Pigment Cells Model Lineage Regulation and Cell Clearance in the Planarian Schmidtea mediterranea
Bibliographic record
Abstract
Billions of cells are replaced in adult humans every day, yet many of the mechanisms of cell turnover are still poorly understood. In particular, the clearance of dead cells by engulfment, a processed termed “efferocytosis”, remains mysterious. In this thesis, I investigate cell turnover using the freshwater planarian Schmidtea mediterranea, a model organism that undergoes constant cell turnover as an adult and is capable of regenerating all of its organs and tissues. Using light-induced ablation of pigment cells, I first characterize the pigment lineage as a model for cell clearance. Next, I investigate the molecular mechanisms of efferocytosis in planarians, and find that the highly conserved engulfment receptor CED-1/Draper/MEGF10 is not conserved in planarians. Instead, I demonstrate that a related gene, megf6, and the extracellular matrix component hemicentin both function to restrict the stem cell compartment by maintaining the integrity of the basement membrane. Finally, by tracking planarian pigment cells following light exposure, I demonstrate that apoptotic cell corpses are transported to the gut, where they are engulfed by gut phagocytes and excreted from the animal. The planarian ortholog of the conserved engulfment gene CED-12/ELMO is required for efferocytosis of pigment cells by gut phagocytes. Together, these results provide the first insight into the mechanisms of cell clearance in planarians.
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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 | 0.001 | 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 | 0.001 | 0.001 |
| 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".