The Axenfeld-Rieger syndrome gene <i>FOXC1</i> contributes to left-right patterning
Bibliographic record
Abstract
Abstract Normal body situs requires precise spatiotemporal expression of the Nodal-Lefty-Pitx2 cascade in the lateral plate mesoderm. The ultimate output of this patterning is establishment of the left-right axis, which provides vital cues for correct organ formation and function. Mutations, deletions and duplications in PITX2 and FOXC1 lead to the rare genetic disease Axenfeld-Rieger syndrome (ARS). While situs defects are not a recognised feature of ARS, partial penetrance of cardiac septal defects and valve incompetence is observed; both of these congenital heart defects (CHDs) also occur following disruption of left-right patterning. Here we investigated whether foxc1 genes have a critical role in specifying organ situs. We demonstrate that CRISPR/Cas9 generated mutants for the zebrafish paralogs foxc1a and foxc1b recapitulate ARS phenotypes including craniofacial dysmorphism, hydrocephalus and intracranial haemorrhage. Furthermore, foxc1a -/- ; foxc1b -/- mutant animals display cardiac and gut situs defects. Modelling FOXC1 duplication by transient mRNA overexpression revealed that increased foxc1 dosage also results in organ situs defects. Analysis of known left-right patterning genes revealed a loss in expression of the NODAL antagonist lefty2 in the lateral plate mesoderm. Consistently, LEFTY2 mutations are known to cause human cardiac situs defects. Our data reveal a novel role for the forkhead-box transcription factor foxc1 in patterning of the left-right axis, and provide a plausible mechanism for the incidence of congenital heart defects in Axenfeld-Rieger syndrome patients. Author Summary This manuscript investigates the functional consequences of abrogating the activity of Foxc1 (Forkhead Box C1). We demonstrate that loss of zebrafish foxc1a and foxc1b results in phenotypes that resemble human patients with deletions in the FOXC1 locus. Notably, such phenotypes include alterations to the morphology of the heart. Investigations into the mechanisms underlying this phenotype led to the discovery that Foxc1 functions as a regulator of left-right patterning. Most components of left-right specification function normally in foxc1a/b mutants, but there is a pronounced loss of lefty2 , a known inhibitor of Nodal signaling. This supports a model in which Foxc1 regulates situs of the heart via the regulation of Lefty2.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".