Fig. 5

Agrin is required for correct axon innervation and AChR patterning in the pectoral fin. (A) Trunk innervation in 120 hpf larvae expressing Tg(mnx1:GFP) to label motor axons and stained with α-Btx to label AChRs. Trunks in agrn mutants form fewer and smaller neuromuscular synapses. (B) Abductor muscle innervation in the pectoral fin from the same animals shown in A. Agrn siblings exhibit an innervation pattern with numerous small AChR clusters, whereas agrn mutants have swellings in the innervation pattern directly opposed to enlarged AChR clusters throughout muscle fibers in the fin. Insets from boxed regions show an even distribution of small AChR clusters (magenta) in siblings, whereas mutants have large AChR clusters that colocalize with green axon swellings. All images are maximum intensity projections that include the same number of slices for each genotype. (C,D) Quantification of the number of AChR clusters per fin (C) and the median cluster size per fin (D). (E) Histogram of the distribution of AChR cluster sizes across all fins quantified (5 μm² bins). ****P<0.0001, unpaired t-test. n=23 (siblings), 21 (mutants).