Role of the Drosophila patched gene in positional signalling

摘要: After cellularization of the Drosophila embryo, positional differences within each primordial segment are maintained and elaborated by processes that require cell interactions. The best-documented examples such intercellular signalling mutual interactions between neighbouring cells expressing homeodomain protein engrailed secreted glycoprotein encoded wingless, homologue murine Wnt-1 gene. Little is known about molecular basis these mechanisms but activities several other genes, notably patched hedgehog, have been implicated in process. Here we show role permissive rather than instructive, its activity being required to suppress wingless transcription predisposed express latter. According this view, expression normally only those receiving an extrinsic signal, antagonizes repressive patched. We suggest may itself be receptor for implying unusual mechanism ligand-dependent inactivation.