参考文献

A number of genes regulate regeneration of peripheral axons,but their ability to drive axon growth and regeneration in the central nervous system (CNS) remains largely untested. To address this question we overexpressed eight transcription factors and one small GTPase alone and in pairwise combinations to test whether combinatorial overexpression would have a synergistic impact on CNS neuron neurite growth. The Jun oncogene/signal transducer and activator of transcription 6 (JUN/STAT6) combination increased neurite growth in dissociated cortical neurons and in injured cortical slices. In injured cortical slices,JUN overexpression increased axon growth to a similar extent as JUN and STAT6 together. Interestingly,JUN overexpression was not associated with increased growth associated protein 43 (GAP43) or integrin alpha 7 (ITGA7) expression,though these are predicted transcriptional targets. This study demonstrates that JUN overexpression in cortical neurons stimulates axon growth,but does so independently of changes in expression of genes thought to be critical for JUNs effects on axon growth. We conclude that JUN activity underlies this CNS axonal growth response,and that it is mechanistically distinct from peripheral regeneration responses,in which increases in JUN expression coincide with increases in GAP43 expression. View Publication

BACKGROUND: Primitive brain tumors are the leading cause of cancer-related death in children. Tumor cells with stem-like properties (TSCs),thought to account for tumorigenesis and therapeutic resistance,have been isolated from high-grade gliomas in adults. Whether TSCs are a common component of pediatric brain tumors and are of clinical relevance remains to be determined. METHODOLOGY/PRINCIPAL FINDINGS: Tumor cells with self-renewal properties were isolated with cell biology techniques from a majority of 55 pediatric brain tumors samples,regardless of their histopathologies and grades of malignancy (57% of embryonal tumors,57% of low-grade gliomas and neuro-glial tumors,70% of ependymomas,91% of high-grade gliomas). Most high-grade glioma-derived oncospheres (10/12) sustained long-term self-renewal akin to neural stem cells (textgreater7 self-renewals),whereas cells with limited renewing abilities akin to neural progenitors dominated in all other tumors. Regardless of tumor entities,the young age group was associated with self-renewal properties akin to neural stem cells (P = 0.05,chi-square test). Survival analysis of the cohort showed an association between isolation of cells with long-term self-renewal abilities and a higher patient mortality rate (P = 0.013,log-rank test). Sampling of low- and high-grade glioma cultures showed that self-renewing cells forming oncospheres shared a molecular profile comprising embryonic and neural stem cell markers. Further characterization performed on subsets of high-grade gliomas and one low-grade glioma culture showed combination of this profile with mesenchymal markers,the radio-chemoresistance of the cells and the formation of aggressive tumors after intracerebral grafting. CONCLUSIONS/SIGNIFICANCE: In brain tumors affecting adult patients,TSCs have been isolated only from high-grade gliomas. In contrast,our data show that tumor cells with stem cell-like or progenitor-like properties can be isolated from a wide range of histological sub-types and grades of pediatric brain tumors. They suggest that cellular mechanisms fueling tumor development differ between adult and pediatric brain tumors. View Publication

Neurodevelopmental defects are observed in the hereditary disorder Cockayne syndrome (CS). The gene most frequently mutated in CS,Cockayne Syndrome B (CSB),is required for the repair of bulky DNA adducts in transcribed genes during transcription-coupled nucleotide excision repair. CSB also plays a role in chromatin remodeling and mitochondrial function. The role of CSB in neural development is poorly understood. Here we report that the abundance of neural progenitors is normal in Csb(-/-) mice and the frequency of apoptotic cells in the neurogenic niche of the adult subependymal zone is similar in Csb(-/-) and wild type mice. Both embryonic and adult Csb(-/-) neural precursors exhibited defective self-renewal in the neurosphere assay. In Csb(-/-) neural precursors,self-renewal progressively decreased in serially passaged neurospheres. The data also indicate that Csb and the nucleotide excision repair protein Xpa preserve embryonic neural stem cell self-renewal after UV DNA damage. Although Csb(-/-) neural precursors do not exhibit altered neuronal lineage commitment after low-dose UV (1J/m(2)) in vitro,neurons differentiated in vitro from Csb(-/-) neural precursors that had been irradiated with 1J/m(2) UV exhibited defective neurite outgrowth. These findings identify a function for Csb in neural precursors. View Publication

Pantothenate kinase-associated neurodegeneration (PKAN) is an early onset and severely disabling neurodegenerative disease for which no therapy is available. PKAN is caused by mutations in PANK2,which encodes for the mitochondrial enzyme pantothenate kinase 2. Its function is to catalyze the first limiting step of Coenzyme A (CoA) biosynthesis. We generated induced pluripotent stem cells from PKAN patients and showed that their derived neurons exhibited premature death,increased ROS production,mitochondrial dysfunctions-including impairment of mitochondrial iron-dependent biosynthesis-and major membrane excitability defects. CoA supplementation prevented neuronal death and ROS formation by restoring mitochondrial and neuronal functionality. Our findings provide direct evidence that PANK2 malfunctioning is responsible for abnormal phenotypes in human neuronal cells and indicate CoA treatment as a possible therapeutic intervention. View Publication

Neurogenesis in the adult brain is important for memory and learning,and the alterations in neural stem cells (NSCs) may be an important part of Alzheimer's disease pathogenesis. The phosphatidylinositol 3-kinase (PI3K) pathway has been suggested to play an important role in neuronal cell survival and is highly involved in adult neurogenesis. Recently,coenzyme Q10 (CoQ10) was found to affect the PI3K pathway. We investigated whether CoQ10 could restore amyloid β (Aβ)25-35 oligomer-inhibited proliferation of NSCs by focusing on the PI3K pathway. To evaluate the effects of CoQ10 on Aβ25-35 oligomer-inhibited proliferation of NSCs,NSCs were treated with several concentrations of CoQ10 and/or Aβ25-35 oligomers. BrdU labeling,Colony Formation Assays,and immunoreactivity of Ki-67,a marker of proliferative activity,showed that NSC proliferation decreased with Aβ25-35 oligomer treatment,but combined treatment with CoQ10 restored it. Western blotting showed that CoQ10 treatment increased the expression levels of p85α PI3K,phosphorylated Akt (Ser473),phosphorylated glycogen synthase kinase-3β (Ser9),and heat shock transcription factor,which are proteins related to the PI3K pathway in Aβ25-35 oligomers-treated NSCs. To confirm a direct role for the PI3K pathway in CoQ10-induced restoration of proliferation of NSCs inhibited by Aβ25-35 oligomers,NSCs were pretreated with a PI3K inhibitor,LY294002; the effects of CoQ10 on the proliferation of NSCs inhibited by Aβ25-35 oligomers were almost completely blocked. Together,these results suggest that CoQ10 restores Aβ25-35 oligomer-inhibited proliferation of NSCs by activating the PI3K pathway. View Publication

Protein synthesis regulation via mammalian target of rapamycin complex 1 (mTORC1) signaling pathway has key roles in neural development and function,and its dysregulation is involved in neurodevelopmental disorders associated with autism and intellectual disability. mTOR regulates assembly of the translation initiation machinery by interacting with the eukaryotic initiation factor eIF3 complex and by controlling phosphorylation of key translational regulators. Collybistin (CB),a neuron-specific Rho-GEF responsible for X-linked intellectual disability with epilepsy,also interacts with eIF3,and its binding partner gephyrin associates with mTOR. Therefore,we hypothesized that CB also binds mTOR and affects mTORC1 signaling activity in neuronal cells. Here,by using induced pluripotent stem cell-derived neural progenitor cells from a male patient with a deletion of entire CB gene and from control individuals,as well as a heterologous expression system,we describe that CB physically interacts with mTOR and inhibits mTORC1 signaling pathway and protein synthesis. These findings suggest that disinhibited mTORC1 signaling may also contribute to the pathological process in patients with loss-of-function variants in CB.European Journal of Human Genetics advance online publication,22 April 2015; doi:10.1038/ejhg.2015.69. View Publication

The PI3K/AKT/mTOR pathway is commonly over activated in glioblastoma (GBM),and Rictor was shown to be an important regulator downstream of this pathway. EGFR overexpression is also frequently found in GBM tumors,and both EGFR and Rictor are associated with increased proliferation,invasion,metastasis and poor prognosis. This research evaluated in vitro and in vivo whether the combined silencing of EGFR and Rictor would result in therapeutic benefits. The therapeutic potential of targeting these proteins in combination with conventional agents with proven activity in GBM patients was also assessed. In vitro validation studies were carried out using siRNA-based gene silencing methods in a panel of three commercially available human GBM cell lines,including two PTEN mutant lines (U251MG and U118MG) and one PTEN-wild type line (LN229). The impact of EGFR and/or Rictor silencing on cell migration and sensitivity to chemotherapeutic drugs in vitro was determined. In vivo validation of these studies was focused on EGFR and/or Rictor silencing achieved using doxycycline-inducible shRNA-expressing U251MG cells implanted orthotopically in Rag2M mice brains. Target silencing,tumor size and tumor cell proliferation were assessed by quantification of immunohistofluorescence-stained markers. siRNA-mediated silencing of EGFR and Rictor reduced U251MG cell migration and increased sensitivity of the cells to irinotecan,temozolomide and vincristine. In LN229,co-silencing of EGFR and Rictor resulted in reduced cell migration,and increased sensitivity to vincristine and temozolomide. In U118MG,silencing of Rictor alone was sufficient to increase this line's sensitivity to vincristine and temozolomide. In vivo,while the silencing of EGFR or Rictor alone had no significant effect on U251MG tumor growth,silencing of EGFR and Rictor together resulted in a complete eradication of tumors. These data suggest that the combined silencing of EGFR and Rictor should be an effective means of treating GBM. View Publication

Considerable progress has been made in identifying signaling pathways that direct the differentiation of human pluripotent stem cells (hPSCs) into specialized cell types,including neurons. However,differentiation of hPSCs with extrinsic factors is a slow,step-wise process,mimicking the protracted timing of human development. Using a small-molecule screen,we identified a combination of five small-molecule pathway inhibitors that yield hPSC-derived neurons at textgreater75% efficiency within 10 d of differentiation. The resulting neurons express canonical markers and functional properties of human nociceptors,including tetrodotoxin (TTX)-resistant,SCN10A-dependent sodium currents and response to nociceptive stimuli such as ATP and capsaicin. Neuronal fate acquisition occurs about threefold faster than during in vivo development,suggesting that use of small-molecule pathway inhibitors could become a general strategy for accelerating developmental timing in vitro. The quick and high-efficiency derivation of nociceptors offers unprecedented access to this medically relevant cell type for studies of human pain. View Publication

The neurosphere assay can detect and expand neural stem cells (NSCs) and progenitor cells,but it cannot discriminate between these two populations. Given two assays have purported to overcome this shortfall,we performed a comparative analysis of the distribution and frequency of NSCs and progenitor cells detected in 400 mum coronal segments along the ventricular neuraxis of the adult mouse brain using the neurosphere assay,the neural colony forming cell assay (N-CFCA),and label-retaining cell (LRC) approach. We observed a large variation in the number of progenitor/stem cells detected in serial sections along the neuraxis,with the number of neurosphere-forming cells detected in individual 400 mum sections varying from a minimum of eight to a maximum of 891 depending upon the rostral-caudal coordinate assayed. Moreover,the greatest variability occurred in the rostral portion of the lateral ventricles,thereby explaining the large variation in neurosphere frequency previously reported. Whereas the overall number of neurospheres (3730 +/- 276) or colonies (4275 +/- 124) we detected along the neuraxis did not differ significantly,LRC numbers were significantly reduced (1186 +/- 188,7 month chase) in comparison to both total colonies and neurospheres. Moreover,approximately two orders of magnitude fewer NSC-derived colonies (50 +/- 10) were detected using the N-CFCA as compared to LRCs. Given only 5% of the LRCs are cycling (BrdU+/Ki-67+) or competent to divide (BrdU+/Mcm-2+),and proliferate upon transfer to culture,it is unclear whether this technique selectively detects endogenous NSCs. Overall,caution should be taken with the interpretation and employment of all these techniques. View Publication

Glioblastomas (GBMs) are highly aggressive,invasive brain tumors with bad prognosis and unmet medical need. These tumors are heterogeneous being constituted by a variety of cells in different states of differentiation. Among these,cells endowed with stem properties,tumor initiating/propagating properties and particularly resistant to chemo- and radiotherapies are designed as the real culprits for tumor maintenance and relapse after treatment. These cells,termed cancer stem-like cells,have been designed as prominent targets for new and more efficient cancer therapies. G-protein coupled receptors (GPCRs),a family of membrane receptors,play a prominent role in cell signaling,cell communication and crosstalk with the microenvironment. Their role in cancer has been highlighted but remains largely unexplored. Here,we report a descriptive study of the differential expression of the endo-GPCR repertoire in human glioblastoma cancer stem-like cells (GSCs),U-87 MG cells,human astrocytes and fetal neural stem cells (f-NSCs). The endo-GPCR transcriptome has been studied using Taqman Low Density Arrays. Of the 356 GPCRs investigated,138 were retained for comparative studies between the different cell types. At the transcriptomic level,eight GPCRs were specifically expressed/overexpressed in GSCs. Seventeen GPCRs appeared specifically expressed in cells with stem properties (GSCs and f-NSCs). Results of GPCR expression at the protein level using mass spectrometry and proteomic analysis are also presented. The comparative GPCR expression study presented here gives clues for new pathways specifically used by GSCs and unveils novel potential therapeutic targets. View Publication