Fig. 3. Growth cone responses to Sema5A in the presence of L1 and netrin 1. (A) Timelapse sequence showing a retinal growth cone extending on an L1 substratum and exhibiting collapse in response to application of oligomerized ECD-Fc. (ECD-Fc was applied at t=0). Numbers at top left are minutes elapsed. During collapse, axons on L1 tended to show an intermediate stage characterized by the shrinkage of the growth cone into a branched structure (t=20). Growth cones eventually progressed to a fully collapsed morphology (t=40). (B) The percentage of growth cones on L1 substratum exhibiting collapse in response to increasing amounts of oligomerized ECD-Fc. (C) The percentage of growth cones on L1 substratum exhibiting collapse in response to increasing amounts of oligomerized sema-Fc or TSP-Fc. (D) The percentage of growth cones extending on laminin in the presence of netrin 1 responding to oligomerized ECD-Fc. The presence of netrin 1 did not alter the ability of ECD-Fc to mediate growth cone collapse. (E) Assay of netrin 1-dependent outgrowth. Sub-optimal levels of laminin resulted in little axon outgrowth (column 1). 100 ng/ml of netrin 1 by itself was not able to support outgrowth (column 2). The combination of sub-optimal laminin levels and 100 ng/ml netrin 1 resulted in robust outgrowth (column 3). This netrin 1-dependent outgrowth was reduced by the addition of an antibody against the netrin receptor DCC (column 4). (F) Axons dependent on netrin 1 for outgrowth remained responsive to ECD-Fc-mediated growth cone collapse. Scale bar: (A) 10 µm.

Return to article