Figure 7.
COPA neurons have limited axonal vesicular fusion
(A) Morphology of COPA axons in the developing zebrafish spinal cord.
(B and C) Two examples of COPA axons, their myelination profiles and SypHy activity. Magenta arrowheads indicate collateral SypHy activity. Kymographs represent SypHy activity of bracketed axonal region.
(D) Myelin coverage is similar in reticulospinal and COPA axons (p = 0.291, Mann-Whitney test, 66 RS axons in 57 animals and 19 COPA axons from 19 animals).
(E) Axonal, but not collateral SypHy frequency is reduced in COPA axons compared to reticulospinal datasets (axonal: p = 0.043 RS1 versus COPA, p = 0.002 RS2 versus COPA; collateral: p > 0.99 RS1 versus COPA, p > 0.99 RS2 versus COPA; Kruskal-Wallis with Dunn’s multiple comparison test; N as in Figures 1 and 2 and D).
(F) Axonal SypHy frequency is comparable in myelinated and unmyelinated COPA axons (p = 0.237, Mann-Whitney test, 8 unmyelinated and 11 myelinated COPA axons from 19 animals).
(G) Within myelinated COPA axons, SypHy frequency is higher in non-myelinated regions (p = 0.024, Wilcoxon matched-pairs signed-rank test, 11 myelinated COPA axons from 11 animals).
Scale bars, 10 μm (A), 5 μm, and 60 s (B and C). Graphs display median and interquartile range.