HDAC2 and memory impairment: Synaptophysin is a synaptic protein marker and provides a structural basis for synaptic plasticity.52 Decrease in synaptophysin is implicated in learning and memory impairment.1, 4, 5 Graff et al35 demonstrated that HDAC2 overexpression reduced synaptophysin protein level and caused memory impairments, HDAC2 inhibition reversed the effects.