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

<b>Background/Objectives:</b><i>Alu</i> element insertion in the exon 4 of the <i>RP1</i> 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 <i>Alu</i> element insertion in the <i>RP1</i> gene, indicating that <i>Alu</i> element insertion could be a cause of RP; <b>Methods:</b> Among patients diagnosed with RP having variants in the <i>RP1</i> gene in the Asan Medical Center, WGS was additionally performed for genetically unsolved cases in previous NGS analysis to detect any presence of <i>Alu</i> element insertion. For cases detected to have <i>Alu</i> element insertion in the exon 4 of the <i>RP1</i> gene, genetic and clinical characteristics were analyzed; <b>Results</b>: Among 16 patients with RP, 3 patients were detected to have <i>Alu</i> element insertion in the <i>RP1</i> gene. <i>Alu</i> element insertion in the <i>RP1</i> gene was also detected using WGS. It was revealed to be a pathogenic variant. Therefore, <i>RP1</i> gene mutation was the confirmed genetic cause of RP for these three cases and genetic counseling was enabled for them; <b>Conclusions</b>: <i>Alu</i> element insertion in the <i>RP1</i> 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 <i>Alu</i> element insertion in patients with compound heterozygous variants in the <i>RP1</i> gene.