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Tenascin C and tenascin R similarly prevent the formation of myelin membranes in a RhoA‐dependent manner, but antagonistically regulate the expression of myelin basic protein via a separate pathway
Author(s) -
Czopka Tim,
Von Holst Alexander,
Schmidt Gudula,
FfrenchConstant Charles,
Faissner Andreas
Publication year - 2009
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.20891
Subject(s) - rhoa , biology , microbiology and biotechnology , oligodendrocyte , myelin , tenascin c , myelin basic protein , cellular differentiation , extracellular matrix , biochemistry , signal transduction , neuroscience , central nervous system , gene
Membrane formation and the initiation of myelin gene expression are hallmarks of the differentiation of oligodendrocytes from their precursors. Here, we compared the roles of the two related extracellular matrix (ECM) glycoproteins Tenascin C (Tnc) and Tenascin R (Tnr) in oligodendrocyte differentiation. Oligodendrocyte precursors from Tnr‐deficient mice exhibited reduced differentiation, as revealed by retarded expression of myelin basic protein (MBP) in culture. This could be rescued with purified Tnr. In contrast, when we cultured oligodendrocytes on a Tnc‐containing, astrocyte‐derived ECM, they barely expressed MBP. This inhibition could be overcome when we used ECM from astrocytes deficient for Tnc, suggesting that Tnc inhibits differentiation. In contrast to their antagonistic effect on differentiation, both Tnc and Tnr similarly inhibited morphologic maturation. When oligodendrocytes were cultured on the purified glycoproteins, process elaboration and membrane expansion were reduced. Both Tnc and Tnr interfered with the activation of the small GTPase RhoA. Conversely, RhoA and Rac1 activation induced by cytotoxic necrotizing factor 1 (CNF1) increased the formation of myelin membranes, whereas Y27632‐mediated inhibition of the Rho‐cascade prevented it without, however, affecting the fraction of MBP‐expressing cells. Because Tnc and Tnr play antagonistic roles for differentiation and comparably inhibit morphologic maturation, we conclude that independent molecular pathways regulate these processes. © 2009 Wiley‐Liss, Inc.