Institute for Animal Physiology, Department of Veterinary Sciences, University of Munich, Veterinärstr. 13, 80539 Munich, Germany.
Mol Immunol. 2010 Jul;47(11-12):1956-62. doi: 10.1016/j.molimm.2010.05.001. Epub 2010 May 26.
The chicken Ig-like receptor (CHIR) gene family is located on microchromosome 31, the orthologous region to the mammalian leukocyte receptor complex. CHIR are equally related to the mammalian killer Ig-like receptors and leukocyte Ig-like transcripts, but they occur in a much higher number and diversity. The chicken microchromosome 31 has been neglected in the genome sequence analysis. Here, we provide a first analysis of this region. For this purpose bacterial artificial chromosome (BAC) sequences originating from a single inbred red jungle fowl that served as basis for the chicken genome project were screened for the presence of CHIR sequences and eight BACs were identified as major CHIR containing regions. Since the sequences of these BACs that were available in the database were not complete, sequence gaps were further closed by novel data from the chicken genome project. The entire sequence was aligned into 26 contigs covering 875kbp that contained 84 functional CHIR and 46 CHIR pseudogenes that were hampered by different reasons such as premature stop codons. The 84 functional CHIR were further categorized into 35 activating (CHIRA), 26 inhibitory (CHIRB) and 23 bifunctional (CHIRAB) genes. A detailed comparison of the annotated sequence taking also into account the previously published CHIR BAC sequence originating from an Lohman selected leghorn chicken revealed that the CHIR locus seems to be a very active region with a high degree of gene reorganization that resembles a constant birth and death evolution. The present report provides a framework for the future completion of the CHIR locus. It further suggests that the entire microchromosome 31 may resemble a locus of extraordinary genomic diversity that is beneficial for the development of a large CHIR repertoire, but that has therefore lost all other genes, where such a diversification would be fatal.
鸡免疫球蛋白样受体 (CHIR) 基因家族位于微染色体 31 上，与哺乳动物白细胞受体复合物的同源区。CHIR 与哺乳动物杀伤免疫球蛋白样受体和白细胞免疫球蛋白样转录物同样相关，但它们的数量和多样性要高得多。鸡微染色体 31 在基因组序列分析中被忽视了。在这里，我们首次对该区域进行了分析。为此，我们筛选了源自作为鸡基因组项目基础的单一近交红原鸡的细菌人工染色体 (BAC) 序列，以检测 CHIR 序列的存在，并确定了 8 个 BAC 作为主要的 CHIR 包含区域。由于这些 BAC 在数据库中的序列不完整，因此通过鸡基因组项目的新数据进一步封闭了序列缺口。整个序列被排列成 26 个重叠群，覆盖 875kbp，包含 84 个功能 CHIR 和 46 个因提前终止密码子等原因受阻的 CHIR 假基因。这 84 个功能 CHIR 进一步分为 35 个激活 (CHIRA)、26 个抑制 (CHIRB) 和 23 个双功能 (CHIRAB) 基因。详细比较注释序列，同时考虑到之前发表的源自 Lohman 选择的来航鸡的 CHIR BAC 序列，结果表明 CHIR 基因座似乎是一个非常活跃的区域，具有高度的基因重排，类似于不断的生与死的进化。本报告为 CHIR 基因座的未来完成提供了一个框架。它进一步表明，整个微染色体 31 可能类似于一个具有非凡基因组多样性的基因座，这有利于发展一个大型 CHIR 库，但也因此失去了所有其他基因，而这种多样化可能是致命的。
