Fig. 5

lama2 Knockdown Enhances gpr126 Hypomorphic Phenotype

(A–I) Dorsal views of mbp expression by WISH in 4 dpf larvae. Insets: magnification of the right PLLn. Control, injected with phenol red dye only; MO, lama2 morpholino-injected.

(A–C) Control-injected larvae.

(A) mbp expression is strong in the PLLn of a WT (gpr126^+/+) larva. Arrows indicate the PLLn, and the arrowhead indicates the CNS.

(B) mbp in a heterozygous (gpr126^+/st63) larva is indistinguishable from WT.

(C) mbp is reduced, but not absent, in the PLLn of a homozygous gpr126^st63/st63 hypomorph.

(D–F) Larvae injected with low-dose (2.5 ng) lama2 MO.

(D) mbp is not disrupted in a gpr126^+/+ larva.

(E) mbp is reduced in the PLLn of a heterozygous gpr126^+/st63 larva relative to control-injected.

(F) mbp is further reduced in a gpr126^st63/st63 larva.

(G–I) Larvae injected with high-dose (5 ng) lama2 MO.

(G) mbp is disrupted in both the CNS (arrowhead) and PLLn in a gpr126^+/+ larva.

(H) mbp is further reduced in a heterozygous gpr126^+/st63 larva.

(I) mbp is nearly absent in the PLLn of a gpr126^st63/st63 larva.

(J) Quantification of WISH expressed as a percentage of larvae with each mbp PLLn phenotype at 4 dpf. Asterisks indicate a significant decrease of “strong” expression. p < 0.05, p < 0.01, Fisher’s exact test. Control, pooled uninjected and phenol red-injected.

(K–N) TEM of 3 dpf zebrafish PLLn. Sorted and myelinated axons are defined and pseudocolored as in Figure 1. The scale bar represents 1 µm.

(K and L) Myelination proceeds normally in a control-injected gpr126^+/+ sibling (K), but radial sorting and myelination are reduced with 5 ng MO in gpr126^+/st63 (L).

(M and N) Myelination is reduced in a gpr126^st63/st63 hypomorph (M), and is further reduced in a gpr126^st63/st63 sibling injected with 5 ng MO (N).

(O–Q) Quantification of TEM images. Bars represent means ± SD. p < 0.05, p < 0.01, p < 0.001, one-way ANOVA with Bonferroni’s multiple comparisons test.

(O) Number of sorted axons per PLLn.

(P) Number of myelinated axons per PLLn.

(Q) Number of total axons per PLLn.