Figure 8.

Impaired proprioceptive synaptic function in all SMA models

(A) Experimental setup for ex vivo spinal cord preparation. Extracellular stimulation of L1 dorsal root (DR) and extracellular recording from L1 ventral root (VR).

(B) Representative traces of the first (black) and fifth (red) VR responses recorded at P11 following stimulation of the homonymous L1 DR at 10 Hz from control, SMNΔ7, Taiwanese at P11, and Smn^2B/- mice at P11. Scale bars = 0.5mV and 3ms.

(C) Quantification of VR response in mV following stimulation of the homonymous L1 DR at 10Hz from the same groups as in (B) at P11. Statistics: two-tailed t-test. n values for VR response: SMNΔ7: control = 6, SMA = 7; Taiwanese: control = 4, SMA = 4; Smn^2B/-: control = 3, SMA = 4.

(D) Quantification of amplitude changes in percent of the monosynaptic ventral root response following 10Hz stimulation at P11 from the same groups as in (B). Control groups were pooled from individual lines. n values for 10Hz stimulation: control = 12; SMNΔ7 = 7; Taiwanese = 5; Smn^2B/- = 4. Statistics: multiple t-test with Holm–Sidak method.

(E) Single optical plane confocal images of L1 ChAT+ motor neurons (blue) expressing Kv2.1 channels (gray) from the same groups as in (B) at P11. Scale bar = 20μm.

(F) Percentage of somatic coverage of Kv2.1 expression in L1 motor neurons for the same groups as in (B) at P11. Statistics: two-tailed t-test. n values for Kv2.1 analysis = 3 for each genotype.

Data are presented as mean ± SEM. Asterisks on top of bars without horizontal line indicate significance compared with the control group.

∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001.