ACO2 and Friedreich ataxia: When hCBOs were analyzed at day 60 by Western blot, various FRDA-associated disease phenotypes were detected including increased levels of activated/cleaved caspase 3, decreased level of aconitase 2 suggesting of mitochondrial dysfunction, and hypoacetylation of histone H4 (H4K5, H4K12) (Figure 6F).