Bioprobes and genetics reveal the signal integration that initiates dendrites in a neuron in vivo

Precise positioning of axons and dendrites in the CNS holds the key to establishing neural networks. To achieve this, each subcellular compartment in differentiating neurons must translate cues from surrounding tissues into cytoskeletal rearrangements by orchestrating intrinsic signaling molecules. Monomeric Rho GTPases are capable of mediating diverse transmembrane signal pathways. However, the means to monitor and dissect molecular signaling within a subcellular compartment are limited, and the role of Rho GTPases and their partners remains unresolved in neurons. Here, I investigate the molecules and mechanisms that initiate dendrites in a uniquely identified neuron in Drosophila embryos. Using bioprobes to corroborate genetic evidence, we show how separate inputs integrate at the Rho GTPase Cdc42 and together restrict the initiation of dendrites to precise time and space within a neuron. My study links Cdc42 activity to dendrogenesis and introduces a powerful approach by which to study molecular integration within differentiating neurons in vivo.