UCSF

Purpose

We applied a recently reported next-generation sequencing (NGS) strategy for screening the ABCA4 gene in a British cohort with ABCA4-associated disease and report novel mutations.

Methods

We identified 79 patients with a clinical diagnosis of ABCA4-associated disease who had a single variant identified by the ABCA4 microarray. Comprehensive phenotypic data were obtained, and the NGS strategy was applied to identify the second allele by means of sequencing the entire coding region and adjacent intronic sequences of the ABCA4 gene. Identified variants were confirmed by Sanger sequencing and assessed for pathogenicity by in silico analysis.

Results

Of the 42 variants detected by prescreening with the microarray, in silico analysis suggested that 34, found in 66 subjects, were disease-causing and 8, found in 13 subjects, were benign variants. We detected 42 variants by NGS, of which 39 were classified as disease-causing. Of these 39 variants, 31 were novel, including 16 missense, 7 splice-site-altering, 4 nonsense, 1 in-frame deletion, and 3 frameshift variants. Two or more disease-causing variants were confirmed in 37 (47%) of 79 patients, one disease-causing variant in 36 (46%) subjects, and no disease-causing variant in 6 (7%) individuals.

Conclusions

Application of the NGS platform for ABCA4 screening enabled detection of the second disease-associated allele in approximately half of the patients in a British cohort where one mutation had been detected with the arrayed primer extension (APEX) array. The time- and cost-efficient NGS strategy is useful in screening large cohorts, which will be increasingly valuable with the advent of ABCA4-directed therapies.