PubMed · 14958104
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A FIGUEIRA. 1952. [Aniridia].. https://pubmed.ncbi.nlm.nih.gov/14958104/
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IMPORTANCE: Approximately 5% to 10% of individuals with classic aniridia do not receive a molecular diagnosis after clinical testing for variants in PAX6 and its downstream regulatory region. OBJECTIVE: To apply optical genome mapping (OGM) and long-read whole-genome sequencing (lrWGS) to diagnose an individual with unexplained classic aniridia. DESIGN, SETTING, AND PARTICIPANTS: High-quality DNA was extracted from the blood of a 16-year-old male patient with classic aniridia and prior negative clinical test results that included sequencing and copy number analysis of PAX6 exons and downstream regulatory region as well as genomic analysis via short-read whole-genome sequencing (srWGS) and analyzed using OGM and lrWGS. All analyses were performed in a research laboratory in Wisconsin from January 2019 to September 2025. INTERVENTIONS: OGM and lrWGS. MAIN OUTCOMES AND MEASURES: Identification of a structural variant disrupting PAX6 expression in an individual with classic aniridia, following negative prior testing including srWGS. RESULTS: OGM identified a 55-kb deletion on 11p13 encompassing all PAX6 exons and exon 12 of ELP4, with insertion of this segment into 11q21. lrWGS delineated the exact breakpoints, confirming that the downstream regulatory region, required for normal PAX6 expression, remained at the 11p13 locus. Consequently, the translocated copy of PAX6 at 11q21 is expected to lack expression due to the loss of its essential regulatory elements. CONCLUSIONS AND RELEVANCE: These findings in an individual with classic aniridia harboring an intrachromosomal rearrangement at the PAX6 locus identified by OGM and lrWGS may represent the smallest reported structural variant to separate the PAX6 coding sequence from its downstream regulatory region. This structural variant may have fallen below the detection threshold of srWGS due to its balanced nature and small size, suggesting OGM and lrWGS would be needed for definitive identification.
BACKGROUND: Mutations in PAX6 gene have been shown to be the genetic cause of aniridia, which is a severe panocular eye disease characterised by iris hypoplasia. However, there is no study to do genetic analysis of aniridia, although there are several case reports in China. Here, we describe a mutation analysis of PAX6 in a large Chinese family with aniridia. METHODS: Genomic DNA from venous blood samples was prepared. Haplotype analysis was performed with two genetic markers (D11S904 and D11S935). Fourteen exons of the PAX6 gene were amplified from genomic DNA. Polymerase chain reaction (PCR) products of each exon were analysed by single strand conformational polymorphism (SSCP). The PCR products having an abnormal pattern were sequenced to confirm the mutation. RESULTS: Significant evidence for allele sharing in affected patients was detected suggesting that PAX6 mutation links to aniridia in this family. An extra band corresponding to exon 9 in PAX6 was found by single strand conformational polymorphism analysis in all the aniridia patients in this family, but not detected in the unaffected members. A mutation of C to T was detected by sequencing at the nucleotide 1080 that converts the Arg codon (CGA) to the termination codon (TGA). CONCLUSIONS: Aniridia is caused by a nonsense mutation of PAX6 gene in the large Chinese kindred. Genetic test is important to prevent the transmission of aniridia to their offsprings in the kindred by prenatal diagnosis.
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