Fig. 1

Aging does not affect ALS-like MN disease onset in rNLS8 mice. a Experimental timeline with life phase equivalencies indicated. b Representative image of a young rNLS8 mouse at symptom onset (notice hindlimb clasping). c Aged rNLS8 mice do not show a difference in onset of symptoms compared to young mice as assessed by appearance of one or more of the following phenotypes: clasping of hindlimbs, tremor, weight loss, and/or hunched posture. Mean ± SEM, p = 0.14. d Representative muscle cryosection from the TA of an aged rNLS8 mouse at 4 wks off Dox, with overlap of VAChT positive motor terminals (red) and acetylcholine receptors (α-bungarotoxin, BTX, green) as an indicator of innervated motor endplates. Denervated NMJs are marked with white asterisks. Scale bar = 100 μm. e After 4 wks of transgene expression, aged Tg mice show no difference in TA innervation when compared to young Tg mice. Data are mean ± SD (n = 3–4 for both young and aged Tg mice; p = 0.38). f Representative immunostaining for VAChT (red, to label MNs) and hTDP-43 (green) on a cryosection of lumbar SC from an aged rNLS8 mouse at 4 weeks off Dox shows that the majority of MNs express the transgene. g When staining with a TDP-43 antibody that labels both hTDP-43 and endogenous mTDP-43, widespread nuclear clearance is observed at this 4 wks off Dox time-point, similar to young rNLS8 SC [32]. Scale bar = 100 μm. h A slight decrease is observed in the number of lumbar SC MNs in young versus aged nTg mice (compare black vs grey bar, p = 0.05), but this MN loss is not exacerbated by 4 wks of transgene expression in rNLS8 animals (compare grey vs. blue bar, p = 0.1). ^∗ p = 0.05, compared to young nTg; # p < 0.05, compared to young rNLS8 mice