of the global fungal pathogen Batrachochytrium dendrobatidis (Bd) across 14 populations. Four populations were sampled across two decades, enabling temporal comparisons of selection and demography. We recovered 37 unique MHC alleles, including 17 that were shared across populations. Phylogenetic and population genetic patterns between MHC and neutral markers were incongruent, and five MHC codon positions associated with peptide binding were under positive selection. MHC heterozygosity, but not neutral marker heterozygosity, was a significant factor explaining spatial patterns of Bd prevalence, whereas only environmental variables predicted Bd intensity. MHC allelic richness (AR) decreased significantly over time but microsatellite-based AR did not, highlighting a loss of functional immunogenetic diversity that may be associated with Bd selective pressures. MHC supertype 4 was significantly associated with an elevated risk of Bd infection, whereas one supertype 2 allele was associated with a nearly significant reduced risk of Bd. Taken together, these results provide evidence that positive selection contributes to MHC class IIß evolution in R. pipiens and suggest that functional MHC differences across populations may contribute to disease adaptation.

MHC Class II Heterozygosity Associated With Attractiveness of Men and Women.

The genes of the Major Histocompatibility Complex (MHC), which plays a fundamental role in the immune system, are some of the most diverse genes in vertebrates and have been connected to mate choice in several species, including humans. While studies suggest a positive relationship between MHC diversity and male facial attractiveness, the connection of MHC diversity to other visual traits and female attractiveness is still unclear. The purpose of this study was to investigate further whether MHC heterozygosity, indicating genetic quality, is associated with visual traits affecting mate preferences in humans. In total 74 Latvian men and 49 women were genotyped for several MHC loci and rated for facial and, in men, also body attractiveness. The results indicate a preference for MHC heterozygous female and male faces. However, the initially positive relationship between MHC heterozygosity and facial attractiveness becomes non-significant in females, when controlling for multiple testing, and in males, when age and fat content is taken into account, referring to the importance of adiposity in immune function and thus also attractiveness. Thus overall the effect of MHC heterozygosity on attractiveness seems weak. When considering separate loci, we show that the main gene related to facial attractiveness is the MHC class II DQB1; a gene important also in viral infections and autoimmune diseases. Indeed, in our study, heterozygous individuals are rated significantly more attractive than their homozygous counterparts, only in relation to gene DQB1. This study is the first to indicate a link between DQB1 and attractiveness in humans.

Depletion of MHC supertype during domestication can compromise immunocompetence.

The major histocompatibility complex (MHC) plays an important role in infectious disease resistance. The presence of certain MHC alleles and functionally similar groups of MHC alleles (i.e., supertypes) has been associated with resistance to particular parasite species. Farmed and domesticated fish stocks are often depleted in their MHC alleles and supertype diversity, possibly as a consequence of artificial selection for desirable traits, inbreeding (loss of heterozygosity), genetic drift (loss of allelic diversity) and/or reduced parasite biodiversity. Here we quantify the effects of depletion of MHC class II genotype and supertype variation on resistance to the parasite Gyrodactylus turnbulli in guppies (Poecilia reticulata). Compared to the descendants of wild‐caught guppies, ornamental fish had a significantly reduced MHC variation (i.e., the numbers of MHC alleles and supertypes per individual, and per population). In addition, ornamental fish were significantly more susceptible to G. turnbulli infections, accumulating peak intensity 10 times higher than that of their wildtype counterparts. Four out of 13 supertypes were associated with a significantly reduced parasite load, and the presence of some supertypes had a dramatic effect on the intensity of infection. Remarkably, the ornamental and wildtype fish differed in the supertypes that were associated with parasite resistance. Analysis with a genetic algorithm showed that resistance‐conferring supertypes of the wildtype and ornamental fish shared two unique amino acids in the peptide‐binding region of the MHC that were not found in any other alleles. These data show that the supertype demarcation captures some, but not all, of the variation in the immune function of the alleles. This study highlights the importance of managing functional MHC diversity in livestock, and suggests there might be some immunological redundancy among MHC supertypes.

MHC-Based Mate Choice in Wild Golden Snub-Nosed Monkeys.

The genes of the major histocompatibility complex (MHC) are an important component of the vertebrate immune system and play a significant role in mate choice in many species. However, it remains unclear whether female mate choice in non-human primates is based on specific functional genes and/or genome-wide genes. The golden snub-nosed monkey (Rhinopithecus roxellana) lives in a multilevel society, which consists of several polygynous one-male-several-female units. Although adult females tend to mainly socialize with one adult male, females often initiate extra-pair copulations with other males resulting in a high proportion of offspring being fathered by extra-pair males. We investigated the effects of adaptive MHC genes and neutral microsatellites on female mate choice in a wild R. roxellana population. We sequenced 54 parent-offspring triads using two MHC class II loci (Rhro-DQA1 and Rhro-DQB1) and 20 microsatellites from 3 years of data. We found that the paternities of offspring were non-randomly associated with male MHC compositions not microsatellite genotypes. Our study showed that the fathers of all infants had significantly less variance for several estimates of genetic similarity to the mothers compared with random males at both MHC loci. Additionally, the MHC diversity of these fathers was significantly higher than random males. We also found support for choice based on specific alleles; compared with random males, Rhro-DQA1∗ 05 and Rhro-DQB1∗ 08 were more common in both the OMU (one-male unit) males and the genetic fathers of offspring. This study provides new evidence for female mate choice for MHC-intermediate dissimilarity (rather than maximal MHC dissimilarity) and highlights the importance of incorporating multiple MHC loci and social structure into studies of MHC-based mate choice in non-human primates.

Homozygosity indicators in canine MHC region of the Standard Poodle and Leonberger populations

Homozygosity indicators in canine MHC region of the Standard Poodle and Leonberger populations