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Background Human embryonic stem cells (hESCs) serve as a potential unlimited ex vivo source of cardiomyocytes for disease modeling,cardiotoxicity screening,drug discovery,and cell-based therapies. Despite the fundamental importance of Ca2+-induced Ca2+ release in excitation-contraction coupling,the mechanistic basis of Ca2+ handling of hESC-derived ventricular cardiomyocytes (VCMs) remains elusive. Objectives To study Ca2+ sparks as unitary events of Ca2+ handling for mechanistic insights. Methods To avoid ambiguities owing to the heterogeneous nature,we experimented with hESC-VCMs,purified on the basis of zeocin resistance and signature ventricular action potential after LV-MLC2v-tdTomato-T2A-Zeo transduction. Results Ca2+ sparks that were sensitive to inhibitors of sarco/endoplasmic reticulum Ca2+-ATPase (thapsigargin and cyclopiazonic acid) and ryanodine receptor (RyR; ryanodine,tetracaine) but not inositol trisphosphate receptors (xestospongin C and 2-aminoethyl diphenylborinate) could be recorded. In a permeabilization model,we further showed that RyRs could be sensitized by Ca2+. Increasing external Ca2+ dramatically escalated the basal Ca2+ and spark frequency. Furthermore,RyR-mediated Ca2+ release sensitized nearby RyRs,leading to compound Ca2+ sparks. Depolarization or L-type Ca2+ channel agonist (FPL 64176 and Bay K8644) pretreatment induced an extracellular Ca2+-dependent cytosolic Ca2+ increase and reduced the sarcoplasmic reticulum content. By contrast,removal of external Na+ or the addition of the Na+-Ca2+ exchanger inhibitor (KB-R7943 and SN-6) had no effect,suggesting that the Na+-Ca2+ exchanger is not involved in triggering sparks. Inhibition of mitochondrial Ca2+ uptake by carbonyl cyanide m-chlorophenyl hydrazone promoted Ca2+ waves. Conclusion Taken collectively,our findings provide the first lines of direct evidence that hESC-VCMs have functional Ca2+-induced Ca2+ release. However,the sarcoplasmic reticulum is leaky and without a mature terminating mechanism in early development. View Publication

A progressive increase in MECP2 protein levels is a crucial and precisely regulated event during neurodevelopment,but the underlying mechanism is unclear. We report that MECP2 is regulated post-transcriptionally during in vitro differentiation of human embryonic stem cells (hESCs) into cortical neurons. Using reporters to identify functional RNA sequences in the MECP2 3' UTR and genetic manipulations to explore the role of interacting factors on endogenous MECP2,we discover combinatorial mechanisms that regulate RNA stability and translation. The RNA-binding protein PUM1 and pluripotent-specific microRNAs destabilize the long MECP2 3' UTR in hESCs. Hence,the 3' UTR appears to lengthen during differentiation as the long isoform becomes stable in neurons. Meanwhile,translation of MECP2 is repressed by TIA1 in hESCs until HuC predominates in neurons,resulting in a switch to translational enhancement. Ultimately,3' UTR-directed translational fine-tuning differentially modulates MECP2 protein in the two cell types to levels appropriate for normal neurodevelopment. View Publication

Rett syndrome (RTT) is an X-linked,neurodevelopmental disorder caused primarily by mutations in the methyl-CpG-binding protein 2 (MECP2) gene,which encodes a multifunctional epigenetic regulator with known links to a wide spectrum of neuropsychiatric disorders. Although postnatal functions of MeCP2 have been thoroughly investigated,its role in prenatal brain development remains poorly understood. Given the well-established importance of microRNAs (miRNAs) in neurogenesis,we employed isogenic human RTT patient-derived induced pluripotent stem cell (iPSC) and MeCP2 short hairpin RNA knockdown approaches to identify novel MeCP2-regulated miRNAs enriched during early human neuronal development. Focusing on the most dysregulated miRNAs,we found miR-199 and miR-214 to be increased during early brain development and to differentially regulate extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase and protein kinase B (PKB/AKT) signaling. In parallel,we characterized the effects on human neurogenesis and neuronal differentiation brought about by MeCP2 deficiency using both monolayer and three-dimensional (cerebral organoid) patient-derived and MeCP2-deficient neuronal culture models. Inhibiting miR-199 or miR-214 expression in iPSC-derived neural progenitors deficient in MeCP2 restored AKT and ERK activation,respectively,and ameliorated the observed alterations in neuronal differentiation. Moreover,overexpression of miR-199 or miR-214 in the wild-type mouse embryonic brains was sufficient to disturb neurogenesis and neuronal migration in a similar manner to Mecp2 knockdown. Taken together,our data support a novel miRNA-mediated pathway downstream of MeCP2 that influences neurogenesis via interactions with central molecular hubs linked to autism spectrum disorders.Molecular Psychiatry advance online publication,25 April 2017; doi:10.1038/mp.2017.86. View Publication

Recurrent chromosomal alterations have been repeatedly reported in cultured human embryonic stem cells (hESCs). The effects of these alterations on the capability of pluripotent cells to differentiate and on growth potential of their specific differentiated derivatives remain unclear. Here,we report that the hESC lines HUES-7 and -9 carrying multiple chromosomal alterations produce in vitro mesenchymal stem cells (MSCs) that show progressive growth arrest and enter senescence after 15 and 16 passages,respectively. There was no difference in their proliferative potential when compared with bone marrow-derived MSCs. Array comparative genomic hybridization analysis (aCGH) of hESCs and their mesenchymal derivatives revealed no significant differences in chromosomal alterations,suggesting that genetically altered hESCs are not selected out during differentiation. Our findings indicate that genetically unstable hESCs maintain their capacity to differentiate in vitro into MSCs,which exhibit an in vitro growth pattern of normal MSCs and not that of transformed cells. View Publication

Mesenchymal stem cells (MSCs) are being tested in a wide range of human diseases; however,loss of potency and inconsistent quality severely limit their use. To overcome these issues,we have utilized a developmental precursor called the hemangioblast as an intermediate cell type in the derivation of a highly potent and replenishable population of MSCs from human embryonic stem cells (hESCs). This method circumvents the need for labor-intensive hand-picking,scraping,and sorting that other hESC-MSC derivation methods require. Moreover,unlike previous reports on hESC-MSCs,we have systematically evaluated their immunomodulatory properties and in vivo potency. As expected,they dynamically secrete a range of bioactive factors,display enzymatic activity,and suppress T-cell proliferation that is induced by either allogeneic cells or mitogenic stimuli. However,they also display unique immunophenotypic properties,as well as a smaller size and textgreater30,000-fold proliferative capacity than bone marrow-derived MSCs. In addition,this is the first report which demonstrates that hESC-MSCs can inhibit CD83 up-regulation and IL-12p70 secretion from dendritic cells and enhance regulatory T-cell populations induced by interleukin 2 (IL-2). This is also the first report which shows that hESC-MSCs have therapeutic efficacy in two different autoimmune disorder models,including a marked increase in survival of lupus-prone mice and a reduction of symptoms in an autoimmune model of uveitis. Our data suggest that this novel and therapeutically active population of MSCs could overcome many of the obstacles that plague the use of MSCs in regenerative medicine and serve as a scalable alternative to current MSC sources. View Publication

Bone marrow-derived mesenchymal stem cells (MSC) have been defined as primitive,undifferentiated cells,capable of self-renewal and with the ability to give rise to different cell lineages,including adipocytes,osteocytes,fibroblasts,chondrocytes,and myoblasts. MSC are key components of the hematopoietic microenvironment. Several studies,including some from our own group,suggest that important quantitative and functional alterations are present in the stroma of patients with myelodysplasia (MDS). However,in most of such studies the stroma has been analyzed as a complex network of different cell types and molecules,thus it has been difficult to identify and characterize the cell(s) type(s) that is (are) altered in MDS. In the present study,we have focused on the biological characterization of MSC from MDS. As a first approach,we have quantified their numbers in bone marrow,and have worked on their phenotypic (morphology and immunophenotype) and cytogenetic properties. MSC were obtained by a negative selection procedure and cultured in a MSC liquid culture medium. In terms of morphology,as well as the expression of certain cell markers,no differences were observed between MSC from MDS patients and those derived from normal marrow. In both cases,MSC expressed CD29,CD90,CD105 and Prolyl-4-hydroxylase; in contrast,they did not express CD14,CD34,CD68,or alkaline phosphatase. Interestingly,in five out of nine MDS patients,MSC developed in culture showed cytogenetic abnormalities,usually involving the loss of chromosomal material. All those five cases also showed cytogenetic abnormalities in their hematopoietic cells. Interestingly,in some cases there was a complete lack of overlap between the karyotypes of hematopoietic cells and MSC. To the best of our knowledge,the present study is the first in which a pure population of MSC from MDS patients is analyzed in terms of their whole karyotype and demonstrates that in a significant proportion of patients,MSC are cytogenetically abnormal. Although the reason of this is still unclear,such alterations may have an impact on the physiology of these cells. Further studies are needed to assess the functional integrity of MDS-derived MSC. View Publication

Stem cell differentiation involves critical changes in gene expression. Identification of these should provide endpoints useful for optimizing stem cell propagation as well as potential clues about mechanisms governing stem cell maintenance. Here we describe the results of a new meta-analysis methodology applied to multiple gene expression datasets from three mouse embryonic stem cell (ESC) lines obtained at specific time points during the course of their differentiation into various lineages. We developed methods to identify genes with expression changes that correlated with the altered frequency of functionally defined,undifferentiated ESC in culture. In each dataset,we computed a novel statistical confidence measure for every gene which captured the certainty that a particular gene exhibited an expression pattern of interest within that dataset. This permitted a joint analysis of the datasets,despite the different experimental designs. Using a ranking scheme that favored genes exhibiting patterns of interest,we focused on the top 88 genes whose expression was consistently changed when ESC were induced to differentiate. Seven of these (103728at,8430410A17Rik,Klf2,Nr0b1,Sox2,Tcl1,and Zfp42) showed a rapid decrease in expression concurrent with a decrease in frequency of undifferentiated cells and remained predictive when evaluated in additional maintenance and differentiating protocols. Through a novel meta-analysis,this study identifies a small set of genes whose expression is useful for identifying changes in stem cell frequencies in cultures of mouse ESC. The methods and findings have broader applicability to understanding the regulation of self-renewal of other stem cell types. View Publication

BACKGROUND: Fetal alcohol spectrum disorders (FASD) are a leading cause of neurodevelopmental disability. The mechanisms underlying FASD are incompletely understood,and biomarkers to identify those at risk are lacking. Here,we perform metabolomic analysis of embryoid bodies and neural lineages derived from human embryonic stem (hES) cells to identify the neural secretome produced in response to ethanol (EtOH) exposure. METHODS: WA01 and WA09 hES cells were differentiated into embryoid bodies,neural progenitors,or neurons. Cells along this progression were cultured for 4 days with 0,0.1,or 0.3% EtOH. Supernatants were subjected to C18 chromatography followed by ESI-QTOF-MS. Features were annotated using public databases,and the identities of 4 putative biomarkers were confirmed with purified standards and comparative MS/MS. RESULTS: EtOH treatment induced statistically significant changes to metabolite abundance in human embryoid bodies (180 features),neural progenitors (76 features),and neurons (42 features). There were no shared significant features between different cell types. Fifteen features showed a dose-response to EtOH. Four chemical identities were confirmed: L-thyroxine,5'-methylthioadenosine,and the tryptophan metabolites,L-kynurenine and indoleacetaldehyde. One feature with a putative annotation of succinyladenosine was significantly increased in both EtOH treatments. Additional features were selective to EtOH treatment but were not annotated in public databases. CONCLUSIONS: EtOH exposure induces statistically significant changes to the metabolome profile of human embryoid bodies,neural progenitors,and neurons. Several of these metabolites are normally present in human serum,suggesting their usefulness as potential serum FASD biomarkers. These findings suggest the biochemical pathways that are affected by EtOH in the developing nervous system and delineate mechanisms of alcohol injury during human development. View Publication

As human embryonic stem cells (hESCs) steadily progress towards regenerative medicine applications there is an increasing emphasis on the development of bioreactor platforms that enable expansion of these cells to clinically relevant numbers. Surprisingly little is known about the metabolic requirements of hESCs,precluding the rational design and optimisation of such platforms. In this study,we undertook an in-depth characterisation of MEL-2 hESC metabolic behaviour during the exponential growth phase,combining metabolic profiling and flux analysis tools at physiological (hypoxic) and atmospheric (normoxic) oxygen concentrations. To overcome variability in growth profiles and the problem of closing mass balances in a complex environment,we developed protocols to accurately measure uptake and production rates of metabolites,cell density,growth rate and biomass composition,and designed a metabolic flux analysis model for estimating internal rates. hESCs are commonly considered to be highly glycolytic with inactive or immature mitochondria,however,whilst the results of this study confirmed that glycolysis is indeed highly active,we show that at least in MEL-2 hESC,it is supported by the use of oxidative phosphorylation within the mitochondria utilising carbon sources,such as glutamine to maximise ATP production. Under both conditions,glycolysis was disconnected from the mitochondria with all of the glucose being converted to lactate. No difference in the growth rates of cells cultured under physiological or atmospheric oxygen concentrations was observed nor did this cause differences in fluxes through the majority of the internal metabolic pathways associated with biogenesis. These results suggest that hESCs display the conventional Warburg effect,with high aerobic activity despite high lactate production,challenging the idea of an anaerobic metabolism with low mitochondrial activity. The results of this study provide new insight that can be used in rational bioreactor design and in the development of View Publication

How metabolism is reprogrammed during neuronal differentiation is unknown. We found that the loss of hexokinase (HK2) and lactate dehydrogenase (LDHA) expression,together with a switch in pyruvate kinase gene splicing from PKM2 to PKM1,marks the transition from aerobic glycolysis in neural progenitor cells (NPC) to neuronal oxidative phosphorylation. The protein levels of c-MYC and N-MYC,transcriptional activators of the HK2 and LDHA genes,decrease dramatically. Constitutive expression of HK2 and LDHA during differentiation leads to neuronal cell death,indicating that the shut-off aerobic glycolysis is essential for neuronal survival. The metabolic regulators PGC-1α and ERRγ increase significantly upon neuronal differentiation to sustain the transcription of metabolic and mitochondrial genes,whose levels are unchanged compared to NPCs,revealing distinct transcriptional regulation of metabolic genes in the proliferation and post-mitotic differentiation states. Mitochondrial mass increases proportionally with neuronal mass growth,indicating an unknown mechanism linking mitochondrial biogenesis to cell size. View Publication

In Wilson disease (WD),functional loss of ATPase copper-transporting $$ (ATP7B) impairs biliary copper excretion,leading to excessive copper accumulation in the liver and fulminant hepatitis. Current US Food and Drug Administration- and European Medicines Agency-approved pharmacological treatments usually fail to restore copper homeostasis in patients with WD who have progressed to acute liver failure,leaving liver transplantation as the only viable treatment option. Here,we investigated the therapeutic utility of methanobactin (MB),a peptide produced by Methylosinus trichosporium OB3b,which has an exceptionally high affinity for copper. We demonstrated that ATP7B-deficient rats recapitulate WD-associated phenotypes,including hepatic copper accumulation,liver damage,and mitochondrial impairment. Short-term treatment of these rats with MB efficiently reversed mitochondrial impairment and liver damage in the acute stages of liver copper accumulation compared with that seen in untreated ATP7B-deficient rats. This beneficial effect was associated with depletion of copper from hepatocyte mitochondria. Moreover,MB treatment prevented hepatocyte death,subsequent liver failure,and death in the rodent model. These results suggest that MB has potential as a therapeutic agent for the treatment of acute WD. View Publication