Hook1 comigrates with Rab5 and Rab7 endosomes. (A) Mid-axons of hippocampal neurons expressing Hook1-Halo and Rab5- or Rab7-GFP. Arrows show colocalized Hook1 with the indicated Rab endosome. Bars, 4 µm. (B) The percentage of endosomes with Hook1-colocalization. Scatter plot shows mean ± SEM. Rab5: n = 17 neurons; Rab7: n = 10 neurons. (C) Kymograph of Rab5-GFP and Hook1-Halo motility in axon of hippocampal neuron. Arrows show comigrating Hook1-Rab5 organelles. Bars: 4 µm (horizontal); 20 s (vertical). (D) The ratio of retrograde to anterograde motility events in neurons expressing Rab5-GFP + Hook1-Halo or Rab5-GFP only. Unpaired t test (*, P = 0.0177). Rab5: n = 16 neurons; Rab5 + Hk1: n = 10 neurons. (E) Cumulative histogram of retrograde instantaneous velocities of events in neurons expressing Rab5-GFP + Hook1-Halo or Rab5-GFP only. Dashed line represents one phase decay regression line; half-life (λ) and 95% CI values are shown. (F) Kymograph of Rab7-GFP and Hook1-Halo motility in axon of hippocampal neuron. Arrows show comigrating Hook1-Rab7 organelles. Bars: 4 µm (horizontal); 20 s (vertical). (G) The ratio of retrograde to anterograde motility events in neurons expressing Rab7-GFP + Hook1-Halo or Rab7-GFP only. Unpaired t test (ns, P = 0.8223). Rab7: n = 13 neurons; Rab7 + Hk1: n = 7 neurons. (H) Cumulative histogram of retrograde instantaneous velocities of events in neurons expressing Rab7-GFP + Hook1-Halo or Rab7-GFP only. Dashed line represents one phase decay regression line; half-life(λ) and 95% CI values are shown.