Novel mutations causing CRB1 associated retinal degeneration in Czech patients and comparison of methods for mutation detection

Abstract

Purpose: To determine the molecular genetic cause of severe early onset retinal dystrophy in three unrelated females of Czech origin.

Methods: Comprehensive ophthalmological examination including autofluorescence and spectral domain optical coherence tomography (SD-OCT). DNA samples for 2 probands were analyzed using a genotyping microarray (Asper) that can detect 780 pathogenic mutations and single nucleotide polymorphisms in 15 genes known to be implicated in early onset retinal dystrophies. Whole exome sequencing (Illumina TruSeq Exome Enrichment Kit) was performed for one proband. Proband 3 was subjected to conventional capillary sequencing of CRB1 exons based on her ocular findings. Mutations were verified by Sanger sequencing.

Results: The disease onset in all three probands was before the age of 7 years. Bilateral cystoid spaces in the macula on SD-OCT were detected in two probands, aged 9 and 7 years. All three probands had a known disease-causing mutation c.2843G>A; p.(Cys948Tyr) in the CRB1 gene. One proband was homozygous for this mutation. Two novel CRB1 mutations c.2308G>A; p.(Gly770Ser) and c.3121A>G; p.(Met1041Val) were identified in the other two probands in the heterozygous state. False negativity was observed using the genotyping microarray in one of the two samples examined by this technique.

Conclusions: The first study reporting on the molecular genetic cause of an early onset retinal dystrophy identified one homozygous and two compound heterozygote probands with CRB1 mutations. The data suggests a possible higher than expected allele frequency for the previously reported mutation c.2843G>A; p.(Cys948Tyr) in the Czech population. Exome sequencing proved to be a fast and cost-effective approach to determine the molecular cause of disease.