P2ry12, a marker associated with broad microglia activation, significantly decreased in the subcortical white matter of only MAPT (also referred to as FTLD-tau) patients and also decreased within layers II-V of the cortex in AD, C9ORF72, MAPT, FTLD-TDP and GRN patients (Fig. 2). Here, P2RY12 is linked to Alzheimer disease.