技术资料

Hypothalamic neurons orchestrate many essential physiological and behavioral processes via secreted neuropeptides,and are relevant to human diseases such as obesity,narcolepsy and infertility. We report the differentiation of human pluripotent stem cells into many of the major types of neuropeptidergic hypothalamic neurons,including those producing pro-opiolemelanocortin,agouti-related peptide,hypocretin/orexin,melanin-concentrating hormone,oxytocin,arginine vasopressin,corticotropin-releasing hormone (CRH) or thyrotropin-releasing hormone. Hypothalamic neurons can be generated using a 'self-patterning' strategy that yields a broad array of cell types,or via a more reproducible directed differentiation approach. Stem cell-derived human hypothalamic neurons share characteristic morphological properties and gene expression patterns with their counterparts in vivo,and are able to integrate into the mouse brain. These neurons could form the basis of cellular models,chemical screens or cellular therapies to study and treat common human diseases. View Publication

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are reprogrammed from human fibroblasts using episomal vectors. Colonies of iPSCs can be observed 30 days after initiation of fibroblast reprogramming. Pluripotent colonies are manually picked and grown in neural induction medium to permit differentiation into neural progenitor cells (NPCs). iPSCs rapidly convert into neuroepithelial cells within 1 week and retain the capability to self-renew when maintained at a high culture density. Primary mouse NPCs are differentiated into astrocytes by exposure to a serum-containing medium for 7 days and form a monolayer upon which embryonic day 18 (E18) rat cortical neurons (transfected with channelrhodopsin-2 (ChR2)) are added. Human NPCs tagged with the fluorescent protein,tandem dimer Tomato (tdTomato),are then seeded onto the astrocyte/cortical neuron culture the following day and allowed to differentiate for 28 to 35 days. We demonstrate that this system forms synaptic connections between iPSC-derived neurons and cortical neurons,evident from an increase in the frequency of synaptic currents upon photostimulation of the cortical neurons. This co-culture system provides a novel platform for evaluating the ability of iPSC-derived neurons to create synaptic connections with other neuronal populations. View Publication

For diseases of the brain,the pig (Sus scrofa) is increasingly being used as a model organism that shares many anatomical and biological similarities with humans. We report that pig induced pluripotent stem cells (iPSC) can recapitulate events in early mammalian neural development. Pig iPSC line (POU5F1(high)/SSEA4(low)) had a higher potential to form neural rosettes (NR) containing neuroepithelial cells than either POU5F1(low)/SSEA4(low) or POU5F1(low)/SSEA4(high) lines. Thus,POU5F1 and SSEA4 pluripotency marker profiles in starting porcine iPSC populations can predict their propensity to form more robust NR populations in culture. The NR were isolated and expanded in vitro,retaining their NR morphology and neuroepithelial molecular properties. These cells expressed anterior central nervous system fate markers OTX2 and GBX2 through at least seven passages,and responded to retinoic acid,promoting a more posterior fate (HOXB4+,OTX2-,and GBX2-). These findings offer insight into pig iPSC development,which parallels the human iPSC in both anterior and posterior neural cell fates. These in vitro similarities in early neural differentiation processes support the use of pig iPSC and differentiated neural cells as a cell therapy in allogeneic porcine neural injury and degeneration models,providing relevant translational data for eventual human neural cell therapies. View Publication

3D suspension culture is generally considered a promising method to achieve efficient expansion and controlled differentiation of human pluripotent stem cells (hPSCs). In this work,we focused on developing an integrated culture platform for expansion and neural commitment of hPSCs into neural precursors using 3D suspension conditions and chemically-defined culture media. We evaluated different inoculation methodologies for hPSC expansion as 3D aggregates and characterized the resulting cultures in terms of aggregate size distribution. It was demonstrated that upon single-cell inoculation,after four days of culture,3D aggregates were composed of homogenous populations of hPSC and were characterized by an average diameter of 139 ± 26 μm,which was determined to be the optimal size to initiate neural commitment. Temporal analysis revealed that upon neural specification it is possible to maximize the percentage of neural precursor cells expressing the neural markers Sox1 and Pax6 after nine days of culture. These results highlight our ability to define a robust method for production of hPSC-derived neural precursors that minimizes processing steps and that constitutes a promising alternative to the traditional planar adherent culture system due to a high potential for scaling-up. View Publication

RTP801 expression is induced by cellular stress and has a pro-apoptotic function in non-proliferating differentiated cells such as neurons. In several neurodegenerative disorders,including Parkinson's disease and Alzheimer's disease,elevated levels of RTP801 have been observed,which suggests a role for RTP801 in neuronal death. Neuronal death is also a pathological hallmark in Huntington's disease (HD),an inherited neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene. Currently,the exact mechanisms underlying mutant huntingtin (mhtt)-induced toxicity are still unclear. Here,we investigated whether RTP801 is involved in (mhtt)-induced cell death. Ectopic exon-1 mhtt elevated RTP801 mRNA and protein levels in nerve growth factor (NGF)-differentiated PC12 cells and in rat primary cortical neurons. In neuronal PC12 cells,mhtt also contributed to RTP801 protein elevation by reducing its proteasomal degradation rate,in addition to promoting RTP801 gene expression. Interestingly,silencing RTP801 expression with short hairpin RNAs (shRNAs) blocked mhtt-induced cell death in NGF-differentiated PC12 cells. However,RTP801 protein levels were not altered in the striatum of Hdh(Q7/Q111) and R6/1 mice,two HD models that display motor deficits but not neuronal death. Importantly,RTP801 protein levels were elevated in both neural telencephalic progenitors differentiated from HD patient-derived induced pluripotent stem cells and in the putamen and cerebellum of human HD postmortem brains. Taken together,our results suggest that RTP801 is a novel downstream effector of mhtt-induced toxicity and that it may be relevant to the human disease. View Publication

Microtubule-associated protein (MAP) 2 has been perceived as a static cytoskeletal protein enriched in neuronal dendritic shafts. Emerging evidence indicates dynamic functions for various MAPs in activity-dependent synaptic plasticity. However,it is unclear how MAP2 is associated with synaptic plasticity mechanisms. Here,we demonstrate that specific silencing of high-molecular-weight MAP2 in vivo abolished induction of long-term potentiation (LTP) in the Schaffer collateral pathway of CA1 pyramidal neurons and in vitro blocked LTP-induced surface delivery of AMPA receptors and spine enlargement. In mature hippocampal neurons,we observed rapid translocation of a subpopulation of MAP2,present in dendritic shafts,to spines following LTP stimulation. Time-lapse confocal imaging showed that spine translocation of MAP2 was coupled with LTP-induced spine enlargement. Consistently,immunogold electron microscopy revealed that LTP stimulation of the Schaffer collateral pathway promoted MAP2 labeling in spine heads of CA1 neurons. This translocation depended on NMDA receptor activation and Ras-MAPK signaling. Furthermore,LTP stimulation led to an increase in surface-expressed AMPA receptors specifically in the neurons with MAP2 spine translocation. Altogether,this study indicates a novel role for MAP2 in LTP mechanisms and suggests that MAP2 participates in activity-dependent synaptic plasticity in mature hippocampal networks. View Publication

Serotonergic axons from the raphe nuclei in the brainstem project to every region of the brain,where they make connections through their extensive terminal arborizations. This serotonergic innervation contributes to various normal behaviors and psychiatric disorders. The protocadherin-alpha (Pcdha) family of clustered protocadherins consists of 14 cadherin-related molecules generated from a single gene cluster. We found that the Pcdhas were strongly expressed in the serotonergic neurons. To elucidate their roles,we examined serotonergic fibers in a mouse mutant (Pcdha(Delta CR/Delta CR)) lacking the Pcdha cytoplasmic region-encoding exons,which are common to the gene cluster. In the first week after birth,the distribution pattern of serotonergic fibers in Pcdha(Delta CR/Delta CR) mice was similar to wild-type,but by 3 weeks of age,when the serotonergic axonal termini complete their arborizations,the distribution of the projections was abnormal. In some target regions,notably the globus pallidus and substantia nigra,the normally even distribution of serotonin axonal terminals was,in the mutants,dense at the periphery of each region,but sparse in the center. In the stratum lacunosum-molecular of the hippocampus,the mutants showed denser serotonergic innervation than in wild-type,and in the dentate gyrus of the hippocampus and the caudate-putamen,the innervation was sparser. Together,the abnormalities suggested that Pcdha proteins are important in the late-stage maturation of serotonergic projections. Further examination of alternatively spliced exons encoding the cytoplasmic tail showed that the A-type (but not the B-type) cytoplasmic tail was essential for the normal development of serotonergic projections. View Publication

Neurobasal®/B27 is a gold standard culture media used to study primary neurons in vitro. An alternative media (BrainPhys®/SM1) was recently developed which robustly enhances neuronal activity vs. Neurobasal® or DMEM. To the best of our knowledge BrainPhys® has not been explored in the setting of neuronal injury. Here we characterized the utility of BrainPhys® in a model of in vitro mechanical-stretch injury. METHODS/RESULTSPrimary rat cortical neurons were maintained in classic Neurobasal®,or sequentially maintained in Neurocult® followed by BrainPhys® (hereafter simply referred to as BrainPhys® maintained neurons?). The levels of axonal markers and proteins involved in neurotransmission were compared on day in vitro 10 (DIV10). BrainPhys® maintained neurons had higher levels of GluN2B,GluR1,Neurofilament light/heavy chain (NF-L & NF-H),and protein phosphatase 2 A (PP2A) vs. neurons in Neurobasal®. Mechanical stretch-injury (50ms/54% biaxial stretch) to BrainPhys® maintained neurons modestly (albeit significantly) increased 24h lactate dehydrogenase (LDH) levels but markedly decreased axonal NF-L levels post-injury vs. uninjured controls or neurons given a milder 38% stretch-injury. Furthermore,two 54% stretch-injuries (in tandem) exacerbated 24h LDH release,increased α-spectrin breakdown products (SBDPs),and decreased Tau levels. Also,BrainPhys® maintained cultures had decreased markers of cell damage 24h after a single 54% stretch-injury vs. neurons in Neurobasal®. Finally,we tested the hypothesis that lentivirus mediated overexpression of the pro-death protein RBM5 exacerbates neuronal and/or axonal injury in primary CNS cultures. RBM5 overexpression vs. empty-vector controls increased 24h LDH release,and SBDP levels,after a single 54% stretch-injury but did not affect NF-L levels or Tau. CONCLUSIONBrainPhys® is a promising new reagent which facilities the investigation of molecular targets involved in axonal and/or neuronal injury in vitro. View Publication

Neuronal morphology is highly sensitive to ischemia,although some re-organization may promote neuroprotection. In this study we investigate the role of actin regulating proteins (ARP2,ARP3 and WAVE-1) and their role in rapid ischemic tolerance. Using an established in vitro model of rapid ischemic tolerance,we show that WAVE-1 protein levels are stabilized following brief tolerance inducing ischemia (preconditioning). The stabilization appears to be due to a reduction in the ubiquitination of WAVE-1. Levels of ARP2,ARP3 and N-WASP were not affected by ischemic preconditioning. Immunocytochemical studies show a relocalization of ARP2 and ARP3 proteins in neurons following preconditioning ischemia,as well as a re-organization of actin. Blocking the protein kinase CK2 using emodin blocks ischemic tolerance,and our data suggests CK2 binds to WAVE-1 in neurons. We observe an increase in binding of the ARP2 subunit with WAVE-1. The neuroprotection observed following preconditioning is inhibited when cells are transduced with an N-WASP CA domain that blocks the activation of ARP2/3. Together these data show that ischemia affects actin regulating enzymes,and that the ARP2/3 pathway plays a role in rapid ischemic tolerance induced neuroprotection. View Publication