Fig. 3

Ephrin-A2 and ephrin-A5 regulate contralateral targeting of VCN axons. a Schematic diagram illustrating circuitry in the VCN pathway. Dye placement in VCN on one side normally results in labeled calyces in contralateral MNTB (MNTBc) but not in ipsilateral MNTB (MNTBi). b In wild type mice numerous calyces are labeled in MNTBc. c Labeled terminations were not formed in MNTBi in wild type mice. d In ephrin-A2/A5 double knockout mice, VCN axons terminated in MNTBc. e In addition to the normal projection, ephrin-A2/A5 double knockout mice also displayed numerous terminations in MNTBi, indicating significant errors in axon targeting. These projections ended in large terminations with morphology similar to the calyx of Held found in contralateral projections. f, g Ephrin-A2 single knockout mice showed a similar phenotype to ephrin-A2/A5 double knockout mice, with normal contralateral calyces as well as terminations in MNTBi. h, i Similarly, Ephrin-A5 single knockout mice showed both contralateral and ipsilateral calyceal terminations. j To compare axon targeting errors between groups we used the ratio of calyces in MNTBi to MNTBc, the I/C ratio. Using ANOVA with post hoc analysis, we found a significant increase in I/C ratio for all three mutant mouse groups compared to wild type mice. I/C ratios for mutant mice did not differ significantly from each other. Scale bar in I indicates 100 μm for B-I