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Fernández-Suárez E, González-Del Pozo M, Méndez-Vidal C, Martín-Sánchez M, Mena M, de la Morena-Barrio B, Corral J, Borrego S, Antiñolo G. Long-read sequencing improves the genetic diagnosis of retinitis pigmentosa by identifying an Alu retrotransposon insertion in the EYS gene. Mob DNA 2024; 15:9. [PMID: 38704576 PMCID: PMC11069205 DOI: 10.1186/s13100-024-00320-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Accepted: 04/10/2024] [Indexed: 05/06/2024] Open
Abstract
BACKGROUND Biallelic variants in EYS are the major cause of autosomal recessive retinitis pigmentosa (arRP) in certain populations, a clinically and genetically heterogeneous disease that may lead to legal blindness. EYS is one of the largest genes (~ 2 Mb) expressed in the retina, in which structural variants (SVs) represent a common cause of disease. However, their identification using short-read sequencing (SRS) is not always feasible. Here, we conducted targeted long-read sequencing (T-LRS) using adaptive sampling of EYS on the MinION sequencing platform (Oxford Nanopore Technologies) to definitively diagnose an arRP family, whose affected individuals (n = 3) carried the heterozygous pathogenic deletion of exons 32-33 in the EYS gene. As this was a recurrent variant identified in three additional families in our cohort, we also aimed to characterize the known deletion at the nucleotide level to assess a possible founder effect. RESULTS T-LRS in family A unveiled a heterozygous AluYa5 insertion in the coding exon 43 of EYS (chr6(GRCh37):g.64430524_64430525ins352), which segregated with the disease in compound heterozygosity with the previously identified deletion. Visual inspection of previous SRS alignments using IGV revealed several reads containing soft-clipped bases, accompanied by a slight drop in coverage at the Alu insertion site. This prompted us to develop a simplified program using grep command to investigate the recurrence of this variant in our cohort from SRS data. Moreover, LRS also allowed the characterization of the CNV as a ~ 56.4kb deletion spanning exons 32-33 of EYS (chr6(GRCh37):g.64764235_64820592del). The results of further characterization by Sanger sequencing and linkage analysis in the four families were consistent with a founder variant. CONCLUSIONS To our knowledge, this is the first report of a mobile element insertion into the coding sequence of EYS, as a likely cause of arRP in a family. Our study highlights the value of LRS technology in characterizing and identifying hidden pathogenic SVs, such as retrotransposon insertions, whose contribution to the etiopathogenesis of rare diseases may be underestimated.
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Affiliation(s)
- Elena Fernández-Suárez
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - María González-Del Pozo
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Cristina Méndez-Vidal
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Marta Martín-Sánchez
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Marcela Mena
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Belén de la Morena-Barrio
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER-ISCIII, Murcia, Spain
| | - Javier Corral
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER-ISCIII, Murcia, Spain
| | - Salud Borrego
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain.
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain.
| | - Guillermo Antiñolo
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain.
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain.
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