Project description:Our study disclosed previously unrecognized heterogeneity in fetal liver (FL) hematopoietic stem cells (HSC), highlighting biosynthetic dormancy as a key to symmetric self-renewal of engraftable HSC and supports recent studies demonstrating distinct developmental origins for multipotent progenitors and HSC in definitive hematopoiesis.

2023-05-24 | GSE233031 | GEO

Comparing dormancy in two distantly related tunicates reveals morphological, molecular, and ecological convergences and repeated co-option

Project description:Many asexually-propagating marine invertebrates can survive extreme environmental conditions by developing dormant structures, i.e., morphologically simplified bodies that retain the capacity to completely regenerate a functional adult when conditions return to normal. Here, we examine the environmental, morphological, and molecular characteristics of dormancy in two distantly related clonal tunicate species: Polyandrocarpa zorritensis and Clavelina lepadiformis. In both species, we report that the dormant structures are able to withstand harsher temperature and salinity conditions compared to the adult, and are the dominant forms these species employ to survive the colder winter months. By finely controlling the entry and exit of dormancy in laboratory-reared individuals, we were able to select and characterize the morphology of dormant structures associated with their transcriptome dynamics. In both species, we identified putative stem and nutritive cells in structures that resemble the earliest stages of asexual propagation. By characterizing gene expression during dormancy and regeneration into the adult body plan (i.e., germination), we observed that genes which control dormancy and environmental sensing in other metazoans, notably HIF-α and insulin signaling genes, are also expressed in tunicate dormancy. Germination-related genes in these two species, such as the retinoic acid pathway, are also found in other unrelated clonal tunicates during asexual development. These results are suggestive of repeated exaptation of conserved eco-physiological and regeneration programs for the origin of novel dormancy-germination processes across distantly related animal taxa.

2022-07-27 | GSE198056 | GEO

Hematopoietic Stem Cells Reversibly Switch from Dormancy to Self-Renewal during Homeostasis and Repair

Project description:Bone marrow hematopoietic stem cells (HSCs) are crucial to maintain lifelong production of all blood cells. Although HSCs divide infrequently, it is thought that the entire HSC pool turns over every few weeks, suggesting that HSCs regularly enter and exit cell cycle. Here, we combine flow cytometry with label-retaining assays (BrdU and histone H2B-GFP) to identify a population of dormant mouse HSCs (d-HSCs) within the lin(-)Sca1+cKit+CD150+CD48(-)CD34(-) population. Computational modeling suggests that d-HSCs divide about every 145 days, or five times per lifetime. d-HSCs harbor the vast majority of multilineage long-term self-renewal activity. While they form a silent reservoir of the most potent HSCs during homeostasis, they are efficiently activated to self-renew in response to bone marrow injury or G-CSF stimulation. After re-establishment of homeostasis, activated HSCs return to dormancy, suggesting that HSCs are not stochastically entering the cell cycle but reversibly switch from dormancy to self-renewal under conditions of hematopoietic stress

2009-05-15 | GSE16100 | GEO

Retinoic acid signaling is essential for HSC development

Project description:To find how RA signaling modulates HSC development This microarray was performed between E11.5 AA4.1/VEC+CD45- and AA4.1/VEC+CD45+ cells

2013-03-12 | E-GEOD-45020 | biostudies-arrayexpress

A critical requirement for IκBα in controlling dormancy in Hematopoietic stem cells via retinoic acid during embryonic development [scRNA-seq_10x]

Project description:Hematopoietic Stem Cells (HSCs) originate from the E11.5 aorta-gonads-and mesonephros (AGM) region during development before they migrate to the foetal liver for proliferation and maturation, and finally seed the bone marrow around birth, their final site of residence. In the AGM, HSCs reside within Intra-aortic hematopoietic clusters (IAHC) along with hematopoietic progenitors (HPC). Molecular pathways that determine HSC fate instead of HPCs are still unknown, although inflammatory signalling has been implicated in the development of all blood cells, including NF-κB. Here, we describe a dormant phenotype of LT-HSCs in the IκBα KO. Although IκBα is critical for retaining inactive NF-κB complexes in the cytoplasm, it can regulate stem cell related genes by interacting with the PRC2 complex in the nucleus. Accordingly, we find decreased PRC2 dependent H3K27me3 accumulation at the promoters of PI3K and retinoic acid signalling molecules by cut and tag assay in AGM derived CD31+ cells, which includes HE/IAHC derived from IκBα KO embryos. Furthermore, this regulation of the retinoic acid signalling by IκBα is further confirmed by cut and tag assay for IκBα itself in CD31+ cells of the AGM and more specifically also in sorted LT-HSCs from the E14.5 foetal liver. Over-activation of the retinoic acid/PI3K levels in LT-HSCs of the IκBα KO is evident in their dormant molecular profile. Functionally, IκBα KO LT-HSCs are less proliferative and respond with delayed activation upon transplantation. Overall, we identify nuclear IκBα as an essential player specifically for HSC specification/proliferation from the onset of HSPC emergence in the AGM.

2024-04-15 | GSE214699 | GEO

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