Gene expression reveals unique skeletal patterning in the limb of the direct‐developing frog, <i>Eleutherodactylus coqui</i>
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Bibliographic record
Abstract
The growing field of skeletal developmental biology provides new molecular markers for the cellular precursors of cartilage and bone. These markers enable resolution of early features of skeletal development that are otherwise undetectable through conventional staining techniques. This study investigates mRNA distributions of skeletal regulators runx2 and sox9 along with the cartilage-dominant collagen 2(alpha)1 (col2a1) in embryonic limbs of the direct-developing anuran, Eleutherodactylus coqui. To date, distributions of these genes in the limb have only been examined in studies of the two primary amniote models, mouse and chicken. In E. coqui, expression of transcription factors runx2 and sox9 precedes that of col2a1 by 0.5-1 developmental stage (approximately 12-24 h). Limb buds of E. coqui contain unique distal populations of both runx2- and sox9-expressing cells, which appear before formation of the primary limb axis and do not express col2a1. The subsequent distribution of col2a1 reveals a primary limb axis similar to that described for Xenopus laevis. Precocious expression of both runx2 and sox9 in the distal limb bud represents a departure from the conserved pattern of proximodistal formation of the limb skeleton that is central to prevailing models of vertebrate limb morphogenesis. Additionally, runx2 is expressed in the early joint capsule perichondria of the autopod and in the perichondria of long bones well before periosteum formation. The respective distributions of sox9 and col2a1 do not reveal the joint perichondria but instead are expressed in the fibrocartilage that fills each presumptive joint capsule. These distinct patterns of runx2- and sox9-expressing cells reveal precursors of chondrocyte and osteoblast lineages well before the appearance of mature cartilage and bone.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.000 | 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 it