Elevation of retrotransposon transcripts in Alzheimer's disease and progressive supranuclear palsy, a primary tauopathy, along with increased transposition in tau transgenic Drosophila12, 13, 14, 99, 100, 101, 102 suggested that retrotransposons are derepressed and may mobilize in human disease. This evidence concerns the gene MAPT and Alzheimer disease.