TREM2 and Alzheimer disease: To test whether the expression of TREM2 risk variants increases neuronal loss and whether these are the same neuronal populations lost in sporadic AD cases, we extended our analyses to include samples from non-diseased control and AD donors heterozygotic for TREM2 R47H or R62H allelic variants (CtrlTREM2, n = 6; 2/6 carrying the R47H allele; AlzTREM2, n = 13; 6/13 carrying R47H allele).