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Optimized testing strategy for the diagnosis of GAA-FGF14 ataxia/spinocerebellar ataxia 27B

2023; Nature Portfolio; Volume: 13; Issue: 1 Linguagem: Inglês

10.1038/s41598-023-36654-8

2045-2322

Céline Bonnet, David Pellerin, Virginie Roth, Guillemette Clément, Marion Wandzel, Laëtitia Lambert, Solène Frismand, Marian Douarinou, Anaïs Grosset, Inès Bekkour, Frédéric Weber, Florent Girardier, Clément Robin, Stéphanie Cacciatore, Myriam Bronner, Carine Bossenmeyer‐Pourié, Natacha Dreumont, Salomé Puisieux, Pablo Iruzubieta, Marie‐Josée Dicaire, François Evoy, Marie‐France Rioux, Armand Hocquel, Roberta La Piana, Matthis Synofzik, Henry Houlden, Matt C. Danzi, Stephan Züchner, Bernard Brais, M. Renaud,

Amyotrophic Lateral Sclerosis Research

Dominantly inherited GAA repeat expansions in FGF14 are a common cause of spinocerebellar ataxia (GAA-FGF14 ataxia; spinocerebellar ataxia 27B). Molecular confirmation of FGF14 GAA repeat expansions has thus far mostly relied on long-read sequencing, a technology that is not yet widely available in clinical laboratories. We developed and validated a strategy to detect FGF14 GAA repeat expansions using long-range PCR, bidirectional repeat-primed PCRs, and Sanger sequencing. We compared this strategy to targeted nanopore sequencing in a cohort of 22 French Canadian patients and next validated it in a cohort of 53 French index patients with unsolved ataxia. Method comparison showed that capillary electrophoresis of long-range PCR amplification products significantly underestimated expansion sizes compared to nanopore sequencing (slope, 0.87 [95% CI, 0.81 to 0.93]; intercept, 14.58 [95% CI, - 2.48 to 31.12]) and gel electrophoresis (slope, 0.84 [95% CI, 0.78 to 0.97]; intercept, 21.34 [95% CI, - 27.66 to 40.22]). The latter techniques yielded similar size estimates. Following calibration with internal controls, expansion size estimates were similar between capillary electrophoresis and nanopore sequencing (slope: 0.98 [95% CI, 0.92 to 1.04]; intercept: 10.62 [95% CI, - 7.49 to 27.71]), and gel electrophoresis (slope: 0.94 [95% CI, 0.88 to 1.09]; intercept: 18.81 [95% CI, - 41.93 to 39.15]). Diagnosis was accurately confirmed for all 22 French Canadian patients using this strategy. We also identified 9 French patients (9/53; 17%) and 2 of their relatives who carried an FGF14 (GAA)≥250 expansion. This novel strategy reliably detected and sized FGF14 GAA expansions, and compared favorably to long-read sequencing.