Fig. 1

TDP-43 Pathology drives a reversible ALS phenotype. A Breeding schema and experimental groups including a bigenic not-induced control group, a bigenic 4 weeks induced group, a bigenic resuppressed group, and a tTA control group. Representative pictures from the tail suspension test are shown demonstrating the reversible ALS phenotype seen in induced bigenic mice. By 4 weeks post-induction mice showed a severe phenotype with extreme clasping of all 4 limbs and recovered after 6–8 weeks of resuppression. B Representative confocal images of motoneurones (labelled with antibodies against ChAT, green) from tTA only mice, bigenic induced mice and bigenic resuppressed mice. This confirms the predominantly nuclear location of the pTDP in both the tTA controls and in the resuppressed mice but a loss of nuclear TDP-43, and cytoplasmic accumulation of phosphorylated TDP-43 (magenta), after removing of the doxycycline diet at 7 weeks of age in the bigenic induced mice. The tTA controls were at the same time point after doxycycline removal as the bigenic induced mice confirming that the tTA alone does not induce TDP-43 pathology (scale bar is 20 µm). C Induced bigenic mice show severely impaired motor function with reduced endurance time on the two minute cage lid test (Median (and IQR), Not-induced: 2 mins (0), Induced: 28.2 seconds (15.1), Mann Whitney, P=0.0022, n= 6 induced bigenic mice (3 female and 3 male) and 6 age matched not induced mice (3 female, 3 male). D-F Longitudinal comparisons between induced bigenic mice and tTA only controls that go through the same DOX-on, DOX-off and DOX-on feeding regime (D) Bigenic mice (green) show extreme weight loss after induction and recovered after resuppression, compared to tTA control littermates. Mixed –effect analysis Šídák's multiple comparisons test, P= 0.0283 (3 weeks), P= 0.0096 (4 weeks), P=0.0411 (1 week after resuppression) and P=0.0425 (2 weeks after resuppression). N=9 tTA mice (5 female, 4 male) and 12 bigenic mice (4 female, 8 male). (E) Endurance time on cage grid test shows that bigenic mice (green) decrease greatly after induction and recover after resuppression, while the tTA group (blue) shows no change. Mixed –effect analysis Šídák's multiple comparisons test, P= 0.0052 (2 weeks), P<0.0001 (3 and 4 weeks post induction and 1 and 2 weeks after resuppression). N=9 tTA mice (5 female, 4 male) and 12 bigenic mice (4 female, 8 male). (F) Endurance time on rotarod shows that bigenic mice (green) decrease greatly after induction and recovered after resuppression, while the tTA group (blue) shows no changes. Mixed –effect analysis Šídák's multiple comparisons test, P= 0.0052 (2 weeks), P<0.0001 (3 and 4 weeks post induction and 1 week after resuppression) and P=0.0015 (2 weeks after resuppression). N=9 tTA mice (5 female, 4 male) and 12 bigenic mice (4 female, 8 male). Data are given as the mean ±SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001