Scientific Reports (Jun 2023)

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

  • Céline Bonnet,
  • David Pellerin,
  • Virginie Roth,
  • Guillemette Clément,
  • Marion Wandzel,
  • Laëtitia Lambert,
  • Solène Frismand,
  • Marian Douarinou,
  • Anais Grosset,
  • Ines Bekkour,
  • Frédéric Weber,
  • Florent Girardier,
  • Clément Robin,
  • Stéphanie Cacciatore,
  • Myriam Bronner,
  • Carine 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 Zuchner,
  • Bernard Brais,
  • Mathilde Renaud

DOI
https://doi.org/10.1038/s41598-023-36654-8
Journal volume & issue
Vol. 13, no. 1
pp. 1 – 11

Abstract

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Abstract 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.