Abstract
Purpose :
To identify the missing heritability of ABCA4-related retinopathy in a Chinese cohort.
Methods :
33 unrelated patients with ABCA4-related retinopathy carrying a monoallelic variant in ABCA4 were recruited. All patients underwent ophthalmic examinations. Next-generation sequencing of the whole ABCA4 sequence, including coding and non-coding regions, was performed to detect deep intronic variants (DIVs) and copy number variations (CNVs).
Results :
Eight missing pathogenic ABCA4 variants were identified including five DIVs and three CNVs in 20 patients (60.6%). The five DIVs, including four novel (c.1555-816T>G, c.2919-169T>G, c.2919-884G>T, and c.5461-1321A>G) and one reported (c.4539+1100A>G), accounted for the missing alleles in 51.5% of the patients. Minigene assays showed that four novel DIVs activated cryptic splice sites leading to the insertions of pseudoexons. The three novel CNVs consisted of one gross deletion of 1273 bp (exon 2), and two gross duplications covering 25.2 kb (exons 28–43) and 9.4 kb (exons 38–44). Three microhomology domains were identified at the breakpoints and revealed the potential mechanisms of CNV formation.
Conclusions :
DIVs and CNVs explained about two-thirds of the unresolved Chinese cases with ABCA4-related retinopathy. Combining results from phenotypic screening, targeted the whole ABCA4 sequencing, and in silico tools can help to identify the missing heritability and lay the foundation for future drug and gene therapy.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.