PTHrP(1‐34)‐mediated repression of the PHEX gene in osteoblastic cells involves the transcriptional repressor E4BP4
Bibliographic record
Abstract
PHosphate-regulating gene with homology to Endopeptidase on the X chromosome (PHEX) has been identified as the gene mutated in X-linked hypophosphatemia (XLH) syndrome, the most prevalent form of rickets in humans. The predominant expression of PHEX in bones and teeth, and the defective mineralization of these tissues in XLH patients indicate that PHEX is an important regulator of mineralization. Parathyroid hormone (PTH) and PTH-related protein (PTHrP) are known to regulate the expression of numerous genes in osteoblastic cells through activation of the protein kinase A pathway, including repression of PHEX. PTH also activates the transcriptional repressor E4BP4 through the same pathway, suggesting that PTH or PTHrP-mediated repression of PHEX expression could involve E4BP4. To evaluate this possibility, we treated UMR-106 osteoblastic cells with PTHrP(1-34), and used RT-PCR and immunoblotting to analyze PHEX and E4BP4 expression. E4BP4 mRNA and protein levels were rapidly increased in cells treated with PTHrP(1-34), with a concomitant decrease in PHEX expression. This downregulation of PHEX could be reproduced by overexpression of E4BP4. Moreover, PTHrP(1-34)-mediated PHEX repression was blocked when cells were transfected with a siRNA targeting E4BP4 mRNA. Finally, DNA pull-down and luciferase assays showed that two E4BP4 response elements located in PHEX promoter were functional. These results underline the important role of E4BP4 in osteoblastic cells and further define the repression mechanism of PHEX gene by PTHrP(1-34).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".