Project description:Epimorphic regeneration commonly relies on the activation of quiescent stem cells to drive new cell production. The planarian Schmidtea mediterranea is among the best regenerators in nature, thanks to its large population of adult stem cells, called neoblasts. While neoblasts have long been known to drive regeneration, whether a subset of neoblasts is reserved for this purpose is unknown. Here, we revisited the idea of reserved neoblasts by approaching neoblast heterogeneity from a regulatory perspective. By implementing a new fluorescence-activated cell sorting strategy in planarians, we identified a population of neoblasts defined by low transcriptional activity. These RNAlow neoblasts are relatively slow-cycling at homeostasis and undergo a morphological regeneration response characterized by cell growth at 48 hours post-amputation. At this time, RNAlow neoblasts proliferated in a TOR-dependent manner. Additionally, knockdown of the tumour suppressor Lrig-1, which is enriched in RNAlow neoblasts, resulted in RNAlow neoblast growth and hyperproliferation at homeostasis, and ultimately delayed regeneration. We propose that slow-cycling RNAlow neoblasts represent a regeneration-reserved neoblast population.
Project description:Slow-cycling subpopulations exist in bacteria, yeast, and mammalian systems. In the case of cancer, slow-cycling subpopulations have been proposed to give rise to drug resistance. However, the origin of slow-cycling human cells is poorly studied, in large part due to lack of markers to identify these rare cells. Slow-cycling cells pass through a non-cycling period marked by low CDK2 activity and high p21 levels. Here, we use this knowledge to isolate these naturally slow-cycling cells from a heterogeneous population and perform RNA-sequencing to delineate the transcriptome underlying the slow-cycling state. We show that cellular stress responses – the p53 transcriptional response and the integrated stress response – are the most salient causes of spontaneous entry into the slow-cycling state.
Project description:We identified slow-cycling cells (SCCs) in Ewing sarcoma using a label retention assay with CFSE. We labeled cells of SK-ES-1, an Ewing sarcoma cell line, with CFSE. After 5 days culture, we isolated cells retaining strong fluorescence (upper, ~10%) as SCCs and other cells (lower, ~90%) as non-slow-cycling cells (non-SCCs) using FACS AriaTM Ⅲ cell sorter.
Project description:The dynamics of the hematopoietic flux responsible for blood cell production in native conditions remains a matter of debate. Using CITE-seq analyses, we uncovered a distinct progenitor population that displays a cell cycle gene signature similar to the one found in quiescent hematopoietic stem cells. We further determined that the CD62L marker can be used to phenotypically enrich this population in the Flt3+ multipotent progenitor (MPP4) compartment. Functional in vitro and in vivo analyses validated the heterogeneity of the MPP4 compartment and established the quiescent/slow-cycling properties of the CD62L– MPP4 cells. Furthermore, studies under native conditions revealed a novel hierarchical organization of the MPP compartments in which quiescent/slow-cycling MPP4 cells sustain a prolonged hematopoietic activity at steady state while giving rise to other lineage-biased MPP populations. Altogether, our data characterize a durable and productive quiescent/slow-cycling hematopoietic intermediary within the MPP4 compartment and highlight early paths of progenitor differentiation during unperturbed hematopoiesis.
Project description:This study was performed to compare transcriptomic changes in the heterogeneous mouse skin epidermal stem cells and hair follicle stem cells (HFSC) populations during chronological aging. Slow-cycling stem cells (label retaining cells, LRCs), fast-cycling stem cells (non-label retaining cells, nLRCs) and hair follicle stem cells express unique gene signatures in young age (2 months old) and have independent stem cell identities. The changes in aging stem cells lineage identities have been a topic of discussion and here we examined if distinct stem cells cycling speed affects their aging process by comparing the transcriptomes of slow-and fast-cycling epidermal stem cells. Our data indicates the loss of unique stem cell identities in aging slow or fast-cycling epidermal stem cells or HFSC at 2 years of age with intermediary effects seen at 1.5 year old.
Project description:SUMMARY: Dormant or slow cycling tumour cells can form a residual chemoresistant reservoir responsible for relapse in patients, years after curative surgery and adjuvant therapy. Since their isolation from human tumors has been a long-stalled technical challenge preventing a direct study of their functional properties, we have adapted the pulse-chase expression and labeling approach using H2BeGFP (Tumbar et al., 2004, DOI:10.1126/science.1092436) to a doxycycline-inducible all-in-one lentiviral vector. In this manner we were able to label and isolate by FACS live slow cycling cancer cells (SCCC) from human colorectal, glioma and melanoma patient-derived tumors as well as from minitumors grown in matrigel (SW1222-cells) or in sphere culture (e225, e216 glioma models). We determined the differentially expressed transcriptional profiles in paired comparisons of slow-cycling cancer cell (SCCC) versus rapid cycling cancer cell (RCCC) sub-populations. H2BeGFP-retention revealed slow cycling as a transient cell state rather than a cellular entity. SCCC showed cancer-initiation potential and enhanced chemoresistance. Cells in this slow cycling status presented a distinctive non-genetic and cell-autonomous gene expression profile shared across different tumour types. We identified TET2 epigenetic enzyme as key factor controlling SCCC numbers and survival. 5-Hydroxymethylcytosine (5hmC), generated by TET2 enzymatic activity, labelled the SCCC genome in carcinomas and was a predictive biomarker of relapse and survival in cancer patients. We demonstrate the enhanced chemoresistance of SCCC, revealed 5hmC as a biomarker for their clinical identification, and identified TET2 as a potential drug-target for SCCC elimination that could extend patients' survival.Experimental Design: Cells from human patient-derived xenografts (PDX) and human cancer cell lines were infected with a doxycycline (DOX)-inducible all-in-one lentivirus coding for the histone2B-eGFP fusion protein. The models were as following: T70 (colorectal cancer); MMPG3 and MMLN9 (melanoma); e225 and e216 (glioma) and human SW1222 colorectal cancer cell line as an infected pool as well as a clone (Clone2) and the following SW1222 derivate cell lines: SW1222-shCTRL (stable expression of nonsilencing shRNA), SW1222-shTET2 (stable expression of TET2-specific shRNA).H2BeGFP-infected cells were isolated and grown/propagated and injected subcutaneously in the flanks of immunocompromised NOD-Scid mice as described (Puig et al., Clin. Cancer Res. 2013; doi: 10.1158/1078-0432.CCR-12-1740.). H2BeGFP-infected SW1222 cells and derivate cell lines were grown in matrigel drops as minitumors. H2BeGFP-infected patient-derived melanoma MMPG3 and MMLN9 minitumor and glioma models e216 and e225 were grown as sphere cultures in their respective conditions as indicated.H2BeGFP expression was induced by DOX treatment in all experimental systems in a pulse-chase fashion and H2BeGFP fusion protein integrated into the host genome labeling all cells. Consecutive cell divisions of proliferating cells diluted and finally eliminated the fluorescent mark in an exponential decay fashion (RCCC or sRCCC), whereas slow-cycling cells (SCCC) retained the fluorescent stain, allowing FACS separation and isolation. Total RNA was separately extracted from both sub-populations of cells of each system and submitted to microarray analyses for characterization.
Project description:A slow cycling, dormant cell state is thought to contribute to the therapeutic resistance of GBM tumour cells, yet not much is known about the biology of this slow-cycling cell population in GBM. By using somatic mouse model of GBM, combined with the inducible H2B-GFP label retention system, we isolated dormant tumour cells from their in vivo niches, and characterised them by single cell RNA sequencing.
Project description:Reprogramming somatic cells to induced pluripotency by Yamanaka factors is usually slow and inefficient, and is thought to be a stochastic process. We identified a privileged somatic cell state, from which acquisition of pluripotency could occur in a non-stochastic manner. Subsets of murine hematopoietic progenitors are privileged, whose progeny cells predominantly adopt the pluripotent fate with activation of endogenous Oct4 locus after 4-5 divisions in reprogramming conditions. Privileged cells display an ultrafast cell cycle of ~8 hours. In fibroblasts, a subpopulation cycling at a similar ultrafast speed is observed after 6 days of factor expression, and is increased by p53-knockdown. This ultrafast-cycling population accounts for >99% of the bulk reprogramming activity in wildtype or p53-knockdown fibroblasts. We compared the transcriptomes of the fast cycling cells with those of slower hematopoietic progenitors, bulk fibroblasts and established iPS cells. 3-5 replicates for each of the six cell types were included: 4 replicates for established iPS cells, 4 replicates for bulk mouse embryonic fibroblasts (MEF), 4 replicates for fast cycling MEF, 4 replicates for slow cycling MEF, 5 replicates for fast cycling granulocyte monocyte progenitors (GMP) and 3 replicates for slow cycling GMP.
Project description:gnp_blan06_torpten - rnai tor time course - The impact of the TOR pathway on growth and stress responses. Modification of translational and transcriptional profiles in Tor-inducible RNAi mutants and identification of TOR targets.
Project description:ra03-07_tor - tor - Study of 2 TOR mutants (7817 Strong, 7846 weak) - Mutant vs wild type on different nitrogen conditions (10mM=control and 100uM) Keywords: treated vs untreated comparison,wt vs mutant comparison