PSEN1 and glioblastoma: To investigate the effects of pathogenic PS1 mutations on EV-associated Aβ, we first isolated EVs from the culture medium of H4 glioblastoma cell lines genetically engineered to express either the PS1Δ9 mutation (H4PS1Δ9) or wild-type PS1 (H4PS1WT) in an inducible manner.