Insight from Frogs: Sonic Hedgehog Gene Expression and a Re‐evaluation of the Vertebrate Odontogenic Band
Bibliographic record
Abstract
While the identification of conserved processes across multiple taxa leads to an understanding of fundamental developmental mechanisms, the ways in which different animals fail to conform to common developmental processes can elucidate how evolution modifies development to result in the vast array of morphologies seen today-the developmental mechanisms that lead to anatomical variation. Odontogenesis-how teeth are initiated and formed-is well suited to the examination of both developmental conservation and phenotypic diversity. We suggest here that the study of early tooth development, the period of odontogenic band development, reveals departures from conserved mechanisms that question the role of players in the developmental process. In the earliest stages of odontogenesis, Sonic hedgehog (Shh) gene expression is interpreted as critical evidence of tooth initiation prior to any histological indication. However, a detailed examination of studies of tooth development across a wide range of taxa reveals that several vertebrate species fail to conform to the expectations of the Shh Consensus Model, calling for a reconsideration of the assumed causality of epithelial Shh in tooth initiation. We present new Shh gene expression data for an amphibian, the frog Silurana (Xenopus) tropicalis. In these animals, craniofacial and odontogenic developmental processes are more disjunct, and thereby provide a natural test of the hypothesis that Shh is immediately required for subsequent tooth development. Our results suggest that Shh expression may actually be related to the formation of the mouth rather than a required precursor to subsequent tooth formation. Anat Rec, 299:1099-1109, 2016. © 2016 Wiley Periodicals, Inc.
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How this classification was reachedexpand
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 | 0.000 | 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) | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".