HDAC9 and Huntington disease: Several studies have shown beneficial effects of HDAC inhibitors in HD mouse models, including broad-acting HDAC inhibitors SAHA, phenylbutyrate and parabinostat (LBH589), as well as compounds RGFP966 and 4b that show moderate selectivity towards HDAC3 (Hockly et al., 2003; Gardian et al., 2005; Thomas et al., 2008; Mielcarek et al., 2011; Jia et al., 2012a; Jia et al., 2012b; Jia et al., 2016; Chopra et al., 2016; Suelves et al., 2017; Siebzehnrübl et al., 2018).