Transient DNA Strand Breaks During Mouse and Human Spermiogenesis:New Insights in Stage Specificity and Link to Chromatin Remodeling1
Bibliographic record
Abstract
In the course of mammalian spermiogenesis, a unique chromatin remodeling process takes place within elongating and condensing spermatid nuclei. The histone-to-protamine exchange results in efficient packaging and increased stability of the paternal genome. Although not fully understood, this change in chromatin architecture must require a global but transient appearance of endogenous DNA strand breaks because most of the DNA supercoiling is eliminated in the mature sperm. To establish the extent of DNA strand breakage and the stage specificity at which these breaks are created and repaired, we performed a sensitive terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) assay to detect in situ DNA strand breaks on both mice and human testis cross sections. In the mouse, we established that DNA strand breaks are indeed detected in the whole population of elongating spermatids between stages IX and XI of the seminiferous epithelium cycle perfectly coincident with the chromatin remodeling as revealed by histone H4 hyperacetylation. Similarly, TUNEL analyses performed on human testis sections revealed an elevated and global increase in the levels of DNA strand breaks present in nuclei of round-shaped spermatids also coincident with chromatin remodeling. The demonstration of the global character of the transient DNA strand breaks in mammalian spermiogenesis suggests that deleterious consequences on genetic integrity of the male gamete may arise from any disturbance in the process. In addition, this investigation may shed some light on the origin of the low success rate that has been encountered so far with intracytoplasmic injection procedures making use of round spermatids in humans.
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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 | 0.001 | 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) | 0.002 | 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 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".