The commissural axon response to PlxnA2 is Sema6B dependent. (A-F) Examples of axon outgrowth of commissural neurons obtained from embryos electroporated with βactin-EBFP2-miS6B on Laminin (A,B), AP only (C,D) and PlexinA2ecto-AP (E,F). Axons were co-immunolabeled for axonin 1 and EBFP2. Co-labeled neurons appear yellow in A,C,E. Scale bar: 50 μm. (G) Quantification of axon lengths on different substrates after electroporation of βactin-EBFP2-miS6B. WT, wild type; Alb, Albumax; AP, concentrated conditioned medium from AP-expressing cells; Lam, Laminin; PA2-AP, concentrated conditioned medium from PlexinA2ecto-AP-expressing cells. ***P<0.001; error bars indicate s.e.m.