Figure 6.

Development of NL is affected by impaired Eph receptor signaling. Representative 40X images of lateral NL following RDA midline tracing of E10 control embryos (A), embryos treated with EphB1-Fc (B), EphA4-Fc (C), or transfected with full-length EphB2 (D). Top panels are a merge of bisbenzamide (BIS, blue) nuclear counterstaining and RDA (red) fluorescence from labeled contralateral NM axons; both channels are shown individually in respective middle and lower panels. NL is normally an elongated, flattened layer with a lateral border (leftmost on these images) well defined by contralateral NM axons (white arrowhead in A). Treatment with EphB1-Fc (B) results in disorganized NM axons projecting lateral to the NL border (white arrowhead in B). Treatment with EphA4-Fc results in an abnormal NL morphology, where the mediolateral length is reduced and the lateral aspect is disorganized and not flattened (C). NM is normally found dorsomedial to NL and not within the same imaging field at 40X magnification, but the positioning of NM relative to NL is altered following transfection with full-length EphB2 at E2 (D) or treatment with EphA4-Fc from E6 to E9 (C). Measurements of NL (E, F) demonstrate the reduced extent of NL along both rostrocaudal (E) and mediolateral (F) axes when EphB2 is overexpressed from E2, and along the rostrocaudal axis (E) when all Eph receptors are inhibited with EphA4-Fc injection from E6 to E9. Scale bar = 100 μm, left is lateral and dorsal is up.