Abstract
RhoA, a member of the Rho family small GTPases, has been shown to play important roles in axon guidance. However, to date, the physiological function of RhoA in axon guidance events in vivo has not been determined genetically in animals. Here we show that RhoA mRNA is strongly expressed by sensory neurons in the developing mouse dorsal root ganglia (DRG). We have deleted RhoA in sensory neurons of the DRG using RhoA-floxed mice under the Wnt1-Cre driver in which Cre is strongly expressed in sensory neurons. Peripheral projections of sensory neurons appear normal and there are no detectable defects in the central projections of either cutaneous or proprioceptive sensory neurons in RhoAf/f; Wnt1-Cre mice. Furthermore, a co-culture assay using DRG explants from RhoAf/f; Wnt1-Cre embryos, and 293T cells expressing semaphorin3A (Sema3A) reveals that RhoA is not required for Sema3A-mediated axonal repulsion of sensory neurons. Expression of RhoC, a closely related family member, is increased in RhoA-deficient sensory neurons and may play a compensatory role in this context. Taken together, these genetic studies demonstrate that RhoA is dispensable for peripheral and central projections of sensory neurons in the DRG.
Highlights
RhoA, a member of the small Rho GTPase family that regulates the cytoskeleton, has been implicated in various processes during the nervous system development, including the formation of adherens junctions, neuronal migration, and axon guidance (Giniger, 2002; Guan and Rao, 2003; Gallo and Letourneau, 2004; Heasman and Ridley, 2008; Hall and Lalli, 2010)
These expression analyses suggest that RhoA may have a role in spinal neurons including motor neurons and dorsal root ganglia (DRG) sensory neurons
We focus on the expression of RhoA in the DRG
Summary
RhoA, a member of the small Rho GTPase family that regulates the cytoskeleton, has been implicated in various processes during the nervous system development, including the formation of adherens junctions, neuronal migration, and axon guidance (Giniger, 2002; Guan and Rao, 2003; Gallo and Letourneau, 2004; Heasman and Ridley, 2008; Hall and Lalli, 2010). The physiological roles and functions of RhoA in the mammalian nervous system have just begun to be elucidated by loss-of-function studies using conditional genetargeting strategies (Herzog et al, 2011; Katayama et al, 2011; Cappello et al, 2012) These recent studies demonstrate that RhoA is essential for proper formation of adherens junctions and proliferation of neural progenitor cells in the mouse nervous system (Herzog et al, 2011; Katayama et al, 2011; Cappello et al, 2012), which is consistent with previous in vitro and invertebrate studies (Fukata and Kaibuchi, 2001; Bloor and Kiehart, 2002; Magie et al, 2002; Yamada and Nelson, 2007). The requirement of RhoA in Sema3A-dependent or -independent axonal repulsion in vivo during mammalian nervous system development remains unanswered
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