Scientific Resources

An increasing number of genetic variants have been implicated in autism spectrum disorders (ASDs),and the functional study of such variants will be critical for the elucidation of autism pathophysiology. Here,we report a de novo balanced translocation disruption of TRPC6,a cation channel,in a non-syndromic autistic individual. Using multiple models,such as dental pulp cells,induced pluripotent stem cell (iPSC)-derived neuronal cells and mouse models,we demonstrate that TRPC6 reduction or haploinsufficiency leads to altered neuronal development,morphology and function. The observed neuronal phenotypes could then be rescued by TRPC6 complementation and by treatment with insulin-like growth factor-1 or hyperforin,a TRPC6-specific agonist,suggesting that ASD individuals with alterations in this pathway may benefit from these drugs. We also demonstrate that methyl CpG binding protein-2 (MeCP2) levels affect TRPC6 expression. Mutations in MeCP2 cause Rett syndrome,revealing common pathways among ASDs. Genetic sequencing of TRPC6 in 1041 ASD individuals and 2872 controls revealed significantly more nonsynonymous mutations in the ASD population,and identified loss-of-function mutations with incomplete penetrance in two patients. Taken together,these findings suggest that TRPC6 is a novel predisposing gene for ASD that may act in a multiple-hit model. This is the first study to use iPSC-derived human neurons to model non-syndromic ASD and illustrate the potential of modeling genetically complex sporadic diseases using such cells.Molecular Psychiatry advance online publication,11 November 2014; doi:10.1038/mp.2014.141. View Publication

Telomerase plays an important role in governing the life span of cells for its capacity to extend telomeres. As high activity of telomerase has been found in stem cells and cancer cells specifically,various methods have been developed for the evaluation of telomerase activity. To overcome the time-consuming procedures and complicated manipulations of existing methods,we developed a novel method named Telomeric Repeat Elongation Assay based on Quartz crystal microbalance (TREAQ) to monitor telomerase activity during the self-renewal and differentiation of human induced pluripotent stem cells (hiPSCs). TREAQ results indicated hiPSCs possess invariable telomerase activity for 11 passages on Matrigel and a steady decline of telomerase activity when differentiated for different periods,which is confirmed with existing golden standard method. The pluripotency of hiPSCs during differentiation could be estimated through monitoring telomerase activity and compared with the expression levels of markers of pluripotency gene via quantitative real time PCR. Regular assessment for factors associated with pluripotency or stemness was expensive and requires excessive sample consuming,thus TREAQ could be a promising alternative technology for routine monitoring of telomerase activity and estimate the pluripotency of stem cells. View Publication

Mammalian synthetic biology may provide novel therapeutic strategies,help decipher new paths for drug discovery and facilitate synthesis of valuable molecules. Yet,our capacity to genetically program cells is currently hampered by the lack of efficient approaches to streamline the design,construction and screening of synthetic gene networks. To address this problem,here we present a framework for modular and combinatorial assembly of functional (multi)gene expression vectors and their efficient and specific targeted integration into a well-defined chromosomal context in mammalian cells. We demonstrate the potential of this framework by assembling and integrating different functional mammalian regulatory networks including the largest gene circuit built and chromosomally integrated to date (6 transcription units,27kb) encoding an inducible memory device. Using a library of 18 different circuits as a proof of concept,we also demonstrate that our method enables one-pot/single-flask chromosomal integration and screening of circuit libraries. This rapid and powerful prototyping platform is well suited for comparative studies of genetic regulatory elements,genes and multi-gene circuits as well as facile development of libraries of isogenic engineered cell lines. View Publication

The fine analysis of cell components during the generation of pluripotent cells and their comparison to bone fide human embryonic stem cells (hESCs) are valuable tools to understand their biological behavior. In this report,human mesenchymal cells (hMSCs) generated from the human ES cell line H9,were reprogrammed back to induced pluripotent state using Oct-4,Sox2,Nanog,and Lin28 transgenes. Human induced pluripotent stem cells (hIPSCs) were analyzed using electron microscopy and compared with regard to the original hESCs and the hMSCs from which they were derived. This analysis shows that hIPSCs and the original hESCs are morphologically undistinguishable but differ from the hMSCs with respect to the presence of several morphological features of undifferentiated cells at both the cytoplasmic (ribosomes,lipid droplets,glycogen,scarce reticulum) and nuclear levels (features of nuclear plasticity,presence of euchromatin,reticulated nucleoli). We show that hIPSC colonies generated this way presented epithelial aspects with specialized junctions highlighting morphological criteria of the mesenchymal-epithelial transition in cells engaged in a successful reprogramming process. Electron microscopic analysis revealed also specific morphological aspects of partially reprogrammed cells. These results highlight the valuable use of electron microscopy for a better knowledge of the morphological aspects of IPSC and cellular reprogramming. View Publication

We report a technology to form human embryoid bodies (hEBs) from singularized human embryonic stem cells (hESCs) without the use of the p160 rho-associated coiled-coil kinase inhibitor (ROCKi) or centrifugation (spin). hEB formation was tested under four conditions: +ROCKi/+spin,+ROCKi/-spin,-ROCKi/+spin,and -ROCKi/-spin. Cell suspensions of BG01V/hOG and H9 hESC lines were pipetted into non-adherent hydrogel substrates containing defined microwell arrays. hEBs of consistent size and spherical geometry can be formed in each of the four conditions,including the -ROCKi/-spin condition. The hEBs formed under the -ROCKi/-spin condition differentiated to develop the three embryonic germ layers and tissues derived from each of the germ layers. This simplified hEB production technique offers homogeneity in hEB size and shape to support synchronous differentiation,elimination of the ROCKi xeno-factor and rate-limiting centrifugation treatment,and low-cost scalability,which will directly support automated,large-scale production of hEBs and hESC-derived cells needed for clinical,research,or therapeutic applications. View Publication

Gastric diseases,including peptic ulcer disease and gastric cancer,affect 10% of the world's population and are largely due to chronic Helicobacter pylori infection. Species differences in embryonic development and architecture of the adult stomach make animal models suboptimal for studying human stomach organogenesis and pathogenesis,and there is no experimental model of normal human gastric mucosa. Here we report the de novo generation of three-dimensional human gastric tissue in vitro through the directed differentiation of human pluripotent stem cells. We show that temporal manipulation of the FGF,WNT,BMP,retinoic acid and EGF signalling pathways and three-dimensional growth are sufficient to generate human gastric organoids (hGOs). Developing hGOs progressed through molecular and morphogenetic stages that were nearly identical to the developing antrum of the mouse stomach. Organoids formed primitive gastric gland- and pit-like domains,proliferative zones containing LGR5-expressing cells,surface and antral mucous cells,and a diversity of gastric endocrine cells. We used hGO cultures to identify novel signalling mechanisms that regulate early endoderm patterning and gastric endocrine cell differentiation upstream of the transcription factor NEUROG3. Using hGOs to model pathogenesis of human disease,we found that H. pylori infection resulted in rapid association of the virulence factor CagA with the c-Met receptor,activation of signalling and induction of epithelial proliferation. Together,these studies describe a new and robust in vitro system for elucidating the mechanisms underlying human stomach development and disease. View Publication

There is no consensus in the stem cell field as to what constitutes the mature cardiac myocyte. Thus,helping formalize a molecular signature for cardiac myocyte maturation would advance the field. In the mammalian heart,inactivation of the fetal" TNNI gene� View Publication

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

Synthetic modified mRNA molecules encoding pluripotency transcription factors have been used successfully in reprogramming human fibroblasts to induced pluripotent stem cells (iPSCs). We have applied this method on bone marrow-derived mesenchymal stromal cells (BM-MSCs) obtained from a patient with $$-thalassemia ($$-thal) with the aim to generate trangene-free $$-thal-iPSCs. Transfection of 10(4) BM-MSCs by lipofection with mRNA encoding the reprogramming factors Oct4,Klf4,Sox2,cMyc,and Lin28 resulted in formation of five iPSC colonies,from which three were picked up and expanded in $$-thal-iPSC lines. After 10 serial passages in vitro,$$-thal-iPSCs maintain genetic stability as shown by array comparative genomic hybridization (aCGH) and are capable of forming embryoid bodies in vitro and teratomas in vivo. Their gene expression profile compared to human embryonic stem cells (ESCs) and BM-MSCs seems to be similar to that of ESCs,whereas it differs from the profile of the parental BM-MSCs. Differentiation cultures toward a hematopoietic lineage showed the generation of CD34(+) progenitors up to 10%,but with a decreased hematopoietic colony-forming capability. In conclusion,we report herein the generation of transgene-free $$-thal-iPSCs that could be widely used for disease modeling and gene therapy applications. Moreover,it was demonstrated that the mRNA-based reprogramming method,used mainly in fibroblasts,is also suitable for reprogramming of human BM-MSCs. View Publication

Neural crest is a population of multipotent progenitor cells that form at the border of neural and non-neural ectoderm in vertebrate embryos,and undergo epithelial-mesenchymal transition and migration. According to the traditional view,the neural crest is specified in early embryos by signaling molecules including BMP,FGF,and Wnt proteins. Here,we identify a novel signaling pathway leading to neural crest specification,which involves Rho-associated kinase (ROCK) and its downstream target nonmuscle Myosin II. We show that ROCK inhibitors promote differentiation of human embryonic stem cells (hESCs) into neural crest-like progenitors (NCPs) that are characterized by specific molecular markers and ability to differentiate into multiple cell types,including neurons,chondrocytes,osteocytes,and smooth muscle cells. Moreover,inhibition of Myosin II was sufficient for generating NCPs at high efficiency. Whereas Myosin II has been previously implicated in the self-renewal and survival of hESCs,we demonstrate its role in neural crest development during ESC differentiation. Inhibition of this pathway in Xenopus embryos expanded neural crest in vivo,further indicating that neural crest specification is controlled by ROCK-dependent Myosin II activity. We propose that changes in cell morphology in response to ROCK and Myosin II inhibition initiate mechanical signaling leading to neural crest fates. View Publication

Cancer stem-like cells represent poorly differentiated multipotent tumor-propagating cells that contribute disproportionately to therapeutic resistance and tumor recurrence. Transcriptional mechanisms that control the phenotypic conversion of tumor cells lacking tumor-propagating potential to tumor-propagating stem-like cells remain obscure. Here we show that the reprogramming transcription factors Oct4 and Sox2 induce glioblastoma cells to become stem-like and tumor-propagating via a mechanism involving direct DNA methyl transferase (DNMT) promoter transactivation,resulting in global DNA methylation- and DNMT-dependent downregulation of multiple microRNAs (miRNAs). We show that one such downregulated miRNA,miRNA-148a,inhibits glioblastoma cell stem-like properties and tumor-propagating potential. This study identifies a novel and targetable molecular circuit by which glioma cell stemness and tumor-propagating capacity are regulated. View Publication

Differentiation of human pluripotent stem cells (hPSCs) into organ-specific subtypes offers an exciting avenue for the study of embryonic development and disease processes,for pharmacologic studies and as a potential resource for therapeutic transplant. To date,limited in vivo models exist for human intestine,all of which are dependent upon primary epithelial cultures or digested tissue from surgical biopsies that include mesenchymal cells transplanted on biodegradable scaffolds. Here,we generated human intestinal organoids (HIOs) produced in vitro from human embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) that can engraft in vivo. These HIOs form mature human intestinal epithelium with intestinal stem cells contributing to the crypt-villus architecture and a laminated human mesenchyme,both supported by mouse vasculature ingrowth. In vivo transplantation resulted in marked expansion and maturation of the epithelium and mesenchyme,as demonstrated by differentiated intestinal cell lineages (enterocytes,goblet cells,Paneth cells,tuft cells and enteroendocrine cells),presence of functional brush-border enzymes (lactase,sucrase-isomaltase and dipeptidyl peptidase 4) and visible subepithelial and smooth muscle layers when compared with HIOs in vitro. Transplanted intestinal tissues demonstrated digestive functions as shown by permeability and peptide uptake studies. Furthermore,transplanted HIO-derived tissue was responsive to systemic signals from the host mouse following ileocecal resection,suggesting a role for circulating factors in the intestinal adaptive response. This model of the human small intestine may pave the way for studies of intestinal physiology,disease and translational studies. View Publication