Bone Morphogenetic Protein 2 Signals via BMPR1A to Regulate Murine Follicle-Stimulating Hormone Beta Subunit Transcription1
Bibliographic record
Abstract
Follicle-stimulating hormone beta subunit (Fshb) expression is regulated by transforming growth factor beta superfamily ligands. Recently, we demonstrated that bone morphogenetic proteins (BMPs) stimulate Fshb transcription alone and in synergy with activins. Also, transfection of the BMP type II receptor (BMPR2) and constitutively active forms of the type I receptors (activin A receptor type I [ACVR1] or BMP receptor type IA [BMPR1A]) in immortalized gonadotroph cells (LbetaT2) stimulated murine Fshb promoter-reporter activity. A third type I receptor (BMP receptor type IB [BMPR1B]) is also expressed in LbetaT2 cells, but we did not previously assess its functional role. A point mutation in BMPR1B (Q249R) is associated with increased ovulation rates and elevated FSH levels in Booroola (FecB) sheep. Herein, we assessed whether BMPR1B can regulate Fshb transcription in LbetaT2 cells and whether its ability to do so is altered by the Q249R mutation. As with ACVR1 and BMPR1A, coexpression of BMPR1B with BMPR2 increased Fshb promoter-reporter activity in BMP2-dependent and BMP2-independent fashions. Unexpectedly, the BMPR1B-Q249R mutant was equivalent to the wild type in its ability to stimulate SMAD1/5 phosphorylation and Fshb transcription. Pharmacological inhibition of ACVR1, BMPR1A, and BMPR1B confirmed that one or more of these receptors are required for BMP2-stimulated SMAD1/5 phosphorylation and Fshb reporter activity. Knockdown of endogenous BMPR1A, but not ACVR1 or BMPR1B, significantly impaired the synergism of BMP2 with activin A. Collectively, these data suggest that BMPR1A is the preferred BMP2 type I receptor in LbetaT2 cells and that neither ACVR1 nor BMPR1B compensates for its loss. The specific mechanism(s) through which the Booroola FecB mutation alters BMPR1B function remains to be determined.
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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".