Fig. 4

Fast-twitch tibialis anterior motor units show significant changes in post-synaptic membrane of NMJ. Post-synaptic membranes of NMJs from tibialis anterior (TA) muscle were labeled with fluorescently tagged α-bungarotoxin (α-BTX). A Transgenic mice showed significantly decreased post-synaptic area (B; p < 0.01) and endplate area (D; p < 0.01) without an increase in AChR compactness (F). Transgenic mice showed a significant increase in the percentage of fragmented NMJs (H; p < 0.05). Knock-in mice did not show an increase in fragmentation (I), post-synaptic area (C) or endplate area (E) but did show an increase in AChR compactness (G; p < 0.05). Mann–Whitney Test was used to evaluate statistical significance for distributions. Student’s t-test was used to evaluate fragmentation. Abbreviations: Ntg, non-transgenic; Tg, transgenic; WT, wild-type; KI, knock-in