Β-Catenin-Tcf/Lef Signaling Promotes Steady State and Emergency Granulopoiesis through G-CSF Receptor Upregulation
Bibliographic record
Abstract
The canonical Wnt signaling pathway is mediated by interaction of β-catenin with the Tcf/Lef transcription factors and subsequent transcriptional activation of Wnt-target genes. This pathway acts as an essential regulator of differentiation and cell fate decisions in various tissues. In the hematopoietic system, the function of the pathway has been investigated mainly by genetic manipulation of β-catenin. However, this approach does not allow to discriminate between Tcf/Lef dependent or independent β-catenin activity. In order to specifically identify the function of β-catenin-Tcf/Lef signaling in hematopoietic cells, we employed a transgenic mouse model expressing a dominant negative form of the human TCF4 transcription factor (dnTCF4). dnTCF4, a truncated protein lacking the β-catenin binding domain, abrogates activation of Wnt target genes, even when β-catenin is stabilized and translocated into the nucleus. In our model, expression of dnTCF4 is activated from the Rosa26 locus only in cells producing Cre recombinase (driven by Vav-iCre). Importantly, all components of Wnt signaling, including endogenous Tcf/Lef proteins and β-catenin, are intact in Cre-expressing cells. We observed that dnTCF4 transgenic mice have reduced numbers of granulocytes together with accumulation of short-term hematopoietic stem cells (ST-HSC) and common myeloid progenitors (CMPs) in bone marrow. Accordingly, dnTCF4-expressing bone marrow consistently showed a block of granulocytic differentiation and retention of an immature phenotype in colony forming assays. This differentiation arrest and accumulation of immature cells was also observed when wild type cells were cultured in semi-solid medium in the presence of a cell-penetrating peptide that disrupts β-catenin-Tcf/Lef interaction. Together, these results indicate that disruption of the β-catenin/Tcf-Lef interaction, either by genetic manipulation or a drug based approach, alters steady-state hematopoiesis. To identify a mechanism through which β-catenin-Tcf/Lef signaling affects granulopoiesis, wild type and dnTCF4 expressing ST-HSCs were subjected to RNA sequencing. Several genes related to myeloid development were differentially expressed in dnTCF4 expressing cells, including downregulation of Csf3r, the gene encoding for the G-CSF receptor. Publicly available datasets from ChIP-seq experiments on human cell lines confirmed TCF4 enrichment in the distal promoter of the CSF3R gene, suggesting that CSF3R is directly regulated by canonical Wnt signaling. Using flow cytometry we verified reduced levels of G-CSF receptor on the cell surface of dnTCF4 progenitor cells, and attenuation of downstream Stat3 phosphorylation after G-CSF treatment. Finally, when grown in the presence of G-CSF, dnTCF4-expressing bone marrow cells showed impaired differentiation abilities and reduced granulocytic counts compared to wild type bone marrow cells. These results encouraged us to investigate the role of the β-catenin-Tcf/Lef signaling pathway during emergency granulopoiesis by challenging mice with lipopolysaccharide (LPS). Remarkably, dnTCF4 mice showed defects upon LPS stimulation, and completely failed to maintain and expand myeloid progenitor populations, a critical step during emergency granulopoiesis. Altogether, we showed that β-catenin-Tcf/Lef signaling axis is crucial for proper differentiation of myeloid progenitors into granulocytes in steady-state and emergency granulopoiesis. Mechanistically, we demonstrated that the β-catenin-Tcf/Lef interaction controls expression of genes involved in myeloid differentiation, and directly enhances expression of the G-CSF receptor, a crucial molecule for proper development of granulocytes. Disclosures No relevant conflicts of interest to declare.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".