PSEN1 and Alzheimer disease: Furthermore, overexpression of L1 by injection of adenoassociated virus encoding L1 decreases the Aβ plaque load, levels of Aβ42, Aβ42/40 ratio, and astrogliosis in a mouse model of AD, which carries human APP with the pathogenic Swedish mutation and the L166P mutated human presenilin-1 [66].