MAPT and Alzheimer disease: Increased APP gene dosage is linked to several AD‐related pathologies, including early endosome enlargement, disrupted neurotrophin signaling and axonal transport, reduced retromer complex and synaptic proteins, tau hyperphosphorylation, microgliosis, astrocytosis, and lysosomal dysfunction.8, 13, 14, 15, 16, 17, 18