| Summary: | <p>Abstract</p> <p>Background</p> <p>Members of the disintegrin metalloproteinase (ADAM) family play important roles in cellular and developmental processes through their functions as proteases and/or binding partners for other proteins. The amphibian <it>Xenopus </it>has long been used as a model for early vertebrate development, but genome-wide analyses for large gene families were not possible until the recent completion of the <it>X. tropicalis </it>genome sequence and the availability of large scale expression sequence tag (EST) databases. In this study we carried out a systematic analysis of the <it>X. tropicalis </it>genome and uncovered several interesting features of ADAM genes in this species.</p> <p>Results</p> <p>Based on the <it>X. tropicalis </it>genome sequence and EST databases, we identified <it>Xenopus </it>orthologues of mammalian ADAMs and obtained full-length cDNA clones for these genes. The deduced protein sequences, synteny and exon-intron boundaries are conserved between most human and <it>X. tropicalis </it>orthologues. The alternative splicing patterns of certain <it>Xenopus </it>ADAM genes, such as <it>adams 22 </it>and <it>28</it>, are similar to those of their mammalian orthologues. However, we were unable to identify an orthologue for ADAM7 or 8. The <it>Xenopus </it>orthologue of ADAM15, an active metalloproteinase in mammals, does not contain the conserved zinc-binding motif and is hence considered proteolytically inactive. We also found evidence for gain of ADAM genes in <it>Xenopus </it>as compared to other species. There is a homologue of ADAM10 in <it>Xenopus </it>that is missing in most mammals. Furthermore, a single scaffold of <it>X. tropicalis </it>genome contains four genes encoding ADAM28 homologues, suggesting genome duplication in this region.</p> <p>Conclusions</p> <p>Our genome-wide analysis of ADAM genes in <it>X. tropicalis </it>revealed both conservation and evolutionary divergence of these genes in this amphibian species. On the one hand, all ADAMs implicated in normal development and health in other species are conserved in <it>X. tropicalis</it>. On the other hand, some ADAM genes and ADAM protease activities are absent, while other novel ADAM proteins in this species are predicted by this study. The conservation and unique divergence of ADAM genes in <it>Xenopus </it>probably reflect the particular selective pressures these amphibian species faced during evolution.</p>
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