253 BOVINE OOCYTE CYCLIN B1 MRNA UNDERGOES CYTOPLASMICPOLYADENYLATION BEFORE THE BEGINNING OF IN VITRO MATURATION
Bibliographic record
Abstract
Maternal oocyte Cyclin B1 mRNA is known to be stored in the cytoplasm with a short poly(A) tail and be translationally dormant at GV stage. During maturation, Cyclin B1 poly(A) tail is elongated by a process called cytoplasmic polyadenylation and driven by A/U-rich cis-acting elements in its 3' untranslated region (UTR) known as cytoplasmic polyadenylation elements (CPEs). The objective of this study was to elucidate whether GV-stage bovine oocytes possess a stockpile of Cyclin B1 mRNA stored with a short a poly(A) tail that is elongated during maturation by CPE regulation. The mRNA poly(A) tail length was measured by Rapid Amplification of cDNA Ends Polyadenylation test (Race-PAT) on oocytes (n = 100) at the GV stage and 3, 5, 8, 10, 15, 20, and 25 h of in vitro maturation. The mRNA poly(A) tail length was also measured in triplicate (n = 20) on cold oocytes in GV (all manipulations on ice), warm oocytes in GV (ovaries transported in warm saline and manipulations on ice) and warm + 2 h 30 min oocytes in GV (oocytes left for an additional 2 h and 30 min at room temperature). To assess for variation in mRNA quantity, Cyclin B1 mRNA level was quantified by real-time PCR (Lightcycler, Roche, Indianapolis, IN, USA) in cold, warm or warm + 2 h 30 min GV oocytes (n = 20). The data were treated as factorial design, using treatment and type of RT as factors, and analysed by ANOVA (SAS Inst., Cary, NC, USA). Differences between means were checked using Tukey’s test. Oocyte Cyclin B1 transcript show two different 3' UTRs. These transcripts had the same ORF but different 3' UTR lengths because of an alternative nuclear polyadenylation element AAUAAA (NPE). The longest form (Cyclin B1L) that possessed a putative CPE (UUUUAAUAAA) fused to the last NPE was studied. In warm GV oocytes, Cyclin B1L had a long poly(A) tail of 100 adenosine residues, and this length did not change during in vitro maturation. Interestingly, we found that Cyclin B1L showed an expected short poly(A) tail when the ovaries and the oocytes were transported and manipulated on ice. We showed that Cyclin B1L mRNA is cytoplasmically polyadenylated (addition of 75 adenosine residues) between the time of collection and the end of manipulation. This lengthening is most probably sufficient to promote translation. There was no significant difference between the Cyclin B1 mRNA quantity of cold oocytes or warm oocytes when the oligo used for the reverse transcription was either dt or decamers. Therefore, we believe that the increase in poly(A) tail length is not the result of Cyclin B1L mRNA degradation in cold oocytes or de novo transcription in warm oocytes. We report for the first time that Cyclin B1L cytoplasmic polyadenylation is carried out well before the beginning of in vitro maturation in bovine oocytes when ovaries are transported from the slaughterhouse in warm saline. Studying the real early mechanisms leading to resumption of meiosis in bovine oocytes is complicated by Cyclin B1 polyadenylation occurring prior to in vitro maturation. (Supported by NSERC.)
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".