三个品系蛋鸭β2m基因的克隆及多态性研究

Cloning and Molecular Polymorphism of β2m Gene from Three Laying Duck Lines

为明确鸭主要组织相容性复合体Ⅰ(major histocompatibility complex,MHCⅠ)β微球蛋白(β2-microglobulin,β2m)分子的多态性和特征,推进相关免疫研究,本试验对我国3个地方品系蛋鸭的多条β2m基因进行克隆,序列经特征分析、同源比对和遗传进化分析后,进行了高变异位点的计算,并将重要变异位点在3D结构上进行了定位。结果表明,鸭β2m基因高度保守,仅个别碱基发生突变,序列中半胱氨酸、免疫球蛋白超基因家族的特征基序"Yx Cx Vx H"和与重链相互作用的位点均保守性存在;筛选的47条β2m氨基酸序列同源性为95%~100%,完全一致序列普遍存在;鸭β2m氨基酸序列与鸡同源性最高,与鱼类和两栖类最低,结果与遗传进化分析相一致;成熟肽中高变异位点和与重链相互作用的变异位点多位于β折叠上,但不会对β2m的功能产生影响。综合来看,鸭β2m基因保守性高,仅存在一种类型,与MHCⅠ重链的作用方式也相对固定。本试验结果有助于深入理解鸭β2m的分子特性,推动MHCⅠ相关免疫研究的开展。

In order to clarify the polymorphism and characteristics of β2-microglobulin（β2m） gene,a major histocompatibility complexⅠ（MHCⅠ） in ducks and promote related immune research,representative β2m genes from three local laying ducks in China were cloned.Subsequently,their sequences were analyzed through multiple sequence alignment,homologous comparison and phylogenetic tree method.The highly variable residue sites（HVSs） were estimated by Wu-kabat variability index,as well as key variable sites,then their location on reported crystal structure model were studied.As a result,duck β2m genes were highly conserved with little mutant bases.The two cysteines,the Ig feature motif YxCxVxH and the interactive residues between heavy and light chains were all highly conserved.The amino acid homology among 47 screened duckβ2m sequences ranged from 95%～100% and identical sequences were ubiquitous.Duck β2m shared thehighest homology with chicken,and the lowest with fish and amphibian,which was consistent with the results of genetic evolution analysis.Most of HVSs and mutant residues interacted with heavy chain of MHCⅠ molecule were mainly located on β-strand,but they would not affect the structure of β2m and the interaction with heavy chains.These results showed that there was only one type β2m in ducks with high conservatism and the interaction with heavy chain were stationary.The results would give us a better understanding for duck β2m and promote further immune research of MHCⅠ.