Regulated Expression and Role of c-Myb in the Cardiovascular-Directed Differentiation of Mouse Embryonic Stem Cells
Bibliographic record
Abstract
RATIONALE: c-myb null (knockout) embryonic stem cells (ESC) can differentiate into cardiomyocytes but not contractile smooth muscle cells (SMC) in embryoid bodies (EB). OBJECTIVE: To define the role of c-Myb in SMC differentiation from ESC. METHODS AND RESULTS: In wild-type (WT) EB, high c-Myb levels on days 0-2 of differentiation undergo ubiquitin-mediated proteosomal degradation on days 2.5-3, resurging on days 4-6, without changing c-myb mRNA levels. Activin-A and bone morphogenetic protein 4-induced cardiovascular progenitors were isolated by FACS for expression of vascular endothelial growth factor receptor (VEGFR)2 and platelet-derived growth factor receptor (PDGFR)α. By day 3.75, hematopoesis-capable VEGFR2+ cells were fewer, whereas cardiomyocyte-directed VEGFR2+/PDGFRα+ cells did not differ in abundance in knockout versus WT EB. Importantly, highest and lowest levels of c-Myb were observed in VEGFR2+ and VEGFR2+/PDGFRα+ cells, respectively. Proteosome inhibitor MG132 and lentiviruses enabling inducible expression or knockdown of c-myb were used to regulate c-Myb in WT and knockout EB. These experiments showed that c-Myb promotes expression of VEGFR2 over PDGFRα, with chromatin immunopreciptation and promoter-reporter assays defining specific c-Myb-responsive binding sites in the VEGFR2 promoter. Next, FACS-sorted VEGFR2+ cells expressed highest and lowest levels of SMC- and fibroblast-specific markers, respectively, at days 7-14 after retinoic acid (RA) as compared with VEGFR2+/PDGFRα+ cells. By contrast, VEGFR2+/PDGFRα+ cells cultured without RA beat spontaneously, like cardiomyocytes between days 7 and 14, and expressed cardiac troponin. Notably, RA was required to more fully differentiate SMC from VEGFR2+ cells and completely blocked differentiation of cardiomyocytes from VEGFR2+/PDGFRα+ cells. CONCLUSIONS: c-Myb is tightly regulated by proteosomal degradation during cardiovascular-directed differentiation of ESC, expanding early-stage VEGFR2+ progenitors capable of RA-responsive SMC formation.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 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".