Improving Molecular Diagnosis of Aniridia and WAGR Syndrome Using Customized Targeted Array-Based CGH

Chromosomal deletions at 11p13 are a frequent cause of
congenital Aniridia, a rare pan-ocular genetic disease, and of WAGR syndrome,
accounting up to 30% of cases. First-tier genetic testing for newborn with
aniridia, to detect 11p13 rearrangements, includes Multiplex Ligation-dependent
Probe Amplification (MLPA) and karyotyping. However, neither of these
approaches allow obtaining a complete picture of the high complexity of
chromosomal deletions and breakpoints in aniridia. Here, we report the development
and validation of a customized targeted array-based comparative genomic
hybridization, so called WAGR-array, for comprehensive high-resolution analysis
of CNV in the WAGR locus. Our approach increased the detection rate in a
Spanish cohort of 38 patients with
aniridia, WAGR syndrome and other related ocular malformations, allowing
to characterize four undiagnosed aniridia cases, and to confirm MLPA findings
in four additional patients. For all patients, breakpoints were accurately established
and a contiguous deletion syndrome, involving a large number of genes, was
identified in three patients. Moreover, we identified novel microdeletions
affecting 3' PAX6 regulatory regions
in three families with isolated aniridia. This tool represents a good strategy
for the genetic diagnosis of aniridia and associated syndromes, allowing for a
more accurate CNVs detection, as well as a better delineation of breakpoints.
Our results underline the clinical importance of performing exhaustive and
accurate analysis of chromosomal rearrangements for patients with aniridia,
especially newborns and those without defects in PAX6 after diagnostic screening.