hTDP-43 protein dose-dependent apoptotic death of NSC34 cells. (A) Higher levels of MT hTDP-43 than WT hTDP-43 at the same dose(s) of DNA transfection. NSC34 and Neuro2a cells were transfected with different doses (μg/ 106 cells) of the expression plasmids. At 72 hr post-transfection, the levels of the exogenous hTDP-43 expressed were compared by Western blotting using the anti-hTDP-43 antibody 2E2D3, with the mouse Hsp70 level as the internal control. The means of the relative levels of hTDP-43 obtained from three independent experiments (S.D.) are then plotted in the 2 panels, with the level of the WT hTDP-43 in cells with the transfection dose of 20 μg DNA/ 106 cells as 100. Note the higher levels of the MT hTDP-43 than WT hTDP-43 in both NSC34 and Neuro2a cells at all doses of transfection. *, p< 0.05; **, p< 0.01; ***, p< 0.001. (B) The % of transfected cells that were cleaved caspase 3-positive as a function of the relative amounts of hTDP-43. The plots were derived from the combined data of Figures 2 and 3A. The amounts of hTDP-43 in NSC34 cells or Neuro2a cells transfected with 20 μg of pEF-hTDP-43N390D are assigned the value of 1.