技术资料

Human apolipoprotein E (ApoE) apolipoprotein is primarily expressed in three isoforms (ApoE2,ApoE3,and ApoE4) that differ only by two residues. ApoE4 constitutes the most important genetic risk factor for Alzheimer's disease (AD),ApoE3 is neutral,and ApoE2 is protective. How ApoE isoforms influence AD pathogenesis,however,remains unclear. Using ES-cell-derived human neurons,we show that ApoE secreted by glia stimulates neuronal Aβ production with an ApoE4< ApoE3< ApoE2 potency rank order. We demonstrate that ApoE binding to ApoE receptors activates dual leucine-zipper kinase (DLK),a MAP-kinase kinase kinase that then activates MKK7 and ERK1/2 MAP kinases. Activated ERK1/2 induces cFos phosphorylation,stimulating the transcription factor AP-1,which in turn enhances transcription of amyloid-β precursor protein (APP) and thereby increases amyloid-β levels. This molecular mechanism also regulates APP transcription in mice in vivo. Our data describe a novel signal transduction pathway in neurons whereby ApoE activates a non-canonical MAP kinase cascade that enhances APP transcription and amyloid-β synthesis. View Publication

Although gene-gene interaction,or epistasis,plays a large role in complex traits in model organisms,genome-wide by genome-wide searches for two-way interaction have limited power in human studies. We thus used knowledge of a biological pathway in order to identify a contribution of epistasis to autism spectrum disorders (ASDs) in humans,a reverse-pathway genetic approach. Based on previous observation of increased ASD symptoms in Mendelian disorders of the Ras/MAPK pathway (RASopathies),we showed that common SNPs in RASopathy genes show enrichment for association signal in GWAS (P = 0.02). We then screened genome-wide for interactors with RASopathy gene SNPs and showed strong enrichment in ASD-affected individuals (P < 2.2 x 10-16),with a number of pairwise interactions meeting genome-wide criteria for significance. Finally,we utilized quantitative measures of ASD symptoms in RASopathy-affected individuals to perform modifier mapping via GWAS. One top region overlapped between these independent approaches,and we showed dysregulation of a gene in this region,GPR141,in a RASopathy neural cell line. We thus used orthogonal approaches to provide strong evidence for a contribution of epistasis to ASDs,confirm a role for the Ras/MAPK pathway in idiopathic ASDs,and to identify a convergent candidate gene that may interact with the Ras/MAPK pathway. View Publication

Basal forebrain cholinergic neurons (BFCNs) are believed to be one of the first cell types to be affected in all forms of AD,and their dysfunction is clinically correlated with impaired short-term memory formation and retrieval. We present an optimized in vitro protocol to generate human BFCNs from iPSCs,using cell lines from presenilin 2 (PSEN2) mutation carriers and controls. As expected,cell lines harboring the PSEN2 N141I mutation displayed an increase in the A$\beta$42/40 in iPSC-derived BFCNs. Neurons derived from PSEN2 N141I lines generated fewer maximum number of spikes in response to a square depolarizing current injection. The height of the first action potential at rheobase current injection was also significantly decreased in PSEN2 N141I BFCNs. CRISPR/Cas9 correction of the PSEN2 point mutation abolished the electrophysiological deficit,restoring both the maximal number of spikes and spike height to the levels recorded in controls. Increased A$\beta$42/40 was also normalized following CRISPR/Cas-mediated correction of the PSEN2 N141I mutation. The genome editing data confirms the robust consistency of mutation-related changes in A$\beta$42/40 ratio while also showing a PSEN2-mutation-related alteration in electrophysiology. View Publication

BACKGROUND Pluripotent human embryonic stem cells (hESC) are a promising source of repopulating cardiomyocytes. We hypothesized that we could improve maturation of cardiomyocytes and facilitate electrical interconnections by creating a model that more closely resembles heart tissue; that is,containing both endothelial cells (ECs) and cardiomyocytes. METHODS We induced cardiomyocyte differentiation in the coculture of an hESC line expressing the cardiac reporter NKX2.5-green fluorescent protein (GFP),and an Akt-activated EC line (E4(+)ECs). We quantified spontaneous beating rates,synchrony,and coordination between different cardiomyocyte clusters using confocal imaging of Fura Red-detected calcium transients and computer-assisted image analysis. RESULTS After 8 days in culture,94% ± 6% of the NKX2-5GFP(+) cells were beating when hESCs embryonic bodies were plated on E4(+)ECs compared with 34% ± 12.9% for controls consisting of hESCs cultured on BD Matrigel (BD Biosciences) without ECs at Day 11 in culture. The spatial organization of beating areas in cocultures was different. The GFP(+) cardiomyocytes were close to the E4(+)ECs. The average beats/min of the cardiomyocytes in coculture was faster and closer to physiologic heart rates compared with controls (50 ± 14 [n = 13] vs 25 ± 9 [n = 8]; p < 0.05). The coculture with ECs led to synchronized beating relying on the endothelial network,as illustrated by the loss of synchronization upon the disruption of endothelial bridges. CONCLUSIONS The coculturing of differentiating cardiomyocytes with Akt-activated ECs but not EC-conditioned media results in (1) improved efficiency of the cardiomyocyte differentiation protocol and (2) increased maturity leading to better intercellular coupling with improved chronotropy and synchrony. View Publication

Induced pluripotent stem cells (iPSCs) are pluripotent cells derived from adult somatic cells. After the pioneering work by Yamanaka,who first generated iPSCs by retroviral transduction of four reprogramming factors,several alternative methods to obtain iPSCs have been developed in order to increase the yield and safety of the process. However,the question remains open on whether the different reprogramming methods can influence the pluripotency features of the derived lines. In this study,three different strategies,based on retroviral vectors,episomal vectors,and Sendai virus vectors,were applied to derive iPSCs from human fibroblasts. The reprogramming efficiency of the methods based on episomal and Sendai virus vectors was higher than that of the retroviral vector-based approach. All human iPSC clones derived with the different methods showed the typical features of pluripotent stem cells,including the expression of alkaline phosphatase and stemness maker genes,and could give rise to the three germ layer derivatives upon embryoid bodies assay. Microarray analysis confirmed the presence of typical stem cell gene expression profiles in all iPSC clones and did not identify any significant difference among reprogramming methods. In conclusion,the use of different reprogramming methods is equivalent and does not affect gene expression profile of the derived human iPSCs. View Publication

Human pluripotent stem cells derived cardiomyocytes (PSC-CMs) have been widely used for disease modeling,drug safety screening,and preclinical cell therapy to regenerate myocardium. Most studies have utilized PSC-CM grown in vitro for a relatively short period after differentiation. These PSC-CMs demonstrated structural,electrophysiological,and mechanical features of primitive cardiomyocytes. A few studies have extended in vitro PSC-CM culture time and reported improved maturation of structural and electromechanical properties. The degree of mitochondrial maturation,however,remains unclear. This study characterized the development of mitochondria during prolonged in vitro culture. PSC-CM demonstrated an improved mitochondrial maturation with prolonged culture,in terms of increased mitochondrial relative abundance,enhanced membrane potential,and increased activity of several mitochondrial respiratory complexes. These are in parallel with the maturation of other cellular components. However,the maturation of mitochondria in PSC-CMs grown for extended in vitro culture exhibits suboptimal maturation when compared with the maturation of mitochondria observed in the human fetal heart during similar time interval. View Publication

The recent Zika virus (ZIKV) outbreak,which mainly affected Brazil and neighbouring states,demonstrated the paucity of information concerning the epidemiology of several flaviruses,but also highlighted the lack of available agents with which to treat such emerging diseases. Here,we show that heparin,a widely used anticoagulant,while exerting a modest inhibitory effect on Zika Virus replication,fully prevents virus-induced cell death of human neural progenitor cells (NPCs). View Publication

Large scale purification of endothelial cells is of great interest as it could improve tissue transplantation,reperfusion of ischemic tissues and treatment of pathologies in which an endothelial cell dysfunction exists. In this study,we describe a novel genetic approach that selects for endothelial cells from differentiating embryonic stem (ES) cells. Our strategy is based on the establishment of ES-cell clones that carry an integrated puromycin resistance gene under the control of a vascular endothelium-specific promoter,tie-1. Using EGFP as a reporter gene,we first confirmed the endothelial specificity of the tie-1 promoter in the embryoid body model and in cells differentiated in 2D cultures. Subsequently,tie-1-EGFP ES cells were used as recipients for the tie-1-driven puror transgene. The resulting stable clones were expanded and differentiated for seven days in the presence of VEGF before puromycin selection. As expected,puromycin-resistant cells were positive for EGFP and also expressed several endothelial markers,including CD31,CD34,VEGFR-1,VEGFR-2,Tie-1,VE-cadherin and ICAM-2. Release from the puromycin selection resulted in the appearance of alpha-smooth muscle actin-positive cells. Such cells became more numerous when the population was cultured on laminin-1 or in the presence of TGF-beta1,two known inducers of smooth muscle cell differentiation. The hypothesis that endothelial cells or their progenitors may differentiate towards a smooth muscle cell phenotype was further supported by the presence of cells expressing both CD31 and alpha-smooth muscle actin markers. Finally,we show that purified endothelial cells can incorporate into the neovasculature of transplanted tumors in nude mice. Taken together,these results suggest that application of endothelial lineage selection to differentiating ES cells may become a useful approach for future pro-angiogenic and endothelial cell replacement therapies. View Publication

Human stem cells derived from human fertilized oocytes,fetal primordial germ cells,umbilical cord blood,and adult tissues provide potential cell-based therapies for repair of degenerating or damaged tissues. However,the diversity of major histocompatibility complex (MHC) antigens in the general population and the resultant risk of immune-mediated rejection complicates the allogenic use of established stem cells. We assessed an alternative approach,employing chemical activation of nonfertilized metaphase II oocytes for producing stem cells homozygous for MHC. By using F1 hybrid mice (H-2-B/D),we established stem cell lines homozygous for H-2-B and H-2-D,respectively. The undifferentiated cells retained a normal karyotype,expressed stage-specific embryonic antigen-1 and Oct4,and were positive for alkaline phosphatase and telomerase. Teratomatous growth of these cells displayed the development of a variety of tissue types encompassing all three germ layers. In addition,these cells demonstrated the potential for in vitro differentiation into endoderm,neuronal,and hematopoietic lineages. We also evaluated this homozygous stem cell approach in human tissue. Five unfertilized blastocysts were derived from a total of 25 human oocytes,and cells from one of the five hatched blastocysts proliferated and survived beyond two passages. Our studies demonstrate a plausible homozygous stem cell" approach for deriving pluripotent stem cells that can overcome the immune-mediated rejection response common in allotransplantation� View Publication

Experimental evidence indicates that shear stress (SS) exerts a morphogenetic function during cardiac development of mouse and zebrafish embryos. However,the molecular basis for this effect is still elusive. Our previous work described that in adult endothelial cells,SS regulates gene expression by inducing epigenetic modification of histones and activation of transcription complexes bearing acetyltransferase activity. In this study,we evaluated whether SS treatment could epigenetically modify histones and influence cell differentiation in mouse embryonic stem (ES) cells. Cells were exposed to a laminar SS of 10 dyne per cm2/s(-1),or kept in static conditions in the presence or absence of the histone deacetylase inhibitor trichostatin A (TSA). These experiments revealed that SS enhanced lysine acetylation of histone H3 at position 14 (K14),as well as serine phosphorylation at position 10 (S10) and lysine methylation at position 79 (K79),and cooperated with TSA,inducing acetylation of histone H4 and phosphoacetylation of S10 and K14 of histone H3. In addition,ES cells exposed to SS strongly activated transcription from the vascular endothelial growth factor (VEGF) receptor 2 promoter. This effect was paralleled by an early induction of cardiovascular markers,including smooth muscle actin,smooth muscle protein 22-alpha,platelet-endothelial cell adhesion molecule-1,VEGF receptor 2,myocyte enhancer factor-2C (MEF2C),and alpha-sarcomeric actin. In this condition,transcription factors MEF2C and Sma/MAD homolog protein 4 could be isolated from SS-treated ES cells complexed with the cAMP response element-binding protein acetyltransferase. These results provide molecular basis for the SS-dependent cardiovascular commitment of mouse ES cells and suggest that laminar flow may be successfully applied for the in vitro production of cardiovascular precursors. View Publication