Project description:Heterogeneity in pluripotent cells marks a metastable state where cells may drift between native and lineage-primed populations. While the role for these heterogeneities are unclear, they may reflect the dynamic equilibriums of signaling networks and have a direct effect on differentiation potentialities. Here, we report the role of the cell cycle in establishing heterogeneity of human pluripotent stem cells. By utilizing the FUCCI cell cycle indicator system coupled to fluorescent activated cell sorting (FACS), we have uncovered that the cell cycle drives heterogeneity at the epigenetic, transcriptional and post-transcriptional levels. Our data show widespread dynamics in 5-hydroxymethylcytosine (5hmC) during the cell cycle. Furthermore, transcript profiling by RNA-sequencing identified >500 genes that were cell cycle-regulated, of which the largest cohort of genes were transcriptional regulators. In sum, we demonstrate the role of the cell cycle in coordinating cellular transitions between metastable states in pluripotent stem cells. mRNA sequencing of the cell cycle phases; early & late G1, S and G2/S from human ES cells in triplicate.
Project description:Heterogeneity in pluripotent cells marks a metastable state where cells may drift between native and lineage-primed populations. While the role for these heterogeneities are unclear, they may reflect the dynamic equilibriums of signaling networks and have a direct effect on differentiation potentialities. Here, we report the role of the cell cycle in establishing heterogeneity of human pluripotent stem cells. By utilizing the FUCCI cell cycle indicator system coupled to fluorescent activated cell sorting (FACS), we have uncovered that the cell cycle drives heterogeneity at the epigenetic, transcriptional and post-transcriptional levels. Our data show widespread dynamics in 5-hydroxymethylcytosine (5hmC) during the cell cycle. Furthermore, transcript profiling by RNA-sequencing identified >500 genes that were cell cycle-regulated, of which the largest cohort of genes were transcriptional regulators. In sum, we demonstrate the role of the cell cycle in coordinating cellular transitions between metastable states in pluripotent stem cells.
Project description:The cyclin-dependent kinase 1 (Cdk1) represents an ancient cell cycle kinase that has been conserved from yeast to humans. Cdk1 is the only essential mammalian Cdk, which drives cytokinesis by phosphorylating a large number of cellular proteins. To uncover additional functions of Cdk1, we generated a knock-in strain of mice expressing an analog-sensitive version of Cdk1 in place of wild-type Cdk1. These mice and cells derived from them allow us to investigate Cdk1 function in essentially any compartment and at any stage of development. In our study, we focused on embryonic stem (ES) cells, as this cell type expresses particularly high levels of Cdk1. Very unexpectedly, we found that in ES cells the majority of Cdk1 substrates are localized on chromatin. Cdk1 phosphorylates a large number of proteins involved in epigenetic regulation, including writers and erasers of all major histone marks. Consistent with this finding, inhibition of Cdk1 altered histone modification status of ES cells. High levels of Cdk1 in ES cells (and in induced pluripotent stem cells) phosphorylate and partially inactivate Dot1l, the histone H3 lysine 79 methyltransferase responsible for placing activating H3K79 marks on gene bodies. Decrease of Cdk1 activity during ES cell differentiation de-represses Dot1l, thereby allowing coordinated expression of differentiation genes. These analyses indicate that Cdk1 functions to maintain the epigenetic identity of ES cells.
Project description:Cell cycle progression is linked to transcriptome dynamics and variations in the response of pluripotent cells to differentiation cues, through mostly unknown determinants. Here, we characterized the cell cycle–associated transcriptome and proteome of mouse embryonic stem cells (mESCs) in naïve ground state. We found that the thymine DNA glycosylase (TDG) is a cell cycle–regulated co-factor of the tumour suppressor p53. Further, TDG and p53 co-bind ESC-specific cis-regulatory elements and thereby control transcription of p53-dependent genes during self-renewal. We determined that the dynamic expression of TDG is required to promote the cell cycle–associated transcriptional heterogeneity. Moreover, we demonstrated that transient depletion of TDG influences cell fate decisions during the early differentiation of mESCs. Our findings reveal an unanticipated role of TDG in promoting molecular heterogeneity during the cell cycle, and highlight the central role of protein dynamics for the temporal control of cell fate during development.
Project description:Quiescent stem cells are periodically activated to maintain tissue homeostasis or occasionally called into action upon injury. Molecular mechanisms that constitutively maintain stem cell identity or promote stem cell proliferation and differentiation upon activation have been extensively studied. However, it is unclear how quiescent stem cells maintain identity and reinforce quiescence when they transition from quiescence to activation. Here we show mouse hair follicle stem cell compartment induces a transcription factor, Foxc1, when activated. Importantly, deletion of Foxc1 in the activated but not quiescent stem cells compromises stem cell identity, fails to re-establish quiescence and subsequently drives premature stem cell activation.These findings uncover a dynamic, cell-intrinsic mechanism employed by hair follicle stem cells to reinforce stemness in response to activation. Poly(A)-enriched transcriptome RNA-seq on HFSCs isolated in WT and K14Cre cKO mice at anagen and early telogen stage of hair cycle.
Project description:Chronic myelomonocyticleukemia (CMML) is a clinically heterogeneous stem cell malignancy with overlapping features of myelodysplasiaand myeloproliferation. CMML is further subclassified according to percentage of leukemic blasts present in blood or bone marrow, reflecting its intrinsic tendency to progression towards acute myeloid leukemia. Over 90% of CMML patients carry founding mutations in epigenetic and/or splicing genes, which typically involve the primitive stem cell compartment. Thus, transcriptional dysregulation at the stem cell level is likely fundamental to disease onset and progression. However, the critical early hematopoietic stem and progenitor cell (HSPC) subpopulation has not been studied in CMML. We performed single cell RNA sequencing on>6,800 Lin-CD34+CD38-primitive HSPCs from seven CMML patients and three healthy controls. We found substantial inter-and intra-patient heterogeneity, with CMML stem cells displaying distinct transcriptional programs, differentiation potential and cellular signaling pathway priming. Pseudotime analyses revealed that CMML-1/CMML-2 HSPCs have distinct cellular trajectories, indicating that transformation events initiate early within the hematopoietic hierarchy and suggesting against a simple linear clonal evolution dynamic in acute leukemic transformation. We further identified several transcription factors uniquely active in distinct sample subsets. Together our findings provide novel insights into the CMML stem cell compartment, revealing an unexpected degree of transcriptional and subclonal heterogeneity and highlighting early mediators of disease initiation and transformation, of potential translational importance
Project description:Motivation: Computational inference of genome organization based on Hi-C sequencing has greatly aided the understanding of chromatin and nuclear organization in three dimensions (3D). However, existing computational methods fail to address the cell population heterogeneity. Here we describe a probabilistic modeling-based method called CscoreTool-M that infers multiple 3D genome sub-compartments from Hi-C data. Results: The compartment scores inferred using CscoreTool-M represents the probability of a genomic region locating in a specific sub-compartment. Compared to published methods, CscoreTool-M is more accurate in inferring sub-compartments corresponding to both active and repressed chromatin. The compartment scores calculated by CscoreTool-M also help to quantify the levels of heterogeneity in sub-compartment localization within cell populations. By comparing proliferating cells and terminally differentiated non-proliferating cells, we show that the proliferating cells have higher genome organization heterogeneity, which is likely caused by cells at different cell-cycle stages. By analyzing 10 sub-compartments, we found a sub-compartment containing chromatin potentially related to the early-G1 chromatin regions proximal to the nuclear lamina in HCT116 cells, suggesting the method can deconvolve cell cycle stage-specific genome organization among asynchronously dividing cells. Finally, we show that CscoreTool-M can identify sub-compartments that contain genes enriched in housekeeping or cell-type-specific functions. Availability: https://github.com/scoutzxb/CscoreTool-M
Project description:We performed cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) of the LSK compartment of TdT-reporter and TdT-fate mapping mice, in order to elucidate the heterogeneity and developmental trajectories within the MPP (lymphoid-primed multipotent progenitor) and HSC (hematopoietic stem cell) compartments.