Phylogenetic analysis of the Wnt gene family and discovery of an arthropodWnt-10 orthologue

Wnt genes encode a conserved family of secreted signaling proteins that pla y many roles in arthropod and vertebrate development. We have investigated both the phylogenetic history and molecular evolution of this gene family. We have identified a novel Wnt gene in a diversity of arthropods that it is likely an orthologue of the vertebrate Wnt-10 group. Wnt-10 is one of only two cases in which orthology between protostome and deuterostome genes cou ld be consistently assigned based on our analyses. Despite difficulties in assessing orthologies, all of our trees suggest that the most recent common ancestor of protostomes and deuterostomes possessed more than the five Wnt genes known from either arthropods or nematodes. This suggests that Wnt ge ne loss has occurred during protostome evolution. In addition, we examined the rate of amino acid evolution in the two arthropod/deuterostome ortholog y groups we identified. We found little rate variation across taxa, with th e exception that Drosophila Wnt-1 is evolving more rapidly than all vertebr ate and most arthropod orthologues. (C) 2000 Wiley-Liss, Inc.