The small GTP-binding protein TC10 promotes nerve elongation in neuronal cells, and its expression is induced during nerve regeneration in rats

We have made a rat cDNA library using nerve-transected hypoglossal nuclei. Using this library, we performed expressed-sequence tag analysis coupled wi th in situ hybridization to identify genes whose expression is altered in r esponse to nerve injury. In this gene screening, a member of Rho family GTP ases, TC10, which had not yet been characterized in neuronal cells, was ide ntified. TC10 mRNA expression was very low in normal motor neurons; however , axotomy induced its expression dramatically. Other family members such as RhoA, Rac1, and Cdc42 were moderately expressed in normal motor neurons an d showed slight upregulation after axotomy. The expression level of TC10 mR NA was low in the embryonic brain and gradually increased with development. However, the expression of TC10 mRNA in the adult brain was lower and more restricted than that of RhoA, Rac1, and Cdc42. Cultured dorsal root gangli a exhibited dramatic neurite extension secondary to adenovirus-mediated exp ression of TC10. It can be concluded that although TC10 expression is lower in developing and mature motor neurons compared with other Rho family memb ers, TC10 expression is induced by nerve injury to play a crucial role in n erve regeneration, particularly neurite elongation, in cooperation with oth er family members.