Finally, pathogenic triplet repeat expansions in the Friedreich ataxia gene FXN concomitantly display a block to transcriptional elongation and the appearance of H3K9me on FXN (Punga and Bühler 2010; Li et al. 2015), raising the possibility that pause-induced heterochromatin underlies disease pathogenesis. Here, FXN is linked to Friedreich ataxia.