KIF1Bβ-Y1087C reduced the capacity to complement surface IGF1Rα expression. (A and B) Fluorescent images of the surface immunocytochemistry against IGF1Rα of Kif1b^−/− and Kif1b^+/+ mouse–dissociated hippocampal neurons at DIV4 (left) together with the images of the transfection marker TagRFP (right) expressing the indicated constructs for 3 d. The neurons were plated at a cell density of 2.6 × 10⁴ cells/cm². Axonal regions at ∼100 µm apart from the somata (A, boxes) are enlarged in B. Bars: 10 µm (A); 5 µm (B). (C) Anti-DDDDK (FLAG) IB of the lysates of Neuro2A cells expressing the indicated constructs. (D) Quantification of the axonal surface IGF1Rα fluorescence intensities in B. n = 30–122. **, P < 0.01; ***, P < 0.001; ns, P > 0.05. Mean ± SEM. Two-sided one-way ANOVA with post Dunnett’s multiple comparisons was adopted.