Contrasting patterns of variation in MHC loci in the Alpine newt
Contrasting patterns of variation in MHC loci in the Alpine newt
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DOI：
10.1111/j.1365-294x.2008.03757.x
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发表时间：
2008-05-01
影响因子：
4.9
通讯作者：
Radwan, J.
中科院分区：
文献类型：
--
作者：
Babik, W.;Pabijan, M.;Radwan, J.
主要组织相容性复合体（MHC）基因在病原体识别和触发适应性免疫应答中是必不可少的。尽管它们是脊椎动物中最具多态性的基因，但关于两栖动物MHC变异和进化模式的信息却很少，而众所周知，两栖动物是一个在全球范围内迅速减少的群体。由于传染病在下降中被调用，MHC变异的信息应有助于制定适当的保护策略。在这项研究中，我们研究了149高山蝾螈（Mesotriton alpestris）从三个异地种群在波兰在东北边缘的分布，这个物种的MHC变异。先前已通过皮肤移植排斥、等位酶和微卫星的研究显示了人群的遗传特异性。两个推定的表达MHC II基因座与对比水平的变化和明确的证据，它们之间的基因转换/重组进行了检测。餐-DAB基因座是高度多态性的（37个等位基因），并显示出历史上的积极选择的氨基酸替代和大量的地理分化的等位基因丰富的证据。相反，Meal-DBB基因座表现出低多态性（三个等位基因相差多达两个同义替换）和三个等位基因在地理区域之间的均匀分布。假定中性的Meal-DBB等位基因的均匀频率可以通过与Meal-DAB的连锁来解释。我们发现在等位基因丰富度的差异，在餐-DAB地区之间，与遗传漂变盛行与冰川避难所的距离增加的假设相一致。假基因位点似乎是中性进化的。DAB的变化水平与微卫星位点的变化相关，这意味着选择和漂移相互作用产生的模式观察到的边缘种群的高山蝾螈的MHC变异。
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.