Kinetics of transcriptome during hepatic conversion [RNA-seq]
Ontology highlight
ABSTRACT: Cell plasticity endows differentiated cells with competence to be reprogrammed to other identities. While reprogramming factors-induced epigenetic changes have been characterized, intrinsic chromatin features underlying cell plasticity remain elusive. By characterizing kinetics of high-order chromatin structures during transdifferentiation from fibroblasts to hepatocytes, we identified contiguous compartment switchable regions (CSRs). Compartment B to A CSRs (B-to-A CSRs), enriched with hepatocyte genes and demarcated by loop anchors, displayed a chimeric status of pre-existing chromatin accessibility in repressive compartment in fibroblasts. Pre-existing accessibility allowed the occupancy of pioneer factor Foxa3 to B-to-A CSRs, triggering compartment switch, H3K27ac gain and H3K27me3 reduction, and hepatocyte gene activation. Moreover, chimeric chromatin status appeared to be related with fibroblasts reprogramming to neurons, cardiomyocytes and pluripotent stem cells. Together, pre-existing accessibility in compartment B defines a chimeric chromatin status that may constitute intrinsic attribute for cell plasticity.
Project description:Cell plasticity endows differentiated cells with competence to be reprogrammed to other identities. While reprogramming factors-induced epigenetic changes have been characterized, intrinsic chromatin features underlying cell plasticity remain elusive. By characterizing kinetics of high-order chromatin structures during transdifferentiation from fibroblasts to hepatocytes, we identified contiguous compartment switchable regions (CSRs). Compartment B to A CSRs (B-to-A CSRs), enriched with hepatocyte genes and demarcated by loop anchors, displayed a chimeric status of pre-existing chromatin accessibility in repressive compartment in fibroblasts. Pre-existing accessibility allowed the occupancy of pioneer factor Foxa3 to B-to-A CSRs, triggering compartment switch, H3K27ac gain and H3K27me3 reduction, and hepatocyte gene activation. Moreover, chimeric chromatin status appeared to be related with fibroblasts reprogramming to neurons, cardiomyocytes and pluripotent stem cells. Together, pre-existing accessibility in compartment B defines a chimeric chromatin status that may constitute intrinsic attribute for cell plasticity.
Project description:Cell plasticity endows differentiated cells with competence to be reprogrammed to other identities. While reprogramming factors-induced epigenetic changes have been characterized, intrinsic chromatin features underlying cell plasticity remain elusive. By characterizing kinetics of high-order chromatin structures during transdifferentiation from fibroblasts to hepatocytes, we identified contiguous compartment switchable regions (CSRs). Compartment B to A CSRs (B-to-A CSRs), enriched with hepatocyte genes and demarcated by loop anchors, displayed a chimeric status of pre-existing chromatin accessibility in repressive compartment in fibroblasts. Pre-existing accessibility allowed the occupancy of pioneer factor Foxa3 to B-to-A CSRs, triggering compartment switch, H3K27ac gain and H3K27me3 reduction, and hepatocyte gene activation. Moreover, chimeric chromatin status appeared to be related with fibroblasts reprogramming to neurons, cardiomyocytes and pluripotent stem cells. Together, pre-existing accessibility in compartment B defines a chimeric chromatin status that may constitute intrinsic attribute for cell plasticity.
Project description:Cell plasticity endows differentiated cells with competence to be reprogrammed to other identities. While reprogramming factors-induced epigenetic changes have been characterized, intrinsic chromatin features underlying cell plasticity remain elusive. By characterizing kinetics of high-order chromatin structures during transdifferentiation from fibroblasts to hepatocytes, we identified contiguous compartment switchable regions (CSRs). Compartment B to A CSRs (B-to-A CSRs), enriched with hepatocyte genes and demarcated by loop anchors, displayed a chimeric status of pre-existing chromatin accessibility in repressive compartment in fibroblasts. Pre-existing accessibility allowed the occupancy of pioneer factor Foxa3 to B-to-A CSRs, triggering compartment switch, H3K27ac gain and H3K27me3 reduction, and hepatocyte gene activation. Moreover, chimeric chromatin status appeared to be related with fibroblasts reprogramming to neurons, cardiomyocytes and pluripotent stem cells. Together, pre-existing accessibility in compartment B defines a chimeric chromatin status that may constitute intrinsic attribute for cell plasticity.
Project description:Suspended animation (e.g. hibernation, diapause) allows organisms to survive extreme environments. But the mechanisms underlying the evolution of suspended animation states are unknown. The African turquoise killifish has evolved diapause as a form of suspended development to survive the complete drought that occurs every summer. Here, we show that gene duplicates – paralogs – exhibit specialized expression in diapause compared to normal development in the African turquoise killifish. Surprisingly, paralogs with specialized expression in diapause are evolutionarily very ancient and are present even in vertebrates that do not exhibit diapause. To determine if evolution of diapause is due to the regulatory landscape rewiring at ancient paralogs, we assessed chromatin accessibility genome-wide in fish species with or without diapause. This analysis revealed an evolutionary recent increase in chromatin accessibility at very ancient paralogs in African turquoise killifish. The increase in chromatin accessibility is linked to the presence of new binding sites for transcription factors, likely due to de novo mutations and transposable element (TE) insertion. Interestingly, accessible chromatin regions in diapause are enriched for lipid metabolism genes, and our lipidomics studies uncover a striking difference in lipid species in African turquoise killifish diapause, which could be critical for long-term survival. Together, our results show that diapause likely originated by repurposing pre-existing gene programs via recent changes in the regulatory landscape. This work raises the possibility that suspended animation programs could be reactivated in other species for long-term preservation via transcription factor remodeling and suggests a mechanism for how complex adaptations evolve in nature.
Project description:Forkhead Box O (FOXO) transcription factors are versatile players in diverse cellular processes, affecting tumorigenesis, metabolism, stem cell maintenance and lifespan. To understand the transcriptional output of FOXO3 activation, we investigate features that define the subset of enhancer binding events that actually contribute to gene regulation. We show FOXO3 transcriptional output is determined by the amount of bound FOXO3, which in turn is determined by motif presence, pre-existing enhancer activity and accessibility. In this manner, FOXO3 amplifies pre-existing levels of activity marks and potentiates enhancer RNA transcription. We conclude that not only enhancer presence and sequence content, but also the pre-existing activity dictates FOXO3 binding and transcriptional output. Considering the flexible and cell type specific nature of regulatory regions and their activity, our observations provide a novel explanation for the diversity in FOXO transcriptional programs and introduce chromatin context as a new player in the regulation of FOXO activity in ageing and disease. Examination of histone modifications and transcriptome changes upon FOXO activation
Project description:The manipulation of cell identity by reprograming holds immense potential in regenerative medicine, but is often limited by the inefficient acquisition of fully functional cells. This problem can potentially be resolved by better understanding the reprogramming process using in vivo genetic models, which are currently scarce. Here we report that both enterocytes (ECs) and enteroendocrine cells (EEs) in adult Drosophila midgut show a surprising degree of cell plasticity. Depleting the transcription factor Tramtrack in the differentiated ECs can initiate Prospero-mediated cell transdifferentiation leading to EE-like cells. On the other hand, depletion of Prospero in the differentiated EEs leads to the loss of EE-specific transcription programs, allowing cell cycle re-entry or differentiation into ECs. We found that intestinal progenitor cells, ECs, and EEs have a similar chromatin accessibility profile, suggesting that cell plasticity is enabled by pre-existing chromatin accessibility with switchable transcription programs. In a pilot genetic screen using this system, we found that cell lineage confliction and epigenetic memory were potential barriers during the EC-to-EE transdifferentiation. The establishment of this genetically tractable in vivo model should facilitate mechanistic investigation of cell plasticity at the molecular and genetic level.
Project description:Chromatin accessibility captures the binding status of protein factors to chromosomes in vivo, and has been considered a highly informative proxy for functional protein-DNA interactions. Existing DNase I and Tn5 transposase based assays generally require tens of thousands to millions of fresh cells. Applying Tn5 tagmentation to single cells yields very sparse maps. Here we present a transposome hypersensitive sites sequencing assay (THS-seq) for highly sensitive characterizations of chromatin accessibility.
Project description:Hematopoiesis consists of step-wise commitment of multiple distinct intermediate differentiation stages before mature blood cells are generated1,2. Early progenitor cells have multiple cell fate potentials and retain plasticity to differentiate to alternative lineages, while later stages are fully committed to certain cell lineages and rarely alter their fates3,4. Although extensive studies have been performed on regulatory pathways in mature blood cells5-8, few have examined chromatin re-organization underlying the transcription programs in early progenitors of hematopoiesis. In particular, what roles chromatin organization plays in the cell fate commitment during the differentiation of early hematopoietic progenitor cells remains unclear. Here, we carried out an integrative analysis of 3D nucleome, chromatin accessibility and gene expression during early T cell development from hematopoietic stem cells (HSC) to CD4/CD8 double positive (DP) T cells. Analysis of these data sets revealed extensive A/B compartment flips and dynamic changes of chromatin accessibility at regulatory regions including promoters and enhancers during the development process. Remarkably, both the compartment flip and changes in chromatin accessibility display a monotonic pattern. While gradual and progressive changes in chromatin re-organization was observed at most development stages, an abrupt and striking genome-wide change in A/B compartment structure and chromatin accessibility occurred during the transition from double negative stage 2 (DN2) to DN3, which was accompanied with the loss of cell fate plasticity of DN3 to differentiate to alternative lineages, suggesting that a chromatin barrier is established at the DN3 stage to lock the cells in the T cell fate. The binding of PU.1, a key factor for the fate choice of early progenitor cells, and BCL11B, critically required for T cell commitment at late stages, was associated with increased long-distance interaction and chromatin accessibility and may coordinately contribute to the establishment of the 3D nucleome structure required for the lineage differentiation and commitment.
Project description:Although genome-wide association study is an important tool for linking genetic variation to common complex diseases, it remains difficult to identify the causal variants underlying susceptibility loci. Recent work demonstrated mapping chromatin accessibility across different individuals can be a powerful method for interpreting genetic variant function, existing assays to measure chromatin landscapes (e.g., DNaseI-seq) are labor intensive and require very large numbers of cells preventing their application in real-world settings. This project aims to assess the ability of a novel assay for chromatin accessibility, ATAC-seq, to detect chromatin structure variation among individuals. We will apply ATAC-seq in 24 GBR HapMap lymphoblastoid cell lines (LCLs), which are a model system for studying the function of human genetic variation. We will also employ a novel approach to molecular quantitative trait locus identification which utilizes both population quantitative trait locus and allele-specific signatures, and gives increased mapping power in small sample sizes.This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/