Expression of the Ubiquitin Proteasome System in Neonatal Rat Gonocytes and Spermatogonia: Role in Gonocyte Differentiation1
Bibliographic record
Abstract
The ubiquitin proteasome system (UPS) consists of a cascade of enzymatic reactions leading to the ubiquitination of proteins, with consequent degradation or altered functions of the proteins. Alterations in UPS genes have been associated with male infertility, suggesting the role of UPS in spermatogenesis. In the present study, we questioned whether UPS is involved in extensive remodeling and functional changes occurring during the differentiation of neonatal testicular gonocytes to spermatogonia, a step critical for the establishment of the spermatogonial stem cell population. We found that addition of the proteasome inhibitor lactacystin to isolated gonocytes inhibited their retinoic acid-induced differentiation in a dose-dependent manner, blocking the induction of the spermatogonial gene markers Stra8 and Dazl. We then compared the UPS gene expression profiles of Postnatal Day (PND) 3 gonocytes and PND8 spermatogonia, using gene expression arrays and quantitative real-time PCR analyses. We identified 205 UPS genes, including 91 genes expressed at relatively high levels. From those, 28 genes were differentially expressed between gonocytes and spermatogonia. While ubiquitin-activating enzymes and ligases showed higher expression in gonocytes, most ubiquitin conjugating and deubiquitinating enzymes were expressed at higher levels in spermatogonia. Concomitant with the induction of spermatogonial gene markers, retinoic acid altered the expression of many UPS genes, suggesting that the UPS is remodeled during gonocyte differentiation. In conclusion, these studies identified novel ubiquitin-related genes in gonocytes and spermatogonia and revealed that proteasome function is involved in gonocyte differentiation. Considering the multiple roles of the UPS, it will be important to determine which UPS genes direct substrates to the proteasome and which are involved in proteasome-independent functions in gonocytes and to identify their target proteins.
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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".