Evolution of a Disintegrin and Metalloproteinase Gene Family in Vertebrates

摘要

A disintegrin and metalloproteinases (ADAMs) are a family of transmembrane proteins which have diverse functions in various tissues. They play important roles in cellular and developmental processes and are present in various species. ADAMs are classified according to their expression in tissues into the somatic ADAMs (sADAMs) and the testicular ADAMs (tADAMs). The sADAMs are expressed in somatic tissues, and the testicular ADAMs (tADAMs) are expressed predominantly in the testis. The tADAMs are further classified into Group I and Group II, based on the absence or presence of introns. The mechanism of evolution of the tADAMs was unknown. Using bioinformatics tools, we performed an analysis of the evolution of ADAM genes in various vertebrates from fish to mammals. Our results show the duplication and loss of tADAMs in certain vertebrate species. In our phylogenetic analysis, all the tADAMs cluster together with ADAM9 and ADAM9-like, which we identified as a close paralog of ADAM9 in certain non-mammalian vertebrates, but are more distantly related to other sADAMs. Our synteny analysis shows that most Group II tADAMs lie next to the Adam9 gene locus and hence likely arose from tandem duplication. On the other hand, Group I tADAMs are intronless, so they likely originated through retroposition. Therefore, we hypothesize that ADAM9/9-like and the tADAM loci are hotspots of gene duplication because many events of tandem duplication and retroposition have occurred in these regions. Some tADAMs were pseudogenized in certain species as a result of duplication events. The rapid duplication of ADAM genes resulted in diverse functions of ADAMs in various species and hence contributed to the evolution of species.