We also observed a significantly increased cytochrome c release from mitochondria to the cytosol (a marker of cell apoptosis) in cells with expanded polyglutamine repeats and in brain extracts of HD transgenic mouse model (R6/2) as compared to the level in the respective controls (Fig 2F), together with a considerably reduced cell viability measured by the colorimetric assay (Fig 2G). Here, CYCS is linked to Huntington disease.