91 INHIBITION OF TELOMERASE REVERSE TRANSCRIPTASE (TERT) INDUCES EMBRYO ARREST IN BOVINE PRE-IMPLANTATION EMBRYOS
Bibliographic record
Abstract
Previous studies from our laboratory have detected telomerase activity in embryos from all stages of early bovine development. However, the regulation of the telomerase subunits remains poorly understood. The objective of this study was to characterize the expression and function of the bovine telomerase reverse transcriptase (bTERT) subunit during bovine pre-implantation embryogenesis. Using RT-PCR and immunofluorescence staining procedures (n = 20 embryos at timed stages of development; r = 3), we demonstrate that mRNA transcripts and protein for bTERT were detected in pre-implantation bovine embryos from 1-cell to the blastocyst stage. The specificity of bTERT PCR products was confirmed by sequencing and exhibited 94% sequence homology to the human hTERT cDNA sequence. In immature oocytes, the bTERT protein was localized within the germinal vesicle and after 18 to 20 h of in vitro maturation, bTERT was observed as doublet foci co-localized with the condensed metaphase II meiotic stage chromosomes. Post-fertilization, the expression of bTERT was observed within the pronuclei. Through the initial cleavage stages, the expression of bTERT was variable, with some blastomeres showing punctate staining, whereas others exhibited a more-uniform staining pattern within the cytoplasm. By the 8- to 16-cell stage, the embryos demonstrated a peri-nuclear presence of bTERT. However, while in morulae and blastocysts, bTERT was localized to the nuclei as demonstrated by co-localization with 4',6-diamidino-2-phenylindole (DAPI) staining. Treatment of zygotes with Telomerase Inhibitor III (telomere mimic that inhibits telomerase activity; Calbiochem, San Diego, CA) significantly induced embryos to permanently arrest in a senescence-like state at the 2- to 4-cell cleavage stage compared with nontreated controls. These arrested embryos showed abnormal nuclear phenotypes (elongated chromosomes, anaphase bridging) and phosphorylated histone ?-H2A.X foci suggesting a critical role(s) of TERT in chromosomal segregation and telomere integrity in early embryos. The translocation of bTERT protein from the cytoplasm to the nucleus in morulae supports the known telomere elongation event, whereas low levels of TERT at the 2- to 4-cell stage are associated with the previously documented state of permanent embryo arrest. Future studies would be directed toward understanding the relationship between TERT expression, telomere dysfunction, and permanent embryo arrest. Operating grants from the Canadian Institutes of Health Research (CIHR) to D.H.B. and W.A.K. supported this research.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".