FGF INDUCES NEW FEATHER BUDS FROM DEVELOPING AVIAN SKIN

Induction of skin appendages involves a cascade of molecular events, T he fibroblast growth factor (FGF) family of peptide growth factors is involved in cell proliferation and morphogenesis. We explored the role of the FGFs during skin appendage induction using developing chicken feather buds as a model. FGF-1, FGF-2, or FGF-1 was added directly to the culture medium or was released from pre-soaked Affigel blue beads, Near the midline, FGFs led to fusion of developing feather buds, repr esenting FGFs' ability to expand feather bud domains in developing ski n, In lateral regions of the explant where feather placodes have not f ormed, FGF treatment produces a zone of condensation and a region with an increased number of feather buds, In ventral epidermis that is nor mally apteric (without feathers), FGFs can also induce new feather bud s, Like normal feather buds, the newly induced buds express Shh. The e xpression of Grb, Ras, Raf, and Erk, intracellular signaling molecules known to be downstream to tyrosine kinase receptors such as the FGF r eceptor, was enriched in feather bud domains. Genistein, an inhibitor of tyrosine kinase, suppressed feather bud formation and the effect of FGF. These results indicate that there are varied responses to FGFs d epending on epithelial competence. All the phenotypic responses, howev er, show that FGFs facilitate the formation of skin appendage domains.