技术资料

Heterozygous loss-of-function mutations in GRIN2B,a subunit of the NMDA receptor,cause intellectual disability and language impairment. We developed clonal models of GRIN2B deletion and loss-of-function mutations in a region coding for the glutamate binding domain in human cells and generated neurons from a patient harboring a missense mutation in the same domain. Transcriptome analysis revealed extensive increases in genes associated with cell proliferation and decreases in genes associated with neuron differentiation,a result supported by extensive protein analyses. Using electrophysiology and calcium imaging,we demonstrate that NMDA receptors are present on neural progenitor cells and that human mutations in GRIN2B can impair calcium influx and membrane depolarization even in a presumed undifferentiated cell state,highlighting an important role for non-synaptic NMDA receptors. It may be this function,in part,which underlies the neurological disease observed in patients with GRIN2B mutations. View Publication

We introduce a novel all-optical assay for functional studies of biological neural networks in vitro. We created a novel optogenetic construct named OptoCaMP which is a combination of a channelrhodopsin variant (CheRiff) and a red genetically encoded calcium indicator (GECI) (jRCaMP1b). It enables simultaneous optical stimulation and recording from large population of neurons with single-cell readout. Additionally,we have developed a spatio-temporal all-optical assay to simultaneously stimulate a sub-section of a neural network and record evoked calcium activity,in both stimulated and non-stimulated neurons,thus allowing the investigation of the spread of excitation through an interconnected network. Finally,we demonstrate the sensitivity of this assay to the change of neural network connectivity. View Publication

Many neuropsychiatric disorders are thought to result from subtle changes in neural circuit formation. We used human embryonic stem cells and induced pluripotent stem cells (hiPSCs) to model mature,post-mitotic excitatory neurons and examine effects of fibroblast growth factor 2 (FGF2). FGF2 gene expression is known to be altered in brain regions of major depressive disorder (MDD) patients and FGF2 has anti-depressive effects in animal models of depression. We generated stable inducible neurons (siNeurons) conditionally expressing human neurogenin-2 (NEUROG2) to generate a homogenous population of post-mitotic excitatory neurons and study the functional as well as the transcriptional effects of FGF2. Upon induction of NEUROG2 with doxycycline,the vast majority of cells are post-mitotic,and the gene expression profile recapitulates that of excitatory neurons within 6 days. Using hES cell lines that inducibly express NEUROG2 as well as GCaMP6f,we were able to characterize spontaneous calcium activity in these neurons and show that calcium transients increase in the presence of FGF2. The FGF2-responsive genes were determined by RNA-Seq. FGF2-regulated genes previously identified in non-neuronal cell types were up-regulated (EGR1,ETV4,SPRY4,and DUSP6) as a result of chronic FGF2 treatment of siNeurons. Novel neuron-specific genes were also identified that may mediate FGF2-dependent increases in synaptic efficacy including NRXN3,SYT2,and GALR1. Since several of these genes have been implicated in MDD previously,these results will provide the basis for more mechanistic studies of the role of FGF2 in MDD. View Publication

Hypoxic stressors contribute to neuronal death in many brain diseases. Astrocyte processes surround most neurons and are therefore anatomically well-positioned to shield them from hypoxic injury. Excitatory amino acid transporters (EAATs),represent the sole mechanism of active reuptake of glutamate into the astrocytes and neurons and are essential to dampen neuronal excitation following glutamate release at synapses. Glutamate clearance impairment from any factors is bound to result in an increase in hypoxic neuronal injury. The brain energy metabolism under hypoxic conditions depends on monocarboxylate transporters (MCTs) that are expressed by neurons and glia. Previous co-immunoprecipitation experiments revealed that MCT4 directly modulate EAAT1 in astrocytes. The reduction in both surface proteins may act synergistically to induce neuronal hyperexcitability and excitotoxicity. Therefore we hypothesized that astrocytes would respond to hypoxic conditions by enhancing their expression of MCT4 and EAAT1,which,in turn,would enable them to better support neurons to survive lethal hypoxia injury. An oxygen deprivation (OD) protocol was used in primary cultures of neurons,astrocytes,and astrocytes-neurons derived from rat hippocampus,with or without MCT4-targeted short hairpin RNA (shRNA) transfection. Cell survival,expression of MCT4,EAAT1,glial fibrillary acidic protein and neuronal nuclear antigen were evaluated. OD resulted in significant cell death in neuronal cultures and up-regulation of MCT4,EAAT1 expression respectively in primary cell cultures,but no injury in neuron-astrocyte co-cultures and astrocyte cultures. However,neuronal cell death in co-cultures was increased exposure to shRNA-MCT4 prior to OD. These findings demonstrate that the MCT4-mediated expression of EAAT1 is involved in the resistance to hypoxia injury in astrocyte-neuron co-cultures. View Publication

A mutation in the centrosomal-P4.1-associated protein (CPAP) causes Seckel syndrome with microcephaly,which is suggested to arise from a decline in neural progenitor cells (NPCs) during development. However,mechanisms ofNPCs maintenance remain unclear. Here,we report an unexpected role for the cilium inNPCs maintenance and identifyCPAPas a negative regulator of ciliary length independent of its role in centrosome biogenesis. At the onset of cilium disassembly,CPAPprovides a scaffold for the cilium disassembly complex (CDC),which includes Nde1,Aurora A,andOFD1,recruited to the ciliary base for timely cilium disassembly. In contrast,mutatedCPAPfails to localize at the ciliary base associated with inefficientCDCrecruitment,long cilia,retarded cilium disassembly,and delayed cell cycle re-entry leading to premature differentiation of patientiPS-derivedNPCs. AberrantCDCfunction also promotes premature differentiation ofNPCs in SeckeliPS-derived organoids. Thus,our results suggest a role for cilia in microcephaly and its involvement during neurogenesis and brain size control. View Publication

NMDA receptors play a central role in shaping the strength of synaptic connections throughout development and in mediating synaptic plasticity mechanisms that underlie some forms of learning and memory formation in the CNS. In the hippocampus and the neocortex,GluN1 is combined primarily with GluN2A and GluN2B,which are differentially expressed during development and confer distinct molecular and physiological properties to NMDA receptors. The contribution of each subunit to the synaptic traffic of NMDA receptors and therefore to their role during development and in synaptic plasticity is still controversial. We report a critical role for the GluN2B subunit in regulating NMDA receptor synaptic targeting. In the absence of GluN2B,the synaptic levels of AMPA receptors are increased and accompanied by decreased constitutive endocytosis of GluA1-AMPA receptor. We used quantitative proteomic analysis to identify changes in the composition of postsynaptic densities from GluN2B(-/-) mouse primary neuronal cultures and found altered levels of several ubiquitin proteasome system components,in particular decreased levels of proteasome subunits. Enhancing the proteasome activity with a novel proteasome activator restored the synaptic levels of AMPA receptors in GluN2B(-/-) neurons and their endocytosis,revealing that GluN2B-mediated anchoring of the synaptic proteasome is responsible for fine tuning AMPA receptor synaptic levels under basal conditions. View Publication

Transient global cerebral ischemia induces profound changes in the transcriptome of brain cells,which is partially associated with the induction or repression of genes that influence the ischemic response. However,the mechanisms responsible for the selective vulnerability of hippocampal neurons to global ischemia remain to be clarified. To identify molecular changes elicited by ischemic insults,we subjected hippocampal primary cultures to oxygen-glucose deprivation (OGD),an in vitro model for global ischemia that resulted in delayed neuronal death with an excitotoxic component. To investigate changes in the transcriptome of hippocampal neurons submitted to OGD,total RNA was extracted at early (7 h) and delayed (24 h) time points after OGD and used in a whole-genome RNA microarray. We observed that at 7 h after OGD there was a general repression of genes,whereas at 24 h there was a general induction of gene expression. Genes related with functions such as transcription and RNA biosynthesis were highly regulated at both periods of incubation after OGD,confirming that the response to ischemia is a dynamic and coordinated process. Our analysis showed that genes for synaptic proteins,such as those encoding for PICK1,GRIP1,TARPγ3,calsyntenin-2/3,SAPAP2 and SNAP-25,were down-regulated after OGD. Additionally,OGD decreased the mRNA and protein expression levels of the GluA1 AMPA receptor subunit as well as the GluN2A and GluN2B subunits of NMDA receptors,but increased the mRNA expression of the GluN3A subunit,thus altering the composition of ionotropic glutamate receptors in hippocampal neurons. Together,our results present the expression profile elicited by in vitro ischemia in hippocampal neurons,and indicate that OGD activates a transcriptional program leading to down-regulation in the expression of genes coding for synaptic proteins,suggesting that the synaptic proteome may change after ischemia. View Publication

Stem cell-based therapies have been reported in protecting cerebral infarction-induced neuronal dysfunction and death. However,most studies used rat/mouse neuron as model cell when treated with stem cell or exosomes. Whether these findings can be translated from rodent to humans has been in doubt. Here,we used human embryonic stem cell-derived neurons to detect the protective potential of exosomes against ischemia. Neurons were treated with in vitro oxygen-glucose deprivation (OGD) for 1 h. For treatment group,different exosomes were derived from neuron,embryonic stem cell,neural progenitor cell and astrocyte differentiated from H9 human embryonic stem cell and added to culture medium 30 min after OGD (100 μg/mL). Western blotting was performed 12 h after OGD,while cell counting and electrophysiological recording were performed 48 h after OGD. We found that these exosomes attenuated OGD-induced neuronal death,Mammalian target of rapamycin (mTOR),pro-inflammatory and apoptotic signaling pathway changes,as well as basal spontaneous synaptic transmission inhibition in varying degrees. The results implicate the protective effect of exosomes on OGD-induced neuronal death and dysfunction in human embryonic stem cell-derived neurons,potentially through their modulation on mTOR,pro-inflammatory and apoptotic signaling pathways. View Publication

BACKGROUND UBQLN2 mutations have recently been associated with familial forms of amyotrophic lateral sclerosis (ALS) and ALS-dementia. UBQLN2 encodes for ubiquilin-2,a member of the ubiquitin-like protein family which facilitates delivery of ubiquitinated proteins to the proteasome for degradation. To study the potential role of ubiquilin-2 in ALS,we used recombinant adeno-associated viral (rAAV) vectors to express UBQLN2 and three of the identified ALS-linked mutants (P497H,P497S,and P506T) in primary neuroglial cultures and in developing neonatal mouse brains. RESULTS In primary cultures rAAV2/8-mediated expression of UBQLN2 mutants resulted in inclusion bodies and insoluble aggregates. Intracerebroventricular injection of FVB mice at post-natal day 0 with rAAV2/8 expressing wild type or mutant UBQLN2 resulted in widespread,sustained expression of ubiquilin-2 in brain. In contrast to wild type,mutant UBQLN2 expression induced significant pathology with large neuronal,cytoplasmic inclusions and ubiquilin-2-positive aggregates in surrounding neuropil. Ubiquilin-2 inclusions co-localized with ubiquitin,p62/SQSTM,optineurin,and occasionally TDP-43,but were negative for α-synuclein,neurofilament,tau,and FUS. Mutant UBLQN2 expression also resulted in Thioflavin-S-positive inclusions/aggregates. Mice expressing mutant forms of UBQLN2 variably developed a motor phenotype at 3-4 months,including nonspecific clasping and rotarod deficits. CONCLUSIONS These findings demonstrate that UBQLN2 mutants (P497H,P497S,and P506T) induce proteinopathy and cause behavioral deficits,supporting a toxic" gain-of-function which may contribute to ALS pathology. These data establish also that our rAAV model can be used to rapidly assess the pathological consequences of various UBQLN2 mutations and provides an agile system to further interrogate the molecular mechanisms of ubiquilins in neurodegeneration. View Publication

A current model posits that cofilin-dependent actin severing negatively impacts dendritic spine volume. Studies suggested that increased cofilin activity underlies activity-dependent spine shrinkage,and that reduced cofilin activity induces activity-dependent spine growth. We suggest instead that both types of structural plasticity correlate with decreased cofilin activity. However,the mechanism of inhibition determines the outcome for spine morphology. RNAi in rat hippocampal cultures demonstrates that cofilin is essential for normal spine maintenance. Cofilin-F-actin binding and filament barbed-end production decrease during the early phase of activity-dependent spine shrinkage; cofilin concentration also decreases. Inhibition of the cathepsin B/L family of proteases prevents both cofilin loss and spine shrinkage. Conversely,during activity-dependent spine growth,LIM kinase stimulates cofilin phosphorylation,which activates phospholipase D-1 to promote actin polymerization. These results implicate novel molecular mechanisms and prompt a revision of the current model for how cofilin functions in activity-dependent structural plasticity. View Publication

Increasing evidence suggests that cellular stress may underlie mood disorders such as bipolar disorder and major depression,particularly as lithium and its targets can protect against neuronal cell death. Here we describe N-methyl-D-aspartate (NMDA)-induced filamentous actin reorganization (NIFAR) as a useful in-vitro model for studying acute neurocellular stress and investigating the effects of mood stabilizers. Brief incubation of cultured neurons with NMDA (50 µM,5 min) induces marked reorganization of F-actin within the somatodendritic domain of a majority of neurons. During NIFAR,F-actin is rapidly depleted from dendritic spines and aberrantly aggregates within the dendrite shaft. The widely used mood stabilizer lithium chloride prevented NIFAR in a time-dependent and dose-dependent manner,consistent with its known efficacy in treating bipolar disorder. Inhibitors of the lithium target glycogen synthase kinase 3 and its upstream activator phosphoinositide-3-kinase also prevented NIFAR. The antidepressant compounds imipramine and fluoxetine also attenuated NIFAR. These findings have potential relevance to neuropsychiatric diseases characterized by excessive glutamate receptor activity and synaptotoxicity. We propose that protection of the dendritic actin cytoskeleton may be a common mechanism shared by various mood stabilizers. View Publication