Expansion of quiescent hematopoietic stem cells in mice
Ontology highlight
ABSTRACT: Hematopoietic stem cells (HSCs) are maintained in the quiescent state for protection from exhaustion by a number of self-renewal divisions. To understand the in vivo kinetics of quiescent HSCs, we analyzed the cell cycle of CD201+150+48-Lin-Kit+Sca-1+ cells after transplantation and during development and aging using fluorescent ubiquitination-based cell cycle indicator (Fucci) mice to distinguish HSCs at the G0, G1, and S/G2/M phases. The quiescent HSC population, representing a functional HSC pool, rapidly expanded by three weeks after transplantation and by three weeks of age in development and gradually accumulated in bone marrow with aging. Single-cell RNA-sequencing with flow cytometric index sorting suggested that high CD201 and Sca-1 expression levels and a low level of mitochondrial activity were associated with quiescent HSCs. A novel set of candidate quiescent genes in HSCs was also provided. This study implied that controlling quiescent HSCs is important for the in vivo expansion and maintenance of functional HSCs.
Project description:Gene editing using engineered nucleases frequently produces unintended genetic lesions in hematopoietic stem cells (HSCs). Gene-edited HSC cultures thus contain heterogenous populations, the majority of which either do not carry the desired edit or harbor unwanted mutations. In consequence, transplanting edited HSCs carries the risks of suboptimal efficiency and of unwanted mutations in the graft. Here, we present an approach for expanding gene-edited HSCs at clonal density, allowing for genetic profiling of individual clones before transplantation. We achieved this by developing a defined, polymer-based expansion system and identifying long-term expanding clones within the CD201+CD150+CD48-c-Kit+Sca-1+Lin-(KSL) population of pre-cultured HSCs. This dataset compares the gene expression in three different populations: (1) CD201+CD150+CD48-KSL (2) CD201+CD150+CD48+KSL and (3) CD201-KSL cells.
Project description:Haematopoietic stem cells (HSCs) are derived early from embryonic precursor cells, such as haemogenic endothelial cells and pre-HSCs. However, the identity of precursor cells remains elusive due to their rareness, transience, and inability to be isolated efficiently. Here we employed potent surface markers to capture the nascent pre-HSCs at 30% purity, as rigorously validated by single-cell-initiated serial transplantation assay. Then we applied single-cell RNA-Seq technique to analyse five populations closely related to HSC formation: endothelial cells, CD45- and CD45+ pre-HSCs in E11 aorta-gonad-mesonephros (AGM) region, and mature HSCs in E12 and E14 foetal liver. In comparison, the pre-HSCs showed unique features in transcriptional machinery, apoptosis, metabolism state, signalling pathway, transcription factor network, and lncRNA expression pattern. Among signalling pathways enriched in pre-HSCs, the mTOR activation was uncovered indispensable for the emergence of HSCs but not haematopoietic progenitors from endothelial cells in vivo. By comparing with proximal populations without HSC potential, the core molecular signature of pre-HSCs was identified. Collectively, our work paves the way for dissection of complex molecular mechanisms regulating the step-wise generation of HSCs in vivo, informing future efforts to engineer HSCs for clinical application. RNA-Seq of 181 single-cell samples from 8 FACS sorted cell types: 1. endothelial cells (samples E11.0_EC_xxxx. CD31+ VE-cadherin+CD41-CD43-CD45-Ter119-); 2. T1 pre-HSCs (samples E11.0_T1_xxxx. CD31+CD45-CD41low c-Kit+CD201high); 3. T1 CD201- cells (samples E11.0_T1CD201neg_xxxx, CD31+CD45-CD41low c-Kit+CD201low/-) ; 4. T2 pre-HSCs (samples E11.0_T2_35xx. CD31+CD45+c-Kit+CD201high), 5. T2 CD41low (samples E11.0_T2_21xx, E11.0_T2_24xx and E11.0_T2_27xx. CD31+CD45+CD41low); 6. E12 HSCs (samples E12.5_FL_xxxx. Lin-Sca-1+Mac-1lowCD201+); 7. E14 HSCs (samples E14.5_FL_xxxx. CD45+CD150+CD48-CD201+); 8. Adult HSCs (samples Adult_HSC_xxxx. CD45+CD150+CD48-CD201+). ECs, T1 pre-HSCs, T1 CD201- cells, T2 pre-HSCs, T2 CD41low cells were sorted from E11 AGM region. Mature HSCs were sorted from E12 or E14 fetal liver and adult bonemarrow.
Project description:Hematopoietic stem cells (HSCs) have been considered to progressively lose the self-renewal and differentiation potentials towards the commitment to each blood lineage. However, recent studies have suggested megakaryocyte progenitors are generated in a close relation with HSCs. In this study, we identified CD201-CD48- or CD48+ CD150+CD34-Kit+Sca-1+Lin- cells as new early megakaryocyte progenitors (MegP) in adult mouse bone marrow by single-cell (sc) transplantation, sc colony assay, sc RT-PCR, and sc RNA-sequencing. These MegP had little repopulating potential in vivo but formed megakaryocyte colonies in vitro. Transcriptome analysis suggested that these MegP lie downstream of HSCs and upstream of multipotent progenitors in a megakaryocyte differentiation pathway. The polyinosinic-polycytidylic acid (polyIC) injection and long-term reconstitution data suggested that a proportion of MegP expand after inflammation and transplantation. Here we propose a new model of HSC differentiation where HSCs give rise to common myeloid progenitors and MegP with little repopulating activity.
Project description:Asrij deletion in mice causes loss of HSC quiescence, myeloid skewing, reduced p53 and increased DNA damage, features attributed to aged hematopoietic stem cells (HSCs). To identify the pathways and processes driving the observed HSC aging-like phenotypes upon asrij depletion and to compare the asrij KO transcriptome with aged wild type HSCs, we performed RNA-seq gene expression profiling of Lin- Sca-1+ c-Kit+ CD150+ CD48- stem cells isolated from asrij KO or asrij floxed (control) mouse bone marrow. Our results identify Asrij as a potential driver of aging-like alterations in HSCs and the RNA-seq based transcriptome could help identify additional aging biomarkers and develop strategies to rejuvenate aged HSCs or prevent premature HSC aging.
Project description:Adult hematopoietic stem cells (HSCs) are predominantly quiescent and can be activated in response to acute stress such as infection or cytotoxic insults. STAT1 is a pivotal mediator of interferon (IFN) signaling and is required for IFN-induced HSC proliferation, but the downstream mechanisms remain unclear and in particular little is known about the role of STAT1 in regulating hematopoietic stem/progenitor cells during homeostasis. Here we show that loss of STAT1 alters the steady state hematopoietic stem and progenitor (HSPC) landscape, impairs HSC function in transplantation assays and delays blood cell regeneration following myeloablation. Under steady state conditions STAT1 was essential for several HSC transcriptional programs including expression of genes involved in virus life cycle, a subset of interferon-stimulated genes, MHC class I genes and genes involved in cell cycle arrest. In addition Stat-1 deficient mice lacked a previously unrecognized quiescent subset of homeostatic HSCs with high levels of MHC II expression (MHC IIhi HSCs). This subset was refractory to 5’-FU induced myeloablation and displayed reduced megakaryocytic potential. Mutant calreticulin, which causes increased megakaryopoiesis in human myeloproliferative neoplasms, gave rise to preferential expansion of MHC IIlo HSCs. These data reveal a STAT1 dependent MHC IIhi quiescent HSC subset and show that STAT1 protects HSCs from proliferative exhaustion.
Project description:Adult hematopoietic stem cells (HSCs) are predominantly quiescent and can be activated in response to acute stress such as infection or cytotoxic insults. STAT1 is a pivotal mediator of interferon (IFN) signaling and is required for IFN-induced HSC proliferation, but the downstream mechanisms remain unclear and in particular little is known about the role of STAT1 in regulating hematopoietic stem/progenitor cells during homeostasis. Here we show that loss of STAT1 alters the steady state hematopoietic stem and progenitor (HSPC) landscape, impairs HSC function in transplantation assays and delays blood cell regeneration following myeloablation. Under steady state conditions STAT1 was essential for several HSC transcriptional programs including expression of genes involved in virus life cycle, a subset of interferon-stimulated genes, MHC class I genes and genes involved in cell cycle arrest. In addition Stat-1 deficient mice lacked a previously unrecognized quiescent subset of homeostatic HSCs with high levels of MHC II expression (MHC IIhi HSCs). This subset was refractory to 5’-FU induced myeloablation and displayed reduced megakaryocytic potential. Mutant calreticulin, which causes increased megakaryopoiesis in human myeloproliferative neoplasms, gave rise to preferential expansion of MHC IIlo HSCs. These data reveal a STAT1 dependent MHC IIhi quiescent HSC subset and show that STAT1 protects HSCs from proliferative exhaustion.
Project description:Hematopoietic stem cells (HSCs) balance self-renewal and differentiation to maintain hematopoietic fitness throughout life. In steady-state conditions, HSC exhaustion is prevented by the maintenance of most HSCs in a quiescent state, with cells entering the cell cycle only occasionally. HSC quiescence is regulated by retinoid and fatty-acid ligands of transcriptional factors of the nuclear retinoid X receptor (RXR) family. Here, we show that dual deficiency for hematopoietic RXRa and RXRb induces HSC exhaustion, myeloid cell/megakaryocyte differentiation, and myeloproliferative-like disease. RXRa and RXRb maintain HSC quiescence, survival, and chromatin compaction; moreover, transcriptome changes in RXRa;RXRb-deficient HSCs include premature acquisition of an aging-like HSC signature, MYC pathway upregulation, and RNA intron retention. Fitness loss and associated RNA transcriptome and splicing alterations in RXRa;RXRb-deficient HSCs are prevented by Myc haploinsufficiency. Our study reveals the critical importance of RXRs for the maintenance of HSC fitness and their protection from premature aging.
Project description:Hematopoietic stem cells (HSCs) balance self-renewal and differentiation to maintain hematopoietic fitness throughout life. In steady-state conditions, HSC exhaustion is prevented by the maintenance of most HSCs in a quiescent state, with cells entering the cell cycle only occasionally. HSC quiescence is regulated by retinoid and fatty-acid ligands of transcriptional factors of the nuclear retinoid X receptor (RXR) family. Here, we show that dual deficiency for hematopoietic RXRa and RXRb induces HSC exhaustion, myeloid cell/megakaryocyte differentiation, and myeloproliferative-like disease. RXRa and RXRb maintain HSC quiescence, survival, and chromatin compaction; moreover, transcriptome changes in RXRa;RXRb-deficient HSCs include premature acquisition of an aging-like HSC signature, MYC pathway upregulation, and RNA intron retention. Fitness loss and associated RNA transcriptome and splicing alterations in RXRa;RXRb-deficient HSCs are prevented by Myc haploinsufficiency. Our study reveals the critical importance of RXRs for the maintenance of HSC fitness and their protection from premature aging.
Project description:Quiescent hematopoietic stem cells (HSCs) are prone to mutagenesis, and accumulation of mutations can result in hematological malignancies. The mechanisms through which HSCs prevent such detrimental accumulation, however, are unclear. Here, we show that Aspp1 coordinates with p53 to maintain the genomic integrity of the HSC pool. Aspp1 is preferentially expressed in HSCs and restricts HSC pool size by attenuating self-renewal under steady state conditions. After genotoxic stress, Aspp1 promotes HSC cycling and induces p53-dependent apoptosis in cells with persistent DNA damage foci. Beyond these p53-dependent functions, Aspp1 attenuates HSC self-renewal and accumulation of DNA damage in p53-null HSCs. Consequently, concomitant loss of Aspp1 and p53 leads to the development of hematological malignancies, especially T-cell leukemia and lymphoma. Together, these data highlights coordination between Aspp1 and p53 in regulating HSC self-renewal and DNA damage tolerance, and suggest that HSCs possess specific mechanisms that prevent accumulation of mutations and malignant transformation. 8-week-old WT, Aspp1-/-, Mx1-Cre(+)p53flox/flox and Mx1-Cre(+)Aspp1-/-p53flox/flox mice were intraperitoneally administered with 400 μg pIpC five times every other day to obtain WT, Aspp1-/-, p53-/- and Aspp1-/-p53-/- bone marrow. 4 weeks after pIpC treatment, bone marrow lineage(-) Sca-1(+) cKit(+) cells were isolated. RNA was extracted and pooled from 3 independent mice per genotype. RNA samples were then amplified, labeled, and hybridized to independent arrays.
Project description:Hematopoietic stem cells (HSCs) and their progeny sustain lifetime hematopoiesis. Aging alters HSC function, number, and composition and increases risk of hematological malignancies, but how these changes occur in HSCs remains unclear. Signaling via p38MAPK has been proposed as a candidate mechanism underlying induction of HSC aging. Here, using genetic models of both chronological and premature aging, we describe a multimodal role for p38α, the major p38MAPK isozyme in hematopoiesis, in HSC aging. We report that p38α regulates differentiation bias and sustains transplantation capacity of HSCs in the early phase of chronological aging (from young to 1-year-old). However, p38α decreased HSC transplantation capacity in the late progression phase of chronological aging (from 1- to 2-years-old). Furthermore, co-deletion of p38α in mice deficient in Ataxia-telangiectasia mutated (Atm), a model of premature aging, exacerbated aging-related HSC phenotypes seen in Atm single mutant mice. Mechanistically, p38α makes a positive contribution to inflammation during the late phase aging, resulting in defects in 2-year-old HSCs. Overall, we propose multiple functions of p38MAPK, which both promotes and suppresses HSC aging context-dependently.