Mushroom spine loss may underlie memory defects in models of AD, as hippocampal neuron mushroom spines are lost in vitro and in vivo in both presenilin-1-M146V knock-in (PS1-KI) and APP knockin (APP-KI) models of AD (Sun et al., 2014; Zhang et al., 2015). This evidence concerns the gene APP and Alzheimer disease.