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The available techniques for directed gene manipulation in the mouse are unprecedented in any multicellular organism and make the mouse an invaluable tool for unraveling all aspects of mammalian biology. To realize fully the potential of these genetic tools requires that phenotypic analysis be efficient,rapid,and complete. Genetic chimeras and mosaics,in which mutant cells are mixed with wild-type cells,can be used to augment standard analysis of intact mutant animals and alleviate the time required and the expense involved in generating and maintaining multiple strains of mutant mice. View Publication

Under appropriate conditions in culture,embryonic stem cells will differentiate and form embryoid bodies that have been shown to contain cells of the hematopoietic,endothelial,muscle and neuronal lineages. Many aspects of the lineage-specific differentiation programs observed within the embryoid bodies reflect those found in the embryo,indicating that this model system provides access to early cell populations that develop in a normal fashion. Recent studies involving the differentiation of genetically altered embryonic stem cells highlight the potential of this in vitro differentiation system for defining the function of genes in early development. View Publication

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We report that embryonic stem cells efficiently undergo differentiation in vitro to mesoderm and hematopoietic cells and that this in vitro system recapitulates days 6.5 to 7.5 of mouse hematopoietic development. Embryonic stem cells differentiated as embryoid bodies (EBs) develop erythroid precursors by day 4 of differentiation,and by day 6,more than 85% of EBs contain such cells. A comparative reverse transcriptase-mediated polymerase chain reaction profile of marker genes for primitive endoderm (collagen alpha IV) and mesoderm (Brachyury) indicates that both cell types are present in the developing EBs as well in normal embryos prior to the onset of hematopoiesis. GATA-1,GATA-3,and vav are expressed in both the EBs and embryos just prior to and/or during the early onset of hematopoiesis,indicating that they could play a role in the early stages of hematopoietic development both in vivo and in vitro. The initial stages of hematopoietic development within the EBs occur in the absence of added growth factors and are not significantly influenced by the addition of a broad spectrum of factors,including interleukin-3 (IL-3),IL-1,IL-6,IL-11,erythropoietin,and Kit ligand. At days 10 and 14 of differentiation,EB hematopoiesis is significantly enhanced by the addition of both Kit ligand and IL-11 to the cultures. Kinetic analysis indicates that hematopoietic precursors develop within the EBs in an ordered pattern. Precursors of the primitive erythroid lineage appear first,approximately 24 h before precursors of the macrophage and definitive erythroid lineages. Bipotential neutrophil/macrophage and multilineage precursors appear next,and precursors of the mast cell lineage develop last. The kinetics of precursor development,as well as the growth factor responsiveness of these early cells,is similar to that found in the yolk sac and early fetal liver,indicating that the onset of hematopoiesis within the EBs parallels that found in the embryo. View Publication

Specifically ablating genes in human induced pluripotent stem cells (iPSCs) allows for studies of gene function as well as disease mechanisms in disorders caused by loss-of-function (LOF) mutations. While techniques exist for engineering such lines,we have developed and rigorously validated a method of simultaneous iPSC reprogramming while generating CRISPR/Cas9-dependent insertions/deletions (indels). This approach allows for the efficient and rapid formation of genetic LOF human disease cell models with isogenic controls. The rate of mutagenized lines was strikingly consistent across experiments targeting four different human epileptic encephalopathy genes and a metabolic enzyme-encoding gene,and was more efficient and consistent than using CRISPR gene editing of established iPSC lines. The ability of our streamlined method to reproducibly generate heterozygous and homozygous LOF iPSC lines with passage-matched isogenic controls in a single step provides for the rapid development of LOF disease models with ideal control lines,even in the absence of patient tissue. View Publication

Fibrodysplasia ossificans progressiva (FOP) is a rare and intractable disease characterized by extraskeletal bone formation through endochondral ossification. Patients with FOP harbor point mutations in ACVR1,a type I receptor for BMPs. Although mutated ACVR1 (FOP-ACVR1) has been shown to render hyperactivity in BMP signaling,we and others have uncovered a mechanism by which FOP-ACVR1 mistransduces BMP signaling in response to Activin-A,a molecule that normally transduces TGF-β signaling. Although Activin-A evokes enhanced chondrogenesis in vitro and heterotopic ossification (HO) in vivo,the underlying mechanisms have yet to be revealed. To this end,we developed a high-throughput screening (HTS) system using FOP patient-derived induced pluripotent stem cells (FOP-iPSCs) to identify pivotal pathways in enhanced chondrogenesis that are initiated by Activin-A. In a screen of 6,809 small-molecule compounds,we identified mTOR signaling as a critical pathway for the aberrant chondrogenesis of mesenchymal stromal cells derived from FOP-iPSCs (FOP-iMSCs). Two different HO mouse models,an FOP model mouse expressing FOP-ACVR1 and an FOP-iPSC-based HO model mouse,revealed critical roles for mTOR signaling in vivo. Moreover,we identified ENPP2,an enzyme that generates lysophosphatidic acid,as a linker of FOP-ACVR1 and mTOR signaling in chondrogenesis. These results uncovered the crucial role of the Activin-A/FOP-ACVR1/ENPP2/mTOR axis in FOP pathogenesis. View Publication

Mutations in WD40-repeat protein 62 (WDR62) are commonly associated with primary microcephaly and other developmental cortical malformations. We used human pluripotent stem cells (hPSC) to examine WDR62 function during human neural differentiation and model early stages of human corticogenesis. Neurospheres lacking WDR62 expression showed decreased expression of intermediate progenitor marker,TBR2,and also glial marker,S100β. In contrast,inhibition of c-Jun N-terminal kinase (JNK) signalling during hPSC neural differentiation induced upregulation of WDR62 with a corresponding increase in neural and glial progenitor markers,PAX6 and EAAT1,respectively. These findings may signify a role of WDR62 in specifying intermediate neural and glial progenitors during human pluripotent stem cell differentiation. View Publication

The human iPSC cell line,RP2-FiPS4F1 (RCPFi001-A),derived from dermal fibroblasts from the patient with retinitis pigmentosa caused by the mutation of the gene PRPF8,was generated by non-integrative reprogramming technology using OCT3/4,SOX2,CMYC and KLF4 reprogramming factors. View Publication

Peripheral blood mononuclear cells (PBMCs) were collected from a clinically characterized patient with autism spectrum disorder (ASD). The PMBCs were reprogrammed with the human OSKM transcription factors using the Sendai-virus delivery system. The pluripotency of transgene-free iPSCs was verified by immunocytochemistry for pluripotency markers and by spontaneous in vitro differentiation towards the 3 germ layers. Furthermore,the iPSC line showed normal karyotype. Our model might offer a good platform to study the pathomechanism of ASD,also for drug testing,early biomarker discovery and gene therapy studies. View Publication

Recent studies have shown that cellular bioenergetics may be involved in stem cell differentiation. Considering that during cancerogenesis cells acquire numerous properties of stem cells,it is possible to assume that the energy metabolism in tumorigenic cells might be differently regulated. The aim of this study was to compare the mitochondrial bioenergetic profile of normal pluripotent human embryonic stem cells (hESC) and relatively nullipotent embryonal carcinoma cells (2102Ep cell line). We examined three parameters related to cellular bioenergetics: phosphotransfer system,aerobic glycolysis,and oxygen consumption. Activities and expression levels of main enzymes that facilitate energy transfer were measured. The oxygen consumption rate studies were performed to investigate the respiratory capacity of cells. 2102Ep cells showed a shift in energy distribution towards adenylate kinase network. The total AK activity was almost 3 times higher in 2102Ep cells compared to hESCs (179.85±5.73 vs 64.39±2.55mU/mg of protein) and the expression of AK2 was significantly higher in these cells,while CK was downregulated. 2102Ep cells displayed reduced levels of oxygen consumption and increased levels of aerobic glycolysis compared to hESCs. The compromised respiration of 2102Ep cells is not the result of increased mitochondrial mass,increased proton leak,and reduced respiratory reserve capacity of the cells or impairment of respiratory chain complexes. Our data showed that the bioenergetic profile of 2102Ep cells clearly distinguishes them from normal hESCs. This should be considered when this cell line is used as a reference,and highlight the importance of further research concerning energy metabolism of stem cells. View Publication

iPSC-derived cells (from induced pluripotent stem cells) are a useful source that provide a powerful and widely accepted tool for the study of various types of human cells in vitro. Indeed,iPSC-derived cells from patients with hereditary diseases have been shown to reproduce the hallmarks of these diseases in vitro,phenotypes that can then also be manipulated in vitro. Quantitative reverse transcription PCR (qRT-PCR) is often used to characterize the progress of iPSC differentiation,validate mature cell types and to determine levels of pathological markers. Quantitative reverse transcription PCR (qRT-PCR) is used to quantify mRNA levels. This method requires some way of normalizing the data,typically by relating the obtained levels of gene expression to the levels of expression of a house keeping gene"� View Publication