FOXC1/PITX2 Mutations and Copy Number Changes in a Belgian-Dutch Cohort of Patients With Axenfeld-Rieger Malformations

Abstract

Purpose:: Axenfeld-Rieger (AR) malformations comprise a spectrum of rare autosomal dominant congenital structural malformations of the anterior eye segment. A primary purpose of this study was to determine the prevalence of disease-causing FOXC1/PITX2 mutations and copy number changes in a Belgian-Dutch cohort of patients with AR malformations. A second goal was to evaluate the contribution of three possible candidate genes: FIBULIN-4, P32 and FOXC2.

Methods:: Genomic DNA was obtained from 36 probands with AR malformations, mostly of Belgian or Dutch origin. The patients were examined for copy number changes of FOXC1/PITX2 with MLPA and screened for subtle FOXC1/PITX2 mutations by sequencing. Array CGH with a tiling BAC array for the FOXC1 region was carried out for the patients with an identified FOXC1 deletion and for all mutation-negative patients. In addition mutation screening of FIBULIN-4, P32 and FOXC2 was performed in the latter group by sequencing.

Results:: In the cohort of 36 probands with AR malformations 5 FOXC1 deletions and 1 PITX2 deletion were identified. All FOXC1 deletions were further delineated by array CGH. Furthermore 6 novel FOXC1 mutations were identified including 1 missense, 2 nonsense and 3 frameshift mutations. In addition the 4 novel PITX2 mutations found were 1 missense, 1 frameshift and 2 nonsense mutations. Downstream screening of 14 probands without identifiable FOXC1/PITX2 mutations through array CGH of the FOXC1 region and sequencing of FIBULIN-4, P32 and FOXC2, has so far revealed no disease-causing mutations.

Conclusions:: In this mutation study of the FOXC1 and PITX2 genes in a Belgian-Dutch cohort with AR malformations a disease-causing genetic defect was found in 44% of the probands. The majority of these are FOXC1 mutations (69%) and one third PITX2 mutations (31%). Thirty-eight percent of these defects are genomic rearrangements. This study sustains a major role of the FOXC1/PITX2 genes in the molecular pathogenesis of the AR spectrum in the Belgian-Dutch population. Our molecular data will be complemented by phenotypic information in order to establish genotype-phenotype correlations.

Keywords: genetics • gene screening • anterior segment