TWIST1 Preserves Hematopoietic Stem Cell Function Via Repression of Cacna1b Expression

The mitochondria of hematopoietic stem cell (HSC) play crucial roles in regulating cell fate and in preserving HSC functionality and survival. However, the mechanism underlying its regulation remain poorly understood. Here, we identify transcription factor TWIST1 as a novel regulator of HSC maintenance through modulating mitochondrial function. We demonstrate that Twist1 deletion results in a significantly decreased long-term HSC (LT-HSC) frequency, markedly reduced dormancy and self-renewal capacities and skewed myeloid differentiation in steady-state hematopoiesis. Twist1-deficient LT-HSC are more compromised in tolerance of irradiation and 5 fluorouracil-induced stresses, and exhibit typical phenotypes of senescence and higher levels of DNA damage and apoptosis. Mechanistically, Twist1 deficiency upregulates the expression of voltage-gated calcium channel Cacna1b in HSC, leading to noticeable increases in mitochondrial calcium levels, biogenesis, metabolic activity and reactive oxygen species production. Suppression of voltage-gated calcium channel by a calcium channel blocker largely rescues the phenotypic and functional defects in Twist1-deleted HSCs under both steady-state and stress conditions. Collectively, our data, for the first time, characterize TWIST1 as a critical regulator of HSC function acting through CACNA1B/Ca2+/mitochondria axis, and highlight the importance of Ca2+ in HSC maintenance. These observations provide new insights into the mechanisms for the control of HSC fate. Disclosures No relevant conflicts of interest to declare.

Download Full-text

A Novel MBT-Containing Protein, Hemp, Plays Essential Roles In Skeletal Formation and Hematopoietic Stem Cell Function.

Blood ◽

10.1182/blood.v116.21.1597.1597 ◽

2010 ◽

Vol 116 (21) ◽

pp. 1597-1597

Author(s):

Phyo Wai Htun ◽

Keiyo Takubo ◽

Hideaki Oda ◽

Feng Ma ◽

Kenjiro Kosaki ◽

...

Keyword(s):

Stem Cell ◽

Hematopoietic Stem Cell ◽

Cell Function ◽

Conflicts Of Interest ◽

Conditional Knockout ◽

Thoracic Vertebrae ◽

Wild Type ◽

Hematopoietic Stem ◽

Epigenetic Regulator ◽

Skeletal Formation

Abstract Abstract 1597 Hemp (hematopoietic expressed mammalian polycomb, also denoted as mbt-containing 1) gene was originally identified in the hematopoietic stem cell (HSC)-enriched fraction of the mouse fetal liver (FL). It encodes a protein containing a putative Cys2-Cys2 zinc-finger region, followed by four tandem malignant brain tumor (MBT) repeats, which is frequently observed in polycomb gene (PcG) proteins. The structural characteristics strongly suggest that Hemp functions as an epigenetic regulator, but its biological role remains unknown. To address this issue, we generated hemp-deficient (hemp–/–) mice. Hemp–/– mice died soon after birth. Although no abnormalities were detected in internal organs, skeletal analysis exhibited a variety of malformations. Severe deformities were observed in the thoracic cavity, strongly suggesting that hemp–/– mice died of respiratory failure. Interestingly, they showed malformations of cervical and thoracic vertebrae, which were different from typical homeotic transformations observed in PcG-deficient mice. These results suggest that Hemp governs downstream target genes in distinct manners from conventional PcG proteins. The hematopoietic analysis of hemp in the FL showed that hemp is preferentially expressed in CD150+LSK and CD150–LSK HSC fractions in the hematopoietic hierarchy. Hemp–/– FL contained a significantly reduced number of hematopoietic cells and produced fewer number of hematopoietic colonies as compared to hemp+/+ FL. The decreases correlated with reduced number of CD150+LSK HSCs in hemp–/– FL, which generated much fewer hematopoietic colonies in the HPP-CFC assay. In addition, the competitive repopulation assay exhibited that the hematopoietic reconstitution ability of hemp–/– FL CD150+LSK HSCs was significantly impaired. Moreover, microarray analysis revealed that expression levels of several genes, such as Prdm16, Sox4, and Erdr1 were altered in hemp–/– FL HSCs. Since hemp–/– mice died at neonate, the role of Hemp in adult hematopoiesis remains to be elucidated. To address this issue, we generated hemp conditional knockout (cKO) mice. Acquired deletion of Hemp in the hematopoietic tissues was successfully achieved by crossing hempflox/flox mice with MxCre mice and stimulating the compound mice with pIpC. Analysis of the hematopoietic tissues revealed that the cell numbers of Mac+Gr1– and Mac+Gr1+ fractions in the hemp cKO bone marrow (BM) were significantly increased and decreased, respectively, as compared to those of the wild-type BM. However, no apparent differences have so far been observed between hemp cKO and wild-type littermates in functional analyses, such as colony forming activity and competitive repopulation ability of the BM cells. Here, we report that a novel MBT-containing protein, Hemp, plays essential roles in skeletal formation and HSC function during embryogenesis and also contributes to myeloid differentiation in adult hematopoiesis. Since Hemp likely functions as an epigenetic regulator, further studies will be required to clarify whether and what methylated lysine residues Hemp interacts with through the MBT repeats, what kind of genes are direct targets of Hemp, and how Hemp exerts its biological activity. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

The cell fate determinant Scribble is required for maintenance of hematopoietic stem cell function

Leukemia ◽

10.1038/s41375-018-0025-0 ◽

2018 ◽

Vol 32 (5) ◽

pp. 1211-1221 ◽

Cited By ~ 7

Author(s):

Juliane Mohr ◽

Banaja P. Dash ◽

Tina M. Schnoeder ◽

Denise Wolleschak ◽

Carolin Herzog ◽

...

Keyword(s):

Stem Cell ◽

Cell Fate ◽

Hematopoietic Stem Cell ◽

Cell Function ◽

Hematopoietic Stem ◽

Cell Fate Determinant

Download Full-text

Characterization of Hematopoietic Stem Cell Function and Sensitivity in the Homologous Recombination Deficient Exonuclease1mut Mouse Model

Blood ◽

10.1182/blood.v118.21.1293.1293 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1293-1293

Author(s):

Amar Desai ◽

Yulan Qing ◽

Stanton L. Gerson

Keyword(s):

Dna Repair ◽

Stem Cell ◽

Homologous Recombination ◽

Hematopoietic Stem Cell ◽

Cell Function ◽

Conflicts Of Interest ◽

Strand Break ◽

Hematopoietic Stem ◽

Quiescent Hscs

Abstract Abstract 1293 Hematopoietic stem cell (HSC) maintenance is essential for sustained longevity and tissue function. The HSC population has lifelong self-renewing capabilities and gives rise to subsets of multipotent progenitor cells, and in turn a progeny of terminally differentiated mature cells consisting of all subtypes of the myeloid and lymphoid lineages. Long term reconstituting HSCs are necessary to replace these differentiated cells after losses caused by normal degradation or damage accumulation, with failure to replenish these stores being linked to a variety of human pathogeneses as well as aging phenotypes. HSC populations require functional DNA repair pathways in order to maintain their reconstitution capabilities but little is known about the pathways involved or the mechanism of regulation. While the majority of HSCs are quiescent at steady state, endogenous or exogenous stress can force these cells into proliferation, and previous evidence has suggested that the HSC reliance on DNA repair changes with this mobilization. Quiescent HSCs are believed to depend on non-homologous end joining (NHEJ) for repair but prior literature has shown that once forced into cycle, the DNA repair dependency shifts and is shared between homologous recombination (HR) and NHEJ. We use Exo1 deficiency as a model for homologous recombination loss in mice and demonstrate in vivo that HR is dispensable in quiescent HSCs. This is in contrast to loss of the complementary double strand break repair pathway NHEJ which has been shown to result in severe defects in HSC function. However when we force mobilize HSCs into cycle in vivo using the anti metabolite 5-fluorouracil we are able to demonstrate that the HR defects become detrimental to the animal as shown by increased cellular IR sensitivity and subsequent animal death. Additionally we use competitive repopulation studies to show that indeed the Exo1mut HSC population is more radiation sensitive after forced mobilization. This work begins to elucidate the consequences of the loss of homologous recombination in hematopoietic stem cells as well as the interplay between cell cycle status and DNA repair dependency. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

FLVCR is necessary for erythroid maturation, may contribute to platelet maturation, but is dispensable for normal hematopoietic stem cell function

Blood ◽

10.1182/blood-2012-10-465104 ◽

2013 ◽

Vol 122 (16) ◽

pp. 2903-2910 ◽

Cited By ~ 7

Author(s):

John C. H. Byon ◽

Jing Chen ◽

Raymond T. Doty ◽

Janis L. Abkowitz

Keyword(s):

Stem Cell ◽

Steady State ◽

Hematopoietic Stem Cell ◽

Cell Function ◽

Stress Conditions ◽

Hematopoietic Stem ◽

Platelet Counts ◽

Key Points ◽

Erythroid Maturation

Key Points FLVCR deletion causes proerythroblast apoptosis and lethal anemia but leads to increased megakaryocyte ploidy and platelet counts. Loss of FLVCR is dispensable for hematopoietic stem cell function during steady-state and stress conditions.

Download Full-text

Mitochondrial Activity Determines Hematopoietic Stem Cell Fate Decisions

Blood ◽

10.1182/blood.v124.21.4327.4327 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4327-4327

Author(s):

Nicola Vannini ◽

Mukul Girotra ◽

Olaia M. Naveiras ◽

Vasco Campos ◽

Evan Williams ◽

...

Keyword(s):

Stem Cell ◽

Cell Fate ◽

Hematopoietic Stem Cell ◽

Conflicts Of Interest ◽

Mitochondrial Activity ◽

Self Renewal ◽

Hematopoietic Stem ◽

Cell Fate Decisions

Abstract A tight control of hematopoietic stem cell (HSC) quiescence, self-renewal and differentiation is crucial for lifelong blood production. The mechanisms behind this control are still poorly understood. Here we show that mitochondrial activity determines HSC fate decisions. A low mitochondrial membrane potential (Δψm) predicts long-term multi-lineage blood reconstitution capability, as we show for freshly isolated and in vitro-cultured HSCs. However, as in vivo both quiescent and cycling HSCs have comparable Δψm distributions, a low Δψm is not per se related to quiescence but is also found in dividing cells. Indeed, using divisional tracking, we demonstrate that daughter HSCs with a low Δψm maintain stemness, whereas daughter cells with high Δψm have undergone differentiation. Strikingly, lowering the Δψm by chemical uncoupling of the electron transport chain leads to HSC self-renewal under culture conditions that normally induce rapid differentiation. Taken together, these data show that mitochondrial activity and fate choice are causally related in HSCs, and provides a novel method for identifying HSC potential after in vitro culture. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Steady-state and regenerative hematopoiesis occurs normally in mice in the absence of GDF11

Blood ◽

10.1182/blood.2019002066 ◽

2019 ◽

Vol 134 (20) ◽

pp. 1712-1716 ◽

Cited By ~ 4

Author(s):

Jill M. Goldstein ◽

Hilal Sengul ◽

Kathleen A. Messemer ◽

Marcos Fernández-Alfara ◽

Jessica C. Garbern ◽

...

Keyword(s):

Stem Cell ◽

Steady State ◽

Blood Cell ◽

Hematopoietic Stem Cell ◽

Red Blood Cell ◽

Cell Function ◽

Cell Formation ◽

Hematopoietic Stem ◽

Key Points ◽

Genetic Deletion

Key Points Genetic deletion of Gdf11 does not affect red blood cell formation during homeostasis or after transplant. Hematopoietic stem cell function is preserved in mice lacking Gdf11 expression within the blood lineage.

Download Full-text

TWIST1 preserves hematopoietic stem cell function via CACNA1B/Ca2+/mitochondria axis

Blood ◽

10.1182/blood.2020007489 ◽

2021 ◽

Author(s):

Nan Wang ◽

Jing Yin ◽

Na You ◽

Shangda Yang ◽

Dan Guo ◽

...

Keyword(s):

Steady State ◽

Calcium Channel ◽

Cell Fate ◽

Cell Function ◽

Myeloid Differentiation ◽

Hematopoietic Stem ◽

Hematopoietic Recovery ◽

Identify Transcription Factor ◽

Species Production ◽

First Time

Mitochondria of hematopoietic stem cells (HSCs) play crucial roles in regulating cell fate and preserving HSC functionality and survival. However, the mechanism underlying its regulation remains poorly understood. Here, we identify transcription factor TWIST1 as a novel regulator of HSC maintenance through modulating mitochondrial function. We demonstrate that Twist1 deletion results in a significantly decreased lymphoid-biased (Ly-biased) HSC frequency, markedly reduced HSC dormancy and self-renewal capacities, and skewed myeloid differentiation in steady-state hematopoiesis. Twist1-deficient HSCs are more compromised in tolerance of irradiation and 5-fluorouracil-induced stresses, and exhibit typical phenotypes of senescence. Mechanistically, Twist1 deletion induces transactivation of voltage-gated calcium channel (VGCC) Cacna1b which exhausts Ly-biased HSCs, impairs genotoxic hematopoietic recovery, and enhances mitochondrial calcium levels, metabolic activity, and reactive oxygen species production. Suppression of VGCC by a calcium channel blocker largely rescues the phenotypic and functional defects in Twist1-deleted HSCs under both steady-state and stress conditions. Collectively, our data, for the first time, characterize TWIST1 as a critical regulator of HSC function acting through the CACNA1B/Ca2+/mitochondria axis, and highlight the importance of Ca2+ in HSC maintenance. These observations provide new insights into the mechanisms for the control of HSC fate.

Download Full-text