PSEN1 and Alzheimer disease: We find that by introducing neuronal microtissues derived from a genetically modified neural progenitor cell line carrying two AD-specific mutations in APP and PSEN1 into the compartmentalized platform, neuron-secreted Aβ is delivered to the BBB network at sufficient concentrations to produce changes in network morphology as well as barrier permeability and results in localized Aβ deposition (Figures 1D, E).