Fig. 6

MuSK extrasynaptic localization and transcript expression are reduced in ∆Ig3-MuSK soleus. A–D MuSK transcript levels in WT and ∆Ig3-MuSK EDL and soleus muscle were quantified by qRT-PCR. Note that MuSK transcript levels are selectively reduced in ∆Ig3-MuSK soleus compared to WT, while the levels in the EDL are comparable in both genotypes. Data are means ± SEM from 3 to 6 different biological replicates (*p < 0.05, unpaired two-tail Student’s t-test). E and F MuSK localization in TA. TA sections from WT and ∆Ig3-MuSK animals were immunolabeled with anti-MuSK (IgG4 serum fraction from MuSK myasthenia gravis patients [24]; 1:1000; red) and α-bungarotoxin (green; to visualize NMJs). In the TA, MuSK is restricted to the NMJ (arrows) in both WT and ∆Ig3-MuSK muscle. No extrajunctional MuSK localization is detected in TA of either genotype. G and H MuSK localization in soleus. In WT soleus (G), MuSK is localized at both the NMJ (arrows) and extrajunctionally (arrowheads). In contrast, in ∆Ig3-MuSK soleus (H), MuSK is present at NMJs at levels comparable to WT, but extrajunctional MuSK was not detected