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Mol Cell Biol. 1995 May;15(5):2625-34.

Identification of distinct classes and functional domains of Wnts through expression of wild-type and chimeric proteins in Xenopus embryos.

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  • 1Department of Pharmacology, University of Washington School of Medicine, Seattle, USA.


Wnts are secreted signaling factors which influence cell fate and cell behavior in developing embryos. Overexpression in Xenopus laevis embryos of a Xenopus Wnt, Xwnt-8, leads to a duplication of the embryonic axis. In embryos ventralized by UV irradiation, Xwnt-8 restores expression of the putative transcription factor goosecoid, and rescues normal axis formation. In contrast, overexpression of Xwnt-5A in normal embryos generates defects in dorsoanterior structures, without inducing goosecoid or a secondary axis. To determine whether Xwnt-4 and Xwnt-11 fall into one of these two previously described classes of activity, synthetic mRNAs were introduced into animal caps, normal embryos, and UV-treated embryos. The results indicate that Xwnt-4, Xwnt-5A, and Xwnt-11 are members of a single functional class with activities that are indistinguishable in these assays. To investigate whether distinct regions of Xwnt-8 and Xwnt-5A were sufficient for eliciting the observed effects of overexpression, we generated a series of chimeric Xwnts. RNAs encoding the chimeras were injected into normal and UV-irradiated Xenopus embryos. Analysis of the embryonic phenotypes and goosecoid levels reveals that chimeras composed of carboxy-terminal regions of Xwnt-8 and amino-terminal regions of Xwnt-5A are indistinguishable from the activities of native Xwnt-8 and that are the reciprocal chimeras elicit effects indistinguishable from overexpression of native Xwnt-5A. We conclude that the carboxy-terminal halves of these Xwnts are candidate domains for specifying responses to Xwnt signals.

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