GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort
Bibliographic record
Abstract
Background GAA- FGF14 disease/spinocerebellar ataxia 27B is a recently described neurodegenerative disease caused by (GAA) ≥250 expansions in the fibroblast growth factor 14 ( FGF14 ) gene, but its phenotypic spectrum, pathogenic threshold, and evidence-based treatability remain to be established. We report on the frequency of FGF14 (GAA) ≥250 and (GAA) 200-249 expansions in a large cohort of patients with idiopathic downbeat nystagmus (DBN) and their response to 4-aminopyridine. Methods Retrospective cohort study of 170 patients with idiopathic DBN, comprising in-depth phenotyping and assessment of 4-aminopyridine treatment response, including re-analysis of placebo-controlled video-oculography treatment response data from a previous randomised double-blind 4-aminopyridine trial. Findings Frequency of FGF14 (GAA) ≥250 expansions was 48% (82/170) in patients with idiopathic DBN. Additional cerebellar ocular motor signs were observed in 100% (82/82) and cerebellar ataxia in 43% (35/82) of patients carrying an FGF14 (GAA) ≥250 expansion. FGF14 (GAA) 200-249 alleles were enriched in patients with DBN (12%; 20/170) compared to controls (0.87%; 19/2191; OR, 15.20; 95% CI, 7.52–30.80; p < 0.0001). The phenotype of patients carrying a (GAA) 200-249 allele closely mirrored that of patients carrying a (GAA) ≥250 allele. Patients carrying a (GAA) ≥250 or a (GAA) 200-249 allele had a significantly greater clinician-reported (80%, 33/41 vs 31%, 5/16; RR, 2.58; 95% CI, 1.23–5.41; Fisher's exact test , p = 0.0011) and self-reported (59%, 32/54 vs 11%, 2/19; RR, 5.63; 95% CI, 1.49–21.27; Fisher's exact test , p = 0.00033) response to 4-aminopyridine treatment compared to patients carrying a (GAA) <200 allele. Placebo-controlled video-oculography data, available for four patients carrying an FGF14 (GAA) ≥250 expansion, showed a significant decrease in slow phase velocity of DBN with 4-aminopyridine, but not placebo. Interpretation This study confirms that FGF14 GAA expansions are a frequent cause of DBN syndromes. It provides preliminary evidence that (GAA) 200-249 alleles might be pathogenic. Finally, it provides large real-world and preliminary piloting placebo-controlled evidence for the efficacy of 4-aminopyridine in GAA- FGF14 disease. Funding This work was supported by the Clinician Scientist program "PRECISE.net" funded by the Else Kröner-Fresenius-Stiftung (to CW, AT, and MSy), the grant 779257 "Solve-RD" from the European's Union Horizon 2020 research and innovation program (to MSy), and the grant 01EO 1401 by the German Federal Ministry of Education and Research (BMBF) (to MSt). This work was also supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) N° 441409627, as part of the PROSPAX consortium under the frame of EJP RD, the European Joint Programme on Rare Diseases, under the EJP RD COFUND-EJP N° 825575 (to MSy, BB and—as associated partner—SZ), the NIH National Institute of Neurological Disorders and Stroke (grant 2R01NS072248-11A1 to SZ), the Fondation Groupe Monaco (to BB), and the Montreal General Hospital Foundation (grant PT79418 to BB). The Care4Rare Canada Consortium is funded in part by Genome Canada and the Ontario Genomics Institute (OGI-147 to KMB), the Canadian Institutes of Health Research (CIHR GP1-155867 to KMB), Ontario Research Foundation, Genome Quebec, and the Children's Hospital of Eastern Ontario Foundation. The funders had no role in the conduct of this study.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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".