Aggregation Chimeras: Combining ES Cells, Diploid and Tetraploid Embryos
Bibliographic record
Abstract
In recent years, chimeras have been providing a powerful way to study mouse development ( 1 ) in combination with invention and improvement of other techniques and materials, including embryonic stem (ES) cells ( 2 ) and tetraploid embryos ( 3 , 4 ). ES cells are pluripotent cell lines derived from late blastocyst-stage embryos, which are capable of differentiating into all derivatives of the primitive ectoderm ( see Fig. 1 ) when aggregated with or injected into diploid embryos ( 5 ). In contrast, tetraploid embryos, which can be made by electrofusing two cell-stage diploid embryos ( 3 , 6 , 7 ), have been found to contribute preferentially to most of the extraembryonic cell lineages, i.e., the trophoblast (trophectoderm derivatives) and primitive endoderm derivatives ( see Fig. 1 ) when aggregated with diploid embryos ( 3 – 8 ). Interestingly, ES cells show a deficiency in extraembryonic lineages, therefore these cells and tetraploid embryo derived cells have a complementary distribution in chimeras made between them. In such chimeras, the embryo proper, the amnion, the yolk sac mesoderm, the allantois and the chorionic mesoderm-derived part of the placenta are completely ES cell-derived, whereas the yolk sac endoderm and the trophoblast cell lineages are tetraploid embryo derived ( 3 , 7 , 9 ). It is certain that the ES cell⇔tetraploid embryo aggregates have an attractive feature in that they are a reliable and simple way of producing completely ES cell-derived embryos from developmentally competent cell lines ( 2 – 10 ). This feature is promoting their application in an increasing number of studies. Schematic representation of the various embryo proper and extraembryonic lineages and their relation to each other. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| 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".