MTHFR and Friedreich ataxia: However, the relative expression levels of MTHFR mRNA were significantly increased 1.89-fold (P<0.001) on the 14th day after culture in the FA-free medium and were clearly increased by 1.48-fold (P<0.01, FA deficiency) and 2.20-fold (P<0.001, FA free), respectively, on the 21st day.