Pivots of pluripotency: The roles of non-coding RNA in regulating embryonic and induced pluripotent stem cells
ABSTRACT BACKGROUND: Induced pluripotent stem cells (iPSC) derived from reprogrammed patient somatic cells possess enormous therapeutic potential. However, unlocking the full capabilities of iPSC will require an improved understanding of the molecular mechanisms which govern the induction and maintenance of pluripotency, as well as directed differentiation to clinically relevant lineages. Induced pluripotency of a differentiated cell is mediated by sequential cascades of genetic and epigenetic reprogramming of somatic histone and DNA CpG methylation marks. These genome-wide changes are mediated by a coordinated activity of transcription factors and epigenetic modifying enzymes. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are now recognized as an important third class of regulators of the pluripotent state. SCOPE OF REVIEW: This review surveys the currently known roles and mechanisms of ncRNAs in regulating the embryonic and induced pluripotent states. MAJOR CONCLUSIONS: Through a variety of mechanisms, ncRNAs regulate constellations of key pluripotency genes and epigenetic regulators, and thus critically determine induction and maintenance of the pluripotent state. GENERAL SIGNIFICANCE: A further understanding of the roles of ncRNAs in regulating pluripotency may help assess the quality of human iPSC reprogramming. Additionally, ncRNA biology may help decipher potential transcriptional and epigenetic commonalities between the self renewal processes that govern both ESC and tumor initiating cancer stem cells (CSC). This article is part of a Special Issue entitled Biochemistry of Stem Cells.
- SourceAvailable from: Matthias Stadtfeld[Show abstract] [Hide abstract]
ABSTRACT: Factor-induced reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) is inefficient, complicating mechanistic studies. Here, we examined defined intermediate cell populations poised to becoming iPSCs by genome-wide analyses. We show that induced pluripotency elicits two transcriptional waves, which are driven by c-Myc/Klf4 (first wave) and Oct4/Sox2/Klf4 (second wave). Cells that become refractory to reprogramming activate the first but fail to initiate the second transcriptional wave and can be rescued by elevated expression of all four factors. The establishment of bivalent domains occurs gradually after the first wave, whereas changes in DNA methylation take place after the second wave when cells acquire stable pluripotency. This integrative analysis allowed us to identify genes that act as roadblocks during reprogramming and surface markers that further enrich for cells prone to forming iPSCs. Collectively, our data offer new mechanistic insights into the nature and sequence of molecular events inherent to cellular reprogramming.Cell 12/2012; 151(7):1617-32. DOI:10.1016/j.cell.2012.11.039 · 33.12 Impact Factor
- The Scientific World Journal 08/2013; 2013:713480. DOI:10.1155/2013/713480 · 1.73 Impact Factor
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ABSTRACT: MicroRNAs are critical mediators of stem cell pluripotency, differentiation, and malignancy. Limited information exists regarding microRNA alterations that facilitate initiation and progression of human lung cancers. In this study, array techniques were used to evaluate microRNA expression in normal human respiratory epithelia and lung cancer cells cultured in the presence or absence of cigarette smoke condensate (CSC). Under relevant exposure conditions, CSC significantly repressed miR-487b. Subsequent experiments demonstrated that miR-487b directly targeted SUZ12, BMI1, WNT5A, MYC, and KRAS. Repression of miR-487b correlated with overexpression of these targets in primary lung cancers and coincided with DNA methylation, de novo nucleosome occupancy, and decreased H2AZ and TCF1 levels within the miR-487b genomic locus. Deoxy-azacytidine derepressed miR-487b and attenuated CSC-mediated silencing of miR-487b. Constitutive expression of miR-487b abrogated Wnt signaling, inhibited in vitro proliferation and invasion of lung cancer cells mediated by CSC or overexpression of miR-487b targets, and decreased growth and metastatic potential of lung cancer cells in vivo. Collectively, these findings indicate that miR-487b is a tumor suppressor microRNA silenced by epigenetic mechanisms during tobacco-induced pulmonary carcinogenesis and suggest that DNA demethylating agents may be useful for activating miR-487b for lung cancer therapy.The Journal of clinical investigation 03/2013; 123(3):1241-61. DOI:10.1172/JCI61271 · 13.77 Impact Factor