Spatial positioning of preimplantation mouse embryo blastomeres is regulated by mTORC1 and 7mG-cap dependent translation at the 8- to 16-cell transition
Bibliographic record
Abstract
ABSTRACT Preimplantation stages of mouse embryo development involve temporal and spatial specification and segregation of three late blastocyst cell lineages; trophectoderm (TE), primitive endoderm (PrE) and epiblast (EPI). Spatial separation of the outer TE lineage from the two inner cell mass (ICM) lineages (PrE and EPI) starts with the 8- to 16-cell transition and concludes following transit through the 16- to 32-cell stages. This results in an early blastocyst ICM derived from descendants of primary founding inner cells and a secondarily contributed population, of which subsequent relative EPI versus PrE potencies are subject to debate. Here, we report generation of primary but not the secondary ICM populations is highly dependent on temporally discreet activation of the mammalian target of Rapamycin (mTOR – specifically mTORC1) during M-phase entry at the 8-cell stage. This role is mediated via regulation of the 7-methylguanosine-(7mG) cap binding initiation complex (EIF4F), linked to translation of a subset of key mRNAs containing 5’ UTR terminal oligopyrimidine (TOP-) or TOP-like sequence motifs; as knockdown of identified TOP-like motif containing transcripts also impairs generation of 16-cell stage primary ICM founders. However, mTOR inhibition induced ICM cell number deficits at the early blastocyst stage can be compensated by the late blastocyst stage, in the absence of inhibition. This compensation is likely initiated at the 32-cell stage when supernumerary outer cells in mTOR-inhibited embryos exhibit molecular characteristics of inner cells. Collectively, the data identify a novel mechanism specifically governing initial spatial segregation of blastomeres in the mouse embryo, that is distinct from those directing subsequent inner cell formation and contributes to germane segregation of late blastocyst lineages.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".