APP and Alzheimer disease: For example, we have previously shown that neurospheres derived from AD-specific neural progenitor cells carrying familial AD mutations in amyloid precursor protein (APP) and presenilin 1 (PSEN1) replicate disease-specific phenotypes in vitro including increased secretion of Aβ42-peptides and elevated Aβ42/40 ratios (Jorfi et al., 2018).