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Quassollo G.,CONICET | Quassollo G.,National University of Cordoba | Wojnacki J.,CONICET | Wojnacki J.,National University of Cordoba | And 14 more authors.
Current Biology | Year: 2015

Summary The neuronal Golgi apparatus (GA) localizes to the perinuclear region and dendrites as tubulo-vesicular structures designated Golgi outposts (GOPs). Current evidence suggests that GOPs shape dendrite morphology and serve as platforms for the local delivery of synaptic receptors. However, the mechanisms underlying GOP formation remain a mystery. Using live-cell imaging and confocal microscopy in cultured hippocampal neurons, we now show that GOPs destined to major "apical" dendrites are generated from the somatic GA by a sequence of events involving: (1) generation of a GA-derived tubule; (2) tubule elongation and deployment into the dendrite; (3) tubule fission; and (4) transport and condensation of the fissioned tubule. A RhoA-Rock signaling pathway involving LIMK1, PKD1, slingshot, cofilin, and dynamin regulates polarized GOP formation by controlling the tubule fission. Our observations identify a mechanism underlying polarized GOP biogenesis and provide new insights regarding involvement of RhoA in dendritic development and polarization. © 2015 Elsevier Ltd All rights reserved.

Mestres I.,National University of Cordoba | Mestres I.,Research Center for Regenerative Therapies | Chuang J.-Z.,Cornell University | Calegari F.,Research Center for Regenerative Therapies | And 3 more authors.
Development (Cambridge) | Year: 2016

Emerging evidence suggests that endocytic trafficking of adhesion proteins plays a crucial role in neuronal migration during neocortical development. However, molecular insights into these processes remain elusive. Here, we study the early endosomal protein Smad anchor for receptor activation (SARA) in the developing mouse brain. SARA is enriched at the apical endfeet of radial glia of the neocortex. Although SARA knockdown did not lead to detectable neurogenic phenotypes, SARA-suppressed neurons exhibited impaired orientation and migration across the intermediate zone. Mechanistically, we show that SARA knockdown neurons exhibit increased surface expression of the L1 cell adhesion molecule. Neurons ectopically expressing L1 phenocopy the migration and orientation defects caused by SARA knockdown and display increased contact with neighboring neurites. L1 knockdown effectively rescues SARA suppressioninduced phenotypes. SARA knockdown neurons eventually overcome their migration defect and enter later into the cortical plate. Nevertheless, these neurons localize at more superficial cortical layers than their control counterparts. These results suggest that SARA regulates the orientation, multipolar-to-bipolar transition and the positioning of cortical neurons via modulating surface L1 expression. © 2016. Published by The Company of Biologists Ltd.

Wojnacki J.,CONICET | Quassollo G.,CONICET | Marzolo M.-P.,University of Santiago de Chile | Caceres A.,CONICET | And 2 more authors.
Small GTPases | Year: 2014

Microtubule (MT) organization and dynamics downstream of external cues is crucial for maintaining cellular architecture and the generation of cell asymmetries. In interphase cells rhoa, rac, and Cdc42, conspicuous members of the family of small rho GTPases, have major roles in modulating MT stability, and hence polarized cell behaviors. However, MTs are not mere targets of rho GTPases, but also serve as signaling platforms coupling MT dynamics to rho GTPase activation in a variety of cellular conditions. In this article, we review some of the key studies describing the reciprocal relationship between small rho-GTPases and MTs during migration and polarization. © 2014 Landes Bioscience.

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