Jing Guo and colleagues [61] suggested that elevated Ser262 hyperphosphorylated tau (pS262-tau), the decreased methylation of methylated protein phosphatase-2A catalytic subunit (M-PP2Ac), and increased de-methylated PP2Ac (DM-PP2Ac) in retina can be used in the early stage of HHcy-induced AD as surveillance biomarkers for diagnosis. This evidence concerns the gene PPP2CA and Alzheimer disease.