Fig. 1. Absence of AChR clusters during initial stages (E13-E15.5) of neuromuscular synaptogenesis in ^-/- embryos. Clustering of AChRs was detected by Texas Red-conjugated -bungarotoxin. In whole-mount diaphragm muscles (A-C,F-H), AChR clusters were distributed along a central region of the muscle in the wild type (arrowheads in A-C), but were absent from the ^-/- muscles (F-H); instead, diffused fluorescence was observed on the surface of the muscles. Broken lines in H indicate the central region of the muscle. Similarly, AChR clusters were detected in EDL or soleus muscles in the wild-type (D,E), but not in the ^-/- muscles (I,J). Scale bars: 25 µm in A-C,F-H; 20 µm in D,E,I,J.