Biology subjects

Tober, J.

Publications and source records attributed to Tober, J..

7 recordsLinked to original sources

bioRxiv2025

Human length telomeres restrict the regenerative potential of hematopoietic stem cells in mice

Extremely short telomeres cause bone marrow failure in telomere biology disorder (TBDs) patients. Here, we employed the recently developed Telomouse with human-length telomeres resulting from a single amino acid substitution in the helicase Rtel1 (Rtel1M492K/M492K) to determine the effects of the short telomeres on the bone marrow and hematopoiesis. Under homeostatic conditions, Telomice have notably short telomeres but normal hematopoiesis. However, when forced to repopulate following repeated treatment with 5-fluoro-uracil or upon bone marrow transplantation into lethally irradiated mice, bone marrow progenitor cells are significantly depleted in Telomice compared to wild-type controls. This effect is associated with increased frequency of telomere repeat arrays too short to be detected by fluorescence in situ hybridization in the bone marrow of Telomice.

genetics↗

bioRxiv2025

Restraint of TGFβ family signaling by SMAD7 is necessary for hematopoietic stem cell maturation in the embryo.

Hematopoietic stem cells (HSCs), defined as cells that can engraft an adult when transplanted, mature from precursors (pre-HSCs) that differentiate from hemogenic endothelial cells (HECs) in the embryo. Many signaling pathways required to generate the first hematopoietic stem and progenitor cells in the embryo are well-characterized, but how HSCs mature from pre-HSCs is poorly understood. Here we show that "mothers against decapentaplegic homolog 7" (SMAD7), a negative regulator of transforming growth factor beta (TGF{beta}) and bone morphogenetic protein (BMP) signaling, is required for pre-HSC to HSC maturation. Deletion of Smad7 in endothelial cells allows the formation of pre-HSCs from HECs but impairs their maturation into HSCs. The data indicate that although TGF{beta} and BMP signaling are required for the generation of HECs and for HECs to undergo an endothelial-to-hematopoietic transition to generate pre-HSCs, one or both pathways must be subsequently down-regulated for effective pre-HSC to HSC maturation.

developmental biology↗

bioRxiv2025

E2f coordinates the cell cycle and cell fate of hematopoietic progenitors to drive stress myelopoiesis

During inflammation, cytokines such as Tnf, Il1{beta} and Il6 stimulate hematopoietic stem and progenitor cells (HSPCs) to proliferate and accelerate the production of inflammatory cells from the myeloid lineage through a process called stress myelopoiesis. Genetic inactivation of repressors of cell cycle activity in HSPCs is sufficient to recapitulate stress myelopoiesis, suggesting that the cell cycle activity and cell fate decision of proliferative HSPCs are coordinated by a cell intrinsic mechanism. However, the nature of this mechanism remains unknown. Here, we show that E2f simultaneously regulates proliferation of HSPCs, repression of alternative cell fates via the activation of Suz12/Ezh2-containing PRC2 complex and promotion of the myeloid fate by enhancing the signaling activity of CD131, the common {beta}chain receptor for {beta}cytokines (i.e. Il3 and Gm-Csf). Accordingly, dual inhibition of Ezh2 and {beta}cytokine signaling activity in a preclinical model of colitis represses stress myelopoiesis and restores colon homeostasis. Our results suggest that dual targeting of {beta}cytokine signaling and Ezh2 activity represents a novel therapeutic strategy to repress the production of pro-inflammatory myeloid cells in a wide spectrum of inflammatory diseases.

cell biology↗

bioRxiv2023

Tropomyosin 1 deficiency facilitates cell state transitions and enhances hemogenic endothelial cell specification during hematopoiesis

Tropomyosins coat actin filaments and impact actin-related signaling and cell morphogenesis. Genome-wide association studies have linked Tropomyosin 1 (TPM1) with human blood trait variation. Prior work suggested that TPM1 regulated blood cell formation in vitro, but it was unclear how or when TPM1 affected hematopoiesis. Using gene-edited induced pluripotent stem cell (iPSC) model systems, TPM1 knockout was found to augment developmental cell state transitions, as well as TNF and GTPase signaling pathways, to promote hemogenic endothelial (HE) cell specification and hematopoietic progenitor cell (HPC) production. Single-cell analyses showed decreased TPM1 expression during human HE specification, suggesting that TPM1 regulated in vivo hematopoiesis via similar mechanisms. Indeed, analyses of a TPM1 gene trap mouse model showed that TPM1 deficiency enhanced the formation of HE during embryogenesis. These findings illuminate novel effects of TPM1 on developmental hematopoiesis.

cell biology↗

bioRxiv2019

Transcriptional regulatory network controlling the ontogeny of hematopoietic stem cells

Hematopoietic stem cell (HSC) ontogeny is accompanied by dynamic changes in gene regulatory networks. We performed RNA-Seq and histone mark ChIP-Seq to define the transcriptomes and epigenomes of cells representing key developmental stages of HSC ontogeny in the mouse. The five populations analyzed were embryonic day 10.5 (E10.5) endothelium and hemogenic endothelium from the major arteries (dorsal aorta, umbilical and vitelline), an enriched population of pre-hematopoietic stem cells (pre-HSCs), fetal liver HSCs, and adult bone marrow HSCs. We observed dynamic and combinatorial epigenetic changes that mark regulatory DNA sequences including gene promoters and enhancers. Using epigenetic signatures, we identified enhancers for each developmental stage. Only 12% of enhancers are primed, and 78% are active, suggesting the vast majority of enhancers are established de novo at the developmental stages where they are required to control their target genes, without prior priming in earlier stages. We constructed developmental-stage-specific transcriptional regulatory networks during HSC ontogeny by linking enhancers and predicted bound transcription factors to their target promoters using a novel computational algorithm. Our computational analyses predicted known transcriptional regulators for the endothelial-to-hematopoietic transition, validating our overall approach, and identified putative novel transcription factors whose regulon activities correlate with the emergence of pre-HSCs. We validated roles for the broadly expressed transcription factors SP3 and MAZ in arterial hemogenic endothelium. Our data and computational analyses provide a useful resource for uncovering regulators of HSC formation.

developmental biology↗

bioRxiv2019

Developmental trajectory of pre-hematopoietic stem cell formation fromendothelium

Hematopoietic stem and progenitor cells (HSPCs) differentiate from hemogenic endothelial (HE) cells through an endothelial to hematopoietic cell transition (EHT). Newly formed HSPCs accumulate in intra-arterial clusters (IACs) before colonizing the fetal liver. To examine the cell and molecular transitions during the EHT, and the heterogeneity of HSPCs within IACs, we profiled [~]37,000 cells from the caudal arteries of embryonic day 9.5 (E9.5) to E11.5 mouse embryos by single-cell transcriptome and chromatin accessibility sequencing. We identified an intermediate developmental stage prior to HE that we termed pre-HE, characterized by increased accessibility of chromatin enriched for SOX, FOX, GATA, and SMAD motifs. A developmental bottleneck separates pre-HE from HE, with RUNX1 dosage regulating the efficiency of the pre-HE to HE transition. Distinct developmental trajectories within IAC cells result in two populations of CD45+ HSPCs; an initial wave of lympho-myeloid-biased progenitors, followed by precursors of hematopoietic stem cells (pre-HSCs).

developmental biology↗

bioRxiv2019

Spatial genome re-organization between fetal and adult hematopoietic stem cells

Fetal hematopoietic stem cells (HSCs) undergo a developmental switch to become adult HSCs. The functional properties of the HSCs change dramatically during this switch, including their cycling behavior, hematopoietic lineage outputs and proliferation rate. The relationship between three-dimensional (3D) genome organization, epigenomic state, and transcriptome is poorly understood during this critical developmental transition. Here we conducted a comprehensive survey of the 3D genome, epigenome and transcriptome of fetal and adult HSCs in mouse. We found that chromosomal compartments and topologically associating domains (TAD) are largely conserved between fetal and adult HSCs. However, there is a global trend of increased compartmentalization and TAD boundary strength in adult HSCs. In contrast, dynamics of intra-TAD chromatin interactions is much higher and more widespread, involving over a thousand gene promoters and distal enhancers. Such dynamic interactions target genes involved in cell cycle, metabolism, and hematopoiesis. These developmental-stage-specific enhancer-promoter interactions appear to be mediated by different sets of transcription factors in fetal and adult HSCs, such as TCF3 and MAFB in fetal HSCs, versus NR4A1 and GATA3 in adult HSCs. Loss-of-function studies of TCF3 confirms the role of TCF3 in mediating condition-specific enhancer-promoter interactions and gene regulation in fetal HSCs. In summary, our data suggest that the fetal-to-adult transition is accompanied by extensive changes in intra-TAD chromatin interactions that target genes underlying the phenotypic differences between fetal and adult HSCs.

molecular biology↗