Fig. 2

Individual axon subtypes support differential initial ensheathment rates. a-b Lateral view images show the progression of myelination on individual spinal axons during the 48-h period following initial wrapping. Images were acquired within a constant spinal cord segment at each time point. Note that although RB and CoPA spinal axons are both located within the spinal cord DLF, RB sensory axon myelination remained sparse and incomplete (a), but CoPA axons became completely ensheathed during the same imaging period (b). Scale bar = 5 μm. c Quantification of the percent length of individual axons ensheathed at each time point. t = 0 was defined as the onset of initial wrapping for each subtype within the spinal cord segment imaged (see Methods). Each row of the table contains two dots indicating the subtypes being compared with the corresponding p-value testing for difference in myelination rates of those two subtypes. For the right-most column, c reports p-values for the indicated axon diameter comparisons using one-way ANOVA and Tukey post-test. Note that subtype comparisons lacking significant differences in axon diameter did show significant differences in myelination rate. Error bars represent the mean ± SEM. n (# larvae imaged at 0, 24, 48 h time points) = 11, 14, 25 (tbx16⁺); 15, 12, 6 (phox2b⁺); 11, 11, 18 (pitx2c⁺); 16, 25, 23 (isl1[ss]⁺). P-value from ANCOVA testing for overall difference in myelination rate was 0.0015. Reported p-values for pairwise comparisons were generated with Tukey adjustment