Fig. 5

stl145 mutants exhibit delays in radial sorting and decreased expression of krox20. a-g) TEM of cross-sections of the PLLn. Myelinated axons are pseudocolored in green and axons associated with promyelinating Schwann cells are pseudocolored in purple. Scale bars = 500 nm. a, b) Micrographs from the same PLLn within a MZdock1^stl145 heterozygote show Schwann cells myelinating axons at 60 hpf. C) An MZdock1^stl145 homozygous larva does not have myelinated axons at 60 hpf, but Schwann cells are extending processes into axon bundles. C′) Magnification of inset from C shows an axon surrounded by a pro-myelinating Schwann cell. d, e) Schwann cells can myelinate and sort axons at 3 dpf in wild-type (n = 6 animals, 10 nerves) and mutant larvae (n = 4 animals, 6 nerves). f, g) More sorted axons are present in mutants (n = 8 animals, 15 nerves) at 5 dpf compared to controls (n = 11 animals, 17 nerves). Quantification of the number of sorted axons at h) 3 dpf and i) 5 dpf shows a statistical difference at 5 dpf (unpaired t Test with Welch’s correction). j, k) Lateral view of WISH for krox20 at 3 dpf. Arrowheads indicate PLLn. Inset panels show a magnified view of the PLLn. Scale bar = 50 μm. j) krox20 is expressed along the PLLn of control larvae (n = 67) whereas k) dock1^stl145 homozygous mutants express little to no krox20 along the PLLn (n = 18/19). l) Quantification of WISH for krox20 at 3 dpf based on phenotypic classes and genotypes for the stl145 lesion (p < 0.0001, Chi-squared analysis). m, n) Lateral view of WISH for sox10 at 3 dpf. Arrowheads indicate the PLLn. Inset panels show a magnified view of the PLLn. Scale bar = 50 μm. m) Control larvae exhibit sox10 positive Schwann cells along the PLLn (n = 37) similar to N) dock1^stl145 homozygous mutants (n = 16). o) Quantification of WISH for sox10 at 3 dpf based on phenotypic classes and genotypes for the stl145 lesion (p = 0.8141, Chi-squared analysis). Bars represent means ± SD, **p < 0.001, **** p < 0.0001