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Grosso V, Marcolungo L, Maestri S, Alfano M, Lavezzari D, Iadarola B, Salviati A, Mariotti B, Botta A, D’Apice MR, Novelli G, Delledonne M, Rossato M. Characterization of FMR1 Repeat Expansion and Intragenic Variants by Indirect Sequence Capture. Front Genet 2021; 12:743230. [PMID: 34646309 PMCID: PMC8504923 DOI: 10.3389/fgene.2021.743230] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 08/26/2021] [Indexed: 11/30/2022] Open
Abstract
Traditional methods for the analysis of repeat expansions, which underlie genetic disorders, such as fragile X syndrome (FXS), lack single-nucleotide resolution in repeat analysis and the ability to characterize causative variants outside the repeat array. These drawbacks can be overcome by long-read and short-read sequencing, respectively. However, the routine application of next-generation sequencing in the clinic requires target enrichment, and none of the available methods allows parallel analysis of long-DNA fragments using both sequencing technologies. In this study, we investigated the use of indirect sequence capture (Xdrop technology) coupled to Nanopore and Illumina sequencing to characterize FMR1, the gene responsible of FXS. We achieved the efficient enrichment (> 200×) of large target DNA fragments (~60-80 kbp) encompassing the entire FMR1 gene. The analysis of Xdrop-enriched samples by Nanopore long-read sequencing allowed the complete characterization of repeat lengths in samples with normal, pre-mutation, and full mutation status (> 1 kbp), and correctly identified repeat interruptions relevant for disease prognosis and transmission. Single-nucleotide variants (SNVs) and small insertions/deletions (indels) could be detected in the same samples by Illumina short-read sequencing, completing the mutational testing through the identification of pathogenic variants within the FMR1 gene, when no typical CGG repeat expansion is detected. The study successfully demonstrated the parallel analysis of repeat expansions and SNVs/indels in the FMR1 gene at single-nucleotide resolution by combining Xdrop enrichment with two next-generation sequencing approaches. With the appropriate optimization necessary for the clinical settings, the system could facilitate both the study of genotype-phenotype correlation in FXS and enable a more efficient diagnosis and genetic counseling for patients and their relatives.
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Affiliation(s)
- Valentina Grosso
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Luca Marcolungo
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Simone Maestri
- Department of Biotechnology, University of Verona, Verona, Italy
| | | | - Denise Lavezzari
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Barbara Iadarola
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Alessandro Salviati
- Department of Biotechnology, University of Verona, Verona, Italy
- GENARTIS srl, Verona, Italy
| | - Barbara Mariotti
- Department of Medicine, Section of General Pathology, University of Verona, Verona, Italy
| | - Annalisa Botta
- Department of Biomedicine and Prevention, Medical Genetics Section, University of Rome "Tor Vergata", Rome, Italy
| | | | - Giuseppe Novelli
- Department of Biomedicine and Prevention, Medical Genetics Section, University of Rome "Tor Vergata", Rome, Italy
- IRCCS Neuromed Mediterranean Neurological Institute, Pozzilli, Italy
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, NV, United States
| | - Massimo Delledonne
- Department of Biotechnology, University of Verona, Verona, Italy
- GENARTIS srl, Verona, Italy
| | - Marzia Rossato
- Department of Biotechnology, University of Verona, Verona, Italy
- GENARTIS srl, Verona, Italy
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