, 1998, Klein and Aplin, 2009 and Riento et al., 2005b). Moreover, RhoA had been previously implicated in the control of cortical neuron migration (Hand et al., 2005 and Kholmanskikh et al., 2003), although how RhoA activity is regulated in migrating neurons had remained unclear. By using an in vivo rescue assay, we provide evidence that Rnd3 antagonizes RhoA pathway in neurons through an interaction with the Rho GTPase-activating protein p190RhoGAP or with another unknown inhibitor that also requires T55 to interact with Rnd3. Other potential interactors with Rnd proteins in migrating neurons

Ruxolitinib datasheet include the semaphorin receptors, Plexins, which have been implicated in cortical DAPT neuron migration (Hirschberg et al., 2010) and have been shown to be bound and regulated by Rnd proteins in neurons and other cell types (Oinuma et al., 2003, Tong et al., 2007 and Uesugi et al., 2009). The finding that Rnd2, like Rnd3, promotes migration of cortical neurons by inhibiting RhoA was more unexpected because Rnd2 does not interfere with RhoA activity in fibroblasts (Chardin, 2006 and Nobes et al., 1998). The mechanism by which Rnd2 inhibits RhoA in neurons, which does not involve interaction with p190RhoGAP and is therefore

different from that of Rnd3, remains to be characterized. Although both Rnd2 and Rnd3 inhibit RhoA in migrating neurons, several lines of evidence indicate that they exert different functions: (1) the two genes cannot replace each other in shRNA rescue experiments; (2) knockdown of Rnd2 and Rnd3 results in very different morphological defects that appear during distinct phases of migration, and (3) the migration defect of Rnd3-silenced mafosfamide neurons, but not that of Rnd2-silenced neurons, can be corrected by F-actin depolymerization. We explain this apparent paradox by the fact that Rnd2 and Rnd3 have different subcellular localizations and only Rnd3 inhibits RhoA at the plasma membrane. In support of this hypothesis, we show that Rnd2 can replace

Rnd3 in migrating neurons if it is targeted to the plasma membrane by replacement of its carboxyl-terminal domain with that of Rnd3. Localization of active RhoA is dynamically regulated in migrating fibroblasts ( Pertz et al., 2006). The finding that Rnd3 and Rnd2 control different phases of radial migration by inhibiting RhoA in different cell compartments suggests that in cortical neurons as well, RhoA acts dynamically in different cellular domains to control different aspects of the migratory process. Analysis of the morphological defects of knockdown neurons provides clues to the function of Rnd3 in cortical neuron migration. Rnd3-silenced neurons present an increased average distance between the centrosome and the nucleus, suggesting that nucleokinesis is disrupted in these cells.