Expression of MTPG-24, a Peptide Derived from a Protein Regulating Dynamic Changes in Cortical Actin, Induces Endomitotic Replication in Megakaryocytic Cells.
Bibliographic record
Abstract
Abstract Prior to the fragmentation of their cytoplasm leading to platelet formation, differentiating megakaryocytes (MKs) increase their ploidy and cellular volume by undergoing repeated rounds of DNA replication without concomitant cell division, a process known as endomitosis. There is now accumulating evidence that endomitotic MKs develop as a result of aberrant regulation of the cleavage furrow formation, the site where dynamic changes in actin, myosin and membrane structure mediate the process of cytokinesis during animal cell division. Here we report that transfection of human megakaryocytic cell lines with vectors expressing a 24mer-peptide (MTPG-24) resulted in remarkable changes in morphology, resulting in cells with the appearance of mature polyploid megakaryocytes. MTPG-24 is derived from a protein involved in regulating actin-based structures and motility which possesses a putative site for PKA phosphorylation. Despite its hydrophilic primary structure, MTPG-24 fused to a fluorescent tag was detected closely associated to the plasma membrane where it accumulated in a punctuate pattern, in addition to co-localizing with a Golgi marker. Interestingly, in each recombinant clone, cells with different ploidy levels developed among normally dividing ones, suggesting that transit from a mitotic cycle to an endomitotic cycle seemed to only occur in cells having completed a given number of cell cycles. These effects were obtained independently of the nature of the tag fused to the peptide (Hemagglutinin, Orange protein, GFP) but were not observed with a control peptide in which the amino acids of MTPG-24 were disposed in an arbitrarily sequence. Because it possibly interferes with some effector molecules required for cleavage furrow membrane assembly in late anaphase, MTPG-24 provides thus a new tool for understanding the molecular basis of endomitosis. Furthermore, since there is a correlation between DNA content and the numbers of platelets released by MK, we are currently testing whether this peptide could be used to increase the ploidy level of CD34+ human cord blood-derived MKs which have a low propensity to become highly polyploid.
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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 | 0.000 |
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 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".