The Short Isoform of the Mouse Actin Adaptor Protein Synaptopodin-2 Activates Actin-Responsive Transcription Factors and Enhances Myoblast Fusion
Bibliographic record
Abstract
ABSTRACT Expression of synaptopodin-2 (SYNPO2), an actin cytoskeleton adaptor protein, is up-regulated following myoblast differentiation into myocytes and subsequently myotubes but no functional role in muscle development has been attributed to SYNPO2. We now show that of the three known mouse SYNPO2 isoforms, only the shortest isoform, SYNPO2As, is upregulated following differentiation of C2C12 myoblasts and primary mouse muscle satellite cells. Consistent with the differentiation-dependent expression pattern of these different isoforms, ectopic expression of SYNPO2As significantly increased myotube formation while the two large SYNPO2 isoforms (SYNPO2A or SYNPO2B) inhibited myocyte fusion into multinucleated myotubes. Irrespective of the fusion phenotype, all three isoforms enhanced migration of differentiating myoblasts. Knockdown studies using shRNA confirmed a pro-myogenic role for the short SYNPO2As isoform. Interestingly, SYNPO2As-transduced cells increased the transcript levels of late myogenic differentiation markers in the STARS (striated muscle activator of Rho signaling) and SRF (serum response factor) pathways that correlated with the enhanced fusion phenotype. These results identify the actin adaptor protein SYNPO2As as a new pro-myogenic factor that upregulates late myogenic differentiation markers and myotube formation.
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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".