Roundabout the Dendritic Tree?

Science's STKE  23 Oct 2007:
Vol. 2007, Issue 409, pp. tw386
DOI: 10.1126/stke.4092007tw386

The secreted protein Slit and its receptor Robo stimulate growth cone collapse and repel axons from the midline during development. Noting that Slit signaling can promote neurite branching in vitro, and that expression of Slit and Robo persists beyond the developmental stage at which axonal repulsion occurs, Furrer et al. investigated their role in vivo in dendritic development of a Drosophila neuron, the anterior corner cell (aCC) motoneuron. Visualization of individual neurons filled with a fluorescent dye revealed that, in Drosophila embryos lacking Robo, aCCs had stunted collateral dendrites. Similar results were seen when RNAi constructs directed against Robo were specifically expressed in aCCs, whereas expression of wild-type Robo in aCCs of flies lacking Robo substantially rescued dendrogenesis. Immunocytochemical analysis of extracellular Slit during embryonic development of the Drosophila central nervous system (CNS) revealed that Slit had begun to accumulate in the region at which aCC dendrites develop (as well as was found at the midline) just as their dendrogenesis began. In developing flies lacking Robo (which would be expected to capture Slit at the cell surface), this secondary site of Slit accumulation was shifted medially, as were the small aCC dendrites. In flies lacking functional Slit, dendrites failed to develop. Ectopic expression of Slit in muscles contacted by motoneurons, however, did not stimulate collateral dendrogenesis; therefore, the effect of Slit may be limited to the CNS environment. Thus, the authors conclude that, in contrast to its effects on axons, in the developing Drosophila CNS Slit signaling through Robo regulates dendrogenesis.

M.-P. Furrer, I. Vasenkova, D. Kamiyama, Y. Rosado, A. Chiba, Slit and Robo control the development of dendrites in Drosophila CNS. Development 134, 3795-3804 (2007). [Abstract] [Full Text]