C9 and Friedreich ataxia: Of notice, there was no overlap between FRDA patients and controls for seven over-represented (SORCS3, PKM, FAM174A, PRCP, GPX3, NBL1, SCG5) and six under-represented DEPs (CNDP1, ISLR, CD14, C3, C9, NRXN2), suggesting that these may be potential biomarkers for clinical studies.