Gene expression and functional deficits underlie TREM2-knockout microglia responses in human models of Alzheimer’s disease

Differential transcriptomic effects of TREM2 stimulation versus deletion in human iPSC-microglia

Because preliminary data on TREM2 function suggests that AD-associated TREM2 mutations result in a partial loss of function¹⁹, we sought to mimic this effect by generating three isogenic sets of CRISPR-modified TREM2 knockout (KO) iPSC lines. Following microglial differentiation²⁷, we verified the loss of TREM2 expression at the protein level in all knockout lines by western blot and homogeneous time resolved fluorescence (HTRF) analysis (Fig. 1a). HTRF analysis of conditioned culture medium further demonstrated secretion of soluble TREM2 exclusively in WT and not in TREM2 knockout cell lines (Fig. 1b). This strongly suggests that WT iPS-microglia exhibit normal trafficking and localization of TREM2, and further confirms lack of TREM2 expression in KO lines.