Sending and receiving the hedgehog signal: control by the Drosophila Gli protein Cubitus interruptus.

Drosophila limb development is organized by interactions between anterior and posterior compartment cells. Posterior cells continuously express and require engrailed (en) and secrete Hedgehog (Hh) protein. Anterior cells express the zinc-finger protein Cubitus interruptus (Ci). It is now shown that anterior cells lacking ci express hh and adopt posterior properties without expressing en. Increased levels of Ci can induce the expression of the Hh target gene decapentaplegic (dpp) in a Hh-independent manner. Thus, expression of Ci in anterior cells controls limb development (i) by restricting hh secretion to posterior cells and (ii) by conferring competence to respond to Hh by mediating the transduction of this signal

Control of Drosophila photoreceptor cell fates by phyllopod, a novel nuclear protein acting downstream of the Raf kinase.

The phyllopod (phyl) gene regulates the fates of a subset of cells in the developing Drosophila eye; in the absence of phyl function, the R1, R6, and R7 photoreceptors are transformed into additional cone cells, whereas ectopic phyl expression in the cone cell precursors transforms these cells into additional R7 cells. Within this group of cells, phyl expression thus mimics activation of the Raf pathway in its ability to induce photoreceptor rather than cone cell development. Furthermore, the transformation of cone cells into R7 cells in response to Raf activation is both accompanied by and dependent upon ectopic phyl expression. phyl thus represents a possible target gene of the Raf pathway during eye development, controlling the fates of a novel subset of photoreceptors