Figure 6

Axons of DRG and sympathetic neurons but not motor axons are repelled by Sema6A. (a) Upon encountering a COS cell expressing Sema6A, 53% of all DRG axons were found to react with avoidance, that is, they turned away from the cell or stopped rather than growing onto the Sema6A-positive COS cell (p = 0.0002 for the comparison between S6A/Ax-1 and S6A/EGFP (indicated by three asterisks)). COS cells expressing Axonin-1 (Ax-1) were perceived as slightly more attractive than control COS cells expressing only EGFP (p = 0.006 for S6A/Ax-1 and 0.02 for S6A/EGFP (indicated by asterisk)). (b) Motor axons were found to be indifferent to all types of COS cells. The majority showed neither attraction nor repulsion when encountering Sema6A or Axonin-1 compared to EGFP-expressing COS cells. (c) The majority of sympathetic axons (68%) were avoiding Sema6A-expressing cells (p < 0.0001 (three asterisks)). Compared to DRG axons and motor axons, sympathetic axons were more strongly attracted by Axonin-1-expressing COS cells (p < 0.0001 for Ax-1/S6A and Ax-1/EGFP). This is reflected by the fact that avoidance of Axonin-1-expressing cells was significantly lower compared to EGFP-expressing cells (p = 0.003 (two asterisks)). Similarly, axons of sympathetic neurons (SG) were significantly less attracted to Sema6A-expressing compared to EGFP-expressing cells (p < 0.0001 (three asterisks)). Values are given as mean ± standard error of the mean.