Detecting Alu Element Insertion Variant in RP1 Gene Using Whole Genome Sequencing in Patients with Retinitis Pigmentosa

Background/Objectives: Alu element insertion in the exon 4 of the RP1 gene was newly identified through whole genome sequencing (WGS). This was not detected in previous next-generation sequencing (NGS) analysis. We report three cases of Korean retinitis pigmentosa (RP) patients with compound heterozygous variants including Alu element insertion in the RP1 gene, indicating that Alu element insertion could be a cause of RP; Methods: Among patients diagnosed with RP having variants in the RP1 gene in the Asan Medical Center, WGS was additionally performed for genetically unsolved cases in previous NGS analysis to detect any presence of Alu element insertion. For cases detected to have Alu element insertion in the exon 4 of the RP1 gene, genetic and clinical characteristics were analyzed; Results: Among 16 patients with RP, 3 patients were detected to have Alu element insertion in the RP1 gene. Alu element insertion in the RP1 gene was also detected using WGS. It was revealed to be a pathogenic variant. Therefore, RP1 gene mutation was the confirmed genetic cause of RP for these three cases and genetic counseling was enabled for them; Conclusions: Alu element insertion in the RP1 gene could be a genetic cause of autosomal recessive RP patients with compound heterozygous variants. Through WGS, the identification of this pathogenic variant was possible. Confirmation is needed to check the presence of Alu element insertion in patients with compound heterozygous variants in the RP1 gene.