Fig. 5

Disruption of gdf6 function exacerbates neuromuscular junction abnormalities in ALS model zebrafish.

ALS model zebrafish possess disruptions to neuromuscular junctions (NMJ), and loss of gdf6 function exacerbates this by 7 months of age. A. The presynaptic junctions (labeled with synaptophysin antibody) and postsynaptic junctions (labeled with fluorescently tagged αBTX) in ALS model zebrafish expressing the mutant SOD1^G93R show punctate morphology, deviations in presynaptic volume and less overall colocalization compared to WT sibling junctions. Some abnormalities are exacerbated in bigenic siblings expressing the mutant SOD1^G93R that are also gdf6^-/- (scale bar is 40 µm). B. Quantification of these NMJs suggests the presynaptic/postsynaptic volume ratios of SOD1^G93R and bigenic gdf6^-/-;SOD1^G93R zebrafish are larger than those of WT siblings at this age, though these differences do not rise to statistical significance (Kruskall-Wallis ANOVA, p = 0.134; n = 6,4,6 for WT, SOD1^G93R, and bigenic fish respectively). Colocalization coefficients, that measure overall colocalization of presynaptic and postsynaptic junctions, are altered in these fish. The values for SOD1^G93R zebrafish are significantly lower than wild type sibling values, indicating that presynapses and postsynapses overlap less, as characterized previously for this transgenic ALS model [28]. Bigenic SOD1^G93R zebrafish that are also gdf6-/- have a dramatically lower coefficient than either sets of siblings, including being 30% lower than ALS model SOD1^G93R fish with normal gdf6a (*p<0.05; ***p<0.001. Kruskall-Wallis ANOVA with pairwise comparisons).