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Microtubules (MTs),key cytoskeletal elements in living cells,are critical for axonal transport,synaptic transmission,and maintenance of neuronal morphology. NAP (NAPVSIPQ) is a neuroprotective peptide derived from the essential activity-dependent neuroprotective protein (ADNP). In Alzheimer's disease models,NAP protects against tauopathy and cognitive decline. Here,we show that NAP treatment significantly affected the alpha tubulin tyrosination cycle in the neuronal differentiation model,rat pheochromocytoma (PC12) and in rat cortical astrocytes. The effect on tubulin tyrosination/detyrosination was coupled to increased MT network area (measured in PC12 cells),which is directly related to neurite outgrowth. Tubulin beta3,a marker for neurite outgrowth/neuronal differentiation significantly increased after NAP treatment. In rat cortical neurons,NAP doubled the area of dynamic MT invasion (Tyr-tubulin) into the neuronal growth cone periphery. NAP was previously shown to protect against zinc-induced MT/neurite destruction and neuronal death,here,in PC12 cells,NAP treatment reversed zinc-decreased tau-tubulin-MT interaction and protected against death. NAP effects on the MT pool,coupled with increased tau engagement on compromised MTs imply an important role in neuronal plasticity,protecting against free tau accumulation leading to tauopathy. With tauopathy representing a major pathological hallmark in Alzheimer's disease and related disorders,the current findings provide a mechanistic basis for further development. NAP (davunetide) is in phase 2/3 clinical trial in progressive supranuclear palsy,a disease presenting MT deficiency and tau pathology. View Publication

Skin-derived precursor (SKP) cells are a valuable resource for tissue engineering and regenerative medicine,because they represent multipotent stem cells that differentiate into neural and mesodermal progenies. Previous studies suggest that the stem cell pool decreases with age. Here,we show that human multipotent SKP cells can be efficiently collected from adult cheek/chin skin,even in aged individuals of 70-78years. SKP cells were isolated from 38 skin samples by serum-free sphere culture and examined for the ability to differentiate into neural and mesodermal lineages. The number of spheres obtained from adult facial skin was significantly higher than that of trunk or extremity skin. SKP cells derived from cheek/chin skin exhibited a high ability to differentiate into neural and mesodermal cells relative to those derived from eyelid,trunk,or extremity skin. Furthermore,cheek/chin skin SKP cells were shown to express markers for undifferentiated stem cells,including a high expression level of the Sox9 gene. These results indicate that cheek/chin skin is useful for the recovery of multipotent stem cells for tissue engineering and regenerative therapy. 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

In human glioblastomas (hGBMs),tumor-propagating cells with stem-like characteristics (TPCs) represent a key therapeutic target. We found that the EphA2 receptor tyrosine kinase is overexpressed in hGBM TPCs. Cytofluorimetric sorting into EphA2(High) and EphA2(Low) populations demonstrated that EphA2 expression correlates with the size and tumor-propagating ability of the TPC pool in hGBMs. Both ephrinA1-Fc,which caused EphA2 downregulation in TPCs,and siRNA-mediated knockdown of EPHA2 expression suppressed TPCs self-renewal ex vivo and intracranial tumorigenicity,pointing to EphA2 downregulation as a causal event in the loss of TPCs tumorigenicity. Infusion of ephrinA1-Fc into intracranial xenografts elicited strong tumor-suppressing effects,suggestive of therapeutic applications. View Publication

UNLABELLED A noninvasive technology that indiscriminately detects tumor tissue in the brain could substantially enhance the management of primary or metastatic brain tumors. Although the documented molecular heterogeneity of diseases that initiate or eventually deposit in the brain may preclude identifying a single smoking-gun molecular biomarker,many classes of brain tumors are generally avid for transferrin. Therefore,we reasoned that applying a radiolabeled derivative of transferrin ((89)Zr-labeled transferrin) may be an effective strategy to more thoroughly identify tumor tissue in the brain,regardless of the tumor's genetic background. METHODS Transferrin was radiolabeled with (89)Zr,and its properties with respect to human models of glioblastoma multiforme were studied in vivo. RESULTS In this report,we show proof of concept that (89)Zr-labeled transferrin ((89)Zr-transferrin) localizes to genetically diverse models of glioblastoma multiforme in vivo. Moreover,we demonstrate that (89)Zr-transferrin can detect an orthotopic lesion with exceptional contrast. Finally,the tumor-to-brain contrast conferred by (89)Zr-transferrin vastly exceeded that observed with (18)F-FDG,currently the most widely used radiotracer to assess tumor burden in the brain. CONCLUSION The results from this study suggest that (89)Zr-transferrin could be a broadly applicable tool for identifying and monitoring tumors in the brain,with realistic potential for near-term clinical translation. View Publication

Here we demonstrate,both in vivo and in vitro,that growth hormone (GH) mediates precursor cell activation in the subventricular zone (SVZ) of the aged (12-month-old) brain following exercise,and that GH signaling stimulates precursor activation to a similar extent to exercise. Our results reveal that both addition of GH in culture and direct intracerebroventricular infusion of GH stimulate neural precursor cells in the aged brain. In contrast,no increase in neurosphere numbers was observed in GH receptor null animals following exercise. Continuous infusion of a GH antagonist into the lateral ventricle of wild-type animals completely abolished the exercise-induced increase in neural precursor cell number. Given that the aged brain does not recover well after injury,we investigated the direct effect of exercise and GH on neural precursor cell activation following irradiation. This revealed that physical exercise as well as infusion of GH promoted repopulation of neural precursor cells in irradiated aged animals. Conversely,infusion of a GH antagonist during exercise prevented recovery of precursor cells in the SVZ following irradiation. View Publication

Since the discovery of neural stem cells (NSC) in the embryonic and adult mammalian central nervous system (CNS),there have been a growing numbers of tissue culture media and protocols to study and functionally characterize NSCs and its progeny in vitro. One of these culture systems introduced in 1992 is referred to as the Neurosphere Assay,and it has been widely used to isolate,expand,differentiate and even quantify NSC populations. Several years later because its application as a quantitative in vitro assay for measuring NSC frequency was limited,a new single-step semisolid based assay,the Neural Colony Forming Cell (NCFC) assay was developed to accurately measure NSC numbers. The NCFC assay allows the discrimination between NSCs and progenitors by the size of colonies they produce (i.e.,their proliferative potential). The evolution and continued improvements made to these tissue culture tools will facilitate further advances in the promising application of NSCs for therapeutic use. View Publication

Herein,we report the use of retinoic acid-loaded polymeric nanoparticles as a potent tool to induce the neuronal differentiation of subventricular zone neural stem cells. The intracellular delivery of retinoic acid by the nanoparticles activated nuclear retinoic acid receptors,decreased stemness,and increased proneurogenic gene expression. Importantly,this work reports for the first time a nanoparticle formulation able to modulate in vivo the subventricular zone neurogenic niche. The work further compares the dynamics of initial stages of differentiation between SVZ cells treated with retinoic acid-loaded polymeric nanoparticles and solubilized retinoic acid. The nanoparticle formulation developed here may ultimately offer new perspectives to treat neurodegenerative diseases. View Publication

Down syndrome cell adhesion molecule,or DSCAM,has been implicated in many neurodevelopmental processes including axon guidance,dendrite arborization,and synapse formation. Here we show that DSCAM plays an important role in regulating the morphogenesis of cortical pyramidal neurons in the mouse. We report that DSCAM expression is developmentally regulated and localizes to synaptic plasma membranes during a time of robust cortical dendrite arborization and spine formation. Analysis of mice that carry a spontaneous mutation in DSCAM (DSCAM(del17)) revealed gross morphological changes in brain size and shape in addition to subtle changes in cortical organization,volume,and lamination. Early postnatal mutant mice displayed a transient decrease in cortical thickness,but these reductions could not be attributed to changes in neuron production or cell death. DSCAM(del17) mutants showed temporary impairments in the branching of layer V pyramidal neuron dendrites at P10 and P17 that recovered to normal by adulthood. Defects in DSCAM(del17) dendrite branching correlated with a temporal increase in apical branch spine density and lasting changes in spine morphology. At P15 and P42,mutant mice displayed a decrease in the percentage of large,stable spines and an increase in the percentage of small,immature spines. Together,our findings suggest that DSCAM contributes to pyramidal neuron morphogenesis by regulating dendrite arborization and spine formation during cortical circuit development. View Publication

In the stem cell field there is a lack of non invasive and fast methods to identify stem cell's metabolic state,differentiation state and cell-lineage commitment. Here we describe a label-free method that uses NADH as an intrinsic biomarker and the Phasor approach to Fluorescence Lifetime microscopy to measure the metabolic fingerprint of cells. We show that different metabolic states are related to different cell differentiation stages and to stem cell bias to neuronal and glial fate,prior the expression of lineage markers. Our data demonstrate that the NADH FLIM signature distinguishes non-invasively neurons from undifferentiated neural progenitor and stem cells (NPSCs) at two different developmental stages (E12 and E16). NPSCs follow a metabolic trajectory from a glycolytic phenotype to an oxidative phosphorylation phenotype through different stages of differentiation. NSPCs are characterized by high free/bound NADH ratio,while differentiated neurons are characterized by low free/bound NADH ratio. We demonstrate that the metabolic signature of NPSCs correlates with their differentiation potential,showing that neuronal progenitors and glial progenitors have a different free/bound NADH ratio. Reducing conditions in NPSCs correlates with their neurogenic potential,while oxidative conditions correlate with glial potential. For the first time we show that FLIM NADH metabolic fingerprint provides a novel,and quantitative measure of stem cell potential and a label-free and non-invasive means to identify neuron- or glial- biased progenitors. View Publication

Glioblastoma multiforme is the most malignant type of primary brain tumor with a poor prognosis. These tumors consist of a heterogeneous population of malignant cells,including well-differentiated tumor cells and less differentiated cells with stem cell properties. These cancer stem cells,known as brain tumor initiating cells,likely contribute to glioma recurrence,as they are highly invasive,mobile,resistant to radiation and chemotherapy,and have the capacity to self-renew. Glioblastoma tumor cells release excitotoxic levels of glutamate,which may be a key process in the death of peritumoral neurons,formation of necrosis,local inflammation,and glioma-related seizures. Moreover,elevated glutamate levels in the tumor may act in paracrine and autocrine manner to activate glutamate receptors on glioblastoma tumor cells,resulting in proliferation and invasion. Using a previously described culturing condition that selectively promotes the growth of brain tumor initiating cells,which express the stem cell markers nestin and SOX-2,we characterize the expression of α-amino-3-hydroxy-5-methyl-4-isozolepropionic acid (AMPA)-type glutamate receptor subunits in brain tumor initiating cells derived from glioblastomas. Here we show for the first time that glioblastoma brain tumor initiating cells express high concentrations of functional calcium-permeable AMPA receptors,compared to the differentiated tumor cultures consisting of non-stem cells. Up-regulated calcium-permeable AMPA receptor expression was confirmed by immunoblotting,immunocytochemistry,and intracellular calcium imaging in response to specific agonists. Our findings raise the possibility that glutamate secretion in the GBM tumor microenvironment may stimulate brain tumor derived cancer stem cells. View Publication

Glioblastoma growth is driven by cancer cells that have stem cell properties,but molecular determinants of their tumorigenic behavior are poorly defined. In cancer,altered activity of the epigenetic modifiers Polycomb and Trithorax complexes may contribute to the neoplastic phenotype. Here,we provide the first mechanistic insights into the role of the Trithorax protein mixed lineage leukemia (MLL) in maintaining cancer stem cell characteristics in human glioblastoma. We found that MLL directly activates the Homeobox gene HOXA10. In turn,HOXA10 activates a downstream Homeobox network and other genes previously characterized for their role in tumorigenesis. The MLL-Homeobox axis we identified significantly contributes to the tumorigenic potential of glioblastoma stem cells. Our studies suggest a role for MLL in contributing to the epigenetic heterogeneity between tumor-initiating and non-tumor-initiating cells in glioblastoma. View Publication