Since PTPRG is expressed at a low level in microglia relative to the other brain cell types (Control TPMmedian: microglia = 1.25, brain homogenate = 6.47), it is plausible that its apparent reduction in homogenate tissue may be explained by the preferential loss of some cell types with higher PTPRG expression in AD. This evidence concerns the gene PTPRG and Alzheimer disease.