APOE and Alzheimer disease: We found that all the 14 control samples clustered with the GTEx “healthy aging” subgroup A. For the 37 PHG AD samples, 5 (3 APOE ε3/ε4 and 2 APOE ε3/ε3) clustered with GTEx subgroup B and 26 clustered with GTEx subgroup C (the two “AD similar” subgroups), only 6 samples (all APOE ε3/ε3) clustered with the “healthy aging” subgroup A. This result suggests that the gene expression of the “healthy aging” subgroup is mainly associated with cognitively normal status in older individuals while the gene expression of the “AD similar” subgroup is largely associated with AD in this older cohort.