HDAC9 and Parkinson disease: In a complementary study, Harrison et al. examined histone acetylation, as well as HDAC levels, in SNpc samples from a gender-balanced cohort composed of eight patients with early (Braak stage 3 /4) PD (79.3 ± 1.8 years), twelve late (Braak stage 6) PD cases (79.3 ± 1.8 years) and ten age-matched controls (82.1 ± 1.9 years) [28].