A deletion 3′ to the PAX6 gene in familial aniridia cases

Purpose: PAX6 mutations cause aniridia as well as other various congenital eye abnormalities. Aniridia can be due to both point mutations and chromosomal deletions/rearrangements. Therefore, a complete search for PAX6 gene alterations in aniridia subjects requires a technically complex approach involving the comprehension of fluorescence in situ hybridization (FISH) analysis. In the present study, an Italian casistic of aniridia patients has been investigated and a quantitative polymerase chain reaction (PCR) assay to detect PAX6 gene deletions was set up. Methods: Twenty-one aniridia patients were screened for point mutations (missense, nonsense, splicing-affecting, and short insertion/deletion) by using single-stranded conformational polymorphism (SSCP) and denaturing high performance liquid chromatograpy (dHPLC). To reveal deletions not detectable by SSCP or dHPLC, a quantitative PCR approach was set up for the PAX6 structural gene and for regions 5' and 3' to it at the level of WT1 and ELP4, respectively. Results: Point mutations were found in 7 out of 21 patients. Three out of twenty-one patients showed deletions at the level of the PAX6 structural gene. In addition, two familial cases showed an undamaged PAX6 gene but a deletion in the region 3' to it at level of the ELP4 gene. In one of the families, the presence of the deletion has been confirmed by linkage analysis of polymorphic markers. Conclusions: In our casistic, a significant fraction of familial aniridia patients appears to be caused by a 3' deletion to PAX6, suggesting that evaluation of this alteration should be included in routine procedures of aniridia patients analysis. The quantitative PCR assay described here represents a simple approach to accomplish this task.