Difference between revisions of "Talk:Stem Cells 2"
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Revision as of 21:02, 24 May 2011
Simultaneous overexpression of Oct4 and Nanog abrogates terminal myogenesis
Am J Physiol Cell Physiol. 2009 Jul;297(1):C43-54. Epub 2009 Apr 29.
Lang KC, Lin IH, Teng HF, Huang YC, Li CL, Tang KT, Chen SL. Source Dept. of Life Sciences, National Central University, 300 Jhongda Rd., Jhongli 32054, Taiwan, ROC.
Oct4 and Nanog are two embryonic stem (ES) cell-specific transcription factors that play critical roles in the maintenance of ES cell pluripotency. In this study, we investigated the effects of Oct4 and Nanog expression on the differentiation state of myogenic cells, which is sustained by a strong positive feedback loop. Oct4 and Nanog, either independently or simultaneously, were overexpressed in C2C12 myoblasts, and the expression of myogenic lineage-specific genes and terminal differentiation was observed by RT-PCR. Overexpression of Oct4 in C2C12 cultures repressed, while exogenous Nanog did not significantly alter C2C12 terminal differentiation. The expression of Pax7 was reduced in all Oct4-overexpressing myoblasts, and we identified a major Oct4-binding site in the Pax7 promoter. Simultaneous expression of Oct4 and Nanog in myoblasts inhibited the formation of myotubes, concomitant with a reduction in the endogenous levels of hallmark myogenic markers. Furthermore, overexpression of Oct4 and Nanog induced the expression of their endogenous counterparts along with the expression of Sox2. Using mammalian two-hybrid assays, we confirmed that Oct4 functions as a transcriptional repressor whereas Nanog functions as a transcriptional activator during muscle terminal differentiation. Importantly, in nonobese diabetic (NOD) severe combined immunodeficiency (SCID) mice, the pluripotency of C2C12 cells was conferred by overexpression of Oct4 and Nanog. These results suggest that Oct4 in cooperation with Nanog strongly suppresses the myogenic differentiation program and promotes pluripotency in myoblasts.
Yamanaka factors critically regulate the developmental signaling network in mouse embryonic stem cells
Cell Res. 2008 Dec;18(12):1177-89.
Liu X, Huang J, Chen T, Wang Y, Xin S, Li J, Pei G, Kang J. Source Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Yamanaka factors (Oct3/4, Sox2, Klf4, c-Myc) are highly expressed in embryonic stem (ES) cells, and their over-expression can induce pluripotency in both mouse and human somatic cells, indicating that these factors regulate the developmental signaling network necessary for ES cell pluripotency. However, systemic analysis of the signaling pathways regulated by Yamanaka factors has not yet been fully described. In this study, we identified the target promoters of endogenous Yamanaka factors on a whole genome scale using ChIP (chromatin immunoprecipitation)-on-chip in E14.1 mouse ES cells, and we found that these four factors co-occupied 58 promoters. Interestingly, when Oct4 and Sox2 were analyzed as core factors, Klf4 functioned to enhance the core factors for development regulation, whereas c-Myc seemed to play a distinct role in regulating metabolism. The pathway analysis revealed that Yamanaka factors collectively regulate a developmental signaling network composed of 16 developmental signaling pathways, nine of which represent earlier unknown pathways in ES cells, including apoptosis and cell-cycle pathways. We further analyzed data from a recent study examining Yamanaka factors in mouse ES cells. Interestingly, this analysis also revealed 16 developmental signaling pathways, of which 14 pathways overlap with the ones revealed by this study, despite that the target genes and the signaling pathways regulated by each individual Yamanaka factor differ significantly between these two datasets. We suggest that Yamanaka factors critically regulate a developmental signaling network composed of approximately a dozen crucial developmental signaling pathways to maintain the pluripotency of ES cells and probably also to induce pluripotent stem cells.
PMID: 19030024 http://www.ncbi.nlm.nih.gov/pubmed/19030024
Developmental signaling network regulated by endogenous Yamanaka factors. http://www.nature.com/cr/journal/v18/n12/fig_tab/cr2008309f6.html#figure-title