Phenotypic Divergence of <i>JAG1</i> ‐ and <i>NOTCH2</i> ‐Associated Alagille Syndrome & Disease‐Specific <i>NOTCH2</i> Variant Classification Guidelines
Bibliographic record
Abstract
BACKGROUND & AIMS: Alagille syndrome (ALGS) is a rare, autosomal dominant disorder with high phenotypic heterogeneity. Disease-causing variants are primarily identified in Jagged1 (JAG1), with fewer reported in NOTCH2. JAG1 variants cause disease through a mechanism of haploinsufficiency, but the mechanism for NOTCH2 variants is not completely understood, making classification of variants more challenging. Using a large, international patient cohort acquired through the Global ALagille Alliance (GALA) study, we sought to improve classification of NOTCH2 variants and study phenotypic differences between NOTCH2- and JAG1-related disease. METHODS: Clinical and molecular data from 952 individuals with ALGS in GALA were analysed and disease features compared between those with JAG1 (n = 902) and NOTCH2 (n = 34) variants. Previously reported and newly identified NOTCH2 variants were reinterpreted based on disease-specific modifications to the American College of Medical Genetics and Genomics (ACMG) guidelines. The Kaplan-Meier method was utilised to assess native liver survival (NLS) and overall survival (OS) and gene comparisons were made with the log-rank test. RESULTS: Thirty NOTCH2 variants, including 18 novel variants, were identified and classified in our GALA cohort. Phenotypic analyses revealed a significantly lower incidence of characteristic facies, posterior embryotoxon, cardiac involvement and butterfly vertebrae in individuals with NOTCH2 variants compared to those with JAG1 variants (p < 0.001). No differences were identified in NLS or OS. Review of 61 previously reported NOTCH2 variants resulted in the re-classification of 19 likely pathogenic or pathogenic to VOUS (31.1%) with less than half retaining their originally published classification (34.4%; n = 21). CONCLUSIONS: We report on a large global study on NOTCH2 genetics and phenotype, which increases the number of reported NOTCH2 variants by 30%. All variants were reclassified using current guidelines, and comparison of the JAG1 and NOTCH2 cohorts demonstrates clear phenotypic divergence between these groups. These data suggest that reliance on classical clinical phenotyping may miss patients with NOTCH2-related disease and supports an inclusive approach to genetic testing.
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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".