Fig. 1: Protrudin is expressed at low levels in mature axons and overexpression restores this deficit.

a Schematic diagram of Protrudin’s domains and structure. b Schematic of wild-type and phosphomimetic Protrudin mutagenesis sites. c mRNA expression levels of six neuronal genes (including Zfyve27—the Protrudin gene) from different stages of development in primary rat cortical neurons in vitro (n = 5–6 samples). d Normalized expression levels of Protrudin and other related genes during embryonic development in the mouse (n = 3 animals for each timepoint), after plating DRG neurons in vitro (n = 3 animals for each timepoint) or after peripheral nerve injury in DRG cells (n = 3 animals for sham and injured samples). e Immunofluorescent images of Protrudin in the proximal axons (white dotted line box) of neurons at different stages of development in culture. Scale bars are 20 µm. The white arrows follow the course of the proximal axon. f Immunofluorescent images of overexpressed, mCherry-tagged wild-type or phosphomimetic Protrudin (magenta) and staining for the axon initial segment marker—neurofascin (cyan). Scale bars are 20 µm. g The axon-to-dendrite ratio of Protrudin at different developmental stages or after overexpression at 14–16 DIV (n = 4 independent experiments for each condition, n numbers on graph show the number of analysed cells) (Kruskal–Wallis with Dunn’s multiple comparison test, p < 0.0001, Kruskal–Wallis statistic = 101.6). Error bars represent mean ± SEM.