INVOLVEMENT OF THE SONIC-HEDGEHOG GENE IN CHICK FEATHER FORMATION

To elucidate the molecular mechanisms of chick feather formation, we o bserved expression patterns of the Sonic hedgehog(Shh) gene, which is one of the vertebrate homologs of the Drosophila segment polarity gene , hedgehog, and encodes a signaling molecule functioning in limb patte rn formation and motor neuron induction. We found that the Shh gene is also expressed in the apical region of the feather placodes and then in nine to eleven longitudinal stripes along feather filaments. The st ripe was found to correspond to one of the outer marginal zones of eac h barb ridge, termed the zone of Shh expression. No significant expres sion signal was detected in the scale bud of developing legs. Thus, Sh h is likely to function as an epithelial signaling molecule in epithel iomesenchymal interaction during feather formation. Furthermore, since genes of bone morphogenetic protein-2 (BMP-2) and fibroblast growth f actor-4 (FGF-4) are coexpressed with Shh during feather formation as o bserved in limb morphogenesis, interactions among FGF-4, Shh and BMP-2 may be involved in formation of feather filaments and barbs in a simi lar fashion as elucidated in limb pattern formation. (C) 1995 Academic Press, Inc.