The Ribosome Biogenesis Factor Ltv1 Is Essential for Digestive Organ Development and Definitive Hematopoiesis in Zebrafish

Ribosome biogenesis is a fundamental activity in cells. Ribosomal dysfunction underlies a category of diseases called ribosomopathies in humans. The symptomatic characteristics of ribosomopathies often include abnormalities in craniofacial skeletons, digestive organs, and hematopoiesis. Consistently, disruptions of ribosome biogenesis in animals are deleterious to embryonic development with hypoplasia of digestive organs and/or impaired hematopoiesis. In this study, ltv1, a gene involved in the small ribosomal subunit assembly, was knocked out in zebrafish by clustered regularly interspaced short palindromic repeats (CRISPRs)/CRISPR associated protein 9 (Cas9) technology. The recessive lethal mutation resulted in disrupted ribosome biogenesis, and ltv1Δ14/Δ14 embryos displayed hypoplastic craniofacial cartilage, digestive organs, and hematopoiesis. In addition, we showed that the impaired cell proliferation, instead of apoptosis, led to the defects in exocrine pancreas and hematopoietic stem and progenitor cells (HSPCs) in ltv1Δ14/Δ14 embryos. It was reported that loss of function of genes associated with ribosome biogenesis often caused phenotypes in a P53-dependent manner. In ltv1Δ14/Δ14 embryos, both P53 protein level and the expression of p53 target genes, Δ113p53 and p21, were upregulated. However, knockdown of p53 failed to rescue the phenotypes in ltv1Δ14/Δ14 larvae. Taken together, our data demonstrate that LTV1 ribosome biogenesis factor (Ltv1) plays an essential role in digestive organs and hematopoiesis development in zebrafish in a P53-independent manner.

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Cohesin-mediated NF-κB signaling limits hematopoietic stem cell self-renewal in aging and inflammation

Journal of Experimental Medicine ◽

10.1084/jem.20181505 ◽

2018 ◽

Vol 216 (1) ◽

pp. 152-175 ◽

Cited By ~ 15

Author(s):

Zhiyang Chen ◽

Elias Moris Amro ◽

Friedrich Becker ◽

Martin Hölzer ◽

Seyed Mohammad Mahdi Rasa ◽

...

Keyword(s):

Stem Cell ◽

Target Genes ◽

Cell Function ◽

Chromatin Accessibility ◽

Dependent Manner ◽

Self Renewal ◽

Hematopoietic Stem ◽

Loss Of Self ◽

Stem And Progenitor Cells ◽

Normal Differentiation

Organism aging is characterized by increased inflammation and decreased stem cell function, yet the relationship between these factors remains incompletely understood. This study shows that aged hematopoietic stem and progenitor cells (HSPCs) exhibit increased ground-stage NF-κB activity, which enhances their responsiveness to undergo differentiation and loss of self-renewal in response to inflammation. The study identifies Rad21/cohesin as a critical mediator of NF-κB signaling, which increases chromatin accessibility in the vicinity of NF-κB target genes in response to inflammation. Rad21 is required for normal differentiation, but limits self-renewal of hematopoietic stem cells (HSCs) during aging and inflammation in an NF-κB–dependent manner. HSCs from aged mice fail to down-regulate Rad21/cohesin and inflammation/differentiation signals in the resolution phase of inflammation. Inhibition of cohesin/NF-κB reverts hypersensitivity of aged HSPCs to inflammation-induced differentiation and myeloid-biased HSCs with disrupted/reduced expression of Rad21/cohesin are increasingly selected during aging. Together, Rad21/cohesin-mediated NF-κB signaling limits HSPC function during aging and selects for cohesin-deficient HSCs with myeloid-skewed differentiation.

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Anti-tumor activity of SKLB-0322, a novel EZH2 covalent inhibitor, in ovarian cancer.

Journal of Clinical Oncology ◽

10.1200/jco.2021.39.15_suppl.e15052 ◽

2021 ◽

Vol 39 (15_suppl) ◽

pp. e15052-e15052

Author(s):

Yongxia Zhu ◽

Xinyi Chen ◽

Qiangsheng Zhang ◽

Lihong Shi ◽

Luoting Yu ◽

...

Keyword(s):

Ovarian Cancer ◽

Target Genes ◽

Competitive Inhibitor ◽

Negative Control ◽

Phase Cell ◽

Dependent Manner ◽

Independent Manner ◽

Western Blot Assay ◽

Concentration Dependent Manner ◽

Covalent Inhibitor

e15052 Background: Enhancer of Zeste Homolog 2 (EZH2) is the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2) that regulate downstream target genes expression, and then promotes tumor cell proliferation, metastasis and drug resistance. EZH2 also performs some functions in a PRC2-independent manner. Most of reported EZH2 inhibitors are S-adenosyle-methionine (SAM)-competitive inhibitor, and are less selective for EZH2 close homolog EZH1, which resulted in safety concerns and insufficient efficacy. To obtain irreversible EZH2 inhibitor, a novel covalent inhibitor was developed and characterized. Methods: SKLB-0322 and its derivatives were designed, synthesized and confirmed as EZH2 covalent inhibitor by us. The anti-tumor activities of SKLB-0322 were investigated by MTT assay, flow cytometry, and western blot assay. The reversible analog of SKLB-0322 (SKLB-0322’) was used as negative control. Results: SKLB-0322 inhibited EZH2 methyltransferase activity with nanomolar potency, while the inhibitory activities of SKLB-0322’ was reduced. The mass spectrometry (MS) analyses revealed that SKLB-0322 could efficiently forms a single modified covalent adduct. SKLB-0322 displayed noteworthy potency against ovarian cancer cell lines at low micromolar level and reduced the expression level of H3K27me3 in a concentration-dependent manner, which was about 5-fold more active than the reversible negative control SKLB-0322’. Besides, SKLB-0322 caused G2/M phase cell cycle arrest in A2780 and PA-1 cells. Furthermore, SKLB-0322 induced A2780 and PA-1 cell apoptosis in a time- and concentration- dependent manner. Conclusions: Our data clarified that SKLB-0322 is an EZH2 covalent inhibitor for ovarian cancer therapy which is worthy of further evaluation.

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Dectin-1 Stimulation of Hematopoietic Stem and Progenitor Cells Occurs In Vivo and Promotes Differentiation Toward Trained Macrophages via an Indirect Cell-Autonomous Mechanism

mBio ◽

10.1128/mbio.00781-20 ◽

2020 ◽

Vol 11 (3) ◽

Cited By ~ 1

Author(s):

Cristina Bono ◽

Alba Martínez ◽

Javier Megías ◽

Daniel Gozalbo ◽

Alberto Yáñez ◽

...

Keyword(s):

Bone Marrow ◽

Candida Albicans ◽

Progenitor Cells ◽

Recipient Mouse ◽

Dependent Manner ◽

Toll Like Receptor ◽

Hematopoietic Stem ◽

Content Type ◽

Stem And Progenitor Cells

ABSTRACT Toll-like receptor (TLR) agonists drive hematopoietic stem and progenitor cells (HSPCs) to differentiate along the myeloid lineage. In this study, we used an HSPC transplantation model to investigate the possible direct interaction of β-glucan and its receptor (dectin-1) on HSPCs in vivo. Purified HSPCs from bone marrow of B6Ly5.1 mice (CD45.1 alloantigen) were transplanted into dectin-1−/− mice (CD45.2 alloantigen), which were then injected with β-glucan (depleted zymosan). As recipient mouse cells do not recognize the dectin-1 agonist injected, interference by soluble mediators secreted by recipient cells is negligible. Transplanted HSPCs differentiated into macrophages in response to depleted zymosan in the spleens and bone marrow of recipient mice. Functionally, macrophages derived from HSPCs exposed to depleted zymosan in vivo produced higher levels of inflammatory cytokines (tumor necrosis factor alpha [TNF-α] and interleukin 6 [IL-6]). These results demonstrate that trained immune responses, already described for monocytes and macrophages, also take place in HSPCs. Using a similar in vivo model of HSPC transplantation, we demonstrated that inactivated yeasts of Candida albicans induce differentiation of HSPCs through a dectin-1- and MyD88-dependent pathway. Soluble factors produced following exposure of HSPCs to dectin-1 agonists acted in a paracrine manner to induce myeloid differentiation and to influence the function of macrophages derived from dectin-1-unresponsive or β-glucan-unexposed HSPCs. Finally, we demonstrated that an in vitro transient exposure of HSPCs to live C. albicans cells, prior to differentiation, is sufficient to induce a trained phenotype of the macrophages they produce in a dectin-1- and Toll-like receptor 2 (TLR2)-dependent manner. IMPORTANCE Invasive candidiasis is an increasingly frequent cause of serious and often fatal infections. Understanding host defense is essential to design novel therapeutic strategies to boost immune protection against Candida albicans. In this article, we delve into two new concepts that have arisen over the last years: (i) the delivery of myelopoiesis-inducing signals by microbial components directly sensed by hematopoietic stem and progenitor cells (HSPCs) and (ii) the concept of “trained innate immunity” that may also apply to HSPCs. We demonstrate that dectin-1 ligation in vivo activates HSPCs and induces their differentiation to trained macrophages by a cell-autonomous indirect mechanism. This points to new mechanisms by which pathogen detection by HSPCs may modulate hematopoiesis in real time to generate myeloid cells better prepared to deal with the infection. Manipulation of this process may help to boost the innate immune response during candidiasis.

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Maximal STAT5-Induced Proliferation and Self-Renewal at Intermediate STAT5 Activity Levels

Molecular and Cellular Biology ◽

10.1128/mcb.01025-08 ◽

2008 ◽

Vol 28 (21) ◽

pp. 6668-6680 ◽

Cited By ~ 61

Author(s):

Albertus T. J. Wierenga ◽

Edo Vellenga ◽

Jan Jacob Schuringa

Keyword(s):

Gene Expression ◽

Cell Fate ◽

Target Genes ◽

Expression Patterns ◽

Activity Levels ◽

Dependent Manner ◽

Self Renewal ◽

Hematopoietic Stem ◽

Cell Fate Decisions

ABSTRACT The level of transcription factor activity critically regulates cell fate decisions, such as hematopoietic stem cell (HSC) self-renewal and differentiation. We introduced STAT5A transcriptional activity into human HSCs/progenitor cells in a dose-dependent manner by overexpression of a tamoxifen-inducible STAT5A(1*6)-estrogen receptor fusion protein. Induction of STAT5A activity in CD34+ cells resulted in impaired myelopoiesis and induction of erythropoiesis, which was most pronounced at the highest STAT5A transactivation levels. In contrast, intermediate STAT5A activity levels resulted in the most pronounced proliferative advantage of CD34+ cells. This coincided with increased cobblestone area-forming cell and long-term-culture-initiating cell frequencies, which were predominantly elevated at intermediate STAT5A activity levels but not at high STAT5A levels. Self-renewal of progenitors was addressed by serial replating of CFU, and only progenitors containing intermediate STAT5A activity levels contained self-renewal capacity. By extensive gene expression profiling we could identify gene expression patterns of STAT5 target genes that predominantly associated with a self-renewal and long-term expansion phenotype versus those that identified a predominant differentiation phenotype.

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Potent Strategy for Treatmet of Gvhd and Autoimmune-Diseased by Infusion of Donor-Typed or Even Third-Party Tolerogenic Dendritic Cells by Psoralen Plus UVA Treatment

Blood ◽

10.1182/blood.v116.21.2777.2777 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2777-2777

Author(s):

Hideaki Maeba ◽

Ryosei Nishimura ◽

Rie Kuroda ◽

Raita Araki ◽

Shintaro Mase ◽

...

Keyword(s):

Dendritic Cells ◽

Neutralizing Antibodies ◽

Conflicts Of Interest ◽

Third Party ◽

Cell Contact ◽

Dependent Manner ◽

Independent Manner ◽

Hematopoietic Stem ◽

Tolerogenic Dendritic Cells ◽

Inhibition Of Alloreaction

Abstract Abstract 2777 We have reported that bone marrow derived dendritic cells with psoralen and UVA (PUVA-DCs) treatment acquired tolerogenicity in mice. With the purpose of potential application of PUVA-DCs in a clinical hematopoietic stem cell transplantations (HSCT) for graft-versus-host disease (GVHD), we showed that mixed lymphocyte reaction (MLR) was strongly inhibited when PUVA-DCs from the stimulator strain were added to the coculture (Stimulator (S): conventional DCs obtained from C57BL/6, Responder (R): splenocytes obtained from Balb/c, PUVA-DCs: C57BL/6). This suggests that infusion of host-typed PUVA-DCs would become a novel therapeutic approach for GVHD. However utilizing host-typed DCs has problems because of leukemic cell contaminations or low efficiency of cell culture from the patients receiving repetitive chemotherapy. Therefore next concern is whether PUVA-DCs generated from BM donor or even strangers would have same tolerogenicity as host-typed PUVA-DCs do. To test this, we performed MLR by adding PUVA-DC generated from the same strain of responder or third party strain (S: conventional DCs obtained from C57BL/6, R: splenocytes obtained from Balb/c, PUVA-DC: C57BL/6 or C3H). Proliferation was significantly inhibited when PUVA-DC generated from the stimulator strain were added to the coculture (p<0.05). Also significant inhibition was observed (p<0.05) when adding PUVA-DCs generated from third party, suggesting that PUVA-DCs have tolerogenicity in a MHC-independent manner. To clarify the mechanisms of how PUVA-DCs induce tolerogenicity, we performed MLR as mentioned above with the addition of neutralizing antibodies against IL-10 or TGF-beta1 or both, which have immunosuppressive effects. Neutralization of immunosuppressive cytokines had no effects on MLR. We then hypothesized that cell-to-cell contact between PUVA-DCs and alloreactive T-cells was needed to mediate the regulatory effect. To this end, we performed MLR using transwell to prevent cell-to cell contact. MLR was not suppressed when transwell was used, suggesting that PUVA-DCs dominantly regulates the alloreaction in a cell contact-dependent manner. This is the first report that PUVA-DCs prepared not only from host-typed but from donor-typed or even third-party could induce strong inhibition of alloreaction. Tolerogenic DCs prepared previously by several ways could not induce inhibition of alloreaction in vitro when these cells were prepared from donor-typed or third-party strains in mice. To apply tolerogenic dendritic cells for GVHD in clinical settings, it is necessary to obtain sufficient doses of PUVA-DCs with ease and safety guaranteed. Therefore in the future PUVA-DCs generated even from HLA mismatched iPS cells would be a promising approach. In conclusion, infusion of PUVA-DCs from donor-typed or even third party strain could have a potent strategy for treatment of lethal GVHD and autoimmune diseases. Disclosure: No relevant conflicts of interest to declare.

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MicroRNA Maestros of Hematopoiesis

Blood ◽

10.1182/blood.v116.21.sci-32.sci-32 ◽

2010 ◽

Vol 116 (21) ◽

pp. SCI-32-SCI-32

Author(s):

Kara A. Scheibner ◽

Diane Heiser ◽

Ian M Kaplan ◽

Wen-Chih Cheng ◽

MinJung Kim ◽

...

Keyword(s):

Target Genes ◽

Conflicts Of Interest ◽

Loss Of Function ◽

Hematopoietic Stem ◽

Cell Functions ◽

Human Cd34 ◽

Leukemia Treatment ◽

Normal Human ◽

Target Molecules ◽

And Function

Abstract Abstract SCI-32 MicroRNAs (miRs) inhibit stability and/or translation of mRNAs, usually by binding to specific sites in the 32′UTRs of their target mRNAs. Due to imperfect (i.e. partially complementary) miR:mRNA base-pairing, miRs can block translation of many mRNAs and serve as powerful master switches to regulate cell functions. Therefore, we profiled miR expression in human CD34+ hematopoietic stem-progenitor cells (HSPCs) and combined human HSPC miR expression, mRNA expression, and miR-mRNA target predictions to hypothesize that certain HSPC-expressed miRs (HE-miRs) target several mRNAs critical to hematopoiesis. On this informatic basis, we formulated a model of hematopoietic differentation in which many genes specifying hematopoietic differentiation are expressed by early HSPCs, but held in check by miRs [1]. In addition, we noted that the miR-23a cluster (i.e. adjacent, co-transcribed miR-23a, miR-27a, and miR-24-2) is not expressed or is expressed at levels >2-fold lower in 50% of acute myeloid leukemias and 80% of acute lymphoid leukemias tested compared to normal human HSPCs. ‘Re-expressing’ 1 or more of these miR-23a cluster members in leukemia cells promotes their apoptosis and reduces their proliferation, thus suggesting that these miRs have a tumor suppressive role. We have identified YWHAQ (14-3-3q) and several other 14-3-3 isoforms, which are anti-apoptotic and have established roles as oncogenes, as miR-23a cluster target molecules. Artificial manipulation of these HE-miRs and their target genes may lead to novel strategies for leukemia treatment and/or for expansion of normal HSPCs. Since the CD34+ HSPCs that we studied initially include rare stem cells and various stages of progenitors, we have expanded our miR profiling to more highly purified subsets of mouse HSPCs. Several previously described (e.g. miR-155 [1], miR-451 [2], miR-146 [3]) and novel HE-miRs are expressed differentially in lineages/stages of HSPCs, and their selective expression has been confirmed in human HSPC subsets. We are using cellular gain- and loss-of-function approaches with hematopoietic functional assays to determine whether these HE-miRs control human hematopoiesis. Understanding the effects of HE-miRs in hematopoiesis may elucidate hematopoietic and general stem cell biologic mechanisms. 1. Georgantas RW, 3rd, Hildreth R, Morisot S, Alder J, Liu CG, Heimfeld S, Calin GA, Croce CM, Civin CI. CD34+ hematopoietic stem-progenitor cell microRNA expression and function. A circuit diagram of differentiation control. Proc Natl Acad Sci USA. 2007;104:2750–2755. 2. Dore LC, Amigo JD, Dos Santos CO, Zhang Z, Gai X, Tobias JW, Yu D, Klein AM, Dorman C, Wu W, Hardison RC, Paw BH, Weiss MJ. A GATA-1-regulated microRNA locus essential for erythropoiesis. Proc Natl Acad Sci USA. 2008;105:3333–3338. 3. Starczynowski DT, Kuchenbauer F, Argiropoulos B, Sung S, Morin R, Muranyi A, Hirst M, Hogge D, Marra M, Wells RA, Buckstein R, Lam W, Humphries RK, Karsan A. Identification of miR-145 and miR-146a as mediators of the 5q- syndrome phenotype. Nat Med. 2010;16:49–58. Disclosures: No relevant conflicts of interest to declare.

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Inherited and Acquired RUNX1 Mutations in Hematologic Disorders

Blood ◽

10.1182/blood.v122.21.sci-5.sci-5 ◽

2013 ◽

Vol 122 (21) ◽

pp. SCI-5-SCI-5

Author(s):

Nancy A. Speck ◽

Xiongwei Cai ◽

Jingping Ge ◽

Philip J. Mason

Keyword(s):

Ribosomal Proteins ◽

Ribosome Biogenesis ◽

Conflicts Of Interest ◽

P53 Protein ◽

Lymphoblastic Leukemia ◽

Genotoxic Stress ◽

Myelogenous Leukemia ◽

Phenotypic Properties ◽

Hematopoietic Stem ◽

Protein Levels

Abstract RUNX1, a DNA binding subunit of core binding factors, is frequently mutated or rearranged in hematopoietic malignancies, including acute myelogenous leukemia (AML), chronic myelomonocytic leukemia, acute lymphoblastic leukemia, and myelodysplastic syndrome (MDS). Mutations in RUNX1 can be early events in leukemia, and generate a long-lived pre-leukemic stem cell (pre-LSC). Additionally, it has been reported that loss of function RUNX1 mutations are particularly frequent in radiation-associated MDS and AML, suggesting that pre-existing RUNX1 mutations in a pre-LSC may predispose patients to MDS/AML following DNA damage. Discussion will focus on the phenotypic properties of Runx1-deficient pre-LSCs, and the mechanisms by which Runx1 deficiency contributes to these phenotypes. Pan-hematopoietic Runx1 loss in mice causes a G1 to S-cell cycle delay and decreases apoptosis of pre-LSCs. Runx1-deficient pre-LSCs are radiation- and chemotherapy-resistant, and this correlates with decreased p53 protein levels and an attenuated p53 pathway response. Both p53 protein levels and apoptosis are increased following treatment with Nutlin-3. Runx1-deficient pre-LSCs are smaller, consume less glucose, and produce less ATP than normal hematopoietic stem cells (HSCs). Runx1-deficient stem and progenitor cells have lower overall ribosomal content and skewing in the relative amounts of rRNA and mRNA encoding ribosomal proteins. Analysis of AKT pathway components suggests that the decreased ribosome biogenesis is unlikely to be primarily caused by lower AKT signaling. We hypothesize that one or more of the above-mentioned properties (low p53 levels, decreased metabolism) render Runx1-deficient pre-LSCs less sensitive to genotoxic stress than normal HSCs, allowing a Runx1-deficient pre-LSC population to both perdure and expand in the bone marrow. Disclosures: No relevant conflicts of interest to declare.

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Inhibition of acute lethal pulmonary inflammation by the IDO–AhR pathway

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1615280114 ◽

2017 ◽

Vol 114 (29) ◽

pp. E5881-E5890 ◽

Cited By ~ 16

Author(s):

Soung-Min Lee ◽

Ha Young Park ◽

Young-Sill Suh ◽

Eun Hye Yoon ◽

Juyang Kim ◽

...

Keyword(s):

T Cells ◽

Epithelial Cells ◽

Pulmonary Inflammation ◽

Lung Parenchyma ◽

Lung Epithelial Cells ◽

Dependent Manner ◽

Independent Manner ◽

Hematopoietic Stem ◽

Lung Epithelial ◽

Ifn Γ

The lung is a prototypic organ that was evolved to reduce immunopathology during the immune response to potentially hazardous endogenous and exogenous antigens. In this study, we show that donor CD4+ T cells transiently induced expression of indoleamine 2,3-dioxygenase (IDO) in lung parenchyma in an IFN-γ–dependent manner early after allogeneic hematopoietic stem cell transplantation (HSCT). Abrogation of host IDO expression by deletion of the IDO gene or the IFN-γ gene in donor T cells or by FK506 treatment resulted in acute lethal pulmonary inflammation known as idiopathic pneumonia syndrome (IPS). Interestingly, IL-6 strongly induced IDO expression in an IFN-γ–independent manner when deacetylation of STAT3 was inhibited. Accordingly, a histone deacetylase inhibitor (HDACi) could reduce IPS in the state where IFN-γ expression was suppressed by FK506. Finally, l-kynurenine produced by lung epithelial cells and alveolar macrophages during IPS progression suppresses the inflammatory activities of lung epithelial cells and CD4+ T cells through the aryl hydrocarbon receptor pathway. Taken together, our results reveal that IDO is a critical regulator of acute pulmonary inflammation and that regulation of IDO expression by HDACi may be a therapeutic approach for IPS after HSCT.

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FDA-Approved Drug Screening for Compounds That Facilitate Hematopoietic Stem and Progenitor Cells (HSPCs) Expansion in Zebrafish

Cells ◽

10.3390/cells10082149 ◽

2021 ◽

Vol 10 (8) ◽

pp. 2149

Author(s):

Zhi Feng ◽

Chenyu Lin ◽

Limei Tu ◽

Ming Su ◽

Chunyu Song ◽

...

Keyword(s):

Progenitor Cells ◽

Ex Vivo ◽

Cord Blood Transplantation ◽

Drug Repurposing ◽

Suitable Model ◽

Dependent Manner ◽

Blood Disorders ◽

Hematopoietic Stem ◽

Blood Transplantation ◽

Stem And Progenitor Cells

Hematopoietic stem cells (HSCs) are a specialized subset of cells with self-renewal and multilineage differentiation potency, which are essential for their function in bone marrow or umbilical cord blood transplantation to treat blood disorders. Expanding the hematopoietic stem and progenitor cells (HSPCs) ex vivo is essential to understand the HSPCs-based therapies potency. Here, we established a screening system in zebrafish by adopting an FDA-approved drug library to identify candidates that could facilitate HSPC expansion. To date, we have screened 171 drugs of 7 categories, including antibacterial, antineoplastic, glucocorticoid, NSAIDS, vitamins, antidepressant, and antipsychotic drugs. We found 21 drugs that contributed to HSPCs expansion, 32 drugs’ administration caused HSPCs diminishment and 118 drugs’ treatment elicited no effect on HSPCs amplification. Among these drugs, we further investigated the vitamin drugs ergocalciferol and panthenol, taking advantage of their acceptability, limited side-effects, and easy delivery. These two drugs, in particular, efficiently expanded the HSPCs pool in a dose-dependent manner. Their application even mitigated the compromised hematopoiesis in an ikzf1−/− mutant. Taken together, our study implied that the larval zebrafish is a suitable model for drug repurposing of effective molecules (especially those already approved for clinical use) that can facilitate HSPCs expansion.

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TBX3 acts as tissue-specific component of the Wnt/β-catenin transcriptional complex

eLife ◽

10.7554/elife.58123 ◽

2020 ◽

Vol 9 ◽

Author(s):

Dario Zimmerli ◽

Costanza Borrelli ◽

Amaia Jauregi-Miguel ◽

Simon Söderholm ◽

Salome Brütsch ◽

...

Keyword(s):

Colorectal Cancer ◽

Cancer Cells ◽

Target Genes ◽

Regulatory Elements ◽

Dependent Manner ◽

Independent Manner ◽

Tissue Specific ◽

Colorectal Cancer Cells ◽

Transcriptional Complex

BCL9 and PYGO are β-catenin cofactors that enhance the transcription of Wnt target genes. They have been proposed as therapeutic targets to diminish Wnt signaling output in intestinal malignancies. Here we find that, in colorectal cancer cells and in developing mouse forelimbs, BCL9 proteins sustain the action of β-catenin in a largely PYGO-independent manner. Our genetic analyses implied that BCL9 necessitates other interaction partners in mediating its transcriptional output. We identified the transcription factor TBX3 as a candidate tissue-specific member of the β-catenin transcriptional complex. In developing forelimbs, both TBX3 and BCL9 occupy a large number of Wnt-responsive regulatory elements, genome-wide. Moreover, mutations in Bcl9 affect the expression of TBX3 targets in vivo, and modulation of TBX3 abundance impacts on Wnt target genes transcription in a β-catenin- and TCF/LEF-dependent manner. Finally, TBX3 overexpression exacerbates the metastatic potential of Wnt-dependent human colorectal cancer cells. Our work implicates TBX3 as context-dependent component of the Wnt/β-catenin-dependent transcriptional complex.

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