搜索结果: 'ipsc'

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

Induced pluripotent stem cell (iPSC)-based technologies offer an unprecedented opportunity to perform high-throughput screening of novel drugs for neurological and neurodegenerative diseases. Such screenings require a robust and scalable method for generating large numbers of mature,differentiated neuronal cells. Currently available methods based on differentiation of embryoid bodies (EBs) or directed differentiation of adherent culture systems are either expensive or are not scalable. We developed a protocol for large-scale generation of neuronal stem cells (NSCs)/early neural progenitor cells (eNPCs) and their differentiation into neurons. Our scalable protocol allows robust and cost-effective generation of NSCs/eNPCs from iPSCs. Following culture in neurobasal medium supplemented with B27 and BDNF,NSCs/eNPCs differentiate predominantly into vesicular glutamate transporter 1 (VGLUT1) positive neurons. Targeted mass spectrometry analysis demonstrates that iPSC-derived neurons express ligand-gated channels and other synaptic proteins and whole-cell patch-clamp experiments indicate that these channels are functional. The robust and cost-effective differentiation protocol described here for large-scale generation of NSCs/eNPCs and their differentiation into neurons paves the way for automated high-throughput screening of drugs for neurological and neurodegenerative diseases. View Publication

Hutchinson-Gilford progeria syndrome (HGPS) is a rare and fatal human premature ageing disease,characterized by premature arteriosclerosis and degeneration of vascular smooth muscle cells (SMCs). HGPS is caused by a single point mutation in the lamin A (LMNA) gene,resulting in the generation of progerin,a truncated splicing mutant of lamin A. Accumulation of progerin leads to various ageing-associated nuclear defects including disorganization of nuclear lamina and loss of heterochromatin. Here we report the generation of induced pluripotent stem cells (iPSCs) from fibroblasts obtained from patients with HGPS. HGPS-iPSCs show absence of progerin,and more importantly,lack the nuclear envelope and epigenetic alterations normally associated with premature ageing. Upon differentiation of HGPS-iPSCs,progerin and its ageing-associated phenotypic consequences are restored. Specifically,directed differentiation of HGPS-iPSCs to SMCs leads to the appearance of premature senescence phenotypes associated with vascular ageing. Additionally,our studies identify DNA-dependent protein kinase catalytic subunit (DNAPKcs,also known as PRKDC) as a downstream target of progerin. The absence of nuclear DNAPK holoenzyme correlates with premature as well as physiological ageing. Because progerin also accumulates during physiological ageing,our results provide an in vitro iPSC-based model to study the pathogenesis of human premature and physiological vascular ageing. View Publication

Huntington's disease (HD) is a fatal neurodegenerative disease,caused by expansion of polyglutamine repeats in the Huntingtin gene,with longer expansions leading to earlier ages of onset. The HD iPSC Consortium has recently reported a new in vitro model of HD based on the generation of induced pluripotent stem cells (iPSCs) from HD patients and controls. The current study has furthered the disease in a dish model of HD by generating new non-integrating HD and control iPSC lines. Both HD and control iPSC lines can be efficiently differentiated into neurons/glia; however,the HD-derived cells maintained a significantly greater number of nestin-expressing neural progenitor cells compared with control cells. This cell population showed enhanced vulnerability to brain-derived neurotrophic factor (BDNF) withdrawal in the juvenile-onset HD (JHD) lines,which appeared to be CAG repeat-dependent and mediated by the loss of signaling from the TrkB receptor. It was postulated that this increased death following BDNF withdrawal may be due to glutamate toxicity,as the N-methyl-d-aspartate (NMDA) receptor subunit NR2B was up-regulated in the cultures. Indeed,blocking glutamate signaling,not just through the NMDA but also mGlu and AMPA/Kainate receptors,completely reversed the cell death phenotype. This study suggests that the pathogenesis of JHD may involve in part a population of 'persistent' neural progenitors that are selectively vulnerable to BDNF withdrawal. Similar results were seen in adult hippocampal-derived neural progenitors isolated from the BACHD model mouse. Together,these results provide important insight into HD mechanisms at early developmental time points,which may suggest novel approaches to HD therapeutics. View Publication

Neurodegenerative diseases are characterized by chronic and progressive structural or functional loss of neurons. Limitations related to the animal models of these human diseases have impeded the development of effective drugs. This emphasizes the need to establish disease models using human-derived cells. The discovery of induced pluripotent stem cell (iPSC) technology has provided novel opportunities in disease modeling,drug development,screening,and the potential for patient-matched" cellular therapies in neurodegenerative diseases. In this study� View Publication

Culturing human embryonic stem and induced pluripotent stem cells (hESCs/iPSCs) is one of the most costly and labor-intensive tissue cultures,as media containing expensive factors/cytokines should be changed every day to maintain and propagate undifferentiated hESCs/iPSCs in vitro. We recently reported that doxycycline,an anti-bacterial agent,had dramatic effects on hESC/iPSC survival and promoted self-renewal. In this study,we extended the effects of doxycycline to a more practical issue to save cost and labor in hESC/iPSC cultures. Regardless of cultured cell conditions,hESCs/iPSCs in doxycycline-supplemented media were viable and proliferating for at least 3 days without media change,while none or few viable cells were detected in the absence of doxycycline in the same conditions. Thus,hESCs/iPSCs supplemented with doxycycline can be cultured for a long period of time with media changes at 3-day intervals without altering their self-renewal and pluripotent properties,indicating that doxycycline supplementation can reduce the frequency of media changes and the amount of media required by 1/3. These findings strongly encourage the use of doxycycline to save cost and labor in culturing hESCs/iPSCs. View Publication

Developing technologies for efficient and scalable disruption of gene expression will provide powerful tools for studying gene function,developmental pathways,and disease mechanisms. Here,we develop clustered regularly interspaced short palindromic repeat interference (CRISPRi) to repress gene expression in human induced pluripotent stem cells (iPSCs). CRISPRi,in which a doxycycline-inducible deactivated Cas9 is fused to a KRAB repression domain,can specifically and reversibly inhibit gene expression in iPSCs and iPSC-derived cardiac progenitors,cardiomyocytes,and T lymphocytes. This gene repression system is tunable and has the potential to silence single alleles. Compared with CRISPR nuclease (CRISPRn),CRISPRi gene repression is more efficient and homogenous across cell populations. The CRISPRi system in iPSCs provides a powerful platform to perform genome-scale screens in a wide range of iPSC-derived cell types,dissect developmental pathways,and model disease. View Publication

An expanded hexanucleotide repeat in a noncoding region of the C9orf72 gene is a major cause of amyotrophic lateral sclerosis (ALS),accounting for up to 40% of familial cases and 7% of sporadic ALS in European populations. We have generated induced pluripotent stem cells (iPSCs) from fibroblasts of patients carrying C9orf72 hexanucleotide expansions,differentiated these to functional motor and cortical neurons and performed an extensive phenotypic characterization. In C9orf72 iPSC-derived motor neurons,decreased cell survival is correlated with dysfunction in Ca(2+) homeostasis,reduced levels of the anti-apoptotic protein Bcl-2,increased endoplasmic reticulum (ER) stress and reduced mitochondrial membrane potential. Furthermore,C9orf72 motor neurons,and also cortical neurons,show evidence of abnormal protein aggregation and stress granule formation. This study is an extensive characterization of iPSC-derived motor neurons as cellular models of ALS carrying C9orf72 hexanucleotide repeats,which describes a novel pathogenic link between C9orf72 mutations,dysregulation of calcium signalling and altered proteostasis and provides a potential pharmacological target for the treatment of ALS and the related neurodegenerative disease frontotemporal dementia (FTD). This article is protected by copyright. All rights reserved. View Publication

There is an urgent need for an efficient approach to obtain a large-scale and renewable source of functional human vascular smooth muscle cells (VSMCs) to establish robust,patient-specific tissue model systems for studying the pathogenesis of vascular disease,and for developing novel therapeutic interventions. Here,we have derived a large quantity of highly enriched functional VSMCs from human induced pluripotent stem cells (hiPSC-VSMCs). Furthermore,we have engineered 3D tissue rings from hiPSC-VSMCs using a facile one-step cellular self-assembly approach. The tissue rings are mechanically robust and can be used for vascular tissue engineering and disease modeling of supravalvular aortic stenosis syndrome. Our method may serve as a model system,extendable to study other vascular proliferative diseases for drug screening. Thus,this report describes an exciting platform technology with broad utility for manufacturing cell-based tissues and materials for various biomedical applications. View Publication

Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare,early-onset retinal dystrophy characterised by distinct bands of circumferential pigmentary degeneration in the peripheral retina and developmental eye defects. ADVIRC is caused by mutations in the Bestrophin1 (BEST1) gene,which encodes a transmembrane protein thought to function as an ion channel in the basolateral membrane of retinal pigment epithelial (RPE) cells. Previous studies suggest that the distinct ADVIRC phenotype results from alternative splicing of BEST1 pre-mRNA. Here,we have used induced pluripotent stem cell (iPSC) technology to investigate the effects of an ADVIRC associated BEST1 mutation (c.704T textgreater C,p.V235A) in patient-derived iPSC-RPE. We found no evidence of alternate splicing of the BEST1 transcript in ADVIRC iPSC-RPE,however in patient-derived iPSC-RPE,BEST1 was expressed at the basolateral membrane and the apical membrane. During human eye development we show that BEST1 is expressed more abundantly in peripheral RPE compared to central RPE and is also expressed in cells of the developing retina. These results suggest that higher levels of mislocalised BEST1 expression in the periphery,from an early developmental stage,could provide a mechanism that leads to the distinct clinical phenotype observed in ADVIRC patients. View Publication

BACKGROUND Individuals with 22q11.2 Deletion Syndrome (22q11.2 DS) are a specific high-risk group for developing schizophrenia (SZ),schizoaffective disorder (SAD) and autism spectrum disorders (ASD). Several genes in the deleted region have been implicated in the development of SZ,e.g.,PRODH and DGCR8. However,the mechanistic connection between these genes and the neuropsychiatric phenotype remains unclear. To elucidate the molecular consequences of 22q11.2 deletion in early neural development,we carried out RNA-seq analysis to investigate gene expression in early differentiating human neurons derived from induced pluripotent stem cells (iPSCs) of 22q11.2 DS SZ and SAD patients. METHODS Eight cases (ten iPSC-neuron samples in total including duplicate clones) and seven controls (nine in total including duplicate clones) were subjected to RNA sequencing. Using a systems level analysis,differentially expressed genes/gene-modules and pathway of interests were identified. Lastly,we related our findings from in vitro neuronal cultures to brain development by mapping differentially expressed genes to BrainSpan transcriptomes. RESULTS We observed ˜2-fold reduction in expression of almost all genes in the 22q11.2 region in SZ (37 genes reached p-value textless 0.05,36 of which reached a false discovery rate textless 0.05). Outside of the deleted region,745 genes showed significant differences in expression between SZ and control neurons (p textless 0.05). Function enrichment and network analysis of the differentially expressed genes uncovered converging evidence on abnormal expression in key functional pathways,such as apoptosis,cell cycle and survival,and MAPK signaling in the SZ and SAD samples. By leveraging transcriptome profiles of normal human brain tissues across human development into adulthood,we showed that the differentially expressed genes converge on a sub-network mediated by CDC45 and the cell cycle,which would be disrupted by the 22q11.2 deletion during embryonic brain development,and another sub-network modulated by PRODH,which could contribute to disruption of brain function during adolescence. CONCLUSIONS This study has provided evidence for disruption of potential molecular events in SZ patient with 22q11.2 deletion and related our findings from in vitro neuronal cultures to functional perturbations that can occur during brain development in SZ. View Publication

X-linked chronic granulomatous disease (X-CGD) is an immune deficiency resulting from defective production of microbicidal reactive oxygen species (ROS) by phagocytes. Causative mutations occur throughout the CYBB gene,resulting in absent or defective gp91(phox) protein expression. To correct CYBB exon 5 mutations while retaining normal gene regulation,we utilized TALEN or Cas9 for exon 5 replacement in induced pluripotent stem cells (iPSCs) from patients,which restored gp91(phox) expression and ROS production in iPSC-derived granulocytes. Alternate approaches for correcting the majority of X-CGD mutations were assessed,involving TALEN- or Cas9-mediated insertion of CYBB minigenes at exon 1 or 2 of the CYBB locus. Targeted insertion of an exon 1-13 minigene into CYBB exon 1 resulted in no detectable gp91(phox) expression or ROS activity in iPSC-derived granulocytes. In contrast,targeted insertion of an exon 2-13 minigene into exon 2 restored both gp91(phox) and ROS activity. This demonstrates the efficacy of two correction strategies: seamless repair of specific CYBB mutations by exon replacement or targeted insertion of an exon 2-13 minigene to CYBB exon 2 while retaining exon/intron 1. Furthermore,it highlights a key issue for targeted insertion strategies for expression from an endogenous promoter: retention of intronic elements can be necessary for expression. View Publication