摘要
主要组织相容性复合体(Major histocompatibility complex,MHC)基因是由一组紧密连锁的基因组成,是哺乳动物免疫系统中最重要的组成部分。本文选择3个MHC基因座位的第二外元,即:MHC-I类基因和II类基因的DRA和DQB座位,初步调查濒危物种中华白海豚的遗传变异。共鉴定了2个DRA、2个DQB和7个MHC-I等位基因。DRA座位遗传变异非常低,而DQB和MHC-I座位具有相对较高水平的遗传变异。并且,在DQB和MHC-I基因座位的假定的抗原结合位点(Antigen binding sites,ABS),非同义替代明显大于同义替代,提示平衡选择(Balancing selection)维持这两个座位的多态性,而在DRA座位上,并没有检测到平衡选择。系统发生分析表明中华白海豚的MHC等位基因没有聚在一起,而是和其他的物种聚在一起,符合MHC跨种进化(Transspecies evolution)的模式。
The major histocompatibility complex ( MHC ) consists of a group of closely linked genes that constitute the most important genetic component of the mammalian immune system. Exon 2 of three MHC loci, i. e. DQB and DRA of MHC class Ⅱ, and class Ⅰ, were chosen to preliminarily characterize the genetic variability of the Indo-Pacific humpback dolphin (Sousa chinensis) , an endangered species found in coastal China. The DRA, DQB and MHC-Ⅰ loci each contained two, two, and seven alleles, respectively. Little sequence variation was detected at the DRA locus, relatively higher at the DQB, but considerable sequence variation at the MHC-Ⅰ. Relatively high rates of non-synonymous ( dN ) vs. synonymous ( ds ) substitution in the antigen binding sites (ABS) suggested balancing selection for maintaining polymorphisms at the MHC-Ⅰ and DQB loci, although this result was not supported by data from the DRA locus. Phylogenetic reconstruction suggested that three MHC loci exon 2 sequences are not separated according to species, but are intermixed with other species, which was consistent with the trans-species evolution model of the MHC.
出处
《兽类学报》
CAS
CSCD
北大核心
2009年第4期372-381,共10页
Acta Theriologica Sinica
基金
国家自然科学基金重点资助项目(30830016)
国家自然科学基金面上项目(30670294)
教育部新世纪优秀人才支持计划项目(NCET-07-0445)
江苏省高校重大基础研究计划(07KJA18016)
关键词
平衡选择
遗传变异
中华白海豚
跨种进化
Balancing selection
Genetic variation
Indo-Pacifie humpback dolphin (Sousa chinensis)
Trans-species evolution