Figure 1. Denervation induces muscle stem cell (MuSC) actions proximal to the neuromuscular junction (NMJ).

(A) Schematic of NMJ from Pax7^CreER/+-Rosa26^nTnG mice, which display red fluorescent protein (RFP) in their nuclei and following administration of tamoxifen, Pax7⁺ MuSCs (labeled with green arrow) and their progeny are labeled with a nuclear green fluorescent protein (nGFP). (B) Representative immunofluorescence image of single myofiber isolated from extensor digitorum longus (EDL) muscle showing GFP expression exclusively in MuSCs and red nuclei. Scale=50 µm. (C) After muscle injury through barium chloride (BaCl₂) injection (top), myofiber degeneration resulted in contribution of MuSC-derived progenitors and centrally located myonuclei along the entire length of the regenerated myofiber. After sciatic nerve transection (SNT), MuSC-derived myonuclei were confined at or near NMJ myofiber regions. Magnified inset images show NMJs (acetylcholine receptor [AChR] labeled with α-bungarotoxin [BTX]) with nGFP⁺ nuclei. Scale bar for myofibers = 200 μm for inset = 25 μm. n = 5 muscles for both injury types and 20–30 myofibers counted from each isolated muscle. (D) Quantification of fraction of nGFP⁺ nuclei underneath and near synapses compared to all positions on myofibers, where **p < 0.01 using two-sided t-test.