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1.
Cells ; 12(23)2023 12 04.
Article in English | MEDLINE | ID: mdl-38067194

ABSTRACT

The bone marrow (BM) hematopoietic system (HS) gives rise to blood cells originating from hematopoietic stem cells (HSCs), including megakaryocytes (MKs) and red blood cells (erythrocytes; RBCs). Many steps of the cell-fate decision remain to be elucidated, being important for cancer treatment. To explore the role of Wnt/ß-catenin for MK and RBC differentiation, we activated ß-catenin signaling in platelet-derived growth factor b (Pdgfb)-expressing cells of the HS using a Cre-lox approach (Ctnnb1BM-GOF). FACS analysis revealed that Pdgfb is mainly expressed by megakaryocytic progenitors (MKPs), MKs and platelets. Recombination resulted in a lethal phenotype in mutants (Ctnnb1BM-GOFwt/fl, Ctnnb1BM-GOFfl/fl) 3 weeks after tamoxifen injection, showing an increase in MKs in the BM and spleen, but no pronounced anemia despite reduced erythrocyte counts. BM transplantation (BMT) of Ctnnb1BM-GOF BM into lethally irradiated wildtype recipients (BMT-Ctnnb1BM-GOF) confirmed the megakaryocytic, but not the lethal phenotype. CFU-MK assays in vitro with BM cells of Ctnnb1BM-GOF mice supported MK skewing at the expense of erythroid colonies. Molecularly, the runt-related transcription factor 1 (RUNX1) mRNA, known to suppress erythropoiesis, was upregulated in Ctnnb1BM-GOF BM cells. In conclusion, ß-catenin activation plays a key role in cell-fate decision favoring MK development at the expense of erythroid production.


Subject(s)
Megakaryocytes , Thrombopoiesis , beta Catenin , Animals , Mice , beta Catenin/metabolism , Megakaryocyte-Erythroid Progenitor Cells , Megakaryocytes/metabolism , Proto-Oncogene Proteins c-sis/metabolism , Thrombopoiesis/physiology
2.
Prog Neurobiol ; 199: 101937, 2021 04.
Article in English | MEDLINE | ID: mdl-33383106

ABSTRACT

Maintenance of the endothelial blood-brain-barrier (BBB) through Wnt/ß-catenin signalling is essential for neuronal function. The cells however, providing Wnt growth factors at the adult neurovascular unit (NVU) are poorly explored. Here we show by conditionally knocking out the evenness interrupted (Evi) gene in astrocytes (EviΔAC) that astrocytic Wnt release is crucial for BBB and NVU integrity. EviΔAC mice developed brain oedema and increased vascular tracer leakage. While brain vascularization and endothelial junctions were not altered in 10 and 40 week-old mice, endothelial caveolin(Cav)-1-mediated vesicle formation was increased in vivo and in vitro. Moreover, astrocytic end-feet were swollen, and aquaporin-4 distribution was disturbed, coinciding with decreased astrocytic Wnt activity. Vascular permeability correlated with increased neuronal activation by c-fos staining, indicative of altered neuronal function. Astrocyte-derived Wnts thus serve to maintain Wnt/ß-catenin activity in endothelia and in astrocytes, thereby controlling Cav-1 expression, vesicular abundance, and end-feet integrity at the NVU.


Subject(s)
Astrocytes , Blood-Brain Barrier , Animals , Astrocytes/metabolism , Blood-Brain Barrier/metabolism , Capillary Permeability , Mice , Wnt Proteins , beta Catenin/metabolism
3.
Mol Cancer ; 14: 17, 2015 Feb 03.
Article in English | MEDLINE | ID: mdl-25645196

ABSTRACT

BACKGROUND: The Wnt/beta-catenin and the Hedgehog (Hh) pathway interact in various cell types while eliciting opposing or synergistic cellular effects. Both pathways are known as exclusive drivers of two distinct molecular subtypes of medulloblastoma (MB). In sonic hedgehog (Shh)-driven MB, activation of Wnt signaling has been shown to suppress tumor growth by either beta-catenin-dependent or -independent inhibition of Shh signaling. However, mechanistic insight in how beta-catenin inhibits the Hh pathway is not known. FINDINGS: Here we show that beta-catenin stabilization by the glycogen synthase kinase 3 inhibitor lithium chloride (LiCl) reduced growth of primary hedgehog-driven MB tumor spheres from patched heterozygous mice (Ptch(+/-)) in vitro. LiCl treatment of MB spheres down-regulated the Hh target Gli1, whereas the repressive Gli3 protein (Gli3R) was increased. Mechanistically, we show by co-immunoprecipitation and proximity ligation assay that stabilized beta-catenin physically interacts with Gli1, leading to Gli1 sequestration and inhibition of its transcriptional activity. Reduction of Hh signaling upon LiCl stimulation resulted in reduced proliferation, sphere self renewal, a G2/M arrest and induction of a senescent-like state, indicated by p21 upregulation and by increased staining of senescence-associated beta-galactosidase (SA-betaGal). Moreover, LiCl treatment of subcutaneously transplanted MB cells significantly reduced tumor initiation defined as "tumor take". Although tumor progression was similar, LiCl-treated tumors showed decreased mitotic figures and phospho-histone H3 staining. CONCLUSION: We propose that beta-catenin stabilization increases its physical interaction with Gli1, leading to Gli1 degradation and inhibition of Hh signaling, thereby promoting tumor cell senescence and suppression of "tumor take" in mice.


Subject(s)
Cell Proliferation/genetics , Cerebellar Neoplasms/metabolism , Cerebellar Neoplasms/pathology , Kruppel-Like Transcription Factors/metabolism , Medulloblastoma/metabolism , Medulloblastoma/pathology , beta Catenin/metabolism , Animals , Cell Cycle Checkpoints/genetics , Cerebellar Neoplasms/genetics , Down-Regulation/genetics , G2 Phase Cell Cycle Checkpoints/genetics , Glycogen Synthase Kinase 3/metabolism , Hedgehog Proteins/metabolism , Medulloblastoma/genetics , Mice , Signal Transduction/genetics , Transcription, Genetic/genetics , Up-Regulation/genetics , Zinc Finger Protein GLI1
4.
J Exp Med ; 209(9): 1611-27, 2012 Aug 27.
Article in English | MEDLINE | ID: mdl-22908324

ABSTRACT

Endothelial Wnt/ß-catenin signaling is necessary for angiogenesis of the central nervous system and blood-brain barrier (BBB) differentiation, but its relevance for glioma vascularization is unknown. In this study, we show that doxycycline-dependent Wnt1 expression in subcutaneous and intracranial mouse glioma models induced endothelial Wnt/ß-catenin signaling and led to diminished tumor growth, reduced vascular density, and normalized vessels with increased mural cell attachment. These findings were corroborated in GL261 glioma cells intracranially transplanted in mice expressing dominant-active ß-catenin specifically in the endothelium. Enforced endothelial ß-catenin signaling restored BBB characteristics, whereas inhibition by Dkk1 (Dickkopf-1) had opposing effects. By overactivating the Wnt pathway, we induced the Wnt/ß-catenin-Dll4/Notch signaling cascade in tumor endothelia, blocking an angiogenic and favoring a quiescent vascular phenotype, indicated by induction of stalk cell genes. We show that ß-catenin transcriptional activity directly regulated endothelial expression of platelet-derived growth factor B (PDGF-B), leading to mural cell recruitment thereby contributing to vascular quiescence and barrier function. We propose that reinforced Wnt/ß-catenin signaling leads to inhibition of angiogenesis with normalized and less permeable vessels, which might prove to be a valuable therapeutic target for antiangiogenic and edema glioma therapy.


Subject(s)
Central Nervous System Neoplasms/blood supply , Central Nervous System Neoplasms/metabolism , Glioma/blood supply , Glioma/metabolism , Proto-Oncogene Proteins c-sis/metabolism , Wnt Signaling Pathway , beta Catenin/metabolism , Adaptor Proteins, Signal Transducing , Animals , Blood-Brain Barrier/metabolism , Brain Neoplasms/blood supply , Brain Neoplasms/genetics , Brain Neoplasms/pathology , Calcium-Binding Proteins , Central Nervous System Neoplasms/pathology , Endothelium, Vascular/metabolism , Female , Forkhead Transcription Factors/genetics , Glioma/pathology , Humans , Intercellular Signaling Peptides and Proteins/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Membrane Proteins/metabolism , Mice , Mice, Nude , Neoplasm Grading , Neovascularization, Pathologic , Proto-Oncogene Proteins c-sis/genetics , Wnt1 Protein/genetics , Wnt1 Protein/metabolism , Xenograft Model Antitumor Assays
5.
Am J Pathol ; 177(1): 404-14, 2010 07.
Article in English | MEDLINE | ID: mdl-20508033

ABSTRACT

Wnt/beta-catenin signaling has been implicated in taste papilla development; however, its role in epithelial maintenance and tumor progression in the adult tongue remains elusive. We show Wnt/beta-catenin pathway activation in reporter mice and by nuclear beta-catenin staining in the epithelium and taste papilla of adult mouse and human tongues. beta-Catenin activation in APC(min/+) mice, which carry a mutation in adenomatous poliposis coli (APC), up-regulates Sonic hedgehog (Shh) and Jagged-2 (JAG2) in the tongue epithelium without formation of squamous cell carcinoma (SCC). We demonstrate that Shh suppresses beta-catenin transcriptional activity in a signaling-dependent manner in vitro and in vivo. A similar regulation and function was observed for JAG2, suggesting that both pathways negatively regulate beta-catenin, thereby preventing SCC formation in the tongue. This was supported by reduced nuclear beta-catenin in the tongue epithelium of Patched(+/-) mice, exhibiting dominant active Shh signaling. At the invasive front of human tongue cancer, nuclear beta-catenin and Shh were increased, suggesting their participation in tumor progression. Interestingly, Shh but not JAG2 was able to reduce beta-catenin signaling in SCC cells, arguing for a partial loss of negative feedback on beta-catenin transcription in tongue cancer. We show for the first time that the putative Wnt/beta-catenin targets Shh and JAG2 control beta-catenin signaling in the adult tongue epithelium, a function that is partially lost in lingual SCC.


Subject(s)
Epithelium/metabolism , Hedgehog Proteins/metabolism , Signal Transduction/physiology , Tongue/anatomy & histology , beta Catenin/metabolism , Adult , Aged , Aged, 80 and over , Animals , Carcinoma, Squamous Cell/metabolism , Carcinoma, Squamous Cell/pathology , Cell Line , Female , Genes, Reporter , Hedgehog Proteins/genetics , Humans , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/metabolism , Jagged-2 Protein , Male , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Mice, Inbred C57BL , Middle Aged , Tongue Neoplasms/metabolism , Tongue Neoplasms/pathology , Transcriptional Activation , beta Catenin/genetics
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