GENE-EXPRESSION OF THE SMALL GTP-BINDING PROTEINS RHOA, RHOB, RAC1, AND CDC42 IN ADULT-RAT BRAIN

GTPases of the Rho subfamily, i.e. Rho, Rac and Cdc42, are molecular s witches in various signaling pathways. Best characterized are their fu nctions in the regulation of the actin cytoskeleton. In neuronal cell lines they are involved in the mechanisms leading to synapse formation and plasticity. It is still unknown whether they have respective func tions in the mammalian CNS. In this case, they should be present in th e adult brain, especially in areas known for their synaptic remodeling . We have studied the expression of the Rho GTPases in adult rat brain with in situ hybridization and Western blot analysis. High amounts of RhoA, RhoB, Rac1 and Cdc42 mRNAs were detected in neurons of the hipp ocampus, i.e. in pyramidal cells of the CA1-CA4 regions as well as in granule cells of the dentate gyrus and in hilar cells. Also in cerebel lum, Purkinje and granular cells expressed the four mRNAs. Strong gene expression was also found in brainstem, thalamus and neocortex. Using Western blot analysis, RhoA and Cdc42 proteins were detected in hippo campus, cerebellum, thalamus and neocortex. It is concluded that GTPas es of the Rho family play a role in the regulation of cellular functio ns in the adult brain. (C) 1997 Elsevier Science B.V.