Project description:Quiescence is essential for the long term maintenance of adult stem cells and tissue homeostasis. However, how stem cells maintain quiescence is still poorly understood. Here we show that stem cells in the dentate gyrus of the adult hippocampus actively transcribe the proactivation factor Ascl1 regardless of their activation state. We found that the inhibitor of DNA binding protein Id4 suppresses Ascl1 activity in neural stem cell cultures. Id4 sequesters Ascl1 heterodimerisation partner, promoting the degradation of Ascl1 protein and neural stem cell quiescence. Accordingly, elimination of Id4 from stem cells in the adult hippocampus results in abnormal accumulation of Ascl1 protein and premature stem cell activation. We also found that multiple signalling pathways converge on the regulation of Id4 to control the activity of hippocampal stem cells. Id4 therefore maintains quiescence of adult neural stem cells, in sharp contrast with its role of promoting the proliferation of embryonic neural progenitors.
Project description:Adult hippocampal neurogenesis is important for certain forms of cognition and failing neurogenesis has been implicated in neuropsychiatric diseases. The neurogenic capacity of hippocampal neural stem/progenitor cells (NSPCs) depends on a balance between quiescent and proliferative states. However, how this balance is regulated remains poorly understood. Here we show that the rate of fatty acid oxidation (FAO) defines quiescence vs. proliferation in NSPCs. Quiescent NSPCs show high levels of carnitine palmitoyltransferase 1a (Cpt1a)-dependent FAO, which is downregulated in proliferating NSPCs. Pharmacological inhibition and conditional deletion of Cpt1a in vitro and in vivo leads to altered NSPC behavior, showing that Cpt1a-dependent FAO is required for stem cell maintenance and proper neurogenesis. Strikingly, experimental manipulation of malonyl-CoA, the metabolite that regulates levels of FAO, is sufficient to induce exit from quiescence and to enhance NSPC proliferation. Thus, the data presented here identify a shift in FAO metabolism that governs NSPC behavior and suggest an instructive role for fatty acid metabolism in regulating NSPC activity.
Project description:Quiescence acquisition of proliferating neural stem cells (NSCs) is required to establish the adult NSC pool yet the underlying molecular mechanisms are not well-understood. Here we showed that conditional deletion of the m6A reader Ythdf2, which promotes mRNA decay, in proliferating NSCs in the early postnatal mouse hippocampus led to elevated quiescence acquisition with decreased neurogenesis. Multimodal profiling of m6A modification, YTHDF2 binding, and mRNA decay in hippocampal NSCs identified shared targets in multiple TGFβ signaling pathway components, including TGFβ ligands, maturation factors, receptors, transcription regulators, and signaling regulators. Functionally, Ythdf2 deletion led to TGFβ signaling activation in NSCs, suppression of which rescued elevated quiescence acquisition of proliferating hippocampal NSCs. Our study reveals the dynamic nature and critical roles of mRNA decay in establishing the quiescent adult hippocampal NSC pool and uncovers a novel mode of epitranscriptomic control via co-regulation of multiple components of the same signaling pathway.
Project description:We have characterized the transcriptome of adult rat hippocampal neural stem and progenitor cell (NSPC) cultures. The NSPCs cultures can be reversibly arrested by the quiescence-promoting signal BMP4. We provide expression data from NSPCs grown as neurospheres for 4 days in vitro in the presence of FGF2 (proliferating NSPCs) or FGF2+BMP4 (quiescent NSPCs) showing that entry into quiescence involves major changes in the transcriptional profile of the cells.
Project description:Transcription profiling by array of adult neural stem cells (hGFAP-GFP+/prominin1+ cells) compared to parenchymal astrocytes that are not neurogenic (hGFAP-GFP+ cells from the diencephalon)