Project description:The transcription factor hepatic leukemia factor (HLF) is highly expressed in hematopoietic stem cells (HSCs) and has been proposed to influence both HSC self-renewal and leukemogenesis. However, the physiological role of HLF in hematopoiesis and HSC function has remained unknown. Here we report that mice lacking Hlf are viable with essentially normal hematopoietic parameters. By contrast, when challenged through transplantation, Hlf deficient HSCs demonstrate an impaired ability to reconstitute hematopoiesis and gradually exhaust upon serial transplantation. Transcriptional profiling displayed changes associated with cellular activation in Hlf deficient HSCs, and cell cycle analysis showed a significant reduction of dormant HSCs. Accordingly, Hlf deficient mice were hypersensitive to toxic insults targeting dividing cells that completely eradicated the HSC pool. In summary, our findings unravel a novel role for HLF as a critical regulator of HSC quiescence and as an essential factor to maintain the HSC pool during regeneration.
Project description:Organismal homeostasis and regeneration are predicated on committed stem cells which, in tissues and organs with low turnover, reside for long periods in a reversible cell cycle arrest, defined as quiescence. Inability to exit or premature escape from quiescence, as occurring in pathological conditions and aging, is detrimental as it results in either lack of stem cell mobilization or pool depletion with consequent defective tissue homeostatis and regeneration. It is therefore unsurprising that quiescence is safeguarded by multilayered regulatory mechanisms. Here, we report that Polycomb Ezh1 confers quiescence to muscle stem cells (MuSCs) through a non-canonical function. In the absence of Ezh1, MuSCs spontaneously exit quiescence and, following repeated injuries, the stem cell pool is depleted resulting in failure to sustain appropriate muscle regeneration. Rather than regulating repressive Polycomb-dependent histone H3K27 methylation, Ezh1 actively maintains the Notch signaling pathway in MuSCs. Accordingly, selective genetic reconstitution of the Notch signaling corrects stem cell number and re-establishes quiescence of Ezh1-/- MuSCs.
Project description:This is a mathematical model describing the hematopoietic lineages with leukemia lineages, as controlled by end-product negative feedback inhibition. Variables include hematopoietic stem cells, progenitor cells, terminally differentiated HSCs, leukemia stem cells, and terminally differentiated leukemia stem cells.
Project description:The hematopoietic system is maintained throughout life by hematopoietic stem cells that are capable of differentiation to all hematopoietic lineages. An intimate balance between self-renewal, differentiation, and quiescence is required to maintain hematopoiesis. Disruption of this balance can result in hematopoietic malignancy, including acute myeloid leukemia (AML). FBXO9, from the F-box ubiquitin E3 ligases, is down-regulated in patients with AML compared to normal bone marrow. FBXO9 is a substrate recognition component of the Skp1-Cullin-F-box (SCF)-type E3 ligase complex. FBXO9 is highly expressed in hematopoietic stem and progenitor populations, which contain the tumor-initiating population in AML. In AML patients, decrease in FBXO9 expression is most pronounced in patients with the inversion of chromosome 16 (Inv(16)), a rearrangement that generates the transcription factor fusion gene, CBFB-MYH11. To study FBXO9 in malignant hematopoiesis, we generated a conditional knockout mouse model using a novel CRISPR/Cas9 strategy. Our data shows that deletion of Fbxo9 in mice expressing Cbfb-MYH11 leads to markedly accelerated and aggressive leukemia development. In addition, we find loss of FBXO9 leads to increased proteasome expression and tumors are more sensitive to bortezomib suggesting that FBXO9 expression may predict patient response to bortezomib treatment.
Project description:Negative elongation factor (NELF) is a critical transcriptional regulator that stabilizes paused RNA polymerase to permit rapid gene expression changes in response to environmental cues. Although NELF is essential for embryonic development, its role in adult stem cells remains unclear. In this study, through a muscle-stem-cell-specific deletion, we showed that NELF is required for efficient muscle regeneration and stem cell pool replenishment. In mechanistic studies using PRO-seq, single-cell trajectory analyses and myofiber cultures revealed that NELF works at a specific stage of regeneration whereby it modulates p53 signaling to permit massive expansion of muscle progenitors. Strikingly, transplantation experiments indicated that these progenitors are also necessary for stem cell pool repopulation, implying that they are able to return to quiescence. Thus, we identified a critical role for NELF in the expansion of muscle progenitors in response to injury and revealed that progenitors returning to quiescence are major contributors to the stem cell pool repopulation.
Project description:Negative elongation factor (NELF) is a critical transcriptional regulator that stabilizes paused RNA polymerase to permit rapid gene expression changes in response to environmental cues. Although NELF is essential for embryonic development, its role in adult stem cells remains unclear. In this study, through a muscle-stem-cell-specific deletion, we showed that NELF is required for efficient muscle regeneration and stem cell pool replenishment. In mechanistic studies using PRO-seq, single-cell trajectory analyses and myofiber cultures revealed that NELF works at a specific stage of regeneration whereby it modulates p53 signaling to permit massive expansion of muscle progenitors. Strikingly, transplantation experiments indicated that these progenitors are also necessary for stem cell pool repopulation, implying that they are able to return to quiescence. Thus, we identified a critical role for NELF in the expansion of muscle progenitors in response to injury and revealed that progenitors returning to quiescence are major contributors to the stem cell pool repopulation.
Project description:Negative Elongation Factor (NELF) is a critical transcriptional regulator that works through stabilizing paused RNA Polymerase to permit rapid gene expression changes in response to environmental cues. Whilst NELF is essential for embryonic development, its role in adult stem cells remains unclear. Here, through a muscle stem cell-specific deletion, we show that NELF is required for efficient muscle regeneration and replenishing the stem cell pool. Mechanistic studies using PRO-seq, single cell trajectory analyses and myofiber cultures revealed that NELF works at a specific stage of muscle regeneration whereby it mediates massive expansion of muscle progenitors. Strikingly, transplantation experiments indicate that these progenitors are also necessary for stem cell pool repopulation implying they are able to return to quiescence. Thus, we identified a critical role for NELF in expansion of muscle progenitors in response to injury and revealed that progenitors returning to quiescence are major contributors to stem cell pool repopulation.
Project description:Negative Elongation Factor (NELF) is a critical transcriptional regulator that works through stabilizing paused RNA Polymerase to permit rapid gene expression changes in response to environmental cues. Whilst NELF is essential for embryonic development, its role in adult stem cells remains unclear. Here, through a muscle stem cell-specific deletion, we show that NELF is required for efficient muscle regeneration and replenishing the stem cell pool. Mechanistic studies using PRO-seq, single cell trajectory analyses and myofiber cultures revealed that NELF works at a specific stage of muscle regeneration whereby it mediates massive expansion of muscle progenitors. Strikingly, transplantation experiments indicate that these progenitors are also necessary for stem cell pool repopulation implying they are able to return to quiescence. Thus, we identified a critical role for NELF in expansion of muscle progenitors in response to injury and revealed that progenitors returning to quiescence are major contributors to stem cell pool repopulation.
Project description:Negative Elongation Factor (NELF) is a critical transcriptional regulator that works through stabilizing paused RNA transcripts to permit rapid gene expression changes in response to environmental cues. Whilst NELF is essential for embryonic development, its role in adult stem cells remains unclear. Here, through a muscle stem cell-specific deletion, we show that NELF is required for efficient muscle regeneration and replenishing the stem cell pool. Mechanistic studies using PRO-seq, single cell trajectory analyses and myofiber cultures revealed that NELF works at a specific stage of muscle regeneration whereby it mediates massive expansion of muscle progenitors. Strikingly, transplantation experiments indicate that these progenitors are also necessary for stem cell pool repopulation implying they are able to return to quiescence. Thus, we identified a critical role for NELF in expansion of muscle progenitors in response to injury and revealed that progenitors returning to quiescence are major contributors to stem cell pool repopulation.
Project description:Negative Elongation Factor (NELF) is a critical transcriptional regulator that works through stabilizing paused RNA Polymerase to permit rapid gene expression changes in response to environmental cues. Whilst NELF is essential for embryonic development, its role in adult stem cells remains unclear. Here, through a muscle stem cell-specific deletion, we show that NELF is required for efficient muscle regeneration and replenishing the stem cell pool. Mechanistic studies using PRO-seq, single cell trajectory analyses and myofiber cultures revealed that NELF works at a specific stage of muscle regeneration whereby it mediates massive expansion of muscle progenitors. Strikingly, transplantation experiments indicate that these progenitors are also necessary for stem cell pool repopulation implying they are able to return to quiescence. Thus, we identified a critical role for NELF in expansion of muscle progenitors in response to injury and revealed that progenitors returning to quiescence are major contributors to stem cell pool repopulation.