Novel mutations in RPE65 identified in consanguineous Pakistani families with retinal dystrophy

PURPOSE: To identify pathogenic mutations responsible for retinal dystrophy in three consanguineous Pakistani families. METHODS: A thorough ophthalmic examination including fundus examination and electroretinography was performed, and blood samples were collected from all participating members. Genomic DNA was extracted, and genome-wide linkage and/or exclusion analyses were completed with fluorescently labeled short tandem repeat microsatellite markers. Two-point Lod scores were calculated, and coding exons along with exon-intron boundaries of RPE65 gene were sequenced, bidirectionally. RESULTS: Ophthalmic examinations of the patients affected in all three families suggested retinal dystrophy with an early, most probably congenital, onset. Genome-wide linkage and/or exclusion analyses localized the critical interval in all three families to chromosome 1p31 harboring RPE65. Bidirectional sequencing of RPE65 identified a splice acceptor site variation in intron 2: c.95–1G>A, a single base substitution in exon 3: c.179T>C, and a single base deletion in exon 5: c.361delT in the three families, respectively. All three variations segregated with the disease phenotype in their respective families and were absent from ethnically matched control chromosomes. CONCLUSIONS: These results strongly suggest that causal mutations in RPE65 are responsible for retinal dystrophy in the affected individuals of these consanguineous Pakistani families.