TREM2 and Brain atrophy: examined Trem2-deletion in the pR5-183 mouse model expressing P301L mutant tau alone (Tau P301L) or in combination with the PS2/APP transgene (Tau/PS2/APP), and found that Trem2-deficiency exacerbates tau propagation and consequent brain atrophy in the Tau/PS2/APP model, but not in the Tau P301L model at both early and late degenerative stages [169].