Table 2.

Summary of Class II and IV zinc-dependent HDAC isoforms

Class	HDAC	Cellular location	Tissue distribution	Known biological functions
IIa	HDAC4	Nucleus and cytoplasm193	Brain, heart and skeletal muscle,211,212 prehypertrophic chondrocytes,78 retina,213 neurons214–216	Myofibroblast development,40 chondrocyte hypertrophy and endochondral ossification,78 muscular differentiation,212 retinal neuronal function,213 regulation of neuronal activity, cell death and survival214,215
	HDAC5	Nucleus and cytoplasm193	Heart, skeletal muscle and brain,211,217 neurons216	Differentiation of neural stem cells,145 and neuronal activity,216 myocardial and endothelial functions,217 memory function218
	HDAC7	Nucleus and cytoplasm193	Thymus,219 heart, muscle and lung211	In embryonic endothelial cells of developing heart, blood vessels, mesenchyme and myocardial layers of heart and in lung tissue,118 role in developing thymocytes,219,220 osteoclast activity,82 inflammatory macrophages221
	HDAC9	Nucleus and cytoplasm193	Heart, skeletal muscle and brain211,222	Redundant role in heart development,123 controls genes affected by motor innervation in muscles167
IIb	HDAC6	Mainly Cytoplasm193	Muscle,223 brain,166 heart,224 liver,225 kidneys,226 and teste227	Neuroprotection and neurodegeneration,166 muscular differentiation,223 arterial modelling,224 tubulin acetylation, bone mass regulation and immune response modulation,227 involved in cellular response to stress,228,229 and macro-autophagy,230 platelet activation231
	HDAC10	Nucleus and cytoplasm193	Liver, spleen, kidney,232 skin233	Expressed in the developing brain with neural oligodendrocyte cells,168 melanin production in the skin,233 promotes autophagy-mediated cell survival in neuroblastoma cells234
IV	HDAC11	Nucleus and cytoplasm193	Brain,168 heart, skeletal muscle, kidney,235 T cells236	Influences immune activation versus immune tolerance236