The mature CNS contains PDGFRA+ oligodendrocyte progenitor cells (OPC) which may remain quiescent, proliferate, or differentiate into oligodendrocytes. In human gliomas, rapidly proliferating Olig2+ cells resembling OPCs are frequently observed. We sought to identify, in vivo, candidate pathways uniquely required for OPC differentiation or quiescence. Using the bacTRAP methodology, we generated and analyzed mouse lines for translational profiling the major cells types (including OPCs), in the normal mouse brain. We then profiled oligodendoglial (Olig2+) cells from a mouse model of Pdgf-driven glioma. This analysis confirmed that Olig2+ tumor cells are most similar to OPCs, yet, it identified differences in key progenitor genes - candidates for promotion of differentiation or quiescence.
Candidate pathways for promoting differentiation or quiescence of oligodendrocyte progenitor-like cells in glioma.
Specimen part
View SamplesIdentification of the coding elements in the genome is a fundamental step to understanding the building blocks of living systems. Short peptides (< 100 aa) have emerged as important regulators of development and physiology, but their identification has been limited by their size. We have leveraged the periodicity of ribosome movement on the mRNA to define actively translated ORFs by ribosome footprinting. This approach identifies several hundred translated small ORFs in zebrafish and human. Computational prediction of small ORFs from codon conservation patterns corroborates and extends these findings and identifies conserved sequences in zebrafish and human, suggesting functional peptide products (micropeptides). These results identify micropeptide-encoding genes in vertebrates, providing an entry point to define their function in vivo. Overall design: Ribosome profiling experiments at five timepoints across zebrafish development in WT embryos
Upstream ORFs are prevalent translational repressors in vertebrates.
No sample metadata fields
View SamplesMicroRNAs regulate gene expression through deadenylation, repression and mRNA decay. However, the contribution of each mechanism in non-steady-state situations remains unclear. We monitored the impact of miR-430 on ribosome occupancy of endogenous mRNAs in wild type and dicer mutants lacking mature miR-430. Our results indicate that miR-430 reduces the number of ribosomes on target mRNAs before causing mRNA decay. Translational repression occurs before complete deadenylation, and disrupting deadenylation using an internal poly(A) tail did not block target repression. Finally, we observe that ribosome density along the length of the target mRNA remains constant, suggesting that translational repression occurs by reducing the initiation rate rather than reducing elongation or causing ribosomal drop-off. In summary, our results show that miR-430 regulates translation initiation before inducing mRNA decay. Overall design: Time course parallel ribosome profiling and input mRNA quantification in wildtype and MZdicer mutant embryos
Ribosome profiling shows that miR-430 reduces translation before causing mRNA decay in zebrafish.
No sample metadata fields
View SamplesPurpose: Investigate cellular heterogeneity in a fresh human ovarian cancer tissue sample Methods: Enzymatic digestion of fresh tissue sample collected from the operating room to produce single cell suspension. Cells were labelled with fluorescent antibodies to CD3, CD14, CD19, CD20, CD56 and FACS sorted to remove immune cells. The negative population was used for sequencing. Single cells were processed using the Fluidigm C1 Chip to generate barcoded cDNA for each cell. Amplifed cDNA was sequenced using an Illumina HiSeq 2500 machine. Results: Single cell RNA sequence data was obtained for 92 cells and a "bulk" sample of 1000 cells. 26 cells were removed from analysis due to quality control standards. The remaining 66 cells and the bulk sample were analyzed. Conclusion: Single cell RNA sequence analysis reveals heterogeneity in gene expression in cells harvested from a high grade ovarian serous cancer Overall design: A single cell suspension generated from a fresh high grade serous ovarian cancer sample was run through two Fluidigm C1 chips to isolate single cells and produce barcoded cDNA. Sequencing was performed in a single lane of an Illumina HiSeq 2500 machine. 92 single cells were sequenced and 1 bulk sample was sequenced, for a total of 93 samples.
Single cell sequencing reveals heterogeneity within ovarian cancer epithelium and cancer associated stromal cells.
Subject
View SamplesPoised enhancers marked by H3K27me3 in pluripotent cells were previously proposed to facilitate the establishment of somatic expression programs upon embryonic stem cell (ESC) differentiation. However, the functional relevance and mechanism of action of poised enhancers remain unknown. Here, we use genetic deletions to demonstrate that poised enhancers are necessary for the induction of major anterior neural regulators. Mechanistically, poised enhancers enable RNA Polymerase II recruitment to their cognate promoters upon differentiation. Interestingly, poised enhancers already establish physical interactions with their target genes in ESC in a Polycomb repressive complex 2 (PRC2) dependent manner. Loss of PRC2 led to neither the activation of poised enhancers nor the induction of their putative target genes in undifferentiated ESC. In contrast, loss of PRC2 severely and specifically compromised the induction of major anterior neural genes representing poised enhancer targets. Overall, our work illuminates a novel function for polycomb proteins, which we propose facilitate neural induction by providing major anterior neural loci with a permissive regulatory topology. Overall design: mRNA profiles were generated by RNA-seq from mESC and AntNPC for the following lines: WT mESC, WT AntNPC, EED-/- mESC and EED-/- AntNPC
PRC2 Facilitates the Regulatory Topology Required for Poised Enhancer Function during Pluripotent Stem Cell Differentiation.
Specimen part, Treatment, Subject
View SamplesPoised enhancers marked by H3K27me3 in pluripotent cells were previously proposed to facilitate the establishment of somatic expression programs upon embryonic stem cell (ESC) differentiation. However, the functional relevance and mechanism of action of poised enhancers remain unknown. Here, we use genetic deletions to demonstrate that poised enhancers are necessary for the induction of major anterior neural regulators. Mechanistically, poised enhancers enable RNA Polymerase II recruitment to their cognate promoters upon differentiation. Interestingly, poised enhancers already establish physical interactions with their target genes in ESC in a Polycomb repressive complex 2 (PRC2) dependent manner. Loss of PRC2 led to neither the activation of poised enhancers nor the induction of their putative target genes in undifferentiated ESC. In contrast, loss of PRC2 severely and specifically compromised the induction of major anterior neural genes representing poised enhancer targets. Overall, our work illuminates a novel function for polycomb proteins, which we propose facilitate neural induction by providing major anterior neural loci with a permissive regulatory topology. Overall design: mRNA profiles were generated by RNA-seq from AntNPC derived from mESC: WT AntNPC (four biological replicates), PE Lhx5(-109)-/- Clon1 AntNPC (two biological replicates) and PE Lhx5(-109)-/- Clon2 AntNPC (two biological replicates).
PRC2 Facilitates the Regulatory Topology Required for Poised Enhancer Function during Pluripotent Stem Cell Differentiation.
Specimen part, Cell line, Treatment, Subject
View SamplesHuman multipotent stromal cells readily form single-cell-derived colonies when plated at clonal densities. However, the colonies are heterogeneous because cells from a colony form new colonies that vary in size and differentiation potential when replated at clonal densities. The experiments here tested the hypothesis that cells in the inner regions of colonies are partially differentiated, but the differentiation is reversible. Cells were separately isolated from the dense inner (IN) regions and less-dense outer regions (OUT) of single-cell-derived colonies. Cells were then compared by assays of their transcriptomes and proteins, and for clonogenicity and differentiation. IN cells expressed fewer cell-cycle genes and higher levels of genes for extracellular matrix than the OUT cells. When transferred to differentiation medium, differentiation of the colonies occurred primarily in the IN regions. However, the IN cells were indistinguishable from OUT cells when replated at clonal densities and assayed for rates of propagation and clonogenicity. Also, colonies formed by IN cells were similar to colonies formed by OUT cells because they had distinct IN and OUT regions. Cultures of IN and OUT cells remained indistinguishable through multiple passages (30-75 population doublings), and both cells formed colonies that were looser and less dense as they were expanded. The results demonstrated that cells in the IN region of single-cell-derived colonies are partially differentiated, but the differentiation can be reversed by replating the cells at clonal densities.
Reversible commitment to differentiation by human multipotent stromal cells in single-cell-derived colonies.
No sample metadata fields
View SamplesTo identify the activity-induced gene expression programs in inhibitory and excitatory neurons, we analyzed RNA extracted from cultured E14 mouse MGE- and CTX-derived neurons (DIV 10) after these cultures were membrane-depolarized for 0, 1 and 6 hrs with 55mM extracellular KCl. To identify the gene programs regulated in these cells by the activity-induced early-response transcription factor Npas4, we repeated the same experiment in the MGE- and CTX-cultures lacking Npas4 (Npas4-KO).
Npas4 regulates excitatory-inhibitory balance within neural circuits through cell-type-specific gene programs.
Specimen part, Treatment, Time
View SamplesInduced pluripotent stem (iPS) cell reprogramming is a gradual epigenetic process that reactivates the pluripotent transcriptional network by erasing and establishing heterochromatin marks. Here, we characterize the physical structure of heterochromatin domains in full and partial mouse iPS cells by correlative Electron Spectroscopic Imaging (ESI). In somatic and partial iPS cells, constitutive heterochromatin marked by H3K9me3 is highly compartmentalized into chromocenter structures of densely packed 10 nm chromatin fibers. In contrast, chromocenter boundaries are poorly defined in pluripotent ES and full iPS cells, and are characterized by unusually dispersed 10 nm heterochromatin fibers in high Nanog-expressing cells, including pluripotent cells of the mouse blastocyst prior to differentiation. This heterochromatin reorganization accompanies retroviral silencing during conversion of partial iPS cells by Mek/Gsk3 2i inhibitor treatment. Thus, constitutive heterochromatin reorganization serves as a novel biomarker with retroviral silencing for identifying iPS cells in the very late stages of reprogramming.
Constitutive heterochromatin reorganization during somatic cell reprogramming.
Specimen part, Cell line
View SamplesRNA-seq libraries purified from the visual cortices of neurons expressing Emx-, GAD2-, PV-, SST-, or VIP-Cre using the Ribotag allele. Seq libraries are provided from mice raised in standard housing, or housed in the dark for two weeks (dark-housed), or dark-housed and then exposed to light for 1, 3, or 7.5 hours. These seq libraries represent the genetic response of distinct types of cortical interneurons to altered sensory experience. Overall design: To explore how sensory experience affects gene expression, we examined this process in the visual cortex of adult mice that were housed in standard conditions, in complete darkness (i.e. dark-housed), or dark-housed and then exposed to light for increasing amounts of time. We generated mice that were heterozygous for alleles of either Emx-,Gad2-,Sst-,Vip- or Pv-Cre, and were also heterozygous for the Rpl22-HA (RiboTag) allele, which expresses an HA-tagged ribosomal protein specifically in Cre-expressing neurons. We performed RNA-Seq on RNA isolated from the dark-housed/light-exposed RiboTag-mice; Experiments were done in 3 biological replicates and the visual cortices of 3 mice were pooled per sample at each time-point and for each Cre line.
Sensory experience regulates cortical inhibition by inducing IGF1 in VIP neurons.
Age, Specimen part, Cell line, Subject
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