MCOLN1 and early-onset autosomal dominant Alzheimer disease: Summary: TRPML1 defects accompany abnormalities in the endolysosomal system in Alzheimer's disease and APOE-ε4 iPSC-derived neurons, which are recapitulated by neuronal PIKfyve inhibition and remediated by the TRPML1 agonist ML-SA1.