HDAC9 and Alzheimer disease: Changes in histone acetylation seem to play a crucial role in the dysregulation of gene expression observed during AD and a number of studies have now repeatedly shown that targeting histone acetylation via administration of HDAC inhibitors can ameliorate cognitive deficits in AD animal models (Francis et al, 2009; Govindarajan et al, 2011; Kilgore et al, 2010; Peleg et al, 2010; Ricobaraza et al, 2009, 2012).