Fig. 4: Cdk12 limits F-actin formation in axons.

A A representative F-actin fluorescence intensity plot of F-actin localization in wild type in wing sensory neurons at 21 days using genetically encoded LifeAct. F-actin is highly expressed in small patches closer to the cell body. B Aged wild-type axons at 35 days also display F-actin in proximal axon regions. C Cdk12^−/− axons display large an increase in F-actin intensity at 21 days compared to age-matched controls. D By 35 days remaining Cdk12^−/− axons display an F-actin fluorescence intensity plot that shows multiple bright axon F-actin patches up to 30 μm away from cell body. E Cdk12^−/− axons displayed a significantly greater area under the curve of fluorescent F-actin intensity across 50 μm of axon. F Quantification shows that loss of Cdk12 is associated with increased F-actin patch formation. G The total fluorescence intensity of Cdk12^−/− axons was significantly greater than control at 35 days. Fluorescence was normalized to td-Tomato expressed in the same cell to label membranes. H Chickadee and the Arp2/3 complex were required for F-actin formation I RNAis targeted against actin-binding proteins rescued the heightened actin phenotype. Data was analyzed by either one or two-way ANOVA and significant differences annotated as p < 0.05* & p < 0.01** between genotypes. Graphs are expressed as Mean ± SEM and N = ≥ 8 per group. Scale bars = 10 µm.