Rapid and repeated evolution of myosin copy number in threespine stickleback
Bibliographic record
Abstract
SUMMARY Copy number variants at genomic loci evolve at a high rate, are linked to many different diseases, and play a role in adaptive evolution in humans and other organisms. Here we show that stickleback fish from freshwater environments have rapidly and repeatedly evolved an expanded number of copies of a gene family involved in muscle development, Myosin Heavy Chain 3 Cluster C ( MYH3C ), compared to marine populations. Differences in copy number between marine and freshwater fish are maintained even in the presence of gene flow, suggesting that MYH3C changes represent adaptive divergence between ecotypes. Copy number expansion occurs by tandem duplication of MYH3C coding and regulatory regions on the stickleback sex chromosome. We identify a muscle regulatory enhancer within the expanded MYH3C region and show that elevated copy number is associated with developmental and tissue-specific increases in corresponding mRNA expression levels in skeletal muscle. Common MYH3C clusters include 3-, 4-, 5-, and 6-copy variants that likely evolved through a combination of microhomology-mediated break repair and non-allelic homologous recombination. Our results provide a new example of copy number changes in a wild species and identify CNVs as potential “hotspots” of repeated adaptive evolution.
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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 | 0.001 | 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".