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Kamiyama D.,University of California at San Francisco | McGorty R.,University of California at San Francisco | Kamiyama R.,University of California at San Francisco | Kim M.D.,Miami Institute of Molecular Imaging and Computation | And 4 more authors.
Developmental Cell | Year: 2015

Precise positioning of dendritic branches is a critical step in the establishment of neuronal circuitry. However, there is limited knowledge on how environmental cues translate into dendrite initiation or branching at a specific position. Here, through a combination of mutation, RNAi, and imaging experiments, we found that a Dscam-Dock-Pak1 hierarchical interaction defines the stereotypical dendrite growth site in the Drosophila aCC motoneuron. This interaction localizes the Cdc42 effector Pak1 to the plasma membrane at the dendrite initiation site before the activation of Cdc42. Ectopic expression of membrane-anchored Pak1 overrides this spatial specification of dendritogenesis, confirming its function in guiding Cdc42 signaling. We further discovered that Dscam1 localization in aCC occurs through an inter-neuronal contact that involves Dscam1 in the partner MP1 neuron. These findings elucidate a mechanism by which Dscam1 controls neuronal morphogenesis through spatial regulation of Cdc42 signaling and, subsequently, cytoskeletal remodeling. Proper neuronal wiring requires precise positioning of dendritic branches. Kamiyama et al. show that a Dscam1-Dock-Pak1 hierarchical interaction defines the site of dendritogenesis in the aCC motoneuron in Drosophila, in part via Dscam1-dependent inter-neuronal interactions that specify Dscam1 localization in aCC. © 2015 Elsevier Inc.. Source

Sharifai N.,University of Miami | Sharifai N.,Miami Institute of Molecular Imaging and Computation | Samarajeewa H.,University of Miami | Samarajeewa H.,Miami Institute of Molecular Imaging and Computation | And 9 more authors.
PLoS ONE | Year: 2014

Protein interactions underlie the complexity of neuronal function. Potential interactions between specific proteins in the brain are predicted from assays based on genetic interaction and/or biochemistry. Genetic interaction reveals endogenous, but not necessarily direct, interactions between the proteins. Biochemistry-based assays, on the other hand, demonstrate direct interactions between proteins, but often outside their native environment or without a subcellular context. We aimed to achieve the best of both approaches by visualizing protein interaction directly within the brain of a live animal. Here, we show a proof-of-principle experiment in which the Cdc42 GTPase associates with its alleged partner WASp within neurons during the time and space that coincide with the newly developing CNS. © 2014 Sharifai et al. Source

Boulina M.,University of Miami | Boulina M.,Miami Institute of Molecular Imaging and Computation | Samarajeewa H.,University of Miami | Samarajeewa H.,Miami Institute of Molecular Imaging and Computation | And 5 more authors.
Development (Cambridge) | Year: 2013

We describe LOLLIbow, a Brainbow-based live imaging system with applications in developmental biology and neurobiology. The development of an animal, including the environmentally sensitive adaptation of its brain, is thought to proceed through continual orchestration among diverse cell types as they divide, migrate, transform and interact with one another within the body. To facilitate direct visualization of such dynamic morphogenesis by individual cells in vivo, we have modified the original Brainbow for Drosophila in which live imaging is practical during much of its development. Our system offers permanent fluorescent labels that reveal fine morphological details of individual cells without requiring dissection or fixation of the samples. It also features a non-invasive means to control the timing of stochastic tricolor cell labeling with a light pulse. We demonstrate applicability of the new system in a variety of settings that could benefit from direct imaging of the developing multicellular organism with single-cell resolution. © 2013. Published by The Company of Biologists Ltd. Source

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