Figure 1

Neurofascin B Is Required for Myelin Targeting in the Zebrafish CNS

(A and B) Images of wild type (A) and ue56 mutant (B) larvae at 5 days post-fertilization (dpf), showing normal morphological development of ue56 mutants. Scale bar, 500 μm.

(C–D′) Confocal images of myelin in a wildtype larva (C and C′) and ue56 mutant (D and D′) at 5dpf, visualized using Tg(mbp:EGFP-CAAX). Lateral views, with anterior to the left. (C) and (D) are maximum intensity projections of z sections taken through the entire spinal cord, with (C′) and (D′) being a projection of a subset of z sections centered closer to the midline in the region where cell bodies are prominent and myelinated in mutants. Scale bars, 20 μm.

(E) Quantitation of myelinated cell body number in wildtype and ue56 mutants at 5dpf in a 3 somite long stretch of spinal cord (wild type median = 2, 25^th percentile 0, 75^th percentile 2.5, n = 13 animals, ue56 median = 53, 25^th percentile 46.5, 75^th percentile 62.75, n = 14 animals, p < 0.0001, t test)

(F) Sequence at amino acid positions where the ue56 mutation generates a stop codon and indication of the conserved region across species.

(G) Schematic of predicted domain structure of mouse neurofascin 186, neurofascin 155, and zebrafish neurofascin B, with indication of where the mutation in ue56 mutants resides.

(H–I′) Z projections of confocal images of neurons (red) and myelin (green) in a wildtype animal (H and H′) and nfascb^ue56 mutant (I and I′), showing myelin sheaths made on axons (H and I) and myelination of cell bodies in mutants in a region with cell bodies only (H′ versus I′). Scale bars, 20 μm.

(J) Schematic cross section of the larval zebrafish spinal cord denoting areas with cell bodies (red) and myelinated axons (green) (Top panel). Dorso-ventral and medio-lateral positions of all myelinated cell bodies (dots) in a 3-somite long stretch of spinal cord of 11 mutants (bottom panel).