技术资料

Organotin compounds,such as tributyltin (TBT),are well-known endocrine disruptors. TBT is also known to cause various forms of cytotoxicity,including neurotoxicity and immunotoxicity. However,TBT toxicity has not been identified in normal stem cells. In the present study,we examined the effects of TBT on cell growth in human induced pluripotent stem cells (iPSCs). We found that exposure to nanomolar concentrations of TBT decreased intracellular ATP levels and inhibited cell viability in iPSCs. Because TBT suppressed energy production,which is a critical function of the mitochondria,we further assessed the effects of TBT on mitochondrial dynamics. Staining with MitoTracker revealed that nanomolar concentrations of TBT induced mitochondrial fragmentation. TBT also reduced the expression of mitochondrial fusion protein mitofusin 1 (Mfn1),and this effect was abolished by knockdown of the E3 ubiquitin ligase membrane-associated RING-CH 5 (MARCH5),suggesting that nanomolar concentrations of TBT could induce mitochondrial dysfunction via MARCH5-mediated Mfn1 degradation in iPSCs. Thus,mitochondrial function in normal stem cells could be used to assess cytotoxicity associated with metal exposure. View Publication

Summary Leber congenital amaurosis (LCA) is an inherited retinal dystrophy that causes childhood blindness. Photoreceptors are especially sensitive to an intronic mutation in the cilia-related gene CEP290,which causes missplicing and premature termination,but the basis of this sensitivity is unclear. Here,we generated differentiated photoreceptors in three-dimensional optic cups and retinal pigment epithelium (RPE) from iPSCs with this common CEP290 mutation to investigate disease mechanisms and evaluate candidate therapies. iPSCs differentiated normally into RPE and optic cups,despite abnormal CEP290 splicing and cilia defects. The highest levels of aberrant splicing and cilia defects were observed in optic cups,explaining the retinal-specific manifestation of this CEP290 mutation. Treating optic cups with an antisense morpholino effectively blocked aberrant splicing and restored expression of full-length CEP290,restoring normal cilia-based protein trafficking. These results provide a mechanistic understanding of the retina-specific phenotypes in CEP290 LCA patients and potential strategies for therapeutic intervention. View Publication

Alternative models for more rapid compound safety testing are of increasing demand. With emerging techniques using human pluripotent stem cells,the possibility of generating human in vitro models has gained interest,as factors related to species differences could be potentially eliminated. When studying potential neurotoxic effects of a compound it is of crucial importance to have both neurons and glial cells. We have successfully developed a protocol for generating in vitro 3D human neural tissues,using neural progenitor cells derived from human embryonic stem cells. These 3D neural tissues can be maintained for two months and undergo progressive differentiation. We showed a gradual decreased expression of early neural lineage markers,paralleled by an increase in markers specific for mature neurons,astrocytes and oligodendrocytes. At the end of the two-month culture period the neural tissues not only displayed synapses and immature myelin sheaths around axons,but electrophysiological measurements also showed spontaneous activity. Neurotoxicity testing - comparing non-neurotoxic to known neurotoxic model compounds - showed an expected increase in the marker of astroglial reactivity after exposure to known neurotoxicants methylmercury and trimethyltin. Although further characterization and refinement of the model is required,these results indicate its potential usefulness for in vitro neurotoxicity testing. View Publication

Retinitis pigmentosa (RP) is the most frequent form of inherited retinal dystrophy. RP is genetically heterogeneous and the genes identified to date encode proteins involved in a wide range of functional pathways,including photoreceptor development,phototransduction,the retinoid cycle,cilia,and outer segment development. Here we report the identification of biallelic mutations in Receptor Expression Enhancer Protein 6 (REEP6) in seven individuals with autosomal-recessive RP from five unrelated families. REEP6 is a member of the REEP/Yop1 family of proteins that influence the structure of the endoplasmic reticulum but is relatively unstudied. The six variants identified include three frameshift variants,two missense variants,and a genomic rearrangement that disrupts exon 1. Human 3D organoid optic cups were used to investigate REEP6 expression and confirmed the expression of a retina-specific isoform REEP6.1,which is specifically affected by one of the frameshift mutations. Expression of the two missense variants (c.383CtextgreaterT [p.Pro128Leu] and c.404TtextgreaterC [p.Leu135Pro]) and the REEP6.1 frameshift mutant in cultured cells suggest that these changes destabilize the protein. Furthermore,CRISPR-Cas9-mediated gene editing was used to produce Reep6 knock-in mice with the p.Leu135Pro RP-associated variant identified in one RP-affected individual. The homozygous knock-in mice mimic the clinical phenotypes of RP,including progressive photoreceptor degeneration and dysfunction of the rod photoreceptors. Therefore,our study implicates REEP6 in retinal homeostasis and highlights a pathway previously uncharacterized in retinal dystrophy. View Publication

Sex chromosome dosage compensation is essential in most metazoans,but the developmental timing and underlying mechanisms vary significantly,even among placental mammals. Here we identify human-specific mechanisms regulating X chromosome activity in early embryonic development. Single-cell RNA sequencing and imaging revealed co-activation and accumulation of the long noncoding RNAs (lncRNAs) XACT and XIST on active X chromosomes in both early human pre-implantation embryos and naive human embryonic stem cells. In these contexts,the XIST RNA adopts an unusual,highly dispersed organization,which may explain why it does not trigger X chromosome inactivation at this stage. Functional studies in transgenic mouse cells show that XACT influences XIST accumulation in cis. Our findings therefore suggest a mechanism involving antagonistic activity of XIST and XACT in controlling X chromosome activity in early human embryos,and they highlight the contribution of rapidly evolving lncRNAs to species-specific developmental mechanisms. View Publication

The study and application of human pluripotent stem cells (hPSCs) will be enhanced by the availability of well-characterised monoclonal antibodies (mAbs) detecting cell-surface epitopes. Here we report generation of seven new mAbs that detect cell surface proteins present on live and fixed human ES cells (hESCs) and human iPS cells (hiPSCs),confirming our previous prediction that these proteins were present on the cell surface of hPSCs. The mAbs all show a high correlation with POU5F1 (OCT4) expression and other hPSC surface markers (TRA-160 and SSEA-4) in hPSC cultures and detect rare OCT4 positive cells in differentiated cell cultures. These mAbs are immunoreactive to cell surface protein epitopes on both primed and naive state hPSCs,providing useful research tools to investigate the cellular mechanisms underlying human pluripotency and states of cellular reprogramming. In addition,we report that subsets of the seven new mAbs are also immunoreactive to human bone marrow-derived mesenchymal stem cells (MSCs),normal human breast subsets and both normal and tumorigenic colorectal cell populations. The mAbs reported here should accelerate the investigation of the nature of pluripotency,and enable development of robust cell separation and tracing technologies to enrich or deplete for hPSCs and other human stem and somatic cell types. This article is protected by copyright. All rights reserved. View Publication

Stem cells have been shown to respond to extracellular mechanical stimuli by regulating their fate through the activation of specific signaling pathways. In this work,an array of iron nanowires (NWs) aligned perpendicularly to the surface was fabricated by pulsed electrodepositon in porous alumina templates followed by a partial removal of the alumina to reveal 2-3 μm of the NWs. This resulted in alumina substrates with densely arranged NWs of 33 nm in diameter separated by 100 nm. The substrates were characterized by scanning electron microscopy (SEM) energy dispersive x-ray analysis and vibrating sample magnetometer. The NW array was then used as a platform for the culture of human mesenchymal stem cells (hMSCs). The cells were stained for the cell nucleus and actin filaments,as well as immuno-stained for the focal adhesion protein vinculin,and then observed by fluorescence microscopy in order to characterize their spreading behavior. Calcein AM/ethidium homodimer-1 staining allowed the determination of cell viability. The interface between the cells and the NWs was studied using SEM. Results showed that hMSCs underwent a re-organization of actin filaments that translated into a change from an elongated to a spherical cell shape. Actin filaments and vinculin accumulated in bundles,suggesting the attachment and formation of focal adhesion points of the cells on the NWs. Though the overall number of cells attached on the NWs was lower compared to the control,the attached cells maintained a high viability (>90%) for up to 6 d. Analysis of the interface between the NWs and the cells confirmed the re-organization of F-actin and revealed the adhesion points of the cells on the NWs. Additionally,a net of filopodia surrounded each cell,suggesting the probing of the array to find additional adhesion points. The cells maintained their round shape for up to 6 d of culture. Overall,the NW array is a promising nanostructured platform for studying and influencing hMSCs differentiation. View Publication

During development,neural crest (NC) cells are induced by signaling events at the neural plate border of all vertebrate embryos. Initially arising within the central nervous system,NC cells subsequently undergo an epithelial to mesenchymal transition to migrate into the periphery,where they differentiate into diverse cell types. Here we provide evidence that postnatal human epidermal keratinocytes (KC),in response to fibroblast growth factor 2 and insulin like growth factor 1 signals,can be reprogrammed toward a NC fate. Genome-wide transcriptome analyses show that keratinocyte-derived NC cells are similar to those derived from human embryonic stem cells. Moreover,they give rise in vitro and in vivo to NC derivatives such as peripheral neurons,melanocytes,Schwann cells and mesenchymal cells (osteocytes,chondrocytes,adipocytes,and smooth muscle cells). By demonstrating that human keratin-14+ KC can form NC cells,even from clones of single cells,our results have important implications in stem cell biology and regenerative medicine. Stem Cells 2017. View Publication

We mutated,by gene targeting,the endogenous hypoxanthine phosphoribosyl transferase (HPRT) gene in mouse embryo-derived stem (ES) cells. A specialized construct of the neomycin resistance (neor) gene was introduced into an exon of a cloned fragment of the Hprt gene and used to transfect ES cells. Among the G418r colonies,1/1000 were also resistant to the base analog 6-thioguanine (6-TG). The G418r,6-TGr cells were all shown to be Hprt- as the result of homologous recombination with the exogenous,neor-containing,Hprt sequences. We have compared the gene-targeting efficiencies of two classes of neor-Hprt recombinant vectors: those that replace the endogenous sequence with the exogenous sequence and those that insert the exogenous sequence into the endogenous sequence. The targeting efficiencies of both classes of vectors are strongly dependent upon the extent of homology between exogenous and endogenous sequences. The protocol described herein should be useful for targeting mutations into any gene. View Publication

This report describes the establishment directly from normal preimplantation mouse embryos of a cell line that forms teratocarcinomas when injected into mice. The pluripotency of these embryonic stem cells was demonstrated conclusively by the observation that subclonal cultures,derived from isolated single cells,can differentiate into a wide variety of cell types. Such embryonic stem cells were isolated from inner cell masses of late blastocysts cultured in medium conditioned by an established teratocarcinoma stem cell line. This suggests that such conditioned medium might contain a growth factor that stimulates the proliferation or inhibits the differentiation of normal pluripotent embryonic cells,or both. This method of obtaining embryonic stem cells makes feasible the isolation of pluripotent cells lines from various types of noninbred embryo,including those carrying mutant genes. The availability of such cell lines should made possible new approaches to the study of early mammalian development. View Publication

Mouse embryonic stem (ES) cells cultured as aggregates and exposed to retinoic acid are induced to express multiple phenotypes normally associated with neurons. A large percentage of treated aggregates produce a rich neuritic outgrowth. Dissociating the induced aggregates with trypsin and plating the cells as a monolayer results in cultures in which a sizable percentage of the cells have a neuronal appearance. These neuron-like cells express class III beta-tubulin and the neurofilament M subunit. Induced cultures express transcripts for neural-associated genes including the neurofilament L subunit,glutamate receptor subunits,the transcription factor Brn-3,and GFAP. Levels of neurofilament L and GAD67 and GAD65 transcripts rise dramatically upon induction. Physiological studies show that the neuron-like cells generate action potentials and express TTX-sensitive sodium channels,as well as voltage-gated potassium channels and calcium channels. We conclude that a complex system of neuronal gene expression can be activated in cultured ES cells. This system should be favorable for investigating some of the mechanisms that regulate neuronal differentiation. View Publication

Xenopus in vitro studies have implicated both transforming growth factor beta (TGF-beta) and fibroblast growth factor (FGF) families in mesoderm induction. Although members of both families are present during mouse mesoderm formation,there is little evidence for their functional role in mesoderm induction. We show that mouse embryonic stem cells,which resemble primitive ectoderm,can differentiate to mesoderm in vitro in a chemically defined medium (CDM) in the absence of fetal bovine serum. In CDM,this differentiation is responsive to TGF-beta family members in a concentration-dependent manner,with activin A mediating the formation of dorsoanterior-like mesoderm and bone morphogenetic protein 4 mediating the formation of ventral mesoderm,including hematopoietic precursors. These effects are not observed in CDM alone or when TGF-beta 1,-beta 2,or -beta 3,acid FGF,or basic FGF is added individually to CDM. In vivo,at day 6.5 of mouse development,activin beta A RNA is detectable in the decidua and bone morphogenetic protein 4 RNA is detectable in the egg cylinder. Together,our data strongly implicate the TGF-beta family in mammalian mesoderm development and hematopoietic cell formation. View Publication