Project description:Ubiquitination is a post-translational mechanism of control of diverse cellular processes. We focus here on the ubiquitin ligase Fbw7, a recently identified hematopoietic tumor suppressor that can target for degradation several important oncogenes including Notch1, c-Myc and cyclin E. We have generated conditional Fbw7 knock-out animals and inactivated the gene in hematopoietic stem cells (HSC) and their differentiated progeny. Deletion of Fbw7 specifically and rapidly affects the HSC compartment in a cell-autonomous manner. Fbw7-/- HSCs show defective maintenance of quiescence, leading to impaired self-renewal and a severe loss of competitive repopulating capacity. Furthermore, Fbw7-/- HSC are unable to colonize the thymus leading to a profound depletion of T cell progenitors. Deletion of Fbw7 in bone marrow stem cells and progenitors leads to the stabilization of c-Myc, a transcription factor previously implicated in HSC self-renewal. On the other hand, neither Notch1 nor cyclin E are stabilized in the bone marrow of Fbw7 deficient mice. Genome-wide transcriptome studies of Fbw7-/- HSC and hematopoietic progenitors indicate that Fbw7 controls, through the regulation of HSC cell cycle entry, the global transcriptional âsignatureâ that is associated with the quiescent, self-renewing HSC phenotype. Transcriptional consequences of inactivating Fbw7 in LKS cells. Experiment Overall Design: Four samples were analyzed: wild-type (WT) control and Fbw7-deficient (FBW7) Lin-ckit+Sca1+ (LSK) cells, as well as Lin-ckit+Sca1- myeloid progenitor (MP) cells, which served as a control for LSK-enriched/specific genes. Total bone marrow cells were pooled from three WT and three FBW7 mice before sorting LSK and MP populations.
Project description:Advances in pluripotent stem cell and reprogramming technologies have given hope of generating hematopoietic stem cells (HSC) in culture. To succeed, greater understanding of the self-renewing HSC during human development is required. We discovered that glycophosphatidylinositol-anchored surface protein GPI-80 (Vanin 2) defines a distinct subpopulation of human fetal hematopoietic stem/progenitor cells (HSPC) with self-renewal ability. CD34+CD90+CD38-GPI-80+ HSPC were the sole population that maintained proliferative potential and undifferentiated state in bone marrow stroma co-culture, and engrafted in immunodeficient mice. GPI-80 expression also enabled tracking of HSC migration between human fetal hematopoietic niches. The most highly enriched surface protein in GPI-80+ HSPC as compared to their progeny was Integrin alpha-M (ITGAM), which in leukocytes cooperates with GPI-80 to support migration. Knockdown of either GPI-80 or ITGAM was sufficient to perturb undifferentiated HSPC in stroma co-culture. These findings indicate that human fetal HSC utilize common mechanisms with leukocytes for cell-cell interactions governing HSC self-renewal. We used microarrays to identify genes enriched in the GPI-80+ hematopoietic stem and progenitor population in fetal liver. RNA was extracted from enriched fetal liver hematopoietic stem and progenitor cells, and downstream progenitors, for comparison based on Affymetrix arrays.
Project description:Advances in pluripotent stem cell and reprogramming technologies have given hope of generating hematopoietic stem cells (HSC) in culture. To succeed, greater understanding of the self-renewing HSC during human development is required. We discovered that glycophosphatidylinositol-anchored surface protein GPI-80 (Vanin 2) defines a distinct subpopulation of human fetal hematopoietic stem/progenitor cells (HSPC) with self-renewal ability. CD34+CD90+CD38-GPI-80+ HSPC were the sole population that maintained proliferative potential and undifferentiated state in bone marrow stroma co-culture, and engrafted in immunodeficient mice. GPI-80 expression also enabled tracking of HSC migration between human fetal hematopoietic niches. The most highly enriched surface protein in GPI-80+ HSPC as compared to their progeny was Integrin alpha-M (ITGAM), which in leukocytes cooperates with GPI-80 to support migration. Knockdown of either GPI-80 or ITGAM was sufficient to perturb undifferentiated HSPC in stroma co-culture. These findings indicate that human fetal HSC utilize common mechanisms with leukocytes for cell-cell interactions governing HSC self-renewal. We used microarrays to identify genes enriched in the CD90+ hematopoietic stem and progenitor population in fetal liver. RNA was extracted from enriched fetal liver hematopoietic stem and progenitor cells, and downstream progenitors, for comparison based on Affymetrix arrays.
Project description:Self-renewal is a defining characteristic of stem cells, however the molecular pathways underlying its regulation are poorly understood. Here we demonstrate that conditional inactivation of the Pbx1 proto-oncogene in the hematopoietic compartment results in a progressive loss of long-term hematopoietic stem cells (LT-HSCs) that is associated with concomitant reduction in their quiescence, leading to a defect in the maintenance of self-renewal as assessed by serial transplantation. Transcriptional profiling revealed that multiple stem cell maintenance factors are perturbed in Pbx1-deficient LT-HSCs, which prematurely express a large subset of genes, including cell cycle regulators, normally expressed in non-self-renewing multipotent progenitors. Experiment Overall Design: LT-HSC (Lin-cKit+Sca1+CD34-CD135-) and ST-HSC (Lin-cKit+Sca1+CD34+CD135-) cells were prospectively sorted from the BM of MxCre-.Pbx1f/f control mice harvested 4 weeks after the last injection of poly(I:C).
Project description:Ubiquitination is a post-translational mechanism of control of diverse cellular processes. We focus here on the ubiquitin ligase Fbw7, a recently identified hematopoietic tumor suppressor that can target for degradation several important oncogenes including Notch1, c-Myc and cyclin E. We have generated conditional Fbw7 knock-out animals and inactivated the gene in hematopoietic stem cells (HSC) and their differentiated progeny. Deletion of Fbw7 specifically and rapidly affects the HSC compartment in a cell-autonomous manner. Fbw7-/- HSCs show defective maintenance of quiescence, leading to impaired self-renewal and a severe loss of competitive repopulating capacity. Furthermore, Fbw7-/- HSC are unable to colonize the thymus leading to a profound depletion of T cell progenitors. Deletion of Fbw7 in bone marrow stem cells and progenitors leads to the stabilization of c-Myc, a transcription factor previously implicated in HSC self-renewal. On the other hand, neither Notch1 nor cyclin E are stabilized in the bone marrow of Fbw7 deficient mice. Genome-wide transcriptome studies of Fbw7-/- HSC and hematopoietic progenitors indicate that Fbw7 controls, through the regulation of HSC cell cycle entry, the global transcriptional “signature” that is associated with the quiescent, self-renewing HSC phenotype. Transcriptional consequences of inactivating Fbw7 in LKS cells. Keywords: cell type comparison
Project description:<p>Mitochondrial fatty acid oxidation (FAO) is essential for hematopoietic stem cell (HSC) self-renewal; however, the mechanism by which mitochondrial metabolism controls HSC fate remains unknown. Here, we show that within the hematopoietic lineage, HSCs have the largest mitochondrial NADPH pools, which are required for proper HSC cell fate and homeostasis. Bioinformatic analysis of the HSC transcriptome, biochemical assays and genetic inactivation of FAO all indicate that FAO-generated NADPH fuels cholesterol synthesis in HSCs. Interference with FAO disturbs the segregation of mitochondrial NADPH toward corresponding daughter cells upon single HSC division. Importantly, we have found that the FAO-NADPH-cholesterol axis drives extracellular vesicle (EV) biogenesis and release in HSCs, while inhibition of EV signaling impairs HSC self-renewal. These data reveal the existence of a mitochondrial NADPH-cholesterol axis for EV biogenesis that is required for hematopoietic homeostasis and highlight the non-stochastic nature of HSC fate determination.</p>
Project description:The transcriptome of Ctrl and Vitamin A-deficient longterm hematopoietic stem cells (LT-HSC) and multipotant progenitors (MPP3/4) was assessed by RNAseq.
Project description:Increasing evidence links metabolic activity and cell growth to decline in hematopoietic stem cell (HSC) function during aging. The Lin28b/Hmga2 pathway controls tissue development and in the hematopoietic system the postnatal downregulation of this pathway causes a decrease in self renewal of adult HSCs compared to fetal HSCs. Igf2bp2 is an RNA binding protein and a mediator of the Lin28b/Hmga2 pathway, which regulates metabolism and growth signaling by influencing RNA stability and translation of its target genes. It is currently unknown whether Lin28/Hmga2/Igf2bp2 signaling impacts on aging-associated impairments in HSC function and hematopoiesis. Here, we analyzed homozygous Igf2bp2 germline knockout mice and wildtype control animals to address this question. The study shows that Igf2bp2 deletion rescues aging phenotypes of the hematopoietic system, such as the expansion of HSC numbers in bone marrow and the biased increase of myeloid cells in peripheral blood. This rescue of hematopoietic aging coincides with reduced mitochondrial metabolism and glycolysis in Igf2bp2-/- HSCs compared to Igf2bp2+/+ HSCs. Conversely, Igf2bp2 overexpression activates protein synthesis pathways in HSCs and leads to a rapid loss of self renewal by enhancing myeloid skewed differentiation in an mTOR/PI3K-dependent manner. Together, these results show that Igf2bp2 regulates energy metabolism and growth signaling in HSCs and that the activity of this pathways influences self renewal, differentiation, and aging of HSCs.
Project description:Advances in pluripotent stem cell and reprogramming technologies have given hope of generating hematopoietic stem cells (HSC) in culture. To succeed, greater understanding of the self-renewing HSC during human development is required. We discovered that glycophosphatidylinositol-anchored surface protein GPI-80 (Vanin 2) defines a distinct subpopulation of human fetal hematopoietic stem/progenitor cells (HSPC) with self-renewal ability. CD34+CD90+CD38-GPI-80+ HSPC were the sole population that maintained proliferative potential and undifferentiated state in bone marrow stroma co-culture, and engrafted in immunodeficient mice. GPI-80 expression also enabled tracking of HSC migration between human fetal hematopoietic niches. The most highly enriched surface protein in GPI-80+ HSPC as compared to their progeny was Integrin alpha-M (ITGAM), which in leukocytes cooperates with GPI-80 to support migration. Knockdown of either GPI-80 or ITGAM was sufficient to perturb undifferentiated HSPC in stroma co-culture. These findings indicate that human fetal HSC utilize common mechanisms with leukocytes for cell-cell interactions governing HSC self-renewal. We used microarrays to identify genes enriched in the GPI-80+ hematopoietic stem and progenitor population in fetal liver.
Project description:Advances in pluripotent stem cell and reprogramming technologies have given hope of generating hematopoietic stem cells (HSC) in culture. To succeed, greater understanding of the self-renewing HSC during human development is required. We discovered that glycophosphatidylinositol-anchored surface protein GPI-80 (Vanin 2) defines a distinct subpopulation of human fetal hematopoietic stem/progenitor cells (HSPC) with self-renewal ability. CD34+CD90+CD38-GPI-80+ HSPC were the sole population that maintained proliferative potential and undifferentiated state in bone marrow stroma co-culture, and engrafted in immunodeficient mice. GPI-80 expression also enabled tracking of HSC migration between human fetal hematopoietic niches. The most highly enriched surface protein in GPI-80+ HSPC as compared to their progeny was Integrin alpha-M (ITGAM), which in leukocytes cooperates with GPI-80 to support migration. Knockdown of either GPI-80 or ITGAM was sufficient to perturb undifferentiated HSPC in stroma co-culture. These findings indicate that human fetal HSC utilize common mechanisms with leukocytes for cell-cell interactions governing HSC self-renewal. We used microarrays to identify genes enriched in the CD90+ hematopoietic stem and progenitor population in fetal liver.