Microarray–Based Mutation Detection and Phenotypic Characterization of Patients With Leber Congenital Amaurosis

Abstract

Purpose: : To test the efficiency of a microarray chip as a molecular diagnostic tool in a cohort of north–western European Leber congenital amaurosis (LCA) patients, and to perform genotype–phenotype analysis in genotyped patients.

Methods: : The LCA microarray chip was used to analyse DNAs of 58 LCA patients and the identified mutations were confirmed by direct sequencing. Upon the identification of one mutation, all protein coding exons of the involved gene were sequenced. Phenotype analyses was performed in patients with proven pathogenic mutations.

Results: : Pathogenic mutations were identified in 32.8% of the 58 LCA patients. Mutations were most frequently found in CRB1 (15.5%), followed by the GUCY2D (10.3%) gene. Four novel sequence variants were identified. The p.R768W mutation was found in 8 of 10 GUCY2D alleles, suggesting it to be a founder mutation in the northwest of Europe. Patients with AIPL1 or GUCY2D mutations showed normal fundi in early childhood, and where AIPL1–associated LCA progresses into an RP–like fundus before the age of 8, patients with GUCY2D–associated LCA had relatively normal fundi till the mid–twenties. Patients with CRB1 mutations had distinct fundus abnormalities at the earliest examination and consistently showed characteristics of RP12. Pathogenic GUCY2D mutations clinically resulted in the most severe form of LCA.

Conclusions: : The LCA microarray proved to be an efficient first–pass screening tool as it allowed the identification of 32% of the LCA sequence variants. Mutations in the CRB1 gene, and to a lesser extent, in the GUCY2D gene, underlie the majority of LCA cases in this cohort. A genotype–phenotype correlation was established for the AIPL1, CRB1 and GUCY2D genes.

Keywords: gene microarray • retinal degenerations: hereditary • clinical (human) or epidemiologic studies: natural history