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Abstract

The formation of epithelial appendages, such as the feather bud depend on interactions between the epithelium and the underlying mesenchyme. These interactions are mediated by the production of soluble signaling molecules such as Sonic hedgehog (SHH) and members of the fibroblast growth factor (FGF) family. SHH and FGF4 are both expressed in the developing feather bud and have previously been shown to be part of a regulatory signaling loop in the limb (Niswander et al. 1994, Nature 371:609). SHH has also been shown to be essential for hair follicle morphogenesis (Chiang et al. 1999, Development 205:1). To examine the role of SHH signaling in the feather bud, we treated skin explants from stage 31 chick embryos with cyclopamine, a plant alkaloid that has been shown to inhibit the response of target cells to SHH (Cooper et al, 1998, Science 280:1603). Cyclopamine treatment profoundly inhibited the growth of feather buds and the expression of both shhand fgf4. This suggests that a regulatory loop of signaling molecules that includes SHH controls feather bud development.