Yuhki Naoya, Beck Thomas, Stephens Robert, Neelam Beena, O'Brien Stephen J
Laboratory of Genomic Diversity, National Cancer Institute at Frederick, Frederick, MD 21702-1201, USA.
J Hered. 2007;98(5):390-9. doi: 10.1093/jhered/esm056. Epub 2007 Aug 3.
Comparisons of the genomic structure of 3 mammalian major histocompatibility complexes (MHCs), human HLA, canine DLA, and feline FLA revealed remarkable structural differences between HLA and the other 2 MHCs. The 4.6-Mb HLA sequence was compared with the 3.9-Mb DLA sequence from 2 supercontigs generated by 7x whole-genome shotgun assembly and 3.3-Mb FLA draft sequence. For FLA, we confirm that 1) feline FLA was split into 2 pieces within the TRIM (member of the tripartite motif) gene family found in human HLA, 2) class II, III, and I regions were placed in the pericentromeric region of the long arm of chromosome B2, and 3) the remaining FLA was located in subtelomeric region of the short arm of chromosome B2. The exact same chromosome break was found in canine DLA structure, where class II, III, and I regions were placed in a pericentromeric region of chromosome 12 whereas the remaining region was located in a subtelomeric region of chromosome 35, suggesting that this chromosome break occurred once before the split of felid and canid more than 55 million years ago. However, significant differences were found in the content of genes in both pericentromeric and subtelomeric regions in DLA and FLA, the gene number, and amplicon structure of class I genes plus 2 other class I genes found on 2 additional chromosomes; canine chromosomes 7 and 18 suggest the dynamic nature in the evolution of MHC class I genes.
对3种哺乳动物主要组织相容性复合体（MHC）——人类HLA、犬类DLA和猫科动物FLA的基因组结构进行比较后发现，HLA与其他两种MHC之间存在显著的结构差异。将4.6兆碱基（Mb）的HLA序列与通过7倍全基因组鸟枪法组装产生的2个超级重叠群中的3.9兆碱基DLA序列以及3.3兆碱基的FLA草图序列进行了比较。对于FLA，我们确认：1）猫科动物FLA在人类HLA中发现的TRIM（三方基序成员）基因家族内被分成了2段；2）II类、III类和I类区域位于B2染色体长臂的着丝粒周围区域；3）其余的FLA位于B2染色体短臂的亚端粒区域。在犬类DLA结构中发现了完全相同的染色体断裂，其中II类、III类和I类区域位于12号染色体的着丝粒周围区域，而其余区域位于35号染色体的亚端粒区域，这表明这种染色体断裂在5500多万年前猫科和犬科动物分化之前就已经发生了一次。然而，在DLA和FLA的着丝粒周围区域和亚端粒区域的基因内容、基因数量以及在另外两条染色体（犬类7号和18号染色体）上发现的I类基因加另外2个I类基因的扩增子结构方面存在显著差异，这表明MHC I类基因在进化过程中具有动态性。
