MAPT and Alzheimer disease: However, there are several possible molecular biomarkers of AD associated with its progressivity: BDNF and Pittsburgh compound B positron emission tomography (PET) in the brain; Aβ1-42, neurogranin, and total and phosphorylated tau protein in cerebrospinal fluid (CSF); and examination of miR-107 mRNA, plasma neurofilament light, platelet amyloid precursor protein isoform ratio, lipid peroxidation products, and vascular cell adhesion molecule-1 in blood24.