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Title: Evolution of Trappin Genes in Mammals

item Rooney, Alejandro - Alex

Submitted to: BMC Evolutionary Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2010
Publication Date: 1/29/2010
Citation: Kato, A., Rooney, A.P., Furutani, Y., Hirose, S. 2010. Evolution of Trappin Genes in Mammals. BMC Evolutionary Biology. 10(31). Available:

Interpretive Summary: Trappins are a group of proteins that function in the immune system of animals by helping to destroy infectious microbes. Because of this ability, they are of potential value to the biomedical and agricultural industries, where they could be developed as alternatives to traditional antibiotics. The purpose of this study was to analyze the genetic diversity of trappin genes from a variety of animals. The results of our study show that trappins have undergone several rounds of gene duplications and show the propensity to diversify rapidly, within the span of a few million years. The knowledge gained from this study will help our understanding of genes contributing to the immune response of livestock as well as other species of animals.

Technical Abstract: Trappins are a family of small proteins that are constituted by an N-terminal transglutaminase-substrate (TGS) domain and a C-terminal whey acidic protein (WAP) domain. It is known that the numbers and compositions of trappin genes are varied among mammalian species: human and sheep have a single trappin-2 gene; mouse and rat have no trappin gene; pig and bovine have multiple trappin genes; and guinea pig has a trappin gene and two other genes that are derived from a trappin gene. The duplications of trappin genes in pig and bovine have occurred recently and independently after the seperation of those species, and the resultant gene duplicates have evolved rapidly. To know if these trappin gene duplications are restricted to only certain mammalian lineages, we analyzed genome databases developed by the Mammalian Genome Project for the presence of duplicate trappin genes. The database analyses revealed that: 1) nine-banded armadillo also have recently duplicated trappin multigenes; 2) elephant have anciently duplicated two trappin genes; 3) a single trappin-2 gene is found from various mammalian species; and 4) trappin-related genes were found from chicken and opossum. Molecular clock analysis estimated the date of the duplication of trappin genes in elephant, guinea pig, armadillo, bovine and pig as 130,68,15,11 and 6 million-years ago. The TGS- and WAP-coding regions of trappin multigenes in armadillo, bovine and pig evolved much higher than other exons, introns and the 5'- and 3'-flanking regions, showing that these genes have undergone accelerated evolution subsequent to gene duplication as a result of positive Darwinian selection. These results suggest that mammalian genomes have potential to form trappin multigenes in several million years.