Core Summary Core B will provide cutting edge tools to measure retrotransposition in multicellular eukaryotes in the context of aging paradigms with a special focus on Alzheimer’s disease and related disorders. In addition to providing appropriate existing assays and mouse models to all of the participants, the core will also develop improved retrotransposition reporters and genomics tools to enable the detection and mapping of retrotransposition events in the various experimental systems under study. The Core will also provide “Driver systems” that lead to high level expression of these elements in both cell systems and animals. Finally, the core will provide cutting edge sequencing and computational tools to analyze both retrotransposition itself and the aberrant forms of LINE-1 expression and reverse transcription observed in aging cells and organisms.