Human induced pluripotent stem cells (iPSCs) present exciting opportunities for studying development and for in vitro disease modeling. However, reported variability in the behavior of iPSCs has ...called their utility into question. We established a test set of 16 iPSC lines from seven individuals of varying age, sex and health status, and extensively characterized the lines with respect to pluripotency and the ability to terminally differentiate. Under standardized procedures in two independent laboratories, 13 of the iPSC lines gave rise to functional motor neurons with a range of efficiencies similar to that of human embryonic stem cells (ESCs). Although three iPSC lines were resistant to neural differentiation, early neuralization rescued their performance. Therefore, all 16 iPSC lines passed a stringent test of differentiation capacity despite variations in karyotype and in the expression of early pluripotency markers and transgenes. This iPSC and ESC test set is a robust resource for those interested in the basic biology of stem cells and their applications.
In embryonic stem (ES) cells, a well-characterized transcriptional network promotes pluripotency and represses gene expression required for differentiation. In comparison, the transcriptional ...networks that promote differentiation of ES cells and the blastocyst inner cell mass are poorly understood. Here, we show that Sox17 is a transcriptional regulator of differentiation in these pluripotent cells. ES cells deficient in Sox17 fail to differentiate into extraembryonic cell types and maintain expression of pluripotency-associated transcription factors, including Oct4, Nanog, and Sox2. In contrast, forced expression of Sox17 down-regulates ES cell-associated gene expression and directly activates genes functioning in differentiation toward an extraembryonic endoderm cell fate. We show these effects of Sox17 on ES cell gene expression are mediated at least in part through a competition between Sox17 and Nanog for common DNA-binding sites. By elaborating the function of Sox17, our results provide insight into how the transcriptional network promoting ES cell self-renewal is interrupted, allowing cellular differentiation.
Complex II (succinate-ubiquinone oxidoreductase) from Escherichia coli is composed of four nonidentical subunits encoded by the sdhCDAB operon. Gene products of sdhC and sdhD are small hydrophobic ...subunits that anchor the hydrophilic catalytic subunits (flavoprotein and iron-sulfur protein) to the cytoplasmic membrane and are believed to be the components of cytochrome b556 in E. coli complex II. In the present study, to elucidate the role of two hydrophobic subunits in the heme b ligation and functional assembly of complex II, plasmids carrying portions of the sdh gene were constructed and introduced into E. coli MK3, which lacks succinate dehydrogenase and fumarate reductase activities. The expression of polypeptides with molecular masses of about 19 and 17 kDa was observed when sdhC and sdhD were introduced into MK3, respectively, indicating that sdhC encodes the large subunit (cybL) and sdhD the small subunit (cybS) of cytochrome b556. An increase in cytochrome b content was found in the membrane when sdhD was introduced, while the cytochrome b content did not change when sdhC was introduced. However, the cytochrome b expressed by the plasmid carrying sdhD differed from cytochrome b556 in its CO reactivity and red shift of the α absorption peak to 557.5 nm at 77 K. Neither hydrophobic subunit was able to bind the catalytic portion to the membrane, and only succinate dehydrogenase activity, not succinate-ubiquinone oxidoreductase activity, was found in the cytoplasmic fractions of the cells. In contrast, significantly higher amounts of cytochrome b556 were expressed in the membrane when sdhC and sdhD genes were both present, and the catalytic portion was found to be localized in the membrane with succinate-ubiquinone oxidoreductase and succinate oxidase activities. These results strongly suggest that both hydrophobic subunits are required for heme insertion into cytochrome b556 and are essential for the functional assembly of E. coli complex II in the membrane. Accumulation of the catalytic portion in the cytoplasm was found when sdhCDAB was introduced into a heme synthesis mutant, suggesting the importance of heme in the assembly of E. coli complex II.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Myeloid differentiation factor 88 (MyD88) plays essential roles in the signaling of the Toll/interleukin (IL)-1 receptor family. Toll–IL-1 receptor domain-containing adaptor inducing interferon-β ...(TRIF)-mediated signals are involved in lipopolysaccharide (LPS)-induced MyD88-independent pathways. Using MyD88-deficient (MyD88−/−) mice and TRIF-deficient (TRIF−/−) mice, we examined roles of MyD88 and TRIF in osteoclast differentiation and function. LPS, diacyl lipopeptide, and IL-1α stimulated osteoclastogenesis in cocultures of osteoblasts and hemopoietic cells obtained from TRIF−/− mice, but not MyD88−/− mice. These factors stimulated receptor activator of nuclear factor-κB ligand mRNA expression in TRIF−/− osteoblasts, but not MyD88−/− osteoblasts. LPS stimulated IL-6 production in TRIF−/− osteoblasts, but not TRIF−/− macrophages. LPS and IL-1α enhanced the survival of TRIF−/− osteoclasts, but not MyD88−/− osteoclasts. Diacyl lipopeptide did not support the survival of osteoclasts because of the lack of Toll-like receptor (TLR)6 in osteoclasts. Macrophages expressed both TRIF and TRIF-related adaptor molecule (TRAM) mRNA, whereas osteoblasts and osteoclasts expressed only TRIF mRNA. Bone histomorphometry showed that MyD88−/− mice exhibited osteopenia with reduced bone resorption and formation. These results suggest that the MyD88-mediated signal is essential for the osteoclastogenesis and function induced by IL-1 and TLR ligands, and that MyD88 is physiologically involved in bone turnover.
Carcinogenic theory is making a unilateral step toward complication, resulting in even apparent chaos. Under such chaotic circumstances, a new theory that stems from the analogy of cancer cells with ...stem cells, called cancer stem cell theory, is gaining attention. This theory, if correct, necessarily urges two major corrections. One is that such complication may not entirely be the cause of carcinogenesis and, thus, at least partly, nothing more than a consequence. The other is need to create a new framework of cancer therapy. Such a new therapy should allow for long-term symbiosis of a patient with cancer cells; a chemical compound (drug)-based sustainable therapy that directs the dormancy of cancer cells, or converts cancer cells to normal cells (or their resemblances), for example.
Background Although no potential homologues of multicellular apoptotic genes (e.g. Bax, Bak, Bcl‐2, caspases and p53) have been identified in a unicellular eukaryote, previous reports contain several ...implications of the apoptotic behaviour of yeasts (i.e. Saccharomyces cerevisiae and Schizosaccharomyces pombe). Therefore, whether or not yeast undergoes apoptosis has been a topic of some debate. hCCG1, which is the largest subunit of TFIID and a histone acetyltransferase, appears to be involved in the regulation of apoptosis. The factor hCIA interacts with hCCG1 and functions as a histone chaperone in mammalian cells; its homologue in yeast is Asf1p/Cia1p. Therefore, we anticipated that a yeast mutant in Asf1p/Cia1p would be a valuable tool for studying apoptosis in yeast.
Results We established a strain of S. cerevisiae lacking the histone chaperone ASF1/CIA1. This disruptant, asf1/cia1, arrested preferentially at the G2/M‐phase and died. We systematically analysed the phenotype associated with the death of this mutant yeast and identified many changes, such as fragmentation of the nuclei, condensation and fragmentation of chromatin, reduction of the mitochondrial membrane‐potential, dysfunction of the mitochondrial proton pump, and a discernible release of cytochrome c to cytoplasm that resembles those in apoptotic multicellular organisms. Other changes potentially associated with the death in our mutant included a reduction in the vacuolar membrane potential, dysfunction of the vacuolar proton pump, reduction of endocytosis, and the presence of many autophagic bodies. However, these mutant yeast cells also showed cellular enlargement, which is characteristic of necrosis.
Conclusions Cell death in S. cerevisiae occurs with a phenotype that largely resembles apoptosis in multicellular organisms, but that has some features of necrosis. Therefore, we indicate that yeast undergoes a ‘prototypal active cell death’ that retains some characteristics of passive cell death (necrosis). In addition, we think that active cell death is ubiquitously the essential attribute of life. Although such an active cell death system in yeast remains open to confirmation, we speculate that deletion of the histone chaperone Asf1p/Cia1p inhibits the normal assembly/disassembly of nucleosomes in yeast and thereby initiates the active cell death system.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Phosphorylated p38 mitogen-activating kinase (MAPK) is observed in osteoclasts under
in vivo inflammatory situations. However, the role of p38 MAPK in osteoclast function has not been elucidated, ...because all external stimuli tested hitherto failed to induce the phosphorylation of p38 MAPK in osteoclasts in culture. In this study, a constitutively active form of MKK6 (MKK6CA) was expressed in osteoclasts using adenoviral gene transfer
in vitro. MKK6CA expressed in osteoclasts phosphorylated p38 MAPK and enhanced the survival of osteoclasts. Dentine-resorbing activity of osteoclasts was not enhanced by the MKK6CA expression. These results suggest that p38 MAPK signaling plays a critical role in the survival of osteoclasts in inflammatory diseases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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