A Novel Mechanistic Spectrum Underlies Glaucoma-Associated Chromosome 6p25 Copy Number Variations
Bibliographic record
Abstract
PurposeDetermining the causation of chromosome 6p25 copy number variations (CNVs) that underlie Axenfeld Rieger Syndrome (ARS), is expected to elucidate the genesis of an important pediatric glaucoma subtype, and facilitate molecular diagnostic testing. MethodsArray comparative genome hybridization was undertaken to localize the breakpoints in the largest ARS pedigree collection worldwide with 6p25 CNVs, prior to long range PCR. Some 240 primer pairs were used to amplify breakpoint-spanning junctional fragments with sequencing and in silico analyses employed to determine the genomic architecture of the regions flanking the breakpoints. ResultsThe 6p25 CNVs' extent were determined at the base pair level in all pedigrees [duplication: # 1-2: 492kb, # 3-6: 480kb, #7: 512kb; deletion: #8: 1216kb and #9: 30kb; ring chromosome #10: 2257kb deletion]. Haplotype analysis confirmed the existence of founder effects with just five unique segmental rearrangements (3 duplications, 2 deletions) identified. In all segmental duplications, a head to tail orientation of duplicons with insertion or deletion of nucleotides were found. In segmental deletion pedigree #8, an unusually large (367bp) novel insert was identified with no significant homology to any known genomic sequences. The forkhead box transcription factor, FOXC1, was the only gene to be encompassed in all 6p25 CNVs. A mechanistic spectrum involving non-allelic homologous recombination (NAHR) and non-homologous end joining (NHEJ), was observed in all pedigrees, with evidence of a novel mechanism in one pedigree. ConclusionsCharacterization of the 6p25 CNVs revealed constant involvement of FOXC1. Their non-recurrent nature, with differing degrees of NAHR & NHEJ in an autosome, extends the range and complexity associated with chromosomal rearrangements. The novel genomic architecture observed in pedigree #8 is compatible with a DNA replication based mechanism that broadens the means by which CNVs are known to occur. From the clinical perspective, identification of a small number of common rearrangements that underlie a substantial portion of ARS, facilitates molecular diagnostic testing with scope for genotype-phenotype correlation and predicting clinical outcome.
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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 | 0.001 |
| 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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 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".