APP and early-onset autosomal dominant Alzheimer disease: Amyloid precursor protein (APP) and APP-like protein, well known in the pathogenesis of Alzheimer’s disease, participate in nAChR clustering via the Lrp4-MuSK signal in cooperation with agrin-mediated signal and also contribute to the presynaptic differentiation of the neuromuscular junction [117,118,119,120].