Translation and mRNA degradation are intimately connected, yet the mechanisms that regulate them are not fully understood. Here we examine the regulation of translation and mRNA stability in mouse embryonic stem cells (ESCs) and during differentiation. In contrast to previous reports, we found that transcriptional changes account for most of the molecular changes during ESC differentiation. Within ESCs translation level and mRNA stability are positively correlated. The RNA-binding protein DDX6 has been implicated in processes involving both translational repression and mRNA destabilization; in yeast DDX6 connects codon optimality and mRNA stability and in mammals DDX6 is involved in microRNA-mediated repression. We generated DDX6 KO ESCs and found that while there was minimal connection between codon usage and stability changes, the loss of DDX6 leads to the translational depression of microRNA targets. Surprisingly, the translational derepression of microRNA targets occurs without affecting mRNA stability. Furthermore, DDX6 KO ESCs share overlapping phenotypes and global molecular changes with ESCs that completely lack all microRNAs. Together our results demonstrate that the loss of DDX6 decouples the two forms of microRNA induced repression and emphasize that translational repression by microRNAs is underappreciated. Overall design: 4-thiouridine (4su) metabolic labeling was performed on mouse embryonic stem cells (ESCs) and Epiblast like cells (EpiLCs).
Decoupling the impact of microRNAs on translational repression versus RNA degradation in embryonic stem cells.
Specimen part, Disease, Subject
View SamplesDgcr8 and Dicer are both important components of the microRNA biogenesis pathway while Dicer is also implicated in biogenesis of other types of small RNAs such as siRNAs and mirtrons. Here we performed microarray analysis of WT, Dgcr8 and Dicer knockout ES cells to identify mRNAs differentially regulated upon loss of Dgcr8 and Dicer.
Genomic analysis suggests that mRNA destabilization by the microprocessor is specialized for the auto-regulation of Dgcr8.
Specimen part
View Sampleslet-7c and miR-294 were transfected into Dgcr8 -/- miRNA deficient ES cells and RNA was harvested after 12 hours
Opposing microRNA families regulate self-renewal in mouse embryonic stem cells.
Specimen part
View SamplesDicer, which is required for the processing of both microRNAs (miRNAs) and small interfering RNAs (siRNAs), is essential for oocyte maturation. Oocytes express both miRNAs and endogenous siRNAs (endo-siRNAs). 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 a 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 (ICM) and trophectoderm. Most surprisingly, the mRNA profiles of wild-type and Dgcr8 null oocytes were essentially identical while 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.
Opposing microRNA families regulate self-renewal in mouse embryonic stem cells.
Specimen part
View SamplesMouse oocyte maturation, fertilization, and reprogramming occur in the absence of transcription and thus must be regulated post-transcriptionally. Surprisingly, a major form of post-transcriptional regulation, microRNA-based transcript destabilization and translational inhibition, is lost during this developmental window. Here we evaluate the conservation, timing, and mechanism behind the loss of microRNA activity in oocytes. In both mouse and frogs, microRNA function was active in growing oocytes, but then lost during oocyte maturation. RNA-sequencing of the maturing oocytes uncovered expression of an alternative isoform of Ago2 lacking domains critical for its function. Introduction of full-length Ago2 together with an exogenous microRNA destabilized microRNA luciferase reporters. However, endogenous targets were still largely unaffected. These findings suggest that while it is possible to re-activate some aspects of microRNA activity by introducing full length Ago2, there are additional mechanisms to protect endogenous transcripts from microRNA activity in oocytes. Overall design: Total RNA from mouse GV and MII oocytes, embryonic stem cells, epi cells
Expression of Alternative Ago2 Isoform Associated with Loss of microRNA-Driven Translational Repression in Mouse Oocytes.
Specimen part, Subject
View SamplesThe dentate gyrus of the hippocampus continues generating new neurons throughout life. These nerve cells originate from radial astrocytes within the subgranular zone (SGZ). We find that Sox1, a member of the SoxB1 family of transcription factors, is expressed in a subset of radial astrocytes. Lineage tracing using Sox1 driven reporter mice shows that the Sox1-expressing cells represent an activated neural stem/progenitor population.
Sox1 marks an activated neural stem/progenitor cell in the hippocampus.
Age, Specimen part
View SamplesDuring early development, pluripotent cells of the epiblast show extensive rewiring of enhancers with little associated change in gene expression. The mechanisms underlying and purpose of this rewiring are largely unknown. Here we identified a transcription factor, GRHL2, that is both necessary and sufficient to activate latent enhancers during the transition from naïve embryonic stem cells (ESC) to primed epiblast cells (EpiC). GRHL2 is necessary to maintain expression of its targets in EpiCs. However, these genes are already expressed at equivalent levels in ESCs, suggesting these genes switch enhancer usage during the transition. Identification of alternative enhancers driving these genes in ESCs uncovered an enrichment for the ESC-specific KLF transcription factors. While many KLF targets remain expressed in EpiCs, GRHL2 only regulates a specific subset promoting an epithelial program. These data suggest a model where a large naïve-specific transcriptional network is partitioned into smaller networks to uncouple their regulation in EpiCs, providing more flexibility in gene regulation during lineage specification. Overall design: RNA-seq in wildtype embryonic stem cells (ESCs) and wildtype epiblast-like cells (EpiLCs)
GRHL2-Dependent Enhancer Switching Maintains a Pluripotent Stem Cell Transcriptional Subnetwork after Exit from Naive Pluripotency.
Specimen part, Treatment, Subject
View SamplesWe performed Fluidigm C1 single cell sequencing analysis of wild-type and microRNA deficient (Dgcr8 knockout) mouse embryonic stem cells mock treated or transfected with either miR-294 or let-7. Overall design: Wild-type and Dgcr8 knockout cells grown in naïve culture conditions were mock transfected or transfected with miRNA mimics for let-7b or miR-294, single cells were captured on Fluidigm C1 24 hours post-transfection and then prepared for sequencing on Illumina HiSeq1000 following manufacturer''s protocol.
The impact of microRNAs on transcriptional heterogeneity and gene co-expression across single embryonic stem cells.
Specimen part, Subject
View SamplesOocyte maturation, fertilization, and early embryonic development occur in the absence of gene transcription. Therefore, it is critical to understand at a global level the post-transcriptional events that are driving these transitions. Here, we have used a systems approach by combining polysome mRNA profiling and bioinformatics to identify RNA binding motifs in mRNAs that either enter or exit the polysome pool during mouse oocyte maturation. Association of mRNA with the polysomes correlates with active translation.
Genome-wide analysis of translation reveals a critical role for deleted in azoospermia-like (Dazl) at the oocyte-to-zygote transition.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Posttranscriptional crossregulation between Drosha and DGCR8.
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