Rac1 controls schwann cell myelination through cAMP and NF2/merlin

Abstract

During peripheral nervous system development, Schwann cells (SCs) surrounding single large axons differentiate into myelinating SCs. Previous studies implicate RhoGTPasesin SC myelination, but the mechanisms involved in RhoGTPase regulationofSC myelination are unknown. Here, we show that SC myelination is arrested in Rac1 conditional knock-out (Rac1-CKO) mice. Rac1 knock-out abrogated phosphorylation of the effector p21-activated kinase and decreased NF2/merlin phosphorylation. Mutation of NF2/merlin rescued the myelin deficitinRac1-CKO micein vivoandthe shortened processesincultured Rac1-CKO SCsin vitro. Mechanistically, cAMPlevels and E-cadherin expression were decreased in the absence of Rac1, and both were restored by mutation of NF2/merlin. Reduced cAMP is a cause of the myelin deficiency in Rac1-CKO mice, because elevation of cAMP by rolipram in Rac1-CKO mice in vivo allowed myelin formation. Thus, NF2/merlin and cAMP function downstream of Rac1 signaling in SC myelination, and cAMP levels control Rac1-regulated SC myelination. © 2012 the authors.