Search

ABSTRACT: The Campero-INTA chicken of Argentina was developed to provide a robust bird that can survive under Argentinian pasture conditions with no significant additional nutrition, producing a source of animal protein for small producers or low-income families. In previous work, we described the AH paternal line of Campero and its Major Histocompatibility Complex B region (MHC-B) variation. In this work we analyzed the three remaining synthetic lines used to produce the Campero-INTA production bird: lines AS, A, and E. Because of the association between variation within the MHC of chickens and disease resistance, MHC variation within this breed is of particular interest. MHC variability within the lines used to produce the Campero-INTA chicken was examined using a 90 SNP panel encompassing the chicken MHC-B region plus the VNTR, LEI0258, located within the chicken MHC. Across all 4lines 12 haplotypes were found, with 7 of these being previously reported in North America/European breeds, reflecting the original breed sources for these birds. Three Campero unique haplotypes were found, 2 of which likely originated from MHC recombination events. MHC-B variation for all lines involved with production of the final Campero-INTA bird has now been determined.

Highly polymorphic genes of the major histocompatibility complex (MHC) encode proteins involved in the immune response that protect vertebrates from parasites and pathogen infections. MHC variation is shaped by a complex and poorly understood interplay of selective and demographic forces. Studies of MHC variation provide biologically meaningful insights useful for conservation of threatened taxa such as amphibians, which are globally declining partly due to the impact of emerging infectious diseases (e.g. chytridiomycosis). Here, we characterized MHC class IIB variation in the Apennine yellow‐bellied toad (Bombina pachypus), an endangered anuran, across its whole distribution range within the Italian peninsula. We compared MHC IIB diversity between refugial (REF) and post‐glacial expansion (PGE) areas and tested for the correlation between MHC and neutral variation to quantify the role of drift in shaping MHC diversity. Overall MHC polymorphism was limited compared to other amphibian species. Despite the clear evidence of historical positive selection acting on antigen‐binding sites, we found a significant correlation between the diversity of MHC and that of putatively neutral microsatellite markers, which suggests that genetic drift has contributed extensively to shaping MHC variation. MHC diversity was higher in the REF populations and decreased northwards into the PGE area, in accordance with the 'southern richness and northern purity' pattern. Past demographic events likely determined the reduction of MHC variation in the PGE area; in particular, the northern populations appeared to survive for a long time with a depleted MHC variation. We discussed recent population declines of B. pachypus in light of our findings. Highly polymorphic genes of the major histocompatibility complex (MHC) encode proteins involved in the immune response that protect vertebrates from parasites and pathogen infections. MHC variation is driven by a complex and poorly understood interplay of selective and demographic forces. Here we demonstrated a substantial role of genetic drift in shaping MHC diversity at the biogeographical scale in the endangered Apennine yellow‐bellied toad (Bombina pachypus), an amphibian distributed in the Italian peninsula. MHC diversity was higher in the refugial area and decreased northwards into the post‐glacial expansion area, in accordance with the "southern richness and northern purity" pattern. Past demographic events likely determined the reduction of MHC variation in the post‐glacial expansion area; in particular the northern populations appeared to survive for a long time with a depleted MHC variation. We discussed recent population declines of B. pachypus in the light of our findings. [ABSTRACT FROM AUTHOR]

Major histocompatibility complex (MHC) genes are essential in pathogen recognition and triggering an adaptive immune response. Although they are the most polymorphic genes in vertebrates, very little information on MHC variation and patterns of evolution are available for amphibians, a group known to be declining rapidly worldwide. As infectious diseases are invoked in the declines, information on MHC variation should contribute to devising appropriate conservation strategies. In this study, we examined MHC variation in 149 Alpine newts ( Mesotriton alpestris) from three allopatric population groups in Poland at the northeastern margin of the distribution of this species. The genetic distinctiveness of the population groups has previously been shown by studies of skin graft rejection, allozymes and microsatellites. Two putative expressed MHC II loci with contrasting levels of variation and clear evidence of gene conversion/recombination between them were detected. The Meal-DAB locus is highly polymorphic (37 alleles), and shows evidence of historical positive selection for amino acid replacements and substantial geographical differentiation in allelic richness. On the contrary, the Meal-DBB locus exhibits low polymorphism (three alleles differing by up to two synonymous substitutions) and a uniform distribution of three alleles among geographical regions. The uniform frequencies of the presumptively neutral Meal-DBB alleles may be explained by linkage to Meal-DAB. We found differences in allelic richness in Meal-DAB between regions, consistent with the hypothesis that genetic drift prevails with increasing distance from glacial refugia. Pseudogene loci appear to have evolved neutrally. The level of DAB variation correlated with variation in microsatellite loci, implying that selection and drift interplayed to produce the pattern of MHC variation observed in marginal populations of the Alpine newt. [ABSTRACT FROM AUTHOR]

The Campero-INTA chicken of Argentina was developed to provide a robust bird that can survive under Argentinian pasture conditions with no significant additional nutrition, producing a source of animal protein for small producers or low-income families. In previous work, we described the AH paternal line of Campero and its Major Histocompatibility Complex B region (MHC-B) variation. In this work we analyzed the three remaining synthetic lines used to produce the Campero-INTA production bird: lines AS, A, and E. Because of the association between variation within the MHC of chickens and disease resistance, MHC variation within this breed is of particular interest. MHC variability within the lines used to produce the Campero-INTA chicken was examined using a 90 SNP panel encompassing the chicken MHC-B region plus the VNTR, LEI0258, located within the chicken MHC. Across all 4lines 12 haplotypes were found, with 7 of these being previously reported in North America/European breeds, reflecting the original breed sources for these birds. Three Campero unique haplotypes were found, 2 of which likely originated from MHC recombination events. MHC-B variation for all lines involved with production of the final Campero-INTA bird has now been determined., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Small populations are likely to have a low genetic ability for disease resistance due to loss of genetic variation through inbreeding and genetic drift. In vertebrates, the highest genetic diversity of the immune system is located at genes within the major histocompatibility complex (MHC). Interestingly, parasite-mediated selection is thought to potentially maintain variation at MHC loci even in populations that are monomorphic at other loci. Therefore, general loss of genetic variation in the genome may not necessarily be associated with low variation at MHC loci. We evaluated inter- and intrapopulation variation in MHC genotypes between an inbred (Aldra) and a relatively outbred population (Hestmannøy) of house sparrows (Passer domesticus) in a metapopulation at Helgeland, Norway. Genomic (gDNA) and transcribed (cDNA) alleles of functional MHC class I and IIB loci, along with neutral noncoding microsatellite markers, were analyzed to obtain relevant estimates of genetic variation. We found lower allelic richness in microsatellites in the inbred population, but high genetic variation in MHC class I and IIB loci in both populations. This suggests that also the inbred population could be under balancing selection to maintain genetic variation for pathogen resistance.

The link between adaptive genetic variation, individual fitness and wildlife population dynamics is fundamental to the study of ecology and evolutionary biology. In this study, a Bayesian modelling approach was employed to examine whether individual variability at two major histocompatibility complex (MHC) class II loci (DQA and DRB) and eight neutral microsatellite loci explained variation in female reproductive success for wild populations of European brown hare (Lepus europaeus). We examined two aspects of reproduction: the ability to reproduce (sterility) and the number of offspring produced (fecundity). Samples were collected from eastern Austria, experiencing a sub-continental climatic regime, and from Belgium with a more Atlantic-influenced climate. As expected, reproductive success (both sterility and fecundity) was significantly influenced by age regardless of sampling locality. For Belgium, there was also a significant effect of DQA heterozygosity in determining whether females were able to reproduce (95% highest posterior density interval of the regression parameter [-3.64, -0.52]), but no corresponding effect was found for Austria. In neither region was reproduction significantly associated with heterozygosity at the DRB locus. DQA heterozygotes from both regions also showed a clear tendency, but not significantly so, to produce a larger number of offspring. Predictive simulations showed that, in Belgium, sub-populations of homozygotes will have higher rates of sterile individuals and lower average offspring numbers than heterozygotes. No similar effect is predicted for Austria. The mechanism for the spatial MHC effect is likely to be connected to mate choice for increased heterozygosity or to the linkage of certain MHC alleles with lethal recessives at other loci., (© 2010 Blackwell Publishing Ltd.)