TREM2 and Alzheimer disease: Specifically, participants carrying the risk allele had lower levels of TREM2 mRNA at autopsy and the relationship between increases in TREM2 mRNA and increases in Aβ1-38 peptide was driven by non-carriers, suggesting this AD risk SNP may impair a potential cortical TREM2 transcriptional response to amyloid (which has been previously characterized by this group using ROS/MAP data [46]).