The generation of transgenic (tg) animals as models overexpressing mutant human amyloid precursor protein (APP) and/or presenilin-1 and -2 (PS1, PS2), tg mice expressing human ApoE isoforms, as well as tau, have made substantial contributions to the understanding of AD-type brain pathology and stimulated renewed interest in EM. The gene discussed is APP; the disease is Alzheimer disease.