We have previously demonstrated that Sox17 regulates cell cycle exit and differentiation in oligodendrocyte progenitor cells. death had ceased. CNP-Sox17 mice showed increased Gli2 protein levels and Gli2+ cells in WM indicating that Sox17 promotes the generation of oligodendrocyte lineage cells through Hedgehog signaling. Sox17 overexpression prevented cell loss after lysolecithin-induced demyelination by increasing Olig2+ and CC1+ cells in response to injury. Furthermore Sox17 overexpression abolished the injury-induced increase in TCF7L2/TCF4+ cells and guarded oligodendrocytes from apoptosis by preventing decreases in Gli2 and Bcl-2 expression that were observed in WT lesions. Our study thus reveals a biphasic effect of Sox17 overexpression on cell survival and oligodendrocyte formation in the developing WM and that its potentiation of oligodendrocyte survival in the adult confers resistance to injury and myelin loss. This study demonstrates that overexpression of this transcription factor might be a viable protective strategy to mitigate the consequences of demyelination in the adult WM. Introduction Oligodendrogenesis from oligodendrocyte (OL) progenitor cells (OPCs) to mature myelinating OLs is usually spatially and temporally regulated by transcription factors under the control of multiple signaling pathways including canonical Wnt Sonic hedgehog Notch bone and morphogenetic proteins (Nicolay et al. SNS-032 2007 Fancy et al. 2009 Members of the SRY-box (Sox) transcription factors have emerged as crucial regulators of OL development and regeneration. Sox transcription factors that contain a conserved high mobility domain name that binds the DNA minor groove (Gubbay et al. 1990 are essential for the differentiation and maturation of OLs in the developing nervous system (Chew and Gallo 2009 Stolt and Wegner Sema3g 2010 Sox9 has an early function in maintaining the OPC populace (Stolt et al. 2003 while Sox10 is essential for terminal differentiation and myelin gene expression (Stolt et al. 2002 Inhibitory Sox factors 4 5 and 6 are also critical for timing OL SNS-032 specification and terminal differentiation (Potzner et al. 2007 Sox17 was found in the postnatal mouse white matter (WM) to be developmentally associated with the expression of multiple myelin genes SNS-032 and its pattern of expression supports a role in proliferative arrest (Sohn et al. 2006 In cultured OPCs Sox17 was shown to perform the dual functions of promoting OPC cycle exit and maturation to SNS-032 OLs (Sohn et al. 2006 Chew et al. 2011 Sox17 downregulation by siRNA increases OPC proliferation and attenuates differentiation. In addition Sox17 knockdown upregulates β-catenin and its targets cyclin D1 and Axin2. Conversely Sox17 overexpression (1) increases OPC cell cycle exit (2) decreases cyclinD1 levels and the levels and activity of b-catenin (3) promotes degradation of b-catenin (4) relieves Wnt repression of myelin protein levels and (5) enhances myelin promoter activity (Sohn et al. 2006 Chew et al. 2011 These findings identify Sox17 as a Wnt/β-catenin antagonist in the lineage and suggest that ectopic Sox17 expression may promote OL formation through Wnt modulation. To study the function of Sox17 in OLs gene promoter. The (2′ 3 nucleotide 3′- phosphodiesterase) promoter has been shown to provide strong OL lineage-specific expression in the WM (Yuan et al. 2002 We wanted to determine whether Sox17 overexpression would lead to increased development of OLs. Since demyelination upregulates Wnt signaling (Fancy et al. 2009 we also wanted to determine whether Sox17 overexpression could block Wnt signaling and alter the course of demyelination in the adult WM. Our present analysis constitutes the first study of Sox17 function in WM. Sox17 overexpression increased WM levels of the Hedgehog mediator Gli2 regulated β-catenin-expressing cells and development of the OL lineage in biphasic fashion and ultimately produced supranormal numbers of OL cells. As lysolecithin-induced demyelination injury failed to increase cell death or affect MBP levels Gli2 and the antiapoptotic protein Bcl-2 in the adult CNP-Sox17 mouse we propose that Sox17 potentiates Hedgehog signaling in its attenuation of WM damage. Materials and Methods Plasmid construct and generation of transgenic mice. The plasmid for generating transgenic mice was constructed as follows: (1) the CNP promoter plasmid CNP4.2 (Gravel et al. 1998 was altered by introducing restriction enzyme AgeI site at HindIII site to obtain CNP3.9 vector; (2) a full length of IRES-ZsGreen1 with added SNS-032 AgeI site at 5′ and XhoI site at 3′ was.