Scale bars: and = 4, = 0.0001 (Prox1), = 0.0002 (Lef1)]; this strongly supports our electroporation and conditional loss of the meningeal Bmp A 77-01 expression. (a downstream target nuclear effector of Bmp signaling) in DG neural stem cells resulted in defects in the postnatal subgranular zone and reduced neurogenesis. These results suggest that Acvr1-mediated meningeal Bmp signaling regulates Lef1 expression in the dentate, regulating embryonic DG neurogenesis, DG neural stem cell niche formation, and maintenance. Introduction The mammalian forebrain has two regions with active ongoing neurogenesis into adulthood: the subgranular zone (SGZ) in the dentate gyrus (DG), and the subventricular zone lining the lateral ventricles. In both sites the stem cell niche is established and maintained by a panoply of signals including Wnt, Sonic hedgehog (Shh), and bone morphogenic proteins (Bmps), which cooperate to maintain the neurogenic capacity of the niche (Galceran et al., 2000; Chenn and Walsh, 2002; Machold et al., 2003; Zhou et al., 2004; Lie et al., 2005; Machon et al., 2007; Favaro et al., 2009; Caronia et al., 2010; Mira et al., 2010; Munji et al., 2011). While many studies address the roles of individual morphogenic signaling pathways, these neural stem cell niches, illuminating the interplay of these signaling pathways is critical to understanding the physiologic and pathophysiologic regulation of new neuron production. Previous studies showed that Wnt signaling is pivotal in the development of the embryonic DG and in postnatal DG stem cell niche signaling. Mice with mutations in critical components of the Wnt signaling pathway A 77-01 show defective DG development and loss of DG neural stem cells (Galceran et al., 2000; Lee et al., 2000; Zhou et al., 2004; Li and Pleasure, 2005). In particular, Lef1, a Wnt-activated transcription factor selectively expressed in the developing dentate, is required for dentate granule neuron production (Galceran et al., 2000). Activation of the Wnt signaling pathway also directs the restricted expression of Prox1 in DG granule neurons and regulates DG neurogenesis in the adult (Lie et al., 2005; Machon et al., 2007; Karalay et al., 2011). The role of Bmp signaling A 77-01 Rabbit Polyclonal to 5-HT-3A in dentate development is far less established, although there have been a few relevant publications. Conditional deletion of Smad4, a common transcriptional regulator for transforming growth factor (Tgf) signaling pathways, in the adult DG radial neural stem cells reduced dentate neurogenesis (Colak et al., 2008; Caronia et al., 2010) and compromised quiescence of adult dentate neural stem cells (Mira et al., 2010). In addition, a recent study showed that post-translational control of Noggin (Nog) expression is probably involved in DG neurogenesis as well (Guo et al., 2011). However, the role of Bmp signaling in establishing the dentate has been far less clear. The one study that explicitly examines this found only modest effects of loss of function for both Bmpr1a and 1b (Caronia et al., 2010). Thus, how Bmp signaling is integrated with other niche signals in regulating DG neurogenesis remains largely unexplored. In the present study, we show that Lef1 is a landmark signaling molecule expressed by the DG neuronal stem cells throughout development of the DG and that activation of the Bmp signaling pathway through Activin receptor type I (Acvr1, also known as Alk2) regulates the expression of Lef1 in the DG stem cells A 77-01 at embryonic and postnatal stages. This study provides novel insight into how multiple signaling pathways regulating DG neurogenesis might cooperate. Materials and Methods Animals. Mice used in this study were previously described (Gli1-CreERt2, Ahn and Joyner, 2004; hGFAP-Cre, Zhuo et al., 2001; Smad4lox, Bardeesy et al., 2006; Acvr1lox, Kaartinen and Nagy, 2001; Tgfr2lox,Chytil et al., 2002; Pdgfr-Cre, Foo et al., 2006; Foxc1lox, Hayashi and Kume, 2008; Wnt1-Cre, Danielian et al., 1998; Bmp7lox, Zouvelou et al., 2009) and ROSA-YFP Cre reporter mice were obtained from The Jackson Laboratory. Experimental mice were obtained by crossing male mice carrying an allele of A 77-01 a Cre recombinase and a heterozygous allele of floxed gene to female mice carrying homozygous floxed alleles. All mice were maintained in a mixed background and experimental mice were compared with littermate controls. The day of vaginal plug was considered to be embryonic day 0.5 (E0.5). Mouse colonies were housed at the University of California, San Francisco(UCSF), in accordance with UCSF Institutional Animal Care and Use Committee (IACUC) guidelines. electroporation. Timed pregnant CD1 mice were purchased from Charles River and the surgery was conducted according to IACUC approved protocols at UCSF. Briefly,.