Michel Christian, Bernatchez Louis, Behrmann-Godel Jasminca
Program MGU, Man-Society-Environment, Department of Environmental Sciences, University of Basel, Basel, Switzerland.
Mol Immunol. 2009 Oct;46(16):3399-410. doi: 10.1016/j.molimm.2009.07.012. Epub 2009 Aug 14.
This study provides the first investigation of the diversity, structure, and molecular evolution of MHII beta genes in a non-model percid species -- the Eurasian perch (Perca fluviatilis L.). PCR primers developed here were highly specific, and documented a high diversity of the MHII beta1 domain in perch. Our results suggest a minimum of eight MHII beta loci in this species -- a finding congruent with several studies suggesting that many Euteleostei posses multiple MHII beta loci. As for other vertebrates, both positive selection and gene-conversion contribute to the reported high allelic diversity. Similarly, the MHII beta1 domain in perch exhibits a characteristic MHC fold known from other vertebrates. In addition, our results suggest some teleost specific differences of the MHII beta1 domain, including: differences in chemical properties of specific amino acids in the beta1 domain, the absence of the tetrapod specific glycolisation signal, and differences in the positions of some of the positively selected codons in the MHII beta1 domain, which are presumably involved in antigen binding. Future studies should investigate the teleost MHII beta genes in more details in order to confirm the suggested differences, and to determine the extent to which these differences prevail in different teleost lineages.
本研究首次对非模式鲈形目物种——欧亚鲈（Perca fluviatilis L.）的MHC IIβ基因的多样性、结构和分子进化进行了调查。在此开发的PCR引物具有高度特异性，并记录了鲈鱼MHC IIβ1结构域的高度多样性。我们的结果表明该物种至少有八个MHC IIβ基因座——这一发现与多项研究一致，这些研究表明许多真骨鱼类拥有多个MHC IIβ基因座。与其他脊椎动物一样，正选择和基因转换都导致了所报道的高等位基因多样性。同样，鲈鱼的MHC IIβ1结构域呈现出其他脊椎动物中已知的特征性MHC折叠。此外，我们的结果表明MHC IIβ1结构域存在一些硬骨鱼特有的差异，包括：β1结构域中特定氨基酸的化学性质差异、四足动物特有的糖基化信号缺失，以及MHC IIβ1结构域中一些可能参与抗原结合的正选择密码子位置的差异。未来的研究应更详细地研究硬骨鱼的MHC IIβ基因，以确认所提出的差异，并确定这些差异在不同硬骨鱼谱系中的普遍程度。
