Intercellular transmission of TDP-43 oligomers. (A) Luciferase activity measurement of intact cells and CM from HEK-293 cells cotransfected with TDP-L1 + TDP-L2. n = 20. (B) Luciferase activity measurements after extensive washing of naive HEK-293 cells cultured for 72 h in CM. CM was obtained from HEK-293 cells transfected either with mock, TDP-L1 + TDP-L2, or TDP-Luc. n = 4 per group. (C) Luciferase activity measurements of naive primary cortical mouse neurons cultured for 72 h in CM. CM was obtained from primary neurons transduced with rAAV6.2 encoding TDP-L1 + TDP-L2 or TDP-Luc. n = 12 per group. Mean ± SEM. ***, P < 0.001.