Local Inhibitory Action of BMPs and Their Relationships with Activators in Feather Formation: Implications for Periodic Patterning

AbstractThe formation of periodic patterns is fundamental in biology. Theoretical models describing these phenomena have been proposed for feather patterning; however, no molecular candidates have been identified. Here we show that the feather tract is initiated by a continuous stripe ofShh, Fgf-4,andPtcexpression in the epithelium, which then segregates into discrete feather primordia that are more stronglyShhandFgf-4positive. The primordia also becomeBmp-2andBmp-4positive. Bead-mediated delivery of BMPs inhibits local feather formation in contrast with the activators, SHH and FGF-4, which induce feather formation. Both FGF-4 and SHH induce local expression ofBmp-4,while BMP-4 suppresses local expression of both. FGF-4 also inducesShh.Based on these findings, we propose a model that involves (1) homogeneously distributed global activators that define the field, (2) a position-dependent activator of competence that propagates across the field, and (3) local activators and inhibitors triggered in sites of individual primordia that act in a reaction–diffusion mechanism. A computer simulation model for feather pattern formation is also presented