RT Journal Article SR Electronic T1 RhoA Regulates Dendrite Branching in Hippocampal Neurons by Decreasing Cypin Protein Levels JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 8378 OP 8386 DO 10.1523/JNEUROSCI.0872-07.2007 VO 27 IS 31 A1 Hongxin Chen A1 Bonnie L. Firestein YR 2007 UL http://www.jneurosci.org/content/27/31/8378.abstract AB The way a dendrite is patterned determines how a neuron will receive information. The Rho GTPases have been reported to play increasingly well defined roles in determining dendritic branch and spine development and morphology. Much is known about how these small GTPases regulate the actin cytoskeleton; however, very little is known about how they alter the microtubule cytoskeleton. Our laboratory previously cloned and characterized cypin, a guanine deaminase that increases dendrite number by binding to tubulin heterodimers and promoting microtubule assembly. In the present study, we show that cypin and RhoA are part of a common pathway that regulates dendrite number. Inhibition of Rho kinase activity does not affect cypin-mediated dendrite branching. Furthermore, cypin does not affect the activity of RhoA, as measured by GTP binding to RhoA. In fact, activated RhoA acts to inhibit cypin protein expression and, by doing so, decreases dendrite number. In addition, this decrease in cypin protein occurs via a translation-dependent mechanism. Together, our data suggest that cypin acts downstream of the small GTPase RhoA to regulate dendrite branching in hippocampal neurons, providing a novel mechanism for RhoA action on microtubule dynamics.