Regulation of mitochondrial DNA accumulation during oocyte growth and meiotic maturation in the mouse
Bibliographic record
Abstract
Oocytes accumulate an enormous quantity of mitochondrial (mt) DNA, and an insufficient amount of mtDNA may underlie some cases of poor oocyte quality leading to infertility. Little is known, however, about the mechanisms that govern the timing and regulation of mtDNA accumulation during oogenesis. We report, through analysis of the mtDNA content of individual oocytes of the mouse, that mtDNA accumulates steadily during oocyte growth to reach a value of ~175 000 copies per cell. MtDNA content ceases to increase once oocytes reach full size and remains unchanged during meiotic maturation. To test whether mtDNA accumulation depends on oocyte growth, we inhibited growth in vitro in two ways - by exposing complexes comprising partially grown oocytes enclosed by granulosa cells to a chemical inhibitor of the phosphatidylinositol-3-kinase signaling pathway and by removing the surrounding granulosa cells from partially grown oocytes. Under both conditions, the oocytes fail to grow, but mtDNA accumulation is unaffected, indicating that the two processes can be mechanistically uncoupled. Quantitative analysis of the mRNAs encoding proteins required for mtDNA replication revealed that Polg (Polga) (polymerase-γ, α-subunit), Polg2 (Polgb), and Tfam (transcription factor A, mitochondrial) increase during oocyte growth but then decrease after fully grown oocytes become transcriptionally silent as indicated by the non-surrounded nucleolus-to-surrounded nucleolus transition. Thus, there is a correlation between the decline in the quantity of mRNAs encoding mtDNA replication factors in fully grown oocytes and the arrest of mtDNA accumulation in these cells, suggesting that the two events may be causally linked.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".