HDAC9 and Parkinson disease: The observation that nuclear α-synuclein can affect histone acetylation supports a need for future studies to investigate the effects of HDAC inhibition on the intracellular pathways involved in dopaminergic neuronal survival and axonal maintenance in models of PD, with the ultimate aim of testing the potential of Class II HDAC inhibitors as neuroprotective therapies for PD (Figure 1B).