Role Of ARC And Caspase-3 During Skeletal Muscle Cell Differentiation And Apoptosis
Bibliographic record
Abstract
Apoptosis is a highly regulated form of cell death that is essential during development and to maintain tissue homeostasis. Healthy skeletal muscle has a relatively apoptotic resistant phenotype which is critical for the preservation of this terminally differentiated tissue. Despite previous studies showing dramatic increases in caspase-3 activity during differentiation, skeletal muscle can retain its resistance to apoptosis. Apoptosis repressor with caspase recruitment domain (ARC) is a potent inhibitor of apoptosis by acting on both the death receptor and mitochondrial pathway. In addition, ARC is mainly expressed in post-mitotic tissues such as skeletal muscle, heart and neurons. PURPOSE: To examine ARC levels during myocyte differentiation in relation to caspase-3 activity, apoptosis and myosin expression. METHODS: L6 myocytes were plated on collagen coated dishes or glass cover slips and grown to approximately 70% confluence. Following this, cells were switched to a differentiation medium containing 2% horse serum in DMEM. Cells were isolated after 0, 3, 5 and 7 days of differentiation, and analyzed for ARC and myosin protein expression, as well as caspase-3 activity. Immunofluorescent microscopy was performed to evaluate myotube formation in conjunction with ARC and myosin expression. RESULTS: After 3, 5 and 7 days of differentiation, ARC levels increased 64%, 314% and 1814% respectively, while caspase-3 activity increased 42%, 84% and 285%, respectively. At day 0, myosin expression was undetectable, but increased exponentially between then and day 7. Immunofluorescent detection of myosin was only observed in myotubes which expressed ARC, whereas some myotubes that expressed ARC did not necessarily contain myosin. CONCLUSION: During myotube formation, ARC levels increase dramatically. This increase in ARC mirrors that of caspase-3 activity and myosin expression. Interestingly, no cells that contained myosin were without ARC protein. Taken together, these results suggest that ARC may be responsible for attenuating apoptosis in differentiating myocytes despite increases in caspase-3 activity. Furthermore, it appears that ARC expression preceded that of myosin, possibly establishing an anti-apoptotic environment within the cell which may be essential for muscle cell differentiation.
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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 | 0.001 |
| 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".