More nodes of Ranvier with shorter length generate more internodes in the absence of R-Ras1 and R-Ras2 in adult mice (P90). A, Double-staining of longitudinal sections of adult (P90) optic nerves with anti-Caspr (green) and anti-NF200 (red) reveal an increase in the number of paranodes (green) in the R-Ras1^−/−;R-Ras2^−/− mice compared with controls. The distance between paranodes (nodal length) in higher-magnification images (boxed insert) was shorter in double mutants than in controls. B, Simplified scheme representing the node of Ranvier between two internodes. C, Western blot of P90 optic nerve lysates showing a significant increase in Caspr protein expression in double mutants compared with controls. Bar graph shows the mean ± SD change in densitometric measurements normalized to GAPDH and relative to controls (*p = 0.016; n = 5). D, Schematic representation of the shorter nodal length and more internodes observed in the R-Ras1^−/−;R-Ras2^−/− mice compared with control. E, Bar graph showing a significant increase in paranodes found in double mutants (80.85 ± 19.71 paranodes/67 × 67 μm) compared with controls (54.09 ± 14.22 paranodes/67 × 67 μm) (***p = 0.000124; n = 4). F, Paranodal length classification does not reveal any differences in R-Ras1^−/−;R-Ras2^−/− compared with controls. G, Node classification by their length reveals more short nodes in R-Ras1^−/−;R-Ras2^−/− mice (30.5 ± 4.5% of nodes <0.5 μm long) than in controls (7.5 ± 5.1% of nodes <0.5 μm long, **p = 0.004) at the expense of longer nodes.