APP and Alzheimer disease: Graff et al. (2012) have demonstrated in their study that elevated levels of HDAC2 could epigenetically repress the synaptic genes that related to cognitive deficits, while Panikker et al. (2018) suggested that decreasing HDAC2 levels in AD-related APP brain could reverse the neuroepigenetic changes in activating synaptic plasticity genes, as well as restoring brain morphology and cognition (Graff et al., 2012; Panikker et al., 2018).