In summary our results have

In summary, our results have shown that Notch signaling could inhibit the expression of miR-342-5p. In NSCs where Notch signaling is activated, the level of miR-342-5p is low and NSCs maintain the potential to differentiate into GFAP-positive astrocytes. When some NSCs gradually differentiate into INPs, RBP-J expression decreases and miR-342-5p expression increases in these cells (Figure S6). These cells might lose the ability to differentiate into GFAP-positive astrocytes, and become neurogenic INPs. Therefore, miR-342-5p could perform as a downstream molecule of Notch signaling to regulate the proliferation and differentiation of NSCs.
Experimental Procedures
Author Contributions
Introduction Neural stem cells (NSCs) resident in the two main neurogenic niches of the adult mammalian apelin receptor (the subventricular zone [SVZ] of the lateral ventricle and the subgranular zone of the hippocampal dentate gyrus [DG]) are two heterogeneous populations of radial glia-like precursor cells that have astrocytic properties, express bona fide stem cell markers and rarely divide. These cells have the capacity to self-renew and differentiate, giving rise to both neurons and glia (reviewed in Bond et al., 2015; Kempermann et al., 2015). The mechanisms of fate determination in adult hippocampal NSC (aNSC) lineage is a highly debated topic (Bonaguidi et al., 2012; Kempermann, 2011) and of fundamental importance. In addition, understanding the molecular mechanisms underlying lineage determination might provide new avenues to prevent age-dependent loss of neurogenesis (Encinas et al., 2011; Marlatt and Lucassen, 2010; Pons-Espinal et al., 2013), or the pathological generation of undesirable cells such as activated glia upon trauma and epilepsy (Dibajnia and Morshead, 2013; Doetsch et al., 2002; Shimada et al., 2012; Sierra et al., 2015). Regulation of aNSC fate determination is known to be possible at the transcriptional level (Beckervordersandforth et al., 2015), but accumulating evidence indicates that additional control layers, such as epigenetics and non-coding RNAs, are involved in this mechanism (Castel and Martienssen, 2013; Cernilogar et al., 2011; Huang and Li, 2014; Li, 2014; Noguchi et al., 2015; Schouten et al., 2012). MicroRNAs (miRNAs) are small (∼22 nt long) single-stranded non-coding RNAs, which post-transcriptionally repress target mRNAs through imperfect miRNA-mRNA binding (Agarwal et al., 2015; Ha and Kim, 2014; Krol et al., 2010). They exert their regulatory functions in a highly combinatorial way: one miRNA can regulate several mRNAs in parallel (Lim et al., 2005), and different miRNAs can target one mRNA simultaneously, thus repressing its expression more efficiently (Selbach et al., 2008). Based on these observations, miRNAs are predicted to regulate the majority of mammalian mRNAs (Friedman et al., 2009). Despite the known functions of miRNAs in fate determination of embryonic and adult SVZ NSCs (Barca-Mayo and De Pietri Tonelli, 2014; Cheng et al., 2009; Zhao et al., 2009), as well as survival and dendritic maturation of adult-born neurons in the DG (Konopka et al., 2010; Magill et al., 2010; Schouten et al., 2015; Smrt et al., 2010), it has been unknown whether miRNAs regulate neuronal versus astrocyte lineage fate determination in the adult hippocampus. Indeed, as single miRNAs could have opposite effects depending on the spatiotemporal expression of their targets (Zhu et al., 2011), it is possible to hypothesize that the same miRNAs might exert different functions in various cell types involved in adult hippocampal neurogenesis. Current approaches to infer miRNA functions in vivo either manipulate single miRNAs/targets or deplete miRNAs by conditional knockouts of genes encoding essential miRNA biogenesis proteins such as DROSHA, DGCR8, or DICER. Although both approaches successfully demonstrated critical functions for specific miRNAs and miRNA biogenesis proteins in neurogenesis (Aksoy-Aksel et al., 2014; Barca-Mayo and De Pietri Tonelli, 2014; Schouten et al., 2012), most of these studies neglected the intrinsic combinatorial nature of miRNA-dependent control (Schmiedel et al., 2015; Siciliano et al., 2013), or left unresolved the question of miRNA-specific versus miRNA-independent functions of miRNA biogenesis proteins (Yang and Lai, 2011).