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1.  MiR-294/-302 promotes proliferation, suppresses G1-S restriction point, and inhibits embryonic stem cell differentiation through separable mechanisms 
Cell reports  2013;4(1):99-109.
The miR-294/miR-302 microRNAs promote the abbreviated G1 phase of the embryonic stem cell (ESC) cell cycle and suppress differentiation induced by let-7. Here we evaluated the role of the Retinoblastoma (Rb) family proteins in these settings. Under normal growth conditions miR-294 promoted the rapid G1-S transition independent of the Rb family. In contrast, miR-294 suppressed the further accumulation of cells in G1 in response to nutrient deprivation and cell-cell contact in an Rb dependent fashion. We uncovered five additional miRNAs (miRs-26a, -99b, -193, -199a-5p, and 218) that silenced ESC self-renewal in the absence of other miRNAs, all of which were antagonized by miR-294/302. Four of the six differentiation-inducing miRNAs induced an Rb-dependent G1 accumulation. However, all six still silenced self-renewal in the absence of the Rb proteins. These results show that the miR-294/miR-302 family acts through Rb dependent and independent pathways to regulate the G1 restriction point and the silencing of self-renewal respectively.
doi:10.1016/j.celrep.2013.05.027
PMCID: PMC3740202  PMID: 23831024
2.  microRNA induced transdifferentiation 
Recent months have seen rapid advances in the field of transdifferentiation, specifically in the conversion of fibroblasts to neurons. Most surprising is the observation that the ability to drive these transitions is not limited to transcription factors, but that they can be promoted by microRNAs as well. Indeed, in one case, microRNAs alone induced the transdifferentiation of fibroblasts to neuron-like cells, albeit at a low efficiency. Here, we review this rapidly advancing field, discuss possible mechanisms underlying microRNA-induced transdifferentiation and the potential for microRNAs to drive such transitions to any cell type of interest in vitro and in vivo.
doi:10.3410/B4-3
PMCID: PMC3270586  PMID: 22312415
3.  MicroRNA Function Is Globally Suppressed in Mouse Oocytes and Early Embryos 
Current biology : CB  2010;20(3):271-277.
Summary
Dicer, which is required for the processing of both micro-RNAs (miRNAs) and small interfering RNAs (siRNAs), is essential for oocyte maturation [1, 2]. Oocytes express both miRNAs and endogenous siRNAs (endo-siRNAs) [3, 4]. To determine whether the abnormalities in Dicer knockout oocytes during meiotic maturation are secondary to the loss of endo-siRNAs and/or miRNAs, we deleted Dgcr8, which encodes an RNA-binding protein specifically required for miRNA processing. In striking contrast to Dicer, Dgcr8-deficient oocytes matured normally and, when fertilized with wild-type sperm, produced healthy-appearing offspring, even though miRNA levels were reduced to similar levels as Dicer-deficient oocytes. Furthermore, the deletion of both maternal and zygotic Dgcr8 alleles did not impair preimplantation development, including the determination of the inner cell mass and trophectoderm. Most surprisingly, the mRNA profiles of wild-type and Dgcr8 null oocytes were essentially identical, whereas Dicer null oocytes showed hundreds of misregulated transcripts. These findings show that miRNA function is globally suppressed during oocyte maturation and preimplantation development and that endo-siRNAs, rather than miRNAs, underlie the Dicer knockout phenotype in oocytes.
doi:10.1016/j.cub.2009.12.044
PMCID: PMC2872512  PMID: 20116247
4.  Genomic Analysis Suggests that mRNA Destabilization by the Microprocessor Is Specialized for the Auto-Regulation of Dgcr8 
PLoS ONE  2009;4(9):e6971.
Background
The Microprocessor, containing the RNA binding protein Dgcr8 and RNase III enzyme Drosha, is responsible for processing primary microRNAs to precursor microRNAs. The Microprocessor regulates its own levels by cleaving hairpins in the 5′UTR and coding region of the Dgcr8 mRNA, thereby destabilizing the mature transcript.
Methodology/Principal Findings
To determine whether the Microprocessor has a broader role in directly regulating other coding mRNA levels, we integrated results from expression profiling and ultra high-throughput deep sequencing of small RNAs. Expression analysis of mRNAs in wild-type, Dgcr8 knockout, and Dicer knockout mouse embryonic stem (ES) cells uncovered mRNAs that were specifically upregulated in the Dgcr8 null background. A number of these transcripts had evolutionarily conserved predicted hairpin targets for the Microprocessor. However, analysis of deep sequencing data of 18 to 200nt small RNAs in mouse ES, HeLa, and HepG2 indicates that exonic sequence reads that map in a pattern consistent with Microprocessor activity are unique to Dgcr8.
Conclusion/Significance
We conclude that the Microprocessor's role in directly destabilizing coding mRNAs is likely specifically targeted to Dgcr8 itself, suggesting a specialized cellular mechanism for gene auto-regulation.
doi:10.1371/journal.pone.0006971
PMCID: PMC2736397  PMID: 19759829
5.  Embryonic Stem Cell Specific MicroRNAs Regulate the G1/S Transition and Promote Rapid Proliferation 
Nature genetics  2008;40(12):1478-1483.
Dgcr8 knockout embryonic stem (ES) cells lack microprocessor activity and hence all canonical microRNAs (miRNAs). These cells proliferate slowly and accumulate in G1 phase of the cell cycle1. Here, by screening a comprehensive library of individual miRNAs in the background of the Dgcr8 knockout ES cells, we report that multiple ES cell-specific miRNAs, members of the miR-290 family, rescue the ES cell proliferation defect. Furthermore, rescued cells no longer accumulate in the G1 phase of the cell cycle. These miRNAs function by suppressing several key regulators of the G1/S transition. These results show that post-transcriptional regulation by miRNAs promotes the G1/S transition of the ES cell cycle enabling their rapid proliferation. Furthermore, our screening strategy provides an alternative and powerful approach for uncovering the role of individual miRNAs in biological processes as it overcomes the common problem of redundancy and saturation in the miRNA system.
doi:10.1038/ng.250
PMCID: PMC2630798  PMID: 18978791

Results 1-5 (5)