Impaired meiotic DNA-damage repair and lack of crossing-over during spermatogenesis in BRCA1 full-length isoform deficient mice
Bibliographic record
Abstract
Breast tumor suppressor gene 1 (BRCA1) plays an essential role in maintaining genomic integrity. Here we show that mouse Brca1 is required for DNA-damage repair and crossing-over during spermatogenesis. Male Brca1(Delta11/Delta11)p53(+/-) mice that carried a homozygous deletion of Brca1 exon 11 and a p53 heterozygous mutation had significantly reduced testicular size and no spermatozoa in their seminiferous tubules. During spermatogenesis, homologous chromosomes from the mutant mice synapsed and advanced to the pachytene stage but failed to progress to the diplotene stage. Our analyses revealed that the Brca1 mutation affected cellular localization of several DNA damage-repair proteins. This included prolonged association of gammaH2AX with sites of DNA damage, reduced sex body formation, diminished Rad51 foci and absence of Mlh1 foci in the pachytene stage. Consequently, chromosomes from mutant mice did not form chiasmata, a point that connects exchanging homologous chromosomes. Brca1-mutant spermatocytes also exhibited decreased RNA expression levels of several genes that are involved in DNA-damage repair, including RuvB-like DNA helicase, XPB, p62 and TFIID. Of note, the premature termination of spermatogenesis at the pachytene stage was accompanied by increased apoptosis by both p53-dependent and p53-independent mechanisms. Thus, our study revealed an essential role of Brca1 in DNA-damage repair and crossing-over of homologous chromosomes during spermatogenesis.
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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) | 0.001 | 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 | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".