Fig. 3
The recovered lower motor circuit in rNLS8 mice is resistant to subsequent hTDP-43ΔNLS challenge. a The experimental approach used to investigate the response of rNLS8 mice to a second instance of hTDP-43ΔNLS expression after recovery from the initial pathological insult. Dox was withdrawn for 6 wks. to initiate a first disease course, after which hTDP-43ΔNLS was suppressed for 10–12 wks. by reintroducing dietary Dox, thus allowing muscle reinnervation by resistant MNs. A second 6-wk. instance of disease was then imposed by withdrawing Dox. Arrows indicate the time points at which mice were analyzed for CMAP, TA innervation and MN counts. b Representative immunofluorescence images of lumbar MNs (VAChT-positive, red) expressing high levels of cytoplasmic hTDP-43 (green) from rNLS8 mice in the first and second disease courses. Scale bar: 100 μm. c Quantitation of the number of MNs per ventral horn in rNLS8 mice at each analysis timepoint in the study outlined in a. The number of animals assayed per timepoint was 4–5, with 10–20 spinal cord sections scored for each animal. T test, ***p < 0.001 for baseline vs. 1st disease course; *p = 0.02 for recovery versus 2nd disease course. d CMAP traces in the GC muscle from rNLS8 mice after the first disease course, after recovery and after the second disease course. e Longitudinal comparison of maximum evoked CMAP amplitude in the GC muscle of rNLS8 mice throughout the experimental time course outlined in (a). The number of animals assayed per timepoint was 5–7. T test, **p = 0.0010 for baseline versus 4 wks. off Dox; ****p < 0.0001 for baseline versus 6 wks. off Dox; other comparisons nonsignificant. f The proportion of intact NMJs in the lateral GC muscle of rNLS8 mice throughout the experimental time course outlined in (a). The number of animals assayed per timepoint was 3–6, with 600–1000 NMJs scored per animal. T test, ***p < 0.001 for baseline versus 4 wks. off Dox; ***p < 0.001 for baseline vs. 6 wks. off Dox; other comparisons nonsignificant