Fig. 6. Midline glial populations are present in Robo1 knockout mice. (A-D) To assess the development of midline glial structures in Robo1 knockout (C,D) or control (A,B) mice, E17.5 brains were sectioned coronally and labelled by glial fibrillary acidic protein (GFAP) immunohistochemistry. Three midline glial populations were present: the glial wedge (GW), glia within the indusium griseum (arrow labelled IGG in B and D) and the midline zipper glia (MZG) in both wild-type and Robo1 knockout brains. Some abnormalities were noted in the MZG but this is probably due to the morphological disruption within the area by the formation of large axon fascicles and the lack of a definitive corpus callosum (arrow labelled MZG in D). Scale bar: 400 µm in A,C; 200 µm in B,D.