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For years,our ability to study pathological changes in neurological diseases has been hampered by the lack of relevant models until the recent groundbreaking work from Yamanaka's group showing that it is feasible to generate induced pluripotent stem cells (iPSCs) from human somatic cells and to redirect the fate of these iPSCs into differentiated cells. In particular,much interest has focused on the ability to differentiate human iPSCs into neuronal progenitors and functional neurons for relevance to a large number of pathologies including mental retardation and behavioral or degenerative syndromes. Current differentiation protocols are time-consuming and generate limited amounts of cells,hindering use on a large scale. We describe a feeder-free method relying on the use of a chemically defined medium that overcomes the need for embryoid body formation and neuronal rosette isolation for neuronal precursors and terminally differentiated neuron production. Four days after induction,expression of markers of the neurectoderm lineage is detectable. Between 4 and 7 days,neuronal precursors can be expanded,frozen,and thawed without loss of proliferation and differentiation capacities or further differentiated. Terminal differentiation into the different subtypes of mature neurons found in the human brain were observed. At 6-35 days after induction,cells express typical voltage-gated and ionotrophic receptors for GABA,glycine,and acetylcholine. This specific and efficient single-step strategy in a chemically defined medium allows the production of mature neurons in 20-40 days with multiple applications,especially for modeling human pathologies. View Publication

Dopaminergic (DA) neurons in the substantia nigra pars compacta (also known as A9 DA neurons) are the specific cell type that is lost in Parkinson's disease (PD). There is great interest in deriving A9 DA neurons from human pluripotent stem cells (hPSCs) for regenerative cell replacement therapy for PD. During neural development,A9 DA neurons originate from the floor plate (FP) precursors located at the ventral midline of the central nervous system. Here,we optimized the culture conditions for the stepwise differentiation of hPSCs to A9 DA neurons,which mimics embryonic DA neuron development. In our protocol,we first describe the efficient generation of FP precursor cells from hPSCs using a small molecule method,and then convert the FP cells to A9 DA neurons,which could be maintained in vitro for several months. This efficient,repeatable and controllable protocol works well in human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) from normal persons and PD patients,in which one could derive A9 DA neurons to perform in vitro disease modeling and drug screening and in vivo cell transplantation therapy for PD. View Publication

Incurable neurological disorders such as Parkinson's disease (PD),Huntington's disease (HD),and Alzheimer's disease (AD) are very common and can be life-threatening because of their progressive disease symptoms with limited treatment options. To provide an alternative renewable cell source for cell-based transplantation and as study models for neurological diseases,we generated induced pluripotent stem cells (iPSCs) from human dermal fibroblasts (HDFs) and then differentiated them into neural progenitor cells (NPCs) and mature neurons by dual SMAD signaling inhibitors. Reprogramming efficiency was improved by supplementing the histone deacethylase inhibitor,valproic acid (VPA),and inhibitor of p160-Rho associated coiled-coil kinase (ROCK),Y-27632,after retroviral transduction. We obtained a number of iPS colonies that shared similar characteristics with human embryonic stem cells in terms of their morphology,cell surface antigens,pluripotency-associated gene and protein expressions as well as their in vitro and in vivo differentiation potentials. After treatment with Noggin and SB431542,inhibitors of the SMAD signaling pathway,HDF-iPSCs demonstrated rapid and efficient differentiation into neural lineages. Six days after neural induction,neuroepithelial cells (NEPCs) were observed in the adherent monolayer culture,which had the ability to differentiate further into NPCs and neurons,as characterized by their morphology and the expression of neuron-specific transcripts and proteins. We propose that our study may be applied to generate neurological disease patient-specific iPSCs allowing better understanding of disease pathogenesis and drug sensitivity assays. View Publication

Physical stimuli can act in either a synergistic or antagonistic manner to regulate cell fate decisions,but it is less clear whether insoluble signals alone can direct human pluripotent stem (hPS) cell differentiation into specialized cell types. We previously reported that stiff materials promote nuclear localization of the Yes-associated protein (YAP) transcriptional coactivator and support long-term self-renewal of hPS cells. Here,we show that even in the presence of soluble pluripotency factors,compliant substrata inhibit the nuclear localization of YAP and promote highly efficient differentiation of hPS cells into postmitotic neurons. In the absence of neurogenic factors,the effective substrata produce neurons rapidly (2 wk) and more efficiently (textgreater75%) than conventional differentiation methods. The neurons derived from substrate induction express mature markers and possess action potentials. The hPS differentiation observed on compliant surfaces could be recapitulated on stiff surfaces by adding small-molecule inhibitors of F-actin polymerization or by depleting YAP. These studies reveal that the matrix alone can mediate differentiation of hPS cells into a mature cell type,independent of soluble inductive factors. That mechanical cues can override soluble signals suggests that their contributions to early tissue development and lineage commitment are profound. View Publication

MED13L is a component subunit of the Mediator complex,an important regulator of transcription that is highly conserved across eukaryotes. Here we report MED13L disruption in a translocation t(12;19) breakpoint of a patient with Pierre-Robin syndrome,moderate intellectual disability (ID),craniofacial anomalies,and muscular defects. The phenotype is similar to previously described patients with MED13L haploinsufficiency. Knockdown of MED13L orthologue in zebrafish,med13b,showed early defective migration of cranial neural crest cells (NCCs) that contributed into cartilage structure deformities in the later stage,recapitulating craniofacial anomalies seen in human patients. Notably,we observed abnormal distribution of developing neurons in different brain regions of med13b morphant embryos,which could be rescued upon introduction of full-length human MED13L mRNA. To compare with mammalian system,we suppressed MED13L expression by short-hairpin RNA in ES-derived human neural progenitors,and differentiated them into neurons. Transcriptome analysis revealed differential expression of components of Wnt and FGF signalling pathways in MED13L-deficient neurons. Our finding provides a novel insight into the mechanism of overlapping phenotypic outcome targeting NCCs derivatives organs in patients with MED13L haploinsufficiency,and emphasizes a clinically recognizable syndromic phenotype in these patients. This article is protected by copyright. All rights reserved. View Publication

Differentiation of neural lineages from human pluripotent stem cells (hPSCs) raises the hope of generating functional cells for the treatment of neural diseases. However,current protocols for differentiating hPSCs into neural lineages remain inefficient and largely variable between different hPSC lines. We report that microRNA 376c (miR-376c) significantly enhanced neural differentiation of hPSCs in a defined condition by suppressing SMAD4,the co-SMAD for TGF-β signaling. Downstream,SMAD4 directly bound and suppressed PAX6,the critical neural lineage specification factor. Interestingly,we also found that SMAD4 binds and suppresses miR-376c clusters in undifferentiated hESCs. In summary,our findings revealed a reciprocal antagonism between miR-376c and SMAD signaling that regulates cell fate during human neural differentiation.-Liu,J.,Wang,L.,Su,Z.,Wu,W.,Cai,X.,Li,D.,Hou,J.,Pei,D.,Pan,G. A reciprocal antagonism between miR-376c and TGF-β signaling regulates neural differentiation of hPSCs. View Publication

Nature Neuroscience 17,1180 (2014). doi:10.1038/nn.3787 View Publication

AbstractBack to TopbackslashnNeurons produced from stem cells have emerged as a tool to identify new therapeutic targets for neurological diseases such as amyotrophic lateral sclerosis (ALS). However,it remains unclear to what extent these new mechanistic insights will translate to animal models,an important step in the validation of new targets. Previously,we found that glia from mice carrying the SOD1G93A mutation,a model of ALS,were toxic to stem cell–derived human motor neurons. We use pharmacological and genetic approaches to demonstrate that the prostanoid receptor DP1 mediates this glial toxicity. Furthermore,we validate the importance of this mechanism for neural degeneration in vivo. Genetic ablation of DP1 in SOD1G93A mice extended life span,decreased microglial activation,and reduced motor neuron loss. Our findings suggest that blocking DP1 may be a therapeutic strategy in ALS and demonstrate that discoveries from stem cell models of disease can be corroborated in vivo. View Publication

Many protocols have been designed to differentiate human embryonic stem cells (ESCs) and human induced pluripotent stem cells (iPSCs) into neurons. Despite the relevance of electrophysiological properties for proper neuronal function,little is known about the evolution over time of important neuronal electrophysiological parameters in iPSC-derived neurons. Yet,understanding the development of basic electrophysiological characteristics of iPSC-derived neurons is critical for evaluating their usefulness in basic and translational research. Therefore,we analyzed the basic electrophysiological parameters of forebrain neurons differentiated from human iPSCs,from day 31 to day 55 after the initiation of neuronal differentiation. We assayed the developmental progression of various properties,including resting membrane potential,action potential,sodium and potassium channel currents,somatic calcium transients and synaptic activity. During the maturation of iPSC-derived neurons,the resting membrane potential became more negative,the expression of voltage-gated sodium channels increased,the membrane became capable of generating action potentials following adequate depolarization and,at day 48-55,50% of the cells were capable of firing action potentials in response to a prolonged depolarizing current step,of which 30% produced multiple action potentials. The percentage of cells exhibiting miniature excitatory post-synaptic currents increased over time with a significant increase in their frequency and amplitude. These changes were associated with an increase of Ca2+ transient frequency. Co-culturing iPSC-derived neurons with mouse glial cells enhanced the development of electrophysiological parameters as compared to pure iPSC-derived neuronal cultures. This study demonstrates the importance of properly evaluating the electrophysiological status of the newly generated neurons when using stem cell technology,as electrophysiological properties of iPSC-derived neurons mature over time. View Publication

Down's syndrome (DS),caused by trisomy of human chromosome 21,is the most common genetic cause of intellectual disability. Here we use induced pluripotent stem cells (iPSCs) derived from DS patients to identify a role for astrocytes in DS pathogenesis. DS astroglia exhibit higher levels of reactive oxygen species and lower levels of synaptogenic molecules. Astrocyte-conditioned medium collected from DS astroglia causes toxicity to neurons,and fails to promote neuronal ion channel maturation and synapse formation. Transplantation studies show that DS astroglia do not promote neurogenesis of endogenous neural stem cells in vivo. We also observed abnormal gene expression profiles from DS astroglia. Finally,we show that the FDA-approved antibiotic drug,minocycline,partially corrects the pathological phenotypes of DS astroglia by specifically modulating the expression of S100B,GFAP,inducible nitric oxide synthase,and thrombospondins 1 and 2 in DS astroglia. Our studies shed light on the pathogenesis and possible treatment of DS by targeting astrocytes with a clinically available drug. View Publication

In Huntington's disease (HD),whether transneuronal spreading of mutant huntingtin (mHTT) occurs and its contribution to non-cell autonomous damage in brain networks is largely unknown. We found mHTT spreading in three different neural network models: human neurons integrated in the neural network of organotypic brain slices of HD mouse model,an ex vivo corticostriatal slice model and the corticostriatal pathway in vivo. Transneuronal propagation of mHTT was blocked by two different botulinum neurotoxins,each known for specifically inactivating a single critical component of the synaptic vesicle fusion machinery. Moreover,healthy human neurons in HD mouse model brain slices displayed non-cell autonomous changes in morphological integrity that were more pronounced when these neurons bore mHTT aggregates. Altogether,our findings suggest that transneuronal propagation of mHTT might be an important and underestimated contributor to the pathophysiology of HD. View Publication

Nature Chemical Biology 10,677 (2014). doi:10.1038/nchembio.1563 View Publication