Predicted evolutionary relationships between members of the Wnt gene family. (a) Predicted relationships between 18 of the 19 known human WNT protein sequences; WNT15 was omitted because only a partial sequence is available. (b) Predicted evolutionary relationships between selected human WNT proteins (representing each large grouping shown in (a)) and Wnt proteins from mouse, Xenopus, Drosophila, and Caenorhabditis elegans. Sequences were aligned using the ClustalW program; trees were constructed from the alignments using the neighbor-joining method and are diagrammed using midpoint rooting. Numbers indicate branch lengths.