Figure 7.

β1 (-/-) mice have fewer optic nerve nodes of Ranvier. A, Optic nerves of P17-P19 β1 (-/-) and β1 (+/+) littermates were cryosectioned and stained for pan-sodium channels (red) and caspr 1 (green). The panels in A show typical FOV. Nodes of Ranvier were defined by a region of high-sodium channel density in the nodal gap, bordered by caspr 1-positive paranodes. Individual nodes had a normal appearance in both β1 (-/-) and β1 (+/+) animals, but there were fewer such sites in the null mutant. B, Over 30 FOV were analyzed for both β1 (-/-) (red bar) and β1 (+/+) (blue bar) mice, and the results are summarized in the bar graph. β1 (-/-) optic nerves had significantly fewer nodes than β1 (+/+) (p < 0.001). C, Left, Ultra structural analysis of optic nerve cross-sections shows similar numbers of myelinated axons per unit area for β1 (+/+) (blue bars) and β1 (-/-) (red bars). However, a greater percentage of myelinated axons per nerve cross-section in β1 (-/-) optic nerves (right, red bar) appear to be degenerating (p = 0.067, Student's t test). Error bars in both panels represent SDs.