Geminin is a small nucleoprotein that neuralizes ectoderm in the Xenopus embryo. Geminin promotes neural fate acquisition of mouse embryonic stem cells: Geminin knockdown during neural fate acquisition decreased expression of neural precursor cell markers (Pax6, Sox1), while increasing expression of Pitx2, Lefty1 and Cited2, genes involved in formation of the mouse node. Here we differentiated mouse embryonic stem cells into embryoid bodies to study Geminin's ability to repress primitive streak mesendoderm fate acquisition. We used microarrays to define the sets of genes that are regulated by Geminin during cell fate acquisition in embryoid bodies, using Dox-inducible Geminin knockdown or overexpression mouse embryonic stem cell lines.
Geminin restrains mesendodermal fate acquisition of embryonic stem cells and is associated with antagonism of Wnt signaling and enhanced polycomb-mediated repression.
Specimen part
View SamplesFormation of the complex vertebrate nervous system begins when pluripotent cells of the early embryo are directed to acquire a neural fate. Although cell intrinsic controls play an important role in this process, the molecular nature of this regulation is not well defined. Here we assessed the role for Geminin, a nuclear protein expressed in embryonic cells, in neural fate acquisition from mouse embryonic stem (ES) cells. While Geminin knockdown does not affect the ability of ES cells to maintain or exit pluripotency, we found that it significantly impairs their ability to acquire a neural fate. Conversely, Geminin overexpression promotes neural gene expression, even in the presence of growth factor signaling that antagonizes neural transcriptional responses. These data demonstrate that Geminins activity contributes to mammalian neural cell fate acquisition. We investigated the mechanistic basis of this phenomenon and found that Geminin maintains a hyperacetylated and open chromatin conformation at neural genes. Interestingly, recombinant Geminin protein also rapidly alters chromatin acetylation and accessibility even when Geminin is combined with nuclear extract and chromatin in vitro. These findings define a novel activity for Geminin in regulation of chromatin structure. Together, these data support a role for Geminin as a cell intrinsic regulator of neural fate acquisition that promotes expression of neural genes by regulating chromatin accessibility and histone acetylation.
Geminin promotes neural fate acquisition of embryonic stem cells by maintaining chromatin in an accessible and hyperacetylated state.
Specimen part, Treatment
View SamplesExpression profile of human donor lungs that have developed primary graft dysfunction (PGD) after lung transplantation and those that have not.
Expression profiling of human donor lungs to understand primary graft dysfunction after lung transplantation.
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View SamplesThe Lim1 gene has essential functions during several stages of kidney development. In particular, a tissue specific knockout in the early metanephric mesenchyme results in the formation of the earliest nephron precursor, the renal vesicle, but failure of this structure to progress to the next stage, the comma shaped body. To better understand the molecular nature of this developmental arrest we used a laser capture microdissection-microarray strategy to examine the perturbed gene expression pattern of the mutant renal vesicles. Among the genes found differently expressed were Chrdl2, an inhibitor of BMP signaling, the pro-apoptotic factor Bmf, as well as myob5, an atypical myosin which modulates chemokine and transferring signaling, and pdgfr1, which is important in epithelial folding. Of particular interest, the microarray data indicated that the Dkk1 gene, which encodes an inhibitor of Wnt signaling, was downregulated nine fold in mutants. This was confirmed by in situ hybridizations. It is interesting to note that Lim1 and Dkk1 mutant mice have striking similarities in phenotype. These results suggest that the Dkk1 gene might be a key downstream effector of Lim1 function.
Laser capture-microarray analysis of Lim1 mutant kidney development.
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View SamplesComplete (whole) embryonic kidneys were dissected from wild type and Hoxa11, Hoxd11 compound null embryons throughout development. Targets from two biological replicates of each were generated and the expression profiles were determined using Affymetrix MOE430A and MOE430B arrays. Comparisons between normal and mutant and comparisons of development samples identified global patterns of gene regulation in kidney development
Comprehensive microarray analysis of Hoxa11/Hoxd11 mutant kidney development.
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View SamplesE11.5 metanephric mesenchyme and ureteric bud were dissected from the E11.5 kidney rudiment using fine manual microdissection (ureteric bud only) or both fine manual microdissection and laser capture microdissection (metanephric mesenchyme) to define the gene expression profiles of these structures. Additionally, HoxA11, HoxD11 compound null E11.5 metanephric mesenchyme was obtained through laser capture microdissection allowing analysis of possible Hox targets in kidney development. Targets from multiple biological replicates of each were generated and the expression profiles were determined using Affymetrix MOE430_v2 arrays.
Comprehensive microarray analysis of Hoxa11/Hoxd11 mutant kidney development.
No sample metadata fields
View SamplesPlants aquire nitrogen from the soil, most commonly in the form of either nitrate or ammonium. Unlike ammonium, nitrate must be reduced (with NADH and ferredoxin as electron donors) prior to assimilation. Thus, nitrate nutrition imposes a substantially greater energetic cost than ammonium nutrition. Our goal was to compare the transcriptomes of nitrate-supplied and ammonium-supplied plants, with a particular interest in characterizing the differences in redox metabolism elicited by different forms of inorganic nitrogen.
Distinct signalling pathways and transcriptome response signatures differentiate ammonium- and nitrate-supplied plants.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Geminin regulates the transcriptional and epigenetic status of neuronal fate-promoting genes during mammalian neurogenesis.
Specimen part, Treatment
View SamplesTranscriptional targets of neurogenin (Ngnr1) were identified by over-expression of an inducible form of neurogenin in Xenopus ectodermal explants. The effects of co-expressing the nucleoprotein geminin on Ngnr1-dependent target gene transactivation were defined.
Geminin regulates the transcriptional and epigenetic status of neuronal fate-promoting genes during mammalian neurogenesis.
Specimen part, Treatment
View SamplesRegulating the transition from lineage-restricted progenitors to terminally differentiated cells is a central aspect of nervous system development. Here, we investigated the role of the nucleoprotein Geminin in regulating neurogenesis at a mechanistic level during both Xenopus primary neurogenesis and mammalian neuronal differentiation in vitro. The latter work utilized both neural cells derived from embryonic stem and embryonal carcinoma cells in vitro and neural stem cells from mouse forebrain. In all of these contexts, Geminin antagonized the ability of neural bHLH transcription factors to activate transcriptional programs promoting neurogenesis. Furthermore, Geminin promoted a bivalent chromatin state, characterized by the presence of both activating and repressive histone modifications, at genes encoding transcription factors that promote neurogenesis. This epigenetic state restrains the expression of genes that regulate commitment of undifferentiated stem and neuronal precursor cells to neuronal lineages. Geminin is highly expressed in undifferentiated neuronal precursor cells but is downregulated prior to differentiation. Therefore, these data support a model whereby Geminin promotes the neuronal precursor cell state by modulating both the epigenetic status and expression of genes encoding neurogenesis-promoting factors. Additional developmental signals acting in these cells can then control their transition toward terminal neuronal or glial differentiation during mammalian neurogenesis. Overall design: A mouse embryonic stem (ES) cell line for inducible knockdown of the small nucleoprotein Geminin was utilized. ES cells were used to generate neural precursor cells by monolayer culture in N2B27 media for 5 days, and doxycycline-inducible knockdown of Geminin was performed from day 3. Changes in gene expression resulting from Geminin knockdown were assessed by RNA sequencing. Three experimental replicates were generated for Geminin knockdown (plus Dox) with a corresponding no-Dox control. These were subjected to sequencing, and data were analyzed using TopHat and Cufflinks/Cuffdiff. Transcripts were considered as differentially expressed upon Gem knockdown if data met statistical significance cutoffs in Cuffdiff (sufficient sequence alignments were obtained for analysis and transcript had significant change in FPKM value (normalized transcript abundance; fragments per kb of exon per million fragments mapped) between the no Dox and plus Dox sample pairs) in at least two of the three replicates.
Geminin regulates the transcriptional and epigenetic status of neuronal fate-promoting genes during mammalian neurogenesis.
Specimen part, Treatment, Subject
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