Impaired adult neurogenesis in mice lacking the transcription factor E2F1.
ABSTRACT During nervous system development the fate of neural stem cells-whether to undergo proliferation, differentiation, or apoptosis-is controlled by various signals, such as growth factors. Here, we demonstrate that the transcription factor E2F1, which is targeted by several signaling cascades that are activated by growth factors, is involved in neurogenesis in the adult brain. When analyzing the brains of E2F1-deficient mice, we found significantly decreased stem cell and progenitor division in the proliferative zones of the lateral ventricle wall and the hippocampus. As a consequence, the production of newborn neurons in the adult olfactory bulb and dentate gyrus was decreased. Neuronal cell counts of the adult cerebellum revealed a mild but significant cerebellar atrophy, whereas neocortical neurons were unaffected, suggesting that E2F1 deficiency produces a predominantly postnatal phenotype. The results indicate an involvement of E2F1 in controlling proliferation and neuronal cell numbers in the postnatal and adult brain.
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ABSTRACT: Neurons of the mammalian neocortex are produced by proliferating cells located in the ventricular zone (VZ) lining the lateral ventricles. This is a complex and sequential process, requiring precise control of cell cycle progression, fate commitment and differentiation. We have analyzed publicly available databases from mouse and human to identify candidate genes that are potentially involved in regulating early neocortical development and neurogenesis. We used a mouse in situ hybridization dataset (The Allen Institute for Brain Science) to identify 13 genes (Cdon, Celsr1, Dbi, E2f5, Eomes, Hmgn2, Neurog2, Notch1, Pcnt, Sox3, Ssrp1, Tead2, Tgif2) with high correlation of expression in the proliferating cells of the VZ of the neocortex at early stages of development (E15.5). We generated a similar human brain network using microarray and RNA-seq data (BrainSpan Atlas) and identified 407 genes with high expression in the developing human VZ and subventricular zone (SVZ) at 8-9 post-conception weeks. Seven of the human genes were also present in the mouse VZ network. The human and mouse networks were extended using available genetic and proteomic datasets through GeneMANIA. A gene ontology search of the mouse and human networks indicated that many of the genes are involved in the cell cycle, DNA replication, mitosis and transcriptional regulation. The reported involvement of Cdon, Celsr1, Dbi, Eomes, Neurog2, Notch1, Pcnt, Sox3, Tead2 and Tgif2 in neural development or diseases resulting from the disruption of neurogenesis validates these candidate genes. Taken together, our knowledge-based discovery method has validated the involvement of many genes already known to be involved in neocortical development and extended the potential number of genes by 100's, many of which are involved in functions related to cell proliferation but others of which are potential candidates for involvement in the regulation of neocortical development.Frontiers in Neuroscience 08/2014; 8. DOI:10.3389/fnins.2014.00257
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ABSTRACT: Fate decisions in neural progenitor cells are orchestrated via multiple pathways, and the role of histone acetylation in these decisions has been ascribed to a general function promoting gene activation. Here, we show that the histone acetyltransferase (HAT) cofactor transformation/transcription domain-associated protein (Trrap) specifically regulates activation of cell-cycle genes, thereby integrating discrete cell-intrinsic programs of cell-cycle progression and epigenetic regulation of gene transcription in order to control neurogenesis. Deletion of Trrap impairs recruitment of HATs and transcriptional machinery specifically to E2F cell-cycle target genes, disrupting their transcription with consequent cell-cycle lengthening specifically within cortical apical neural progenitors (APs). Consistently, Trrap conditional mutants exhibit microcephaly because of premature differentiation of APs into intermediate basal progenitors and neurons, and overexpressing cell-cycle regulators in vivo can rescue these premature differentiation defects. These results demonstrate an essential and highly specific role for Trrap-mediated histone regulation in controlling cell-cycle progression and neurogenesis.Cell stem cell 05/2014; 14(5):632-43. DOI:10.1016/j.stem.2014.04.001 · 22.15 Impact Factor
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ABSTRACT: Neural stem/progenitor cell (NSPC) proliferation and self-renewal, as well as insult-induced differentiation, decrease markedly with age. The molecular mechanisms responsible for these declines remain unclear. Here, we show that levels of NAD+ and nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme in mammalian NAD+ biosynthesis, decrease with age in the hippocampus. Ablation of Nampt in adult NSPCs reduced their pool and proliferation in vivo. The decrease in the NSPC pool during aging can be rescued by enhancing hippocampal NAD+ levels. Nampt is the main source of NSPC NAD+ levels and required for G1/S progression of the NSPC cell cycle. Nampt is also critical in oligodendrocytic lineage fate decisions through a mechanism mediated redundantly by Sirt1 and Sirt2. Ablation of Nampt in the adult NSPCs in vivo reduced NSPC-mediated oligodendrogenesis upon insult. These phenotypes recapitulate defects in NSPCs during aging, giving rise to the possibility that Nampt-mediated NAD+ biosynthesis is a mediator of age-associated functional declines in NSPCs.The EMBO Journal 01/2014; 33(12). DOI:10.1002/embj.201386917 · 10.75 Impact Factor