PSEN1 and Alzheimer disease: The APP/PS1 transgenic mouse line carries human APP and PS1 (presenilin 1) transgenes that harbor mutations associated with early onset AD, as a result of which Aβ (particularly the aggregation-prone longer form, Aβ42) is overproduced and accumulates as plaques in the brains of these animals (Jankowsky et al., 2004).