Histone deacetylases (HDACs) play a pivotal role in regulating gene expression in pathological cardiac hypertrophy, primarily through chromatin remodeling that affects gene transcription.[126,127] Within the HDAC superfamily, divided into 4 classes, Classes I, II, and IV are zinc-dependent, whereas Class III operates via an NAD-dependent mechanism.[128–131] Class Iia HDACs, despite their lower enzymatic activity compared to other classes, significantly influence cardiac hypertrophy. The gene discussed is HDAC9; the disease is cardiac hypertrophy.