DBN1 and Alzheimer disease: Previous studies have shown that expression of the drebrin protein and mRNA decreases in the AD human hippocampus, frontal cortex, and temporal cortex, although the levels of presynaptic proteins, such as synapsin I and synaptophysin, remain unchanged (Harigaya et al., 1996; Julien et al., 2008; Shim & Lubec, 2002; Shirao et al., 2017).