技术资料

We measured the dynamics of an essential epigenetic modifier,HP1β,in human cells at different stages of differentiation using Fluorescence Recovery After Photobleaching (FRAP). We found that HP1β mobility is similar in human embryonic stem cells (hES) and iPS cells where it is more mobile compared to fibroblasts; HP1β is less mobile in senescent fibroblasts than in young (dividing) fibroblasts. Introduction of reprogramming factors"� View Publication

Herpes simplex type 1 (HSV-1) amplicon vectors possess a number of features that make them excellent vectors for the delivery of transgenes into stem cells. HSV-1 amplicon vectors are capable of efficiently transducing both dividing and nondividing cells and since the virus is quite large,152 kb,it is of sufficient size to allow for incorporation of entire genomic DNA loci with native promoters. HSV-1 amplicon vectors can also be used to incorporate and deliver to cells a variety of sequences that allow extrachromosomal retention. These elements offer advantages over integrating vectors as they avoid transgene silencing and insertional mutagenesis. The construction of amplicon vectors carrying extrachromosomal retention elements,their packaging into HSV-1 viral particles,and the use of HSV-1 amplicons for stem cell transduction will be described. View Publication

Epstein-Barr virus (EBV) is associated with the development of malignant lymphomas and lymphoproliferative disorders in immunocompromised individuals. The LMP2A protein of EBV is thought to play a central role in this process by allowing the virus to persist in latently infected B lymphocytes. We have demonstrated that LMP2A,when expressed in B cells of transgenic mice,allows normal B-cell developmental checkpoints to be bypassed. To identify cellular genes targeted by LMP2A that are involved in this process,we have utilized DNA microarrays to compare gene transcription in B cells from wild-type versus LMP2A transgenic mice. In B cells from LMP2A transgenic mice,we observed decreased expression of many genes associated with normal B-cell development as well as reduced levels of the transcription factors that regulate their expression. In particular,expression of the transcription factor E2A was down-regulated in bone marrow and splenic B cells. Furthermore,E2A activity was inhibited in these cells as determined by decreased DNA binding and reduced expression of its target genes,including the transcription factors early B-cell factor and Pax-5. Expression of two E2A inhibitors,Id2 and SCL,was up-regulated in splenic B cells expressing LMP2A,suggesting a possible mechanism for E2A inhibition. These results indicate that LMP2A deregulates transcription factor expression and activity in developing B cells,and this likely allows for a bypass of normal signaling events required for proper B-cell development. The ability of LMP2A to interfere with B-cell transcription factor regulation has important implications regarding its role in EBV latency. View Publication

Endoplasmic reticulum (ER) stress occurs during early embryonic development. The aim of this study is to determine whether ER stress occurs during human embryonic stem cell differentiation induced by retinoic acid (RA). H9 human embryonic stem cells were subjected to RA treatment for up to 29. days to induce differentiation. HEK293 cells were treated with RA as a control. The results demonstrate that several ER stress-responsive genes are differentially regulated in H9 and HEK293 cells in response to 5. days of RA treatment. GRP78/Bip was upregulated in H9 cells but downregulated in HEK293 cells. eIF2?? was downregulated in H9 cells but not in HEK293 cells. Phosphorylation of eIF2?? was downregulated in H9 cells but upregulated in HEK293 cells. XBP-1 was downregulated immediately after RA treatment in H9 cells,but its downregulation was much slower in HEK293 cells. Additionally,two ER-resident E3 ubiquitin ligases,gp78 and Hrd1,were both upregulated in H9 cells following 5. days of exposure to RA. Moreover,the protein Bcl2 was undetectable in H9 cells and H9-derived cells but was expressed in HEK293 cells,and it expression in the two types of cells was unaltered by RA treatment. In H9 cells treated with RA for 29. days,GRP78/Bip,XBP-1 and Bcl2 were all upregulated. These results suggest that ER stress is involved in H9 cell differentiation induced by RA. ?? 2011 Elsevier Inc. View Publication

Mechanisms determining intrinsic differentiation bias inherent to human pluripotent stem cells (hPSCs) toward cardiogenic fate remain elusive. We evaluated the interplay between ErbB4 and EGFR in determining cardiac differentiation in vitro as these receptor tyrosine kinases (RTKs) are key to heart and brain development in vivo. Our results demonstrate that during cardiac differentiation,cell fate biases exist in hPSCs due to cardiac/neuroectoderm divergence post cardiac mesoderm stage. Stage-specific up-regulation of EGFR in concert with persistent Wnt3a signaling post cardiac mesoderm favors commitment towards neural progenitor cells (NPCs). Inhibition of EGFR abrogates these effects with enhanced (textgreater2-fold) cardiac differentiation efficiencies by increasing proliferation of Nkx2-5 expressing cardiac progenitors while reducing proliferation of Sox2 expressing NPCs. Forced overexpression of ErbB4 rescued cardiac commitment by augmenting Wnt11 signaling. Convergence between EGFR/ErbB4 and canonical/non-canonical Wnt signaling determines cardiogenic fate in hPSCs. This article is protected by copyright. All rights reserved. View Publication

Activation of ErbB4 receptor signaling is instrumental in heart development,lack of which results in embryonic lethality. However,mechanism governing its intracellular signaling remains elusive. Using human pluripotent stem cells,we show that ErbB4 is critical for cardiogenesis whereby its genetic knockdown results in loss of cardiomyocytes. Phospho-proteome profiling and Western blot studies attribute this loss to inactivation of p38$\$ isoform which physically interacts with NKx2.5 and GATA4 transcription factors. Post-cardiomyocyte formation p38$\$/NKx2.5 downregulation is followed by p38$\$/MEF2c upregulation suggesting stage-specific developmental roles of p38 MAPK isoforms. Knockdown of p38$\$ similarly disrupts cardiomyocyte formation in spite of the presence of NKx2.5. Cell fractionation and NKx2.5 phosphorylation studies suggest inhibition of ErbB4-p38$\$ hinders NKx2.5 nuclear translocation during early cardiogenesis. This study reveals a novel pathway that directly links ErbB4 and p38$\$ the transcriptional machinery of NKx2.5-GATA4 complex which is critical for cardiomyocyte formation during mammalian heart development. View Publication

Although distinct human induced pluripotent stem cell (hiPSC) lines can display considerable epigenetic variation,it has been unclear whether such variability impacts their utility for disease modeling. Here,we show that although low-passage female hiPSCs retain the inactive X chromosome of the somatic cell they are derived from,over time in culture they undergo an erosion" of X chromosome inactivation (XCI). This erosion of XCI is characterized by loss of XIST expression and foci of H3-K27-trimethylation� View Publication

Genome stability of human embryonic stem cells (hESC) is an important issue because even minor genetic alterations can negatively impact cell functionality and safety. The incorrect repair of DNA double-stranded breaks (DSBs) is the ultimate cause of the formation of chromosomal aberrations. Using G2 radiosensitivity assay,we analyzed chromosomal aberrations in pluripotent stem cells and somatic cells. The chromatid exchange aberration rates in hESCs increased manifold 2 hours after irradiation as compared with their differentiated derivatives,but the frequency of radiation-induced chromatid breaks was similar. The rate of radiation-induced chromatid exchanges in hESCs and differentiated cells exhibited a quadratic dose response,revealing two-hit mechanism of exchange formation suggesting that a non-homologous end joining (NHEJ) repair may contribute to their formation. Inhibition of DNA-PK,a key NHEJ component,by NU7026 resulted in a significant decrease in radiation-induced chromatid exchanges in hESCs but not in somatic cells. In contrast,NU7026 treatment increased the frequency of radiation-induced breaks to a similar extent in pluripotent and somatic cells. Thus,DNA-PK dependent NHEJ efficiently participates in the elimination of radiation-induced chromatid breaks during the late G2 in both cell types and DNA-PK activity leads to a high level of misrejoining specifically in pluripotent cells. View Publication

Erythropoietin (Epo) has been used in the treatment of anemia resulting from numerous etiologies,including renal disease and cancer. However,its effects are controversial and the expression pattern of the Epo receptor (Epo-R) is debated. Using in vivo lineage tracing,we document that within the hematopoietic and mesenchymal lineage,expression of Epo-R is essentially restricted to erythroid lineage cells. As expected,adult mice treated with a clinically relevant dose of Epo had expanded erythropoiesis because of amplification of committed erythroid precursors. Surprisingly,we also found that Epo induced a rapid 26% loss of the trabecular bone volume and impaired B-lymphopoiesis within the bone marrow microenvironment. Despite the loss of trabecular bone,hematopoietic stem cell populations were unaffected. Inhibition of the osteoclast activity with bisphosphonate therapy blocked the Epo-induced bone loss. Intriguingly,bisphosphonate treatment also reduced the magnitude of the erythroid response to Epo. These data demonstrate a previously unrecognized in vivo regulatory network coordinating erythropoiesis,B-lymphopoiesis,and skeletal homeostasis. Importantly,these findings may be relevant to the clinical application of Epo. View Publication

Primitive erythroid cells,the first red blood cells produced in the mammalian embryo,are necessary for embryonic survival. Erythropoietin and its receptor EpoR,are absolutely required for survival of late-stage definitive erythroid progenitors in the fetal liver and adult bone marrow. Epo- and Epor-null mice die at E13.5 with a lack of definitive erythrocytes. However,the persistence of circulating primitive erythroblasts raises questions about the role of erythropoietin/EpoR in primitive erythropoiesis. Using Epor-null mice and a novel primitive erythroid 2-step culture we found that erythropoietin is not necessary for specification of primitive erythroid progenitors. However,Epor-null embryos develop a progressive,profound anemia by E12.5 as primitive erythroblasts mature as a synchronous cohort. This anemia results from reduced primitive erythroblast proliferation associated with increased p27 expression,from advanced cellular maturation,and from markedly elevated rates of apoptosis associated with an imbalance in pro- and anti-apoptotic gene expression. Both mouse and human primitive erythroblasts cultured without erythropoietin also undergo accelerated maturation and apoptosis at later stages of maturation. We conclude that erythropoietin plays an evolutionarily conserved role in promoting the proliferation,survival,and appropriate timing of terminal maturation of primitive erythroid precursors. View Publication

Erythropoietin (Epo) stimulation of its receptor's downstream signaling pathways and optimum function of GATA-1 transcription factor are both essential for normal erythroid cell development. Epo-receptor (EpoR) signaling and GATA-1 regulate proliferation,survival,differentiation,and maturation of erythroid cells. Whether any signal that is generated by EpoR targets GATA-1 or affects GATA-1 transcriptional activity is not known. Here,we demonstrate that stimulation of EpoR results in phosphorylation of GATA-1 at serine 310 (S310) in primary fetal liver erythroid progenitors and in cultured erythroid cells. We show that phosphorylation of GATA-1 is important for Epo-induced maturation of fetal liver erythroid progenitor cells. The PI3-kinase/AKT signaling pathway is identified as a mediator of Epo-induced phosphorylation of GATA-1. AKT serine threonine kinase phosphorylates GATA-1S310 in vitro and in erythroid cells and enhances GATA-1 transcriptional activity. These data demonstrate that EpoR signaling phosphorylates GATA-1 and modulates its activity via the PI3-kinase/AKT signaling pathway. View Publication

Src homology 2 domain-containing phosphatase 2 (Shp2),encoded by Ptpn11,is a member of the nonreceptor protein-tyrosine phosphatase family,and functions in cell survival,proliferation,migration,and differentiation in many tissues. Here we report that loss of Ptpn11 in murine hematopoietic cells leads to bone marrow aplasia and lethality. Mutant mice show rapid loss of hematopoietic stem cells (HSCs) and immature progenitors of all hematopoietic lineages in a gene dosage-dependent and cell-autonomous manner. Ptpn11-deficient HSCs and progenitors undergo apoptosis concomitant with increased Noxa expression. Mutant HSCs/progenitors also show defective Erk and Akt activation in response to stem cell factor and diminished thrombopoietin-evoked Erk activation. Activated Kras alleviates the Ptpn11 requirement for colony formation by progenitors and cytokine/growth factor responsiveness of HSCs,indicating that Ras is functionally downstream of Shp2 in these cells. Thus,Shp2 plays a critical role in controlling the survival and maintenance of HSCs and immature progenitors in vivo. View Publication