Figure 3.
The postnatal morphological maturation of the neuromuscular synapse is impaired in mice lacking MACF1 in muscle. (A) Diaphragm muscles from Macf1f/+ control and Hsa::Cre; Macf1f/− mice at E18.5 were stained with Alexa Fluor 488–α-BGT to label AChRs (red) and antibodies to Neurofilament/Synapsin to label motor axons/nerve terminals (green). Bar, 50 µm. (B) The size of the synapse, the density of synaptic AChRs, and percent of AChR-rich areas that are apposed by nerve terminals were quantified. At E18.5, synaptic size is normal, but the density of synaptic AChRs is reduced by 13% in Macf1 mutant muscle. The mean ± SEM values from three mice (100 synapses per mouse) are shown (***, P < 0.0005). (C) At P90, neuromuscular synapses in Macf1 muscle-conditional mutant mice show signs of deterioration. Synapses, marked by staining for AChRs (red), are smaller in size, and their pretzel-like shape is less elaborate. Bar, 10 µm. (D) Neuromuscular synapses in Macf1 muscle-conditional mutant mice deteriorate further, as synaptic size fails to increase between P90 and P365, and the extent of synaptic fragmentation worsens in Macf1 mutant mice. Moreover, the density of synaptic AChRs is reduced by 20%. The mean ± SEM values from three mice (100 synapses per mouse) are shown (*, P < 0.05; **, P < 0.005; ***, P < 0.0005; ****, P < 0.00005).