Project description:To investigate the cause(s) of the phenotype induced by PDGFA versus EGF/FGF (control) in p53-null neural progenitor cells, we performed a transcriptomic analysis in 3 independent cell lines exposed to those different growth factor conditions for 4 days.
Project description:Neural progenitor proliferation and cell fate decision from self-renewal to differentiation are crucial factors in determining brain size and morphology. The cytoskeletal dependent regulation of these processes is not entirely known. The actin-binding filamin A (FlnA) was shown to regulate proliferation of progenitors by directing changes in cell cycles proteins such as Cdk1 during G2/M phase. Here we report that functional loss of FlnA not only affects the rate of proliferation by altering cell cycle length but also causes a defect in early differentiation through changes in cell fate specification. FlnA interacts with Rho GTPase RhoA, and FlnA loss impairs RhoA activation. Disruption of either of these cytoskeletal associated proteins delays neurogenesis and promotes neural progenitors to remain in proliferative states. Aurora kinase B (Aurkb) has been implicated in cytokinesis, and peaks in expression during the G2/M phase. Inhibition of FlnA or RhoA impairs Aurkb degradation and alters its localization during mitosis. Overexpression of Aurkb replicates the same delay in neurogenesis seen with loss of FlnA or RhoA. Our findings suggest that shared cytoskeletal processes can direct neural progenitor proliferation by regulating the expression and localization of proteins that are implicated in the cell cycle progression and cell fate specification.
Project description:We performed genomic subtraction coupled to microarray-based gene expression profiling and identified the PDZ (postsynaptic density-95/Discs large/zona occludens-1)-binding kinase/T-LAK (lymphokine-activated killer T cell) cell originating protein kinase (PBK/TOPK) as a gene highly enriched in neural stem cell cultures. Previous studies have identified PBK/TOPK as a mitogen-activated protein kinase (MAPK) kinase that phosphorylated P38 MAPK but with no known expression or function in the nervous system. First, using a novel, bioinformatics-based approach to assess cross-correlation in large microarray datasets, we generated the hypothesis of a cell-cycle-related role for PBK/TOPK in neural cells. We then demonstrated that both PBK/TOPK and P38 are activated in a cell-cycle-dependent manner in neuronal progenitor cells in vitro, and inhibition of this pathway disrupts progenitor proliferation and self-renewal, a core feature of progenitors. In vivo, PBK/TOPK is expressed in rapidly proliferating cells in the adult subependymal zone (SEZ) and early postnatal cerebellar external granular layer. Using an approach based on transgenically targeted ablation and lineage tracing in mice, we show that PBK/TOPK-positive cells in the SEZ are GFAP negative but arise from GFAP-positive neural stem cells during adult neurogenesis. Furthermore, ablation of the adult stem cell population leads to concomitant loss of PBK/TOPK-positive cells in the SEZ. Together, these studies demonstrate that PBK/TOPK is a marker for transiently amplifying neural progenitors in the SEZ. Additionally, they suggest that PBK/TOPK plays an important role in these progenitors, and further implicates the P38 MAPK pathway in general, as an important regulator of progenitor proliferation and self-renewal.
Project description:We report genome wide mapping of the histone variant H2A.Z during G0/G1 and mitosis in T24 bladder cancer cells. The results show that the broad enrichment pattern of H2A.Z near transcription start sites of active genes is maintained during mitosis. Furthermore, using H2A.Z localization to visualize nucleosome positioning near the start site, we see that the +1 nucleosome of active genes shifts upstream to occupy the transcription start sites during mitosis and the nucleosome depleted region is shortened. H2A.Z is also maintained on the -2 nucleosome which also shifts towrds the transcription start site during mitosis, further contributing to the shorteneing of the nucleosome depleted region. Examination of H2A.Z duing G0/G1 and mitosis in bladder cancer cells
Project description:Entry into and exit from mitosis is driven by precisely-timed changes in protein abundance, and involves transcriptional regulation and protein degradation. However, the role of translational regulation in modulating cellular protein content during mitosis remains poorly understood. Here, using ribosome profiling, we show that translational, rather than transcriptional regulation is the dominant mechanism for modulating protein synthesis at mitotic entry. The vast majority of regulated mRNAs are translationally repressed, which contrasts previous findings of selective mRNA translational activation at mitotic entry. One of the most pronounced translationally repressed genes in mitosis is Emi1, an inhibitor of the anaphase promoting complex (APC), which is degraded during mitosis. We show that Emi1 degradation is insufficient for full APC activation and that simultaneous translational repression is required. These results provide a genome-wide view of protein translation during mitosis and suggest that translational repression may be used to ensure complete protein inactivation Ribosome profiling and mRNA-seq from 3 time points in the cell cycle