Epidermal stem cells ensure that skin homeostasis is maintained. In murine skin, epidermal stem cells cluster at specific niches where, under steady-state conditions, they undergo cycles of dormancy and activation1. When cellular replenishment is required, epidermal stem cells egress from the niche and proliferate for a limited number of times to subsequently feed into the differentiated compartment1-3. However, only a subset of stem cells becomes active during each round of morphogenesis, suggesting that stem cells coexist in heterogeneous responsive states within the same niche. Using a circadian clock fluorescent reporter mouse model, we show that the dormant epidermal stem cell niche contains two coexisting populations of stem cells at opposite phases of the clock, which are differentially predisposed to respond to homeostatic cues. In dormant niches, the core molecular clock protein Bmal1 transcriptionally modulates the expression of stem cell regulatory genes, including modulators of Wnt and TGFb, to create two coexisting stem cell populations, one predisposed, and the other less prone, to activation. Unbalancing this equilibrium of epidermal stem cells, through conditional epidermal deletion of Bmal1, resulted in a long-term progressive accumulation of non-responsive stem cells, premature impairment of tissue self-renewal, and a significant reduction in the development of squamous cell carcinomas. Our results indicate that the molecular clock machinery fine-tunes the spatiotemporal behavior of epidermal stem cells within their niche, and that perturbation of this mechanism affects tissue homeostasis and the predisposition to neoplastic transformation. The goals of this study was to compare the transcriptome of epidermal stem cells according to their circadian rhythm phase. We isolated epidermal stem cells (bulge cells; alpha6bright/CD34+ population) from 19 days old Per1-Venus mice and separated them according to Venusbright (clock positive) and Venus dim (clock negative). The goals of this study was to compare the transcriptome of epidermal stem cells in which their circadian rhythm machinery has been perturbed by deleting the gene that encodes for Bmal1. We compared the transcriptomes of basal interfollicular epidermis cells (alpha6 integrin bright/CD34- cells) from the dorsal skin of 1 year old BmalKO mice and their respective control littermates. Each array corresponds to purified cells from approximately 5 mice.
The circadian molecular clock creates epidermal stem cell heterogeneity.
Specimen part
View SamplesReprogramming resident glia into functional and subtype-specific neurons in vivo by delivering reprogramming genes directly to the brain provides a step forward towards the possibility of treating brain injuries or diseases. Here, we show that neurons reprogrammed using Ascl1, Lmx1a and Nurr1 functionally mature and integrate into existing brain circuitry, and that the majority of the reprogrammed neurons have properties of fast spiking, parvalbumin-containing interneurons. Overall design: A total of 6 samples were analyzed. Each sample is consists of approximately 33 laser-captured reprogrammed-neurons identified by nuclear GFP and expressing the transcription factors Ascl1, Lmx1a and Nurr1 (ALN).
Direct Reprogramming of Resident NG2 Glia into Neurons with Properties of Fast-Spiking Parvalbumin-Containing Interneurons.
Sex, Specimen part, Subject
View SamplesThe mammalian circadian clock system is made up of individual cell and tissue clocks that function as a coherent network, however it remains unclear which rhythmic functions of the liver clock are autonomous or rely on clocks in other tissues. Here, using mice which only have a functioning liver clock, we investigate the autonomous vs non-autonomous reatures of the liver clock and diurnal rhythmicity in the liver Overall design: 8-12 week-old, female WT, KO and Liver-RE BMAL1-stop-FL mice (see referenced paper for details) were fed ad libitum normal chow under 12hr light/ 12hr dark schedule. Livers were harvested every 4 hours over the circadian cycle at ZT0, 4, 8, 12, 16, 20 (n=3 per time point per group). Total RNA was extracted and used for RNA-seq.
Defining the Independence of the Liver Circadian Clock.
Specimen part, Subject
View SamplesOrganisms have adapted to the changing environmental conditions within the 24h cycle of the day by temporally segregating tissue physiology to the optimal time of the day. On the cellular level temporal segregation of physiological processes is established by the circadian clock, a Bmal1 dependent transcriptional oscillator network. The circadian clocks within individual cells of a tissue are synchronised by environmental signals, mainly light, in order to reach temporally segregated physiology on the tissue level. However, how light mediated synchronisation of peripheral tissue clocks is achieved mechanistically and whether circadian clocks in different organs are autonomous or interact with each other to achieve rhythmicity is unknown. Here we report that light can synchronise core circadian clocks in two peripheral tissues, the epidermis and liver hepatocytes, even in the complete absence of functional clocks in any other tissue within the whole organism. On the other hand, tissue extrinsic circadian clock rhythmicity is necessary to retain rhythmicity of the epidermal clock in the absence of light, proving for the first time that the circadian clockwork acts as a memory of time for the synchronisation of peripheral clocks in the absence of external entrainment signals. Furthermore, we find that tissue intrinsic Bmal1 is an important regulator of the epidermal differentiation process whose deregulation leads to a premature aging like phenotype of the epidermis. Thus, our results establish a new model for the segregation of peripheral tissue physiology whereby the synchronisation of peripheral clocks is acquired by the interaction of a light dependent but circadian clock independent pathway with circadian clockwork dependent cues. Overall design: Determining the epidermal circadian transcriptome in the presence or absence of non-epidermal clocks after 6-7 days in complete darkness (DD).
BMAL1-Driven Tissue Clocks Respond Independently to Light to Maintain Homeostasis.
Age, Specimen part, Cell line, Subject
View SamplesOrganisms have adapted to the changing environmental conditions within the 24h cycle of the day by temporally segregating tissue physiology to the optimal time of the day. On the cellular level temporal segregation of physiological processes is established by the circadian clock, a Bmal1 dependent transcriptional oscillator network. The circadian clocks within individual cells of a tissue are synchronised by environmental signals, mainly light, in order to reach temporally segregated physiology on the tissue level. However, how light mediated synchronisation of peripheral tissue clocks is achieved mechanistically and whether circadian clocks in different organs are autonomous or interact with each other to achieve rhythmicity is unknown. Here we report that light can synchronise core circadian clocks in two peripheral tissues, the epidermis and liver hepatocytes, even in the complete absence of functional clocks in any other tissue within the whole organism. On the other hand, tissue extrinsic circadian clock rhythmicity is necessary to retain rhythmicity of the epidermal clock in the absence of light, proving for the first time that the circadian clockwork acts as a memory of time for the synchronisation of peripheral clocks in the absence of external entrainment signals. Furthermore, we find that tissue intrinsic Bmal1 is an important regulator of the epidermal differentiation process whose deregulation leads to a premature aging like phenotype of the epidermis. Thus, our results establish a new model for the segregation of peripheral tissue physiology whereby the synchronisation of peripheral clocks is acquired by the interaction of a light dependent but circadian clock independent pathway with circadian clockwork dependent cues. Overall design: Determining the epidermal circadian transcriptome in the presence or absence of non-epidermal clocks under light entrainment (LD).
BMAL1-Driven Tissue Clocks Respond Independently to Light to Maintain Homeostasis.
Age, Specimen part, Cell line, Subject
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Genomic targets, and histone acetylation and gene expression profiling of neural HDAC inhibition.
Sex, Age, Specimen part, Treatment
View SamplesHistone deacetylase inhibitors (HDACis) have been shown to potentiate hippocampal-dependent memory and synaptic plasticity and to ameliorate cognitive deficits and degeneration in animal models for different neuropsychiatric conditions. However, the impact of these drugs on hippocampal histone acetylation and gene expression profiles at the genomic level, and the molecular mechanisms that underlie their specificity and beneficial effects in neural tissue, remains obscure. Here, we mapped four relevant histone marks (H3K4me3, AcH3K9,14, AcH4K12 and pan-AcH2B) in hippocampal chromatin and investigated at the whole-genome level the impact of HDAC inhibition on acetylation profiles and basal and activity-driven gene expression. HDAC inhibition caused a dramatic histone hyperacetylation that was largely restricted to active loci pre-marked with H3K4me3 and AcH3K9,14. In addition, the comparison of Chromatin immunoprecipitation sequencing and gene expression profiles indicated that Trichostatin A-induced histone hyperacetylation, like histone hypoacetylation induced by histone acetyltransferase deficiency, had a modest impact on hippocampal gene expression and did not affect the transient transcriptional response to novelty exposure. However, HDAC inhibition caused the rapid induction of a homeostatic gene program related to chromatin deacetylation. These results illuminate both the relationship between hippocampal gene expression and histone acetylation and the mechanism of action of these important neuropsychiatric drugs.
Genomic targets, and histone acetylation and gene expression profiling of neural HDAC inhibition.
Specimen part
View SamplesWe sequenced the mRNAs of embryonic stem cells (ESCs) cultured in different conditions. The two lines M (male) and F (female) used in this study were derived from E4 blastocysts of the same cross between a C57BL/6J (Mus musculus domesticus) and CAST/EiJ (Mus castaneus) male. mESCs were cultured in 2i and LIF as the ground state condition or in serum and LIF as the conventional condition. Epistem cell lines were also generated from the two lines by culturing them with Activin A and FGF2. In order to study more advanced development, we differentiated the two mESC lines through embryonic body formation to postmitotic motor neurons using retinoic acid and the smoothened agonist SAG. This differentiation process also results in the derivation of several types of interneurons. We picked single cells from all different conditions and generated sequencing libraries using the Smart-seq2 and Tn5 protocol. For simplicity, we designate the different condition as ES2i, ES, Epi and Neuron from hereon. We also obtained preimplantation inner cell mass and epiblast cells from E3.5 ICM (inner cell mass) and E4.5 blastocysts of the crossbred mice (male CAST/EiJ × female C57BL/6J) as well as postimplantation epiblast cells from E5.5 embryos of C57BL/6J mice Overall design: Examination of gene expression profile in individual male and female embryonic stem cell lines along developmental progression
Single-cell analyses of X Chromosome inactivation dynamics and pluripotency during differentiation.
Sex, Specimen part, Cell line, Subject
View SamplesThe regulatory logic underlying global transcriptional programs controlling development of visceral organs like the pancreas remains undiscovered. Here, we profiled gene expression in 12 purified populations of fetal and adult pancreatic epithelial cells representing crucial progenitor cell subsets, and their endocrine or exocrine progeny. Using probabilistic models to decode the general programs organizing gene expression, we identified co-expressed gene modules in cell subsets that revealed patterns and processes governing progenitor cell development, lineage specification, and endocrine cell maturation. Module network analysis linked established regulators like Neurog3 to unrecognized roles in endocrine secretion and protein transport, and nominated multiple candidate regulators of pancreas development. Phenotyping mutant mice revealed that candidate regulatory genes encoding transcription factors, including Bcl11a, Etv1, Prdm16 and Runx1t1, are essential for pancreas development or glucose control. Our integrated approach provides a unique framework for identifying regulatory networks underlying pancreas development and diseases like diabetes mellitus.
An integrated cell purification and genomics strategy reveals multiple regulators of pancreas development.
Specimen part
View SamplesWe sequenced mRNA from three age groups (3months (3M), 24 months (24M) and 29 months (29M)) from the full hippocampus Overall design: There were two independent experiments: 3M vs 24M (n=5 to 6, single-end sequencing) and 3M vs 29M (n=3, paired-end sequencing))
De-regulation of gene expression and alternative splicing affects distinct cellular pathways in the aging hippocampus.
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