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. 2021 Oct 30;24(11):103376. doi: 10.1016/j.isci.2021.103376

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© 2021 The Author(s)

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

PMC Copyright notice

Smn^2B/- and SMNΔ7 mice exhibit vast NMJ denervation and dysfunction

(A) NMJ staining with bungarotoxin (BTX, red), synaptophysin (Syn, gray), and neurofilament (NF, green) in quadratus lumborum (QL) muscles from control, SMNΔ7, Taiwanese mice at P11, and Smn^2B/- mice at P22. Scale bar = 50μm.

(B-C) Percentage of denervation of QL in (B) and tibialis anterior (TA) in (C) of SMNΔ7 at P1, P4, and P11, Taiwanese at P6, P11, and Smn^2B/- mice at P1, P10, and P22. Statistics: two-way ANOVA with Tukey’s correction. n values for QL denervation = SMNΔ7: P1 control = 4, SMA = 5; P4 control = 3, SMA = 5; P11 control = 3, SMA = 4; Taiwanese: P6 control = 3, SMA = 3; P11 control = 3, SMA = 6; Smn^2B/- = 3 for all groups and ages.

(D) Experiment setup of ex vivo extracellular compound motor action potential (CMAP) recording. L1 ventral root is sucked into the stimulation electrode and the recording electrode is inserted ∼2mm away into the QL.

(E) CMAP recordings from the QL muscle following L1 ventral root (VR) stimulation from the same groups as in (A) at P11. Black triangles indicate stimulation artifact and blue arrows indicate the time from stimulation to response (latency). Scale bars = 1mV, 2ms.

(F, G) Quantification of (F) CMAP amplitude and conduction velocity (CV) recorded from the QL muscle in the same groups as in (A) at P11. Statistics: two-tailed t-test. n values for CMAP and CV = SMNΔ7: control = 9 and SMA = 9; Taiwanese: control = 9, SMA = 8; Smn^2B/-: control = 10, SMA = 7.

(H) Example trains of CMAP recordings at 50Hz stimulation from P11 QL muscles of the same groups as in (A). Blue boxes indicate first and tenth muscle response of each train. Scale bars = 0.5mV, 50ms.

(I) Percentage of CMAP amplitude change at 50Hz stimulation from P11 QL muscles of the same groups as in (A) at P11. Statistics: multiple t-test with Holm–Sidak method. Control group is pooled from controls of each individual line. n values for 50 Hz stimulation: control = 24; SMNΔ7 = 5; Taiwanese = 8; Smn^2B/- = 7.

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.