SONIC HEDGEHOG IN FEATHER MORPHOGENESIS - INDUCTION OF MESENCHYMAL CONDENSATION AND ASSOCIATION WITH CELL-DEATH

Sonic hedgehog is involved in vertebrate tissue interactions during de velopment. During early feather development, Sonic hedgehog appears ve ry early in epithelial placodes, During late feather development, Soni c hedgehog expression precedes the development of the marginal plates and is specifically localized in the marginal plate epithelium, which will later undergo cell death, By using retroviral vectors, exogenous Sonic hedgehog overexpression in developing feathers induced enlarged feather buds that have either lost their anterior-posterior polarity o r exhibited reverse orientation, The enlarged dermal condensations may be mediated through broader TGF-beta 2 expression and reduced protein kinase C (PKC) expression. Reciprocal mesenchymal interaction is requ ired for the induction and maintenance of Sonic hedgehog in the epithe lial placodes. In scaleless mutant, Sonic hedgehog is absent in the ap teric region and aberrantly expressed in the mesenchyme of the abnorma l feather ridge, These findings suggest that Sonic hedgehog mediates k ey interactions between the epithelium and mesenchyme during feather m orphogenesis. (C) 1996 Wiley-Liss, Inc.