In contrast, Harrison and colleagues reported that there were no significant differences in the expression of class I HDACs (HDAC1, 2, 3 and HDAC8), class IIa HDACs (HDAC4, 5, 7 and HDAC9), class IIb HDACs (HDAC6, 10) or class III (SIRT 1, 2) in PD SNpc, compared with age-matched controls [28]. Here, HDAC9 is linked to Parkinson disease.