Importantly, tau phosphorylation was only observed at Ser422 in the contralateral hippocampus of AD P-tau-seeded Tg/hTau mice, implying that Ser422 phosphorylation may be an early event in AD P-tau-induced tau hyperphosphorylation and occurs in the early stage of tau spreading [31]. The gene discussed is MAPT; the disease is Alzheimer disease.