技术资料

The glial cell line-derived neurotrophic factor (GDNF) has an important role in neuronal survival through binding to the GFRα1 (GDNF family receptor alpha-1) receptor and activation of the receptor tyrosine kinase Ret. Transient brain ischemia alters the expression of the GDNF signaling machinery but whether the GDNF receptor proteins are also affected,and the functional consequences,have not been investigated. We found that excitotoxic stimulation of cultured hippocampal neurons leads to a calpain-dependent downregulation of the long isoform of Ret (Ret51),but no changes were observed for Ret9 or GFRα1 under the same conditions. Cleavage of Ret51 by calpains was selectively mediated by activation of the extrasynaptic pool of N-methyl-d-aspartate receptors and leads to the formation of a stable cleavage product. Calpain-mediated cleavage of Ret51 was also observed in hippocampal neurons subjected to transient oxygen and glucose deprivation (OGD),a model of global brain ischemia,as well as in the ischemic region in the cerebral cortex of mice exposed to transient middle cerebral artery occlusion. Although the reduction of Ret51 protein levels decreased the total GDNF-induced receptor activity (as determined by assessing total phospho-Ret51 protein levels) and their downstream signaling activity,the remaining receptors still showed an increase in phosphorylation after incubation of hippocampal neurons with GDNF. Furthermore,GDNF protected hippocampal neurons when present before,during or after OGD,and the effects under the latter conditions were more significant in neurons transfected with human Ret51. These results indicate that the loss of Ret51 in brain ischemia partially impairs the neuroprotective effects of GDNF. View Publication

BACKGROUND Definitive endoderm (DE) is one of the three germ layers which during in vivo vertebrate development gives rise to a variety of organs including liver,lungs,thyroid and pancreas; consequently efficient in vitro initiation of stem cell differentiation to DE cells is a prerequisite for successful cellular specification to subsequent DE-derived cell types [1,2]. In this study we present a novel approach to rapidly and efficiently down regulate pluripotency genes during initiation of differentiation to DE cells by addition of dimethyl sulfoxide (DMSO) to Activin A-based culture medium and report its effects on the downstream differentiation to hepatocyte-like cells. MATERIALS AND METHODS Human embryonic stem cells (hESC) were differentiated to DE using standard methods in medium supplemented with 100ng/ml of Activin A and compared to cultures where DE specification was additionally enhanced with different concentrations of DMSO. DE cells were subsequently primed to generate hepatic-like cells to investigate whether the addition of DMSO during formation of DE improved subsequent expression of hepatic markers. A combination of flow cytometry,real-time quantitative reverse PCR and immunofluorescence was applied throughout the differentiation process to monitor expression of pluripotency (POUF5/OCT4 & NANOG),definitive endoderm (SOX17,CXCR4 & GATA4) and hepatic (AFP & ALB) genes to generate differentiation stage-specific signatures. RESULTS Addition of DMSO to the Activin A-based medium during DE specification resulted in rapid down regulation of the pluripotency genes OCT4 and NANOG,accompanied by an increase expression of the DE genes SOX17,CXCR4 and GATA4. Importantly,the expression level of ALB in DMSO-treated cells was also higher than in cells which were differentiated to the DE stage via standard Activin A treatment. View Publication

The intestinal mucosa undergoes a continual process of proliferation,differentiation and apoptosis,which is regulated by multiple signaling pathways. Notch signaling is critical for the control of intestinal stem cell maintenance and differentiation. However,the precise mechanisms involved in the regulation of differentiation are not fully understood. Previously,we have shown that tuberous sclerosis 2 (TSC2) positively regulates the expression of the goblet cell differentiation marker,MUC2,in intestinal cells. Using transgenic mice constitutively expressing a dominant negative TSC2 allele,we observed that TSC2 inactivation increased mTORC1 and Notch activities,and altered differentiation throughout the intestinal epithelium,with a marked decrease in the goblet and Paneth cell lineages. Conversely,treatment of mice with either Notch inhibitor dibenzazepine (DBZ) or mTORC1 inhibitor rapamycin significantly attenuated the reduction of goblet and Paneth cells. Accordingly,knockdown of TSC2 activated,whereas knockdown of mTOR or treatment with rapamycin decreased,the activity of Notch signaling in the intestinal cell line LS174T. Importantly,our findings demonstrate that TSC2/mTORC1 signaling contributes to the maintenance of intestinal epithelium homeostasis by regulating Notch activity. View Publication

Cardiac progenitor cells (CPCs) have the capacity to differentiate into cardiomyocytes,smooth muscle cells (SMC),and endothelial cells and hold great promise in cell therapy against heart disease. Among various methods to isolate CPCs,differentiation of embryonic stem cell (ESC) into CPCs attracts great attention in the field since ESCs can provide unlimited cell source. As a result,numerous strategies have been developed to derive CPCs from ESCs. In this protocol,differentiation and purification of embryonic CPCs from both mouse and human ESCs is described. Due to the difficulty of using cell surface markers to isolate embryonic CPCs,ESCs are engineered with fluorescent reporters activated by CPC-specific cre recombinase expression. Thus,CPCs can be enriched by fluorescence-activated cell sorting (FACS). This protocol illustrates procedures to form embryoid bodies (EBs) from ESCs for CPC specification and enrichment. The isolated CPCs can be subsequently cultured for cardiac lineage differentiation and other biological assays. This protocol is optimized for robust and efficient derivation of CPCs from both mouse and human ESCs. View Publication

Neurogenin3 (NEUROG3) is a basic helix-loop-helix transcription factor required for development of the endocrine pancreas in mice. In contrast,humans with NEUROG3 mutations are born with endocrine pancreas function,calling into question whether NEUROG3 is required for human endocrine pancreas development. To test this directly,we generated human embryonic stem cell (hESC) lines where both alleles of NEUROG3 were disrupted using CRISPR/Cas9-mediated gene targeting. NEUROG3(-/-) hESC lines efficiently formed pancreatic progenitors but lacked detectible NEUROG3 protein and did not form endocrine cells in vitro. Moreover,NEUROG3(-/-) hESC lines were unable to form mature pancreatic endocrine cells after engraftment of PDX1(+)/NKX6.1(+) pancreatic progenitors into mice. In contrast,a 75-90% knockdown of NEUROG3 caused a reduction,but not a loss,of pancreatic endocrine cell development. We conclude that NEUROG3 is essential for endocrine pancreas development in humans and that as little as 10% NEUROG3 is sufficient for formation of pancreatic endocrine cells. View Publication

Factor induced reprogramming of fibroblasts is an orchestrated but inefficient process. At the epigenetic level,it results in drastic chromatin changes to erase the existing somatic memory" and to establish the pluripotent state. Accordingly View Publication

Mitochondrial disease is a group of disorders caused by dysfunctional mitochondria,of which the mutation in the mitochondrial DNA is one of the primary factors. However,the molecular pathogenesis of mitochondrial diseases remains poorly understood due to lack of cell models. Patient-specific induced pluripotent stem cells (iPS cells or iPSCs) are originated from individuals suffering different diseases but carrying unchanged disease causing gene. Therefore,patient-specific iPS cells can be used as excellent cell models to elucidate the mechanisms underlying mitochondrial diseases. Here we present a detailed protocol for generating iPS cells from urine cells and fibroblasts for instance,as well as a series of characterizations. View Publication

Familial transthyretin amyloidosis (ATTR) is an autosomal dominant protein-folding disorder caused by over 100 distinct mutations in the transthyretin (TTR) gene. In ATTR,protein secreted from the liver aggregates and forms fibrils in target organs,chiefly the heart and peripheral nervous system,highlighting the need for a model capable of recapitulating the multisystem complexity of this clinically variable disease. Here,we describe detailed methodologies for the directed differentiation of protein folding disease-specific iPSCs into hepatocytes that produce mutant protein,and neural-lineage cells often targeted in disease. Methodologies are also described for the construction of multisystem models and drug screening using iPSCs. View Publication

BACKGROUND The therapeutic use of human embryonic stem cells (hESCs) is dependent on an efficient cryopreservation protocol for long-term storage. The aim of this study was to determine whether the combination of three cryoprotecting reagents using two freezing systems might improve hESC recovery rates with maintenance of hESC pluripotency properties for potential cell therapy application. METHODS Recovery rates of hESC colonies which were frozen in three cryoprotective solutions: Me2SO/HES/SR medium,Defined-medium® and Me2SO/SFB in medium solution were evaluated in ultra-slow programmable freezing system (USPF) and a slow-rate freezing system (SRF). The hESC pluripotency properties after freezing-thawing were evaluated. RESULTS We estimated the distribution frequency of survival colonies and observed that independent of the freezing system used (USPF or SRF) the best results were obtained with Me2SO/HES/SR as cryopreservation medium. We showed a significant hESC recovery colonies rate after thawing in Me2SO/HES/SR medium were 3.88 and 2.9 in USPF and SRF,respectively. The recovery colonies rate with Defined-medium® were 1.05 and 1.07 however in classical Me2SO medium were 0.5 and 0.86 in USPF and SRF,respectively. We showed significant difference between Me2SO/HES/SR medium×Defined-medium® and between Me2SO/HES/SR medium×Me2SO medium,for two cryopreservation systems (Ptextless0.05). CONCLUSION We developed an in house protocol using the combination of Me2SO/HES/SR medium and ultra-slow programmable freezing system which resulted in hESC colonies that remain undifferentiated,maintain their in vitro and in vivo pluripotency properties and genetic stability. This approach may be suitable for cell therapy studies. View Publication

HIV-1 infection leads to numerous B cell abnormalities,including hypergammaglobulinemia,nonspecific B cell activation,nonspecific class switching,increased cell turnover,breakage of tolerance,increased immature/transitional B cells,B cell malignancies,as well as a loss of capacity to generate and maintain memory,all of which contribute to a global impairment of the immune humoral compartment. Several cytokines and soluble factors,which are increased in sera of HIV-1-infected individuals,have been suggested to directly or indirectly contribute to these B cell dysfunctions,and one of these is the B cell-activating factor (BAFF). We report in this study that HIV-1 (X4- and R5-tropic) upregulates BAFF expression and secretion by human monocytes. Moreover,we show that the virus-mediated production of BAFF by monocytes relies on a type I IFN response by a small percentage of plasmacytoid dendritic cells (pDCs) present in the monocyte cultures. HIV-1-induced type I IFN by pDCs triggers BAFF production in both classical and intermediate monocytes,but not in nonclassical monocytes,which nonetheless display a very strong basal BAFF production. We report also that basal BAFF secretion was higher in monocytes obtained from females compared with those from male donors. This study provides a novel mechanistic explanation for the increased BAFF levels observed during HIV-1 infection and highlights the importance of pDC/monocyte crosstalk to drive BAFF secretion. View Publication

Manipulation of the CD28/CTLA-4 pathway is at the heart of a number of immunomodulatory approaches used in both autoimmunity and cancer. Although it is clear that CTLA-4 is a critical regulator of T cell responses,the immunological contexts in which CTLA-4 controls immune responses are not well defined. In this study,we show that whereas CD80/CD86-dependent activation of resting human T cells caused extensive T cell proliferation and robust CTLA-4 expression,in this context CTLA-4 blocking Abs had no impact on the response. In contrast,in settings where CTLA-4(+) cells were present as regulators View Publication

Mitochondrial dynamics play an important role in numerous physiological and pathophysiological phenomena in the developing and adult human heart. Alterations in structural aspects of cellular mitochondrial composition as a function of changes in physiology can easily be visualized using fluorescence microscopy. Commonly,mitochondrial location,number,and morphology are reported qualitatively due to the lack of automated and user-friendly computer-based analysis tools. Mitochondrial Quantification using MATLAB (MQM) is a computer-based tool to quantitatively assess these parameters by analyzing fluorescently labeled mitochondria within the cell; in particular,MQM provides numerical information on the number,area,and location of mitochondria within a cell in a time-efficient,automated,and unbiased way. This chapter describes the use of MQM's capabilities to quantify mitochondrial changes during human pluripotent stem cell (hPSC) differentiation into spontaneously contracting cardiomyocytes (SC-CMs),which follows physiological pathways of human heart development. View Publication