To identify the hippocampus-mediated pathway from gene expression to AD, we performed mediation analysis, in which the predicted cis-GReX of QPCTL or ERCC2 in hippocampal tissue was set as an independent variable, mean hippocampal volume as a mediator variable, and disease state (AD versus CN) as a dependent variable. The gene discussed is ERCC2; the disease is Alzheimer disease.