Bone Morphogenic Protein (Smad)-Mediated Repression of Proopiomelanocortin Transcription by Interference with Pitx/Tpit Activity
Bibliographic record
Abstract
The signaling molecules bone morphogenic protein (BMP) 4 and 2 have been implicated in early organogenesis and cell differentiation of the pituitary. However, the use of different experimental paradigms has led to conflicting interpretations with regard to the action of these factors on differentiation of corticotroph cells and on expression of the proopiomelanocortin (POMC) gene. We have now directly assessed the action of BMP signaling on POMC expression and found that BMP4 represses POMC mRNA levels and promoter activity. This repression appears to be dependent on the classical BMP signaling pathway that involves the activin-like kinase 3/6 receptors and the Smad1/4 transcription factors. The repression is reversed by overexpression of the inhibitory Smads, Smad6 or Smad7. Collectively, the evidence suggests that autocrine BMP signaling may be acting upon AtT-20 cells to set the level of POMC expression. Upon BMP4 stimulation, activated phospho-Smad1 is recruited to the POMC promoter, where it apparently acts through interactions with the Pitx and Tpit transcription factors. It is postulated that these interactions interfere with the transcriptional activity of Pitx and/or Tpit, thus resulting in transcriptional repression.
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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".