As MARK3 is a tau kinase associated with tau S262 phosphorylation in the early stages of AD pathogenesis (24), and because mutations in closely related MARK4 can significantly increase AD risk, promote hyperphosphorylation of tau, and induce neuron toxicity (33), we sought to investigate the functional consequences of MARK3 APA in neurons. This evidence concerns the gene MARK4 and Alzheimer disease.