Survival motor neuron (SMN) protein: role in neurite outgrowth and neuromuscular maturation during neuronal differentiation and development
Bibliographic record
Abstract
Childhood spinal muscular atrophy (SMA) is a common neuromuscular disorder caused by absent or deficient full-length survival motor neuron (SMN) protein. Clinical studies and animal models suggest that SMA is a developmental defect in neuromuscular interaction; however, the role of SMN in this process remains unclear. In the present study, we have determined the subcellular localization of SMN during retinoic-acid-induced neuronal differentiation of mouse embryonal teratocarcinoma P19 cells as well as in skeletal muscle during the critical period of neuromuscular maturation. We demonstrate, for the first time, SMN accumulation in growth-cone- and filopodia-like structures in both neuronal- and glial-like cells, identifying SMN as a new growth cone marker. Indeed, SMN was present at the leading edge of neurite outgrowths, suggesting that SMN may play a role in this process. In addition, SMN was detected as small dot-like particles within the cytoplasm of skeletal muscle during the first 2 weeks after birth, but their number peaked by P6. Intense SMN staining in neuromuscular junctions was observed throughout the entire postnatal period examined. Taken together, these results suggest that SMN may indeed fulfill neuronal- and muscle-specific functions, providing a more plausible mechanism explaining motor neuron degeneration and associated denervation atrophy of skeletal muscles in SMA. The primary SMA pathology most likely initiates in the peripheral axon--the result of deficient neurite outgrowth and/or neuromuscular maturation.
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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".