Long-read sequencing uncovers novel pathogenic duplications in the PRPH2 gene in patients with macular dystrophy.

Abstract

Purpose: Clinical variability and incomplete penetrance characterize retinal dystrophies associated with PRPH2 gene variants. Here, we utilized adaptive nanopore long-read sequencing (LRS) to solve a genetic diagnosis for dominantly inherited macular dystrophies in two families.

Methods: Patient 1 (P1) and her daughter, Patient 2 (P2) were clinically evaluated using multimodal imaging and electrophysiological testing at Helsinki University Hospital, Finland, and Patient 3 (P3) from a different family, at Loma Linda University, USA. The patients were subjected to retinal dystrophy gene panels and the suspected duplications were characterized with nanopore LRS.

Results: P1 presented with butterfly-shaped pattern dystrophy (BPD) and P2 with vitelliform macular dystrophy. P3 showed BPD in the right eye and late-stage BPD in the left. Gene panels suggested that the patients shared the same heterozygous 482 bp PRPH2 exon 2 duplication. LRS revealed the duplications to be almost 4kb in size with breakpoints (BP) in intronic Alu-elements. In P1 and P2, the 3'BP resides within a novel Alu-element. The duplication has not been reported earlier and is missing from the gnomAD database.

Conclusion: This study presents novel PRPH2 exon 2 duplications associated with macular dystrophies.