A combined nucleic acid and protein analysis in Friedreich ataxia: Implications for diagnosis, pathogenesis and clinical trial design

Francesco Saccà, Giorgia Puorro, Antonella Antenora, Angela Marsili, Alessandra Denaro, Raffaele Piro, Pierpaolo Sorrentino, Chiara Pane, Alessandra Tessa, Vincenzo Brescia Morra, Sergio Cocozza, Giuseppe de Michele, Filippo M. Santorelli, Alessandro Filla

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Friedreich's ataxia (FRDA) is the most common hereditary ataxia among caucasians. The molecular defect in FRDA is the trinucleotide GAA expansion in the first intron of the FXN gene, which encodes frataxin. No studies have yet reported frataxin protein and mRNA levels in a large cohort of FRDA patients, carriers and controls. Methodology/Principal Findings: We enrolled 24 patients with classic FRDA phenotype (cFA), 6 late onset FRDA (LOFA), all homozygous for GAA expansion, 5 pFA cases who harbored the GAA expansion in compound heterozygosis with FXN point mutations (namely, p.I154F, c.482+3delA, p.R165P), 33 healthy expansion carriers, and 29 healthy controls. DNA was genotyped for GAA expansion, mRNA/FXN was quantified in real-time, and frataxin protein was measured using lateral-flow immunoassay in peripheral blood mononuclear cells (PBMCs). Mean residual levels of frataxin, compared to controls, were 35.8%, 65.6%, 33%, and 68.7% in cFA, LOFA, pFA and healthy carriers, respectively. Comparison of both cFA and pFA with controls resulted in 100% sensitivity and specificity, but there was overlap between LOFA, carriers and controls. Frataxin levels correlated inversely with GAA1 and GAA2 expansions, and directly with age at onset. Messenger RNA expression was reduced to 19.4% in cFA, 50.4% in LOFA, 52.7% in pFA, 53.0% in carriers, as compared to controls (p

Original languageEnglish
Article numbere17627
JournalPLoS One
Volume6
Issue number3
DOIs
Publication statusPublished - 2011

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

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