Fig. 2
Human BIN1iso1 is neurotoxic in Drosophila photoreceptor neurons. a Visualization of retina photoreceptor neurons expressing BIN1 isoforms (rh1 promoter) by cornea neutralization in living flies. b Quantification (Kruskal Wallis p = 0.013 followed by Mann–Whitney comparison, ***p < 0.001, ****p < 0.0001). At the bottom of the graph, upper numbers indicate the number of quantified eyes per condition and lower numbers indicate the mean number of ommatidia quantified per eye. Contrary to BIN1iso8 and BIN1iso9, BIN1iso1 expression induced a progressive age-dependent neurodegeneration, which was not dose-dependent. c, d Western blot analysis of BIN1 isoforms expression in the retina and quantification (n = 3, ANOVA F-value = 12.98, Df = 5, p = 0.00017, with post-hoc Tukey, *p < 0.05, **p < 0.01, ***p < 0.001). e Quantification of BIN1iso1-induced photoreceptor neuron degeneration over 4 weeks under a 12 h/12 h light/dark cycle (Ctrl L and BIN1iso1 L) or under constant darkness (Ctrl D and BIN1iso1 D) (Kruskal Wallis p = 0.0005344 for Day8-11, p = 3.264 × 10−05 for Day15-16, p = 1.36 × 10−07 for Day28-29, followed by Mann Whitney comparison, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). Loss of light did not prevent neurodegeneration although the intensity of degeneration was reduced. f Localization of BIN1 isoforms in one-day-old fly photoreceptor neurons. Luciferase was used as a control. Na/K ATPase staining labelled the plasma membrane and actin staining mostly labelled rhabdomere of photoreceptor neurons. Upper panels are longitudinal views of retina, whereas lower panels exhibit sectional views of ommatidium. g, h Scheme of the truncated BIN1iso1 tested protein and quantification of their toxicity in 15 day-old flies (Kruskal Wallis p = 5.686 × 10−11 followed by Mann Whitney comparison, ***p < 0.001, *****p < 0.00001). Loss of the CLAP domain totally abrogated BIN1iso1 toxicity