For example, skin cancer phenotypes were induced in both Presenilin knockout mice and when a γ secretase inhibitor was used,51, 52 reduced spine density and altered synaptic plasticity were observed in Bace1 knockout mice,53 and cognitive worsening and brain atrophy occurred after treatment with BACE1 inhibitors.54, 55. This evidence concerns the gene BACE1 and Brain atrophy.