Rab5‐positive early endosome dysfunction occurs early in AD,16 and Rab5 hyperactivation in transgenic mice recapitulate the primary features of AD, such as early endosome enlargement, hippocampal synaptic plasticity impairment, hyperphosphorylation of the Tau protein, and cholinergic neurodegeneration.24 The gene discussed is RAB5A; the disease is Alzheimer disease.