exosc8 and exosc9 homozygous mutant zebrafish have reduced motor neuron density.(A) Immunofluorescence in 5-dpf wild-type, exosc8 homozygous mutant, and exosc9 homozygous mutant zebrafish larvae with an antibody raised against SV2 to stain presynaptic vesicles (red) and alpha bungarotoxin conjugated to Alexa Fluor 488 (green, staining postsynaptic acetylcholine receptors). (B) Quantification of the SV2-positive area in 5-dpf wild-type, exosc8 homozygous, mutant and exosc9 homozygous mutant zebrafish larvae. 5-dpf motor axons manage to migrate to neuromuscular junctions. However, there is significantly less motor axon branching in the exosc8 (c.26_27del) and exosc9 (c.198_208del) homozygous larvae than WT and heterozygous clutchmates. Seven control, nine exosc8 (c.26_27del), and 8 exosc9 (c.198_208del) homozygous larvae were measured for the quantification. Error bars represent the standard error (±SEM), and statistical analysis was performed using unpaired t tests (exosc8 versus wt and exosc9 versus wt, respectively). Scale bar: 50 μm.
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