Fig. 5

Failure to execute cross-midline divisions results in duplicated neuraxes in EphA4 and EfnB2a MO mosaics. Immunostaining of 18 hpf mosaic embryos shown in dorsal view with anterior to the left. (A–C) merged images showing α-aPKC (green) and MO host cells labelled with rhodamine (red). (A) aPKC is expressed on the apical surface of neuroepithelial cells, which is at the midline. (B) WT EphA4+ donor cells (unlabelled) fail to cross the midline and form unilateral clusters in r3 and r5 when transplanted into an EphA4MO host (white arrowheads); these clusters have an ectopic aPKC+ apical region. Likewise WT EfnB2a+ donor cells form a unilateral cluster in r4 of an EfnB2a MO host (data not shown). (C) WT cells transplanted into an EphA4; EfnB2a double MO host form three separate clumps with ectopic apical surfaces (data not shown) or fuse to give rise to a partially duplicated neuroepithelium in the r3–r5 region; cell clustering is also sometimes evident in r7 (N=6). OV (otic vesicle). (D,E) α-laminin staining (left panels); right panel is a merge showing the rhodamine-labeled double MO host cells (red); host cells contain the pGFP5.3 transgene and express GFP in r3 and r5 (green). (D) Laminin is expressed along the lateral edges of the neuroepithelium in WT (not shown) and in double MO host embryos (N=24). (E) Laminin is ectopically expressed around the edges of the cluster of unlabelled WT cells in a WT to double MO mosaic embryo (N=27). Scale bars: 50 μm.