MTHFR and Friedreich ataxia: Notably, the function of miR-22-3p in HL-7702 cells might be replaced by the increase in miR-149-5p on the 21st day, and we also found a potential substitution effect between miR-22-3p and miR-149-3p (Fig 1) Our results indicated that FA deficiency induces miR-22-3p and miR-149-5p upregulation and suggested the inhibition of MTHFR expression by miR-22-3p and miR-149-5p in QGY-7703 and HL-7703 cells.