DISTINCT EXPRESSION AND SHARED ACTIVITIES OF MEMBERS OF THE HEDGEHOG GENE FAMILY OF XENOPUS-LAEVIS

The hedgehog family of signaling proteins is associated with a variety of spatial patterning activities in insects and vertebrates. Here we show that new members of this family isolated from Xenopus laevis are expressed embryonically in patterns suggestive of roles in patterning in the ectoderm, nervous system and somites, Banded hedgehog is expres sed throughout the neural plate and subsequently in both the nervous s f;stem and in the dermatome of somites, Cephalic hedgehog is expressed in anterior ectoderm and endodermal structures, and sonic hedgehog is expressed in patterns which parallel those in other species. Injectio n of RNAs encoding Xenopus hedgehogs induces ectopic cement gland form ation in embryos, Similar to reported activities of noggin and follist atin, Xenopus hedgehogs share a common ability to induce cement glands in animal cap explants. However, hedgehog activities in naive ectoder m appear capable of acting independently of noggin and follistatin sin ce, although all three are induced by activin in animal cap explants, X-hh expression does not induce noggin or follistatin.