Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan.
BMC Evol Biol. 2010 Jan 29;10:31. doi: 10.1186/1471-2148-10-31.
Trappin is a multifunctional host-defense peptide that has antiproteolytic, antiinflammatory, and antimicrobial activities. The numbers and compositions of trappin paralogs vary among mammalian species: human and sheep have a single trappin-2 gene; mouse and rat have no trappin gene; pig and cow have multiple trappin genes; and guinea pig has a trappin gene and two other derivative genes. Independent duplications of trappin genes in pig and cow were observed recently after the species were separated. To determine whether these trappin gene duplications are restricted only to certain mammalian lineages, we analyzed recently-developed genome databases for the presence of duplicate trappin genes.
The database analyses revealed that: 1) duplicated trappin multigenes were found recently in the nine-banded armadillo; 2) duplicated two trappin genes had been found in the Afrotherian species (elephant, tenrec, and hyrax) since ancient days; 3) a single trappin-2 gene was found in various eutherians species; and 4) no typical trappin gene has been found in chicken, zebra finch, and opossum. Bayesian analysis estimated the date of the duplication of trappin genes in the Afrotheria, guinea pig, armadillo, cow, and pig to be 244, 35, 11, 13, and 3 million-years ago, respectively. The coding regions of trappin multigenes of almadillo, bovine, and pig evolved much faster than the noncoding exons, introns, and the flanking regions, showing that these genes have undergone accelerated evolution, and positive Darwinian selection was observed in pig-specific trappin paralogs.
These results suggest that trappin is an eutherian-specific molecule and eutherian genomes have the potential to form trappin multigenes.
Trappin 是一种多功能宿主防御肽，具有抗蛋白水解、抗炎和抗菌活性。Trappin 基因的数量和组成在哺乳动物物种中有所不同：人类和绵羊只有一个 trappin-2 基因；小鼠和大鼠没有 trappin 基因；猪和牛有多个 trappin 基因；豚鼠有一个 trappin 基因和另外两个衍生基因。最近在物种分离后观察到猪和牛的 trappin 基因独立重复。为了确定这些 trappin 基因的重复是否仅限于某些哺乳动物谱系，我们分析了最近开发的基因组数据库中重复 trappin 基因的存在情况。
数据库分析显示：1）最近在九带犰狳中发现了重复的 trappin 多基因；2）在古老的非洲有蹄类动物（大象、针鼹和蹄兔）中发现了重复的两个 trappin 基因；3）在各种真兽类物种中发现了单个 trappin-2 基因；4）在鸡、斑胸草雀和负鼠中未发现典型的 trappin 基因。贝叶斯分析估计 trappin 基因在非洲有蹄类动物、豚鼠、犰狳、牛和猪中的重复时间分别为 244、35、11、13 和 300 万年前。犰狳、牛和猪的 trappin 多基因的编码区比非编码外显子、内含子和侧翼区进化得更快，表明这些基因经历了加速进化，并且在猪特异性 trappin 基因中观察到了正达尔文学选择。
这些结果表明 trappin 是一种真兽类特异性分子，并且真兽类基因组有形成 trappin 多基因的潜力。
