ES-derived Cells Research Articles

Dissecting the impact of regional identity and the oncogenic role of human-specific NOTCH2NL in an hESC model of H3.3G34R-mutant glioma

H3.3G34R-mutant gliomas are lethal tumors of the cerebral hemispheres with unknown mechanisms of regional specificity and tumorigenicity. We developed a human embryonic stem cell (hESC)-based model of H3.3G34R-mutant glioma that recapitulates the key features of the tumors with cell-type specificity to forebrain interneuronal progenitors but not hindbrain precursors. We show that H3.3G34R, ATRX, and TP53 mutations cooperatively impact alternative RNA splicing events, particularly suppression of intron retention. This leads to increased expression of components of the Notch pathway, notably NOTCH2NL, a human-specific gene family. We also uncover a parallel mechanism of enhanced NOTCH2NL expression via genomic amplification of its locus in some H3.3G34R-mutant tumors. These findings demonstrate a novel mechanism whereby evolutionary pathways that lead to larger brain size in humans are co-opted to drive tumor growth.

Novel histone deacetylase inhibitors and embryo aggregation enhance cloned embryo development and ES cell derivation in pigs.

The histone deacetylase inhibitor (HDACi) has been investigated for treating cancers and many other diseases as well as enhancing the reprogramming efficiency in cloned embryos for decades. In the present study, we investigated the effects of two novel HDAC inhibitors, i.e., HDACi-14 and -79, at the concentrations of 0, 1, 2, or 4 μM on the development of embryos cloned by the oocyte bisection cloning technique (OBCT). Blastocyst rates for the reconstructed embryos reached 60% in the 2 μM HDACi-14-treated groups, which was higher (P < 0.05) compared to the untreated group (36.9%). Similarly, HDACi-79 treatment at 2 and 4 μM also conferred higher (P < 0.05) blastocyst rates than that of the untreated group (79.4, 74.2, and 50.0%, respectively). Both HDACi-14 and -79 treatments had no beneficial effect on total cell numbers and apoptotic indices of cloned embryos (P > 0.05). Histone acetylation profile by both HDACi-14 (2 μM) and -79 (2 μM) treatments demonstrated a drastic increase (P < 0.05) mainly in two-cell stage embryos when compared to the control group. After seeding on the feeder cells, the aggregated cloned blastocysts produced by the HDACi-79 treatment showed a significant increase of primary outgrowths compared to the control group (60.0% vs. 42.9%; P < 0.05). Finally, the cloned embryo-derived ES cell lines from aggregated cloned embryos produced from the HDACi-79-treated, HDACi-14-treated and control groups were established (5, 3, and 2 lines, respectively). In conclusion, the novel histone deacetylation inhibitors improve blastocyst formation and potentially increase the derivation efficiency of ES cell lines from the cloned porcine embryos produced in vitro. Depending on the purposes, some fine-tuning may be required to maximize its beneficial effects of these newly synthesized chemicals.

Glucocorticoid Signaling Enhances Expression of Glucose-Sensing Molecules in Immature Pancreatic Beta-Like Cells Derived from Murine Embryonic Stem Cells In Vitro

Pluripotent stem cells may serve as an alternative source of beta-like cells for replacement therapy of type 1 diabetes; however, the beta-like cells generated in many differentiation protocols are immature. The maturation of endogenous beta cells involves an increase in insulin expression starting in late gestation and a gradual acquisition of the abilities to sense glucose and secrete insulin by week 2 after birth in mice; however, what molecules regulate these maturation processes are incompletely known. In this study, we aim to identify small molecules that affect immature beta cells. A cell-based assay, using pancreatic beta-like cells derived from murine embryonic stem (ES) cells harboring a transgene containing an insulin 1-promoter driven enhanced green fluorescent protein reporter, was used to screen a compound library (NIH Clinical Collection-003). Cortisone, a glucocorticoid, was among five positive hit compounds. Quantitative reverse transcription-polymerase chain reaction analysis revealed that glucocorticoids enhance the gene expression of not only insulin 1 but also glucose transporter-2 (Glut2; Slc2a2) and glucokinase (Gck), two molecules important for glucose sensing. Mifepristone, a pharmacological inhibitor of glucocorticoid receptor (GR) signaling, reduced the effects of glucocorticoids on Glut2 and Gck expression. The effects of glucocorticoids on ES-derived cells were further validated in immature primary islets. Isolated islets from 1-week-old mice had an increased Glut2 and Gck expression in response to a 4-day treatment of exogenous hydrocortisone in vitro. Gene deletion of GR in beta cells using rat insulin 2 promoter-driven Cre crossed with GRflox/flox mice resulted in a reduced gene expression of Glut2, but not Gck, and an abrogation of insulin secretion when islets were incubated in 0.5 mM d-glucose and stimulated by 17 mM d-glucose in vitro. These results demonstrate that glucocorticoids positively regulate glucose sensors in immature murine beta-like cells.

Donor Dependent Variations in Hematopoietic Differentiation among Embryonic and Induced Pluripotent Stem Cell Lines.

Hematopoiesis generated from human embryonic stem cells (ES) and induced pluripotent stem cells (iPS) are unprecedented resources for cell therapy. We compared hematopoietic differentiation potentials from ES and iPS cell lines originated from various donors and derived them using integrative and non-integrative vectors. Significant differences in differentiation toward hematopoietic lineage were observed among ES and iPS. The ability of engraftment of iPS or ES-derived cells in NOG mice varied among the lines with low levels of chimerism. iPS generated from ES cell-derived mesenchymal stem cells (MSC) reproduce a similar hematopoietic outcome compared to their parental ES cell line. We were not able to identify any specific hematopoietic transcription factors that allow to distinguish between good versus poor hematopoiesis in undifferentiated ES or iPS cell lines. There is a relatively unpredictable variation in hematopoietic differentiation between ES and iPS cell lines that could not be predicted based on phenotype or gene expression of the undifferentiated cells. These results demonstrate the influence of genetic background in variation of hematopoietic potential rather than the reprogramming process.

Evaluation of biological effects of intermediate frequency magnetic field on differentiation of embryonic stem cell.

The embryotoxic effect of intermediate frequency (IF) magnetic field (MF) was evaluated using murine embryonic stem (ES) cells and fibroblast cells based on the embryonic stem cell test (EST). The cells were exposed to 21 kHz IF–MF up to magnetic flux density of 3.9 mT during the cell proliferation process (7 days) or the cell differentiation process (10 days) during which an embryonic body differentiated into myocardial cells. As a result, there was no significant difference in the cell proliferation between sham- and IF–MF-exposed cells for both ES and fibroblast cells. Similarly, the ratio of the number of ES-derived cell aggregates differentiated to myocardial cells to total number of cell aggregates was not changed by IF–MF exposure. In addition, the expressions of a cardiomyocytes-specific gene, Myl2, and an early developmental gene, Hba-x, in the exposed cell aggregate were not altered. Since the magnetic flux density adopted in this study is much higher than that generated by an inverter of the electrical railway, an induction heating (IH) cooktop, etc. in our daily lives, these results suggested that IF–MF in which the public is exposed to in general living environment would not have embryotoxic effect.

Embryonic stem cell-derived exosomes promote endogenous repair mechanisms and enhance cardiac function following myocardial infarction.

Embryonic stem cells (ESCs) hold great promise for cardiac regeneration but are susceptible to various concerns. Recently, salutary effects of stem cells have been connected to exosome secretion. ESCs have the ability to produce exosomes, however, their effect in the context of the heart is unknown. Determine the effect of ESC-derived exosome for the repair of ischemic myocardium and whether c-kit(+) cardiac progenitor cells (CPCs) function can be enhanced with ESC exosomes. This study demonstrates that mouse ESC-derived exosomes (mES Ex) possess ability to augment function in infarcted hearts. mES Ex enhanced neovascularization, cardiomyocyte survival, and reduced fibrosis post infarction consistent with resurgence of cardiac proliferative response. Importantly, mES Ex augmented CPC survival, proliferation, and cardiac commitment concurrent with increased c-kit(+) CPCs in vivo 8 weeks after in vivo transfer along with formation of bonafide new cardiomyocytes in the ischemic heart. miRNA array revealed significant enrichment of miR290-295 cluster and particularly miR-294 in ESC exosomes. The underlying basis for the beneficial effect of mES Ex was tied to delivery of ESC specific miR-294 to CPCs promoting increased survival, cell cycle progression, and proliferation. mES Ex provide a novel cell-free system that uses the immense regenerative power of ES cells while avoiding the risks associated with direct ES or ES-derived cell transplantation and risk of teratomas. ESC exosomes possess cardiac regeneration ability and modulate both cardiomyocyte and CPC-based repair programs in the heart.

334 FACTORS AFFECTING HEMATOPOIETIC ENGRAFTMENT OF MONKEY EMBRYONIC STEM CELLS IN SHEEP FETUSES

Previously, we generated monkey/sheep haematopoietic chimeras by in utero transplantation (IUT) of monkey embryonic stem (ES); however, the factors that control how the ES cells successfully engraft and differentiate into haematopoietic tissue in sheep fetuses remain uncertain. Here, we examined factors that might influence donor cells and recipient sheep and affect successful ES cell engraftment. We transplanted either undifferentiated monkey ES cells or ES-derived cells at an early haematopoietic differentiation stage into sheep fetuses. The latter cells were allowed to differentiate by culturing on OP9 cell layers for 6 days. Cells were transplanted into the liver or subcutaneous tissue of recipient sheep fetuses at 43 to 50 or 51 to 67 days of gestation (full term = 147 days) using ultrasound to identify the site for transplantation. After birth, monkey haematopoietic engraftment in the bone marrow was analysed in 40 lambs using colony-PCR with cells grown in methylcellulose in the presence of defined cytokines; teratoma formation was analysed by biopsy and immunohistochemistry. We found that haematopoietic engraftment was only observed when ES-derived cells at the early differentiation stage were transplanted into fetal livers at 51 to 67 days of gestation (6/9). However, teratoma formation with mature monkey tissue structures was only observed following transplantation of undifferentiated ES cells into fetal subcutaneous tissues at 43 to 50 days of gestation (4/6), but that was not observed when both types of cells were transplanted into the liver (0/18) or at 51 to 67 days of gestation (0/24). These results demonstrate that the differentiation status of the donor cells, the transplantation site, and the age of the fetus at transplantation are important factors in engraftment and differentiation into haematopoietic tissue or teratoma formation in sheep fetuses.

Potentially immunogenic proteins expressed similarly in human embryonic stem cells and induced pluripotent stem cells

A major limitation of the use of cellular therapies is the loss of donor-derived cells because of immune incompatibility. While induced pluripotent stem (iPS) cells offer the potential for autologous transplant therapies, questions have been raised using a mouse model that specific antigens mediate the rejection of grafts after syngeneic transplants with iPS, but not embryonic stem (ES) cells. In this study, we examined whether the human homologs of these markers, HORMAD1, ZG16, and Cyp3A, are differentially expressed in human iPS versus ES cells, as well as undifferentiated and in vitro-differentiated cells. Both qRT-PCR and flow cytometric analyses demonstrated similar gene and protein expression profiles for iPS and ES cells regardless of differentiation state. Our data are consistent with a recent study in mice that showed no evidence of rejection of differentiated syngeneic iPS cells. Furthermore, our results suggest that expression of these gene products cannot predict differences in clinical outcomes between human iPS and ES-derived cells.

Regulation of pluripotent cell differentiation by a small molecule, staurosporine

Research in the embryo and in culture has resulted in a sophisticated understanding of many regulators of pluripotent cell differentiation. As a consequence, protocols for the differentiation of pluripotent cells generally rely on a combination of exogenous growth factors and endogenous signalling. Little consideration has been given to manipulating other pathways to achieve pluripotent cell differentiation. The integrity of cell:cell contacts has been shown to influence lineage choice during pluripotent cell differentiation, with disruption of cell:cell contacts promoting mesendoderm formation and maintenance of cell:cell contacts resulting in the preferential formation of neurectoderm. Staurosporine is a broad spectrum inhibitor of serine/threonine kinases which has several effects on cell function, including interruption of cell:cell contacts, decreasing focal contact size, inducing epithelial to mesenchyme transition (EMT) and promoting cell differentiation. The possibility that staurosporine could influence lineage choice from pluripotent cells in culture was investigated. The addition of staurosporine to differentiating mouse EPL resulted in preferential formation of mesendoderm and mesoderm populations, and inhibited the formation of neurectoderm. Addition of staurosporine to human ES cells similarly induced primitive streak marker gene expression. These data demonstrate the ability of staurosporine to influence lineage choice during pluripotent cell differentiation and to mimic the effect of disrupting cell:cell contacts. Staurosporine induced mesendoderm in the absence of known inducers of formation, such as serum and BMP4. Staurosporine induced the expression of mesendoderm markers, including markers that were not induced by BMP4, suggesting it acted as a broad spectrum inducer of molecular gastrulation. This approach has identified a small molecule regulator of lineage choice with potential applications in the commercial development of ES cell derivatives, specifically as a method for forming mesendoderm progenitors or as a culture adjunct to prevent the formation of ectoderm progenitors during pluripotent cell differentiation.

Telomere elongation in parthenogenetic stem cells

Telomere elongation in parthenogenetic stem cells

Three‐dimensional self‐assembling peptide matrix enhances the formation of embryoid bodies and their neuronal differentiation

We have tailored the properties of a self-assembling peptide (SAP) matrix to direct embryonic stem cells towards neuronal differentiation by adopting a three-dimensional (3D) culture, matching mechanical strength with that of neural tissue, and incorporating fixed laminin-derived pentapeptide signals (IKVAV). We report here that such a matrix alone can induce mouse embryonic stem (ES) cells to first develop into embryoid body (EB) and increase their propensity for subsequent neuronal differentiation. Embryoid bodies were observed by day 5 of culture in SAP matrix. βIII-tubulin as an early neuronal commitment marker was more prominently detected in cells cultured in the matrix containing IKVAV signals. Interestingly, ES-derived cells did not display distinct neuron morphology within the 3D culture; however, 55 ± 10% of those cells within IKVAV conjugated matrix and 38 ± 6% of those within base matrix displayed higher potential towards neuronal differentiation after 7 days. When retrieved and recultured on a tissue culture plate, they exhibited extended neurite outgrowths and networks in the absence of any additional neuronal differentiation growth factor. The up-regulated expression of neuronal development markers (MAP2 and MeCP2) and the down-regulation of glial marker (GFAP) support that further neuronal differentiation takes place upon reculture. The results showed that an artificial matrix composed of designer SAPs could prompt the formation of EB and provides the cues favoring neuronal differentiation of ES cells.

Enhanced motor performance and motor learning in 3xTg-AD mice in two tests: A longitudinal study

Background: Genetically engineered mouse models are critical tools to study the genetics and pathogenesis of Alzheimer’s disease (AD), and are widely used in preclinical research. The Jackson Laboratory AD resource provides a large set of strains expressing mutant forms of human APP, MAPT (tau), APOE, Baces, Presenilins, and other relevant genes, as well as information supporting their selection and usage. All strains are rederived to a high health status, and genetic quality control measures are used to verify the strain’s genetic background and the presence of the human allele. Here we describe our efforts to expand genetic quality control by using high throughput sequencing for transgene insertion site discovery. We are also expanding the resource to include in vitro tools for AD research. Here, we describe the development of novel ES cell lines from some of our most widely utilized AD strains.Methods: To identify transgene insertion sites, we are using high throughput sequencing of mate pair libraries and a novel analysis pipeline to identify transgene insertion sites. To develop novel ES cell lines, we are using well-established ES cell derivation techniques and have introduced a tau promoter driven GFP transgene to provide a marker for neuronal differentiation. Results: To date the transgenic integration events in the “5XFAD”, “APP/PS1”, and “3xTg-AD” strains have been defined and are currently being validated. In addition, we have now generated ES cell lines from “5XFAD”, “APP/PS1” and “J20” models and we are currently testing the capacity of these ES cells for neuronal differentiation.Conclusions:Many of the most widely cited mouse models are currently available through The Jackson Laboratory AD resource, and we continue to maintain the genetic integrity of these models and to expand the resource according to the needs of the AD research community. Our transgene insertion site data enable us to determine whether insertion sites disrupt genomic sequences that are physiologically relevant, and to develop simplified genotyping assays. The ES cells we are creating will provide in vitro tools for the study of neuronal phenotypes related to over-expression of human AD genes. Detailed strain, ES cell, and availability information can be found at http://research.jax.org/grs/alzheimers.html

Abstract 153: Creation of Cell Sheet-Based Bioengineered Cardiac Tissue Using Pluripotent Stem Cell-Derived Cells

Recent evidences have suggested that current cardiac cell therapy contributes to the improved cardiac function through mainly the paracrine effects. Thereby the bioengineered functional heart tissue is expected to function for repairing the broad injured heart. We have developed the cell sheet-based bioengineered vascularized cardiac tissue, however the system to collect the enough amount of cells from ES/iPS cells and the function of ES-derived cardiac tissue remain elusive. Recently we have established the cultivation system with the suitable conditions for expansion and cardiac differentiation of mouse ES cells and human iPS cells via embryoid body formation using three-dimensional bioreactor with the continuous perfusion system. For the cardiac differentiation experiments, we used several mouse ES cells that express EGFP or neomycin resistant gene under the control of αMHC promoter. At 10 days of differentiation, mouse ES cells increased up to 300 times (6.0×10 6 cells/mL). After the further 8 days of cultivation with the purification step, we collected around 5.0×10 8 cells in the 1L bioreactor culture and 99% of cells were positive for myosin heavy chain. The co-culture of ES-derived cardiomyocytes with the appropriate number of primary cultured fibroblasts on the temperature-responsive culture dishes enabled to form the cardiac cell sheets. Furthermore, when ES-derived cardiomyocytes were co-cultured with ES-derived endothelial cells, robust endothelial cell network was observed in the cardiac cell sheets. Mouse ES- or human iPS-derived cardiomyocytes in cell sheets beat spontaneously and synchronously and connexin43 was expressed at the edge of the adjacent cardiomyocytes. Furthermore the action potential propagation was observed between ES/iPS-derived cardiac cell sheets. These findings suggest that pluripotent stem cell-derived cardiomyocytes and endothelial cells might be useful for creating cell-sheet-based functional cardiac tissue and the layered stem cell-derived cardiac tissue might promote not only the cardiac regenerative medicine but also the understanding the molecular mechanisms of heart diseases.

Satb1 Determines Hematopoietic Stem Cell Differentiation Toward the Lymphoid Lineages

Abstract 388There is accumulating evidence that combinations of transcription factors coordinately and sequentially regulate lymphopoiesis. Five transcription factors, PU.1, Ikaros, E2A, EBF, and Pax5 are known to be hierarchically involved in early steps in B-lineage differentiation. However, it remains unclear whether the initiation of lymphoid differentiation is regulated entirely by transcription factors in a hierarchical manner. A major goal of our study was to find key genes involved in specification of lymphoid fates. For this purpose, we compared gene expression profiles between hematopoietic stem cells (HSC) and early lymphoid progenitors (ELP), which were sorted from E14.5 fetal liver of Rag1/GFP knock-in heterozygous embryos. As a result, we found that the expression of Satb1, a global chromatin regulator, was significantly increased along the differentiation of HSC to ELP. To explore roles of Satb1 in early lymphoid specification, we performed transplantation experiments, injecting HSC isolated from bone marrow of 2 weeks old Satb1-null mice into wild-type (WT) mice. We observed that Satb1-null HSC could not reconstitute CD3+ T cells in lethally irradiated WT recipients. Indeed, CD3+ T lineage recoveries from Satb1-null HSC were decreased approximately 10-fold compared with WT HSC. On the other hand, we observed varied levels of reconstitution of the B lineage and no reduction in reconstitution of the myeloid lineage resulted from Satb1 ablation. These results demonstrate that expression of Satb1 in HSC is indispensable for lymphopoiesis, but not for myelopoiesis. Furthermore, our data indicate that abnormalities of lymphoid development observed in Satb1-null mice are intrinsic to Satb1-deficient HSC. Next we conducted over-expression experiments to define the role of Satb1 in lineage fate decisions of HSC. Limiting dilution assays in MS5 co-culture condition revealed 1 in 41 Satb1-transduced Flt3−Lineage−Sca1+c-Kit+ (LSK) cells produced B cells. However, only 1 in 143 control ones were lymphopoietic under these conditions. These results suggest that Satb1 affects the lineage fate of HSC and promotes their commitment to lymphoid cells. Next we examined if the exogenous expression of Satb1 promotes B lymphocyte growth from ES cells in the OP9 co-culture system. We established ES cell clones, which can be induced to express Satb1/GFP on removal of tetracycline (Tet) from the culture medium. Eight days after Tet deprivation, 22 % of GFP+ cells expressed CD45 and CD19. On the other hand, only 1% of GFP− cells expressed same cell-surface markers. A majority of the CD19+ cells in Satb1/GFP+ ES-derived cells were positive for CD11b/Mac1 and/or CD5, suggesting that B1-B lineage cells were produced. In addition, Igh rearrangement assay revealed that DH-JH recombination occurred in the Satb1/GFP+ ES-derived cells. These results indicate that Satb1 over-expression directs even ES cells to differentiate toward the lymphoid lineage.Lymphopoietic activity becomes compromised during aging. Accumulating evidence suggests that the earliest lymphoid progenitor pools proximal to HSC are deficient in aged bone marrow. It is likely that the down-regulation of genes mediating lymphoid specification and function is involved as a major cause. Satb1 has been listed in microarray panels as one of the genes that are down-regulated in aged HSC (Rossi et al., 2005). To confirm this observation, we sorted CD150+ LSK cells from bone marrow of 6-weeks or 2-years old mice and examined expressions of Satb1. As a result, the aged CD150+LSK cells showed reduced expression (about 6-fold) of Satb1 compared with these cells from young mice. We then examined whether Satb1 expression could restore the lymphopoietic activity of progenitors derived from aged mice. Satb1-transduced Rag1/GFP− LSK cells produced significantly higher percentages of B220+ cells than control cells. With respect to the recovered B-lineage cell counts, about 3-fold more B220+ Rag1/GFP+ Mac1−cells were obtained by Satb1transduction than mock transduction. These results demonstrate that Satb1 can at least partially restore the lymphopoietic activity of aged hematopoietic progenitors. In conclusion, our results indicate that Satb1 plays critical roles in producing lymphoid lineage from primitive stem/progenitor cells. Such activity in generating lymphoid cells may be of clinical significance and useful to overcome immuno-senescence. Disclosures:No relevant conflicts of interest to declare.

Human hypoblast formation is not dependent on FGF signalling

Mouse embryos segregate three different lineages during preimplantation development: trophoblast, epiblast and hypoblast. These differentiation processes are associated with restricted expression of key transcription factors (Cdx2, Oct4, Nanog and Gata6). The mechanisms of segregation have been extensively studied in the mouse, but are not as well characterised in other species. In the human embryo, hypoblast differentiation has not previously been characterised. Here we demonstrate co-exclusive immunolocalisation of Nanog and Gata4 in human blastocysts, implying segregation of epiblast and hypoblast, as in rodent embryos. However, the formation of hypoblast in the human is apparently not dependent upon FGF signalling, in contrast to rodent embryos. Nonetheless, the persistence of Nanog-positive cells in embryos following treatment with FGF inhibitors is suggestive of a transient naïve pluripotent population in the human blastocyst, which may be similar to rodent epiblast and ES cells but is not sustained during conventional human ES cell derivation protocols.

Une nouvelle ère pour la génétique du rat

Rat and mice are privileged tools for scientists. However, despite obvious advantages, such as a larger size, more faithful reproduction of human diseases, and utility for physiological and cognitive studies, rats have suffered from limited genetic technologies such as targeted mutagenesis. However, the gap between rat and mouse for genetic approaches will soon disappear with the recent advances of zinc finger nucleases applicable to early-stage rat embryos and the successful derivation of germ line competent rat ES cells, almost thirty years after murine ES cells. This will lead to new opportunities and to increase our capacity to model human pathologies.

Gene therapy by allele selection in a mouse model of beta-thalassemia

To be of therapeutic use, autologous stem cells derived from patients with inherited genetic disorders require genetic modification via gene repair or insertion. Here, we present proof of principle that, for diseases associated with dominant alleles (gain-of-function or haploinsufficient loss-of-function), disease allele–free ES cells can be derived from afflicted individuals without genome manipulation. This approach capitalizes on the derivation of uniparental cells, such as parthenogenetic (PG) ES cell lines from disease allele–free gametes. Diploid mammalian uniparental embryos with only maternally (oocyte-) or paternally (sperm-)derived genomes fail early in development due to the nonequivalence of parental genomes caused by genomic imprinting. However, these uniparental embryos develop to the blastocyst stage, allowing the derivation of ES cell lines. Using a mouse model for dominant beta-thalassemia, we developed disease allele–free PG ES cell lines from the oocytes of affected animals. Phenotype correction was obtained in donor-genotype recipients after transplantation of in vitro hematopoietic ES cell derivatives. This genetic correction strategy without gene targeting is potentially applicable to any dominant disease. It could also be the sole approach for larger or more complex mutations that cannot be corrected by homologous recombination.

Pluripotency Maintenance in Mouse Somatic Cell Nuclear Transfer Embryos and Its Improvement by Treatment with the Histone Deacetylase Inhibitor TSA

Reprogramming of somatic cells to pluripotency can be achieved by nuclear transfer into enucleated oocytes (SCNT). A key event of this process is the demethylation of the Oct4 gene and its temporally and spatially regulated expression. Different studies have shown that it occurs abnormally in some SCNT embryos. TSA is a histone deacetylase inhibitor known to increase the efficiency of development to term of SCNT embryos, but its impact on the developmental features of SCNT embryos is poorly understood. Here, we have followed the fate of the pluripotent cells within SCNT embryos, from the late blastocyst to the early epiblast prior to gastrulation. Our data show a delay in development correlated with a defect in forming and maintaining a correct number of Oct4 expressing ICM and epiblast cells in SCNT embryos. As a consequence, during the outgrowth phase of embryonic stem cell derivation as well as during diapause in vivo, part of the SCNT blastocysts completely lose their ICM cells. Meanwhile, the others display a correctly reprogrammed ICM compatible with the derivation of ES cells and development of the epiblast. Our data also indicate that TSA favors the establishment of pluripotency in SCNT embryos.

Injection of Wild Type Embryonic Stem Cells into Mst1 Transgenic Blastocysts Prevents Adult-Onset Cardiomyopathy

Embryonic stem cells have the capacity to differentiate into a wide range of cell types. We previously described that blastocyst injection of wild type (WT) embryonic stem cells (ESCs) into various knockout (KO) mouse models of human disease prevents disease from occurring. In this study we ask if the blastocyst approach can also correct defects in a mouse model of transgenic (Tg) overexpression of a pro-apoptotic factor. We injected ROSA26 (LacZ-marked) WT ESCs into human mammalian sterile 20 like-kinase 1 (Mst1) Tg blastocysts. Mst1 Tg mice overexpress Mst1, a pro-apoptotic factor, in a cardiac-specific manner. As a result, Mst1 Tg mice develop adult dilated cardiomyopathy driven by apoptosis, reduction in cell density and no hypertrophic compensation. Incorporation of WT ESCs generated WT/Mst1 chimeric mice with normal hearts at histological and functional levels. Accordingly, apoptosis and cell density parameters were normalized. The experiments suggest that an adult-onset cardiac myopathy induced by overexpression of the pro-apoptotic Mst1 can be reversed by developmental incorporation of WT ESCs. The findings also suggest that since forced expression of the Mst1 transgene is not abolished in the rescued chimeras, the WT ES-derived cells normalize pathways that lie downstream of Mst1. The results expand the therapeutic capability of the ESCs to mouse models that overproduce detrimental proteins.

A genome-wide RNAi screen reveals determinants of human embryonic stem cell identity

The derivation of human ES cells (hESCs) from human blastocysts represents one of the milestones in stem cell biology. The full potential of hESCs in research and clinical applications requires a detailed understanding of the genetic network that governs the unique properties of hESCs. Here, we report a genome-wide RNA interference screen to identify genes which regulate self-renewal and pluripotency properties in hESCs. Interestingly, functionally distinct complexes involved in transcriptional regulation and chromatin remodelling are among the factors identified in the screen. To understand the roles of these potential regulators of hESCs, we studied transcription factor PRDM14 to gain new insights into its functional roles in the regulation of pluripotency. We showed that PRDM14 regulates directly the expression of key pluripotency gene POU5F1 through its proximal enhancer. Genome-wide location profiling experiments revealed that PRDM14 colocalized extensively with other key transcription factors such as OCT4, NANOG and SOX2, indicating that PRDM14 is integrated into the core transcriptional regulatory network. More importantly, in a gain-of-function assay, we showed that PRDM14 is able to enhance the efficiency of reprogramming of human fibroblasts in conjunction with OCT4, SOX2 and KLF4. Altogether, our study uncovers a wealth of novel hESC regulators wherein PRDM14 exemplifies a key transcription factor required for the maintenance of hESC identity and the reacquisition of pluripotency in human somatic cells.