Edwards S V, Grahn M, Potts W K
Center for Mammalian Genetics, University of Florida, Gainesville 32610, USA.
Mol Ecol. 1995 Dec;4(6):719-29. doi: 10.1111/j.1365-294x.1995.tb00272.x.
Genes of the major histocompatibility complex (Mhc) are the most polymorphic functional loci in mammalian populations, but little is known of Mhc variability in natural populations of nonmammalian vertebrates. To help extend such studies to birds and relatives, we present a pair of degenerate primers that amplify polymorphic segments of one chain (the beta chain) of the class II genes from the major histocompatibility complex (Mhc) of archosaurs (birds+crocodilians). The primers target two conserved regions lying within portions of the antigen-binding site (ABS) encoded by the second exon and amplify multiple genes from both genomic DNA and cDNA. The pattern of nucleotide substitution in ABS codons of 51 sequences amplified and cloned from five species of passerine birds and an alligator (Alligator mississippiensis) indicates that archosaurian class II beta genes are subject to selective forces similar to those operating in mammalian populations. Hybridization of a genomic clone generated by the primers revealed highly polymorphic bands in a sample of Florida scrub jays (Aphelocoma coerulescens coerulescens). Because the primers amplify only part of the ABS from multiple class II genes, they will be useful primarily for generating species specific clones, thereby providing a critical inroad to more detailed structural and evolutionary studies.
主要组织相容性复合体（Mhc）的基因是哺乳动物群体中多态性最高的功能基因座，但对于非哺乳动物脊椎动物自然群体中的Mhc变异性却知之甚少。为了有助于将此类研究扩展到鸟类及其亲缘动物，我们提供了一对简并引物，可从主龙类（鸟类+鳄鱼）的主要组织相容性复合体（Mhc）中扩增II类基因一条链（β链）的多态性片段。这些引物靶向位于由第二个外显子编码的抗原结合位点（ABS）部分内的两个保守区域，并从基因组DNA和cDNA中扩增多个基因。从五种雀形目鸟类和一只短吻鳄（密西西比鳄）扩增并克隆的51个序列的ABS密码子中的核苷酸取代模式表明，主龙类II类β基因受到与在哺乳动物群体中起作用的选择力相似的选择力影响。由这些引物产生的一个基因组克隆在佛罗里达灌丛鸦（Aphelocoma coerulescens coerulescens）样本中显示出高度多态性条带。由于这些引物仅从多个II类基因中扩增ABS的一部分，它们将主要用于产生物种特异性克隆，从而为更详细的结构和进化研究提供关键切入点。
