Identification and characterization of the epithelial polarity receptor "Frizzled" in Hydra vulgaris

The Wnt signaling pathway plays an important role in the specification of c ell patterning during development in many species. Here we report the isola tion and characterization of a putative Wnt receptor, Frizzled, in Hydra vu lgaris. Analysis of the amino acid sequence of Frizzled in hydra reveals th at this receptor contains many strong sequence similarities to other known Frizzled receptors. Hydra divergence is estimated to have occurred about on e billion years ago; thus comparison of the Frizzled sequence of hydra with that of other species is likely to provide important information on the st ructure and function of those highly conserved regions. Northern and Southe rn blotting reveal that the Frizzled receptor in hydra has a 2.34-kb messag e size, and that it is encoded by a single gene. In situ hybridization usin g hydra frizzled as a probe reveals that the receptor message is restricted to the endoderm in adult hydra. This distribution supports the hypothesis that the Frizzled receptor is functioning in a pathway that controls cell d ifferentiation in hydra.