Phosphorylation State of Olig2 Regulates Proliferation of Neural Progenitors

SummaryThe bHLH transcription factors that regulate early development of the central nervous system can generally be classified as either antineural or proneural. Initial expression of antineural factors prevents cell cycle exit and thereby expands the pool of neural progenitors. Subsequent (and typically transient) expression of proneural factors promotes cell cycle exit, subtype specification, and differentiation. Against this backdrop, the bHLH transcription factor Olig2 in the oligodendrocyte lineage is unorthodox, showing antineural functions in multipotent CNS progenitor cells but also sustained expression and proneural functions in the formation of oligodendrocytes. We show here that the proliferative function of Olig2 is controlled by developmentally regulated phosphorylation of a conserved triple serine motif within the amino-terminal domain. In the phosphorylated state, Olig2 maintains antineural (i.e., promitotic) functions that are reflected in human glioma cells and in a genetically defined murine model of primary glioma

std1, a Gene Involved in Glucose Transport in Schizosaccharomyces pombe

A wild-type strain, Sp972 h(−), of Schizosaccharomyces pombe was mutagenized with ethylmethanesulfonate (EMS), and 2-deoxyglucose (2-DOG)-resistant mutants were isolated. Out of 300 independent 2-DOG-resistant mutants, 2 failed to grow on glucose and fructose (mutants 3/8 and 3/23); however, their hexokinase activity was normal. They have been characterized as defective in their sugar transport properties, and the mutations have been designated as std1-8 and std1-23 (sugar transport defective). The mutations are allelic and segregate as part of a single gene when the mutants carrying them are crossed to a wild-type strain. We confirmed the transport deficiency of these mutants by [(14)C]glucose uptake. They also fail to grow on other monosaccharides, such as fructose, mannose, and xylulose, as well as disaccharides, such as sucrose and maltose, unlike the wild-type strain. Lack of growth of the glucose transport-deficient mutants on maltose revealed the extracellular breakdown of maltose in S. pombe, unlike in Saccharomyces cerevisiae. Both of the mutants are unable to grow on low concentrations of glucose (10 to 20 mM), while one of them, 3/23, grows on high concentrations (50 to 100 mM) as if altered in its affinity for glucose. This mutant (3/23) shows a lag period of 12 to 18 h when grown on high concentrations of glucose. The lag disappears when the culture is transferred from the log phase of its growth on high concentrations. These mutants complement phenotypically similar sugar transport mutants (YGS4 and YGS5) reported earlier by Milbradt and Hoefer (Microbiology 140:2617–2623, 1994), and the clone complementing YGS4 and YGS5 was identified as the only glucose transporter in fission yeast having 12 transmembrane domains. These mutants also demonstrate two other defects: lack of induction and repression of shunt pathway enzymes and defective mating

PNJ scaffolds promote microenvironmental regulation of glioblastoma stem-like cell enrichment and radioresistance

Glioblastoma (GBM) brain tumors contain a subpopulation of self-renewing multipotent Glioblastoma stem-like cells (GSCs) that are believed to drive the near inevitable recurrence of GBM. We previously engineered temperature responsive scaffolds based on the polymer poly(N-isopropylacrylamide-co-Jeffamine M-1000 acrylamide) (PNJ) for the purpose of enriching GSCs in vitro from patient-derived samples. Here, we used PNJ scaffolds to study microenvironmental regulation of self-renewal and radiation response in patient-derived GSCs representing classical and proneural subtypes. GSC self-renewal was regulated by the composition of PNJ scaffolds and varied with cell type. PNJ scaffolds protected against radiation-induced cell death, particularly in conditions that also promoted GSC self-renewal. Additionally, cells cultured in PNJ scaffolds exhibited increased expression of the transcription factor HIF2α, which was not observed in neurosphere culture, providing a potential mechanistic basis for differences in radio-resistance. Differences in PNJ regulation of HIF2α in irradiated and untreated conditions also offered evidence of stem plasticity. These data show PNJ scaffolds provide a unique biomaterial for evaluating dynamic microenvironmental regulation of GSC self-renewal, radioresistance, and stem plasticity

Nonredundant, isoform-specific roles of HDAC1 in glioma stem cells

Glioblastoma (GBM) is characterized by an aberrant yet druggable epigenetic landscape. One major family of epigenetic regulators, the histone deacetylases (HDACs), are considered promising therapeutic targets for GBM due to their repressive influences on transcription. Although HDACs share redundant functions and common substrates, the unique isoform-specific roles of different HDACs in GBM remain unclear. In neural stem cells, HDAC2 is the indispensable deacetylase to ensure normal brain development and survival in the absence of HDAC1. Surprisingly, we find that HDAC1 is the essential class I deacetylase in glioma stem cells, and its loss is not compensated for by HDAC2. Using cell-based and biochemical assays, transcriptomic analyses, and patient-derived xenograft models, we find that knockdown of HDAC1 alone has profound effects on the glioma stem cell phenotype in a p53-dependent manner. We demonstrate marked suppression in tumor growth upon targeting of HDAC1 and identify compensatory pathways that provide insights into combination therapies for GBM. Our study highlights the importance of HDAC1 in GBM and the need to develop isoform-specific drugs

Targetable Gene Fusions Associate With The Idh Wild-Type Astrocytic Lineage In Adult Gliomas

Gene fusions involving oncogenes have been reported in gliomas and may serve as novel therapeutic targets. Using RNA-sequencing, we interrogated a large cohort of gliomas to assess for the incidence of targetable genetic fusions. Gliomas (n=390) were profiled using the ArcherDx FusionPlex Assay. Fifty-two gene targets were analyzed and fusions with preserved kinase domains were investigated. Overall, 36 gliomas (9%) harbored a total of 37 potentially targetable fusions, the majority of which were found in astrocytomas (n=34). Within this lineage 11% (25/235) of glioblastomas, 12% (5/42) of anaplastic astrocytomas, 8% (2/25) of grade II astrocytomas, and 33% (2/6) of pilocytic astrocytoma harbored targetable fusions. Fusions were significantly more frequent in IDH wild-type tumors (12%, n=31/261) relative to IDH mutants (4%; n=4/109) (p=0.011). No fusions were seen in oligodendrogliomas. The most frequently observed therapeutically targetable fusions were in FGFR (n=12), MET (n=11), and NTRK (n=8). Several additional novel fusions that have not been previously described in gliomas were identified including EGFR:VWC2 and FGFR3:NBR1. In summary, targetable gene fusions are enriched in IDH wild-type high-grade astrocytic tumors, which will influence enrollment in and interpretation of clinical trials of glioma patients