Fig. 5

Functional Assessment of Mutation Burden Hypothesis in a Zebrafish Model

First and second column panels show representative images of acetylated-tubulin (α-AcTub) staining of peripheral neurons in 2-day MO knockdown, single or in pairwise combinations, zebrafish larvae. Third column panel shows qualitative assessment of morphant fish evaluated as defects in peripheral neuron axon extension, branching or pathfinding according to the scoring system developed. For pairwise combinations, sub-effective concentrations of each of the gene-specific MOs were injected as shown in the graphs by the number of abnormal larvae in each category. However, when injected together increased severity in the phenotype was observed for all the pairwise combinations, suggesting in vivo epistatic effects between these pairs of genes as observed in the α-AcTub fluorescence images and quantified in the graphs. Asterisks highlight some evidently affected axons. The scoring system used for assessing PNS defects in zebrafish was developed ad hoc and implemented here in order to best reflect the observations resulting from our experiments. Class I category refers to single axon defects; class II category refers to two or more axons exhibiting defects with the presence of some normal axons; class III category refers to generalized axonal defects; class IV category refers to complete absence of axonal extension.