TREM2 and Alzheimer disease: Potential novel AD biomarkers include neurogranin and visinin-like protein 1 (VILIP-1) (promising synaptic and neuronal degeneration biomarkers of AD) [105,118], neurofilament light polypeptide (NfL, a possible tau-independent marker of neuroaxonal degeneration) [107], glial fibrillary acidic protein (a promising plasma biomarker of AD) [119,120], and soluble triggering receptor expressed on myeloid cells 2 (TREM2) (a possible biomarker of microglial activation) to which ApoE can bind [121,122].