PATTERNING OF THE NEURAL ECTODERM OF XENOPUS-LAEVIS BY THE AMINO-TERMINAL PRODUCT OF HEDGEHOG AUTOPROTEOLYTIC CLEAVAGE

The patterns of embryonic expression and the activities of Xenopus mem bers of the hedgehog gene family are suggestive of roles in neural ind uction and patterning, We report that these hedgehog polypeptides unde rgo autoproteolytic cleavage. Injection into embryos of mRNAs encoding Xenopus banded-hedgehog (X-bhh) or the amino-terminal domain (N) demo nstrates that the direct inductive activities of X-bhh are encoded by N, In addition, both N and X-bhh pattern neural tissue by elevating ex pression of anterior neural genes, Unexpectedly, an internal deletion of X-bhh (Delta N-C) was found to block the activity of X-bhh and N in explants and to reduce dorsoanterior structures in embryos. As elevat ed hedgehog activity increases the expression of anterior neural genes , and as Delta N-C reduces dorsoanterior structures, these complementa ry data support a role for hedgehog in neural induction and anteropost erior patterning.