Initially, we studied 2D cultures of AD hiPSC-derived cerebrocortical neurons (‘AD neurons’) with one allele bearing the PS1 ΔE9 mutation (ΔE9/WT), PS1M146V mutation (M146V/WT), or APPswe mutation (APPswe/WT) vs. isogenic WT/WT controls (Figure 1—figure supplement 1A). Here, PSEN1 is linked to Alzheimer disease.