Pathogenic variants in RPGR account for 80% of cases with X-linked retinitis pigmentosa (XLRP). The C-terminal 567-aa exon ORF15 is a mutational hotspot for RPGR-associated retinitis pigmentosa. However, it generally performs poorly in standard sequencing-based assays due to a highly repetitive glutamic acid/glycine-rich sequence.
To address the clinical importance of the RPGR ORF15 and the lack of high-quality next generation sequencing (NGS)-based diagnostics, we aimed to develop a comprehensive high-throughput clinical test for inherited retinal dystrophies (IRD), and to specifically evaluate the performance of RPGR ORF15 sequencing in a patient cohort.
- In our clinical cohort of 1587 IRD patients, the overall diagnostic yield was 58%.
- A molecular diagnosis in RPGR was identified in 5.7% (90/1587) of the patients.
- Female patients accounted for 24% of the diagnostic cases. A majority (70%) of the pathogenic (P) / likely pathogenic (LP) variants were frameshifts.
- Seventy-one out of 90 (79%) P/LP variants were detected in the ORF15 (31% in the most difficult-to sequence central region p.824 – p.1077) and 19 (21%) within the exons 1- 14.
- RPGR explains approximately 9% of cases with RP. Diagnostic variants in ORF15 were confirmed using a custom Sanger sequencing method optimized for purine-rich sequence.
Keywords: Retinitis pigmentosa, inherited retinal dystrophy (IRD), diagnostic yield, NGS
Authors: Johanna Sistonen, Sari Tuupanen, Kati Kämpjärvi, Pauli Siivonen, Miika Mehine, Johanna Känsäkoski, Kirsty Wells, Jennifer Schleit, Miko Valori, Pertteli Salmenperä,
Eeva-Marja Sankila, Eveliina Salminen, Tero-Pekka Alastalo, Juha Koskenvuo, Samuel Myllykangas