Radial glial cells have many pivotal roles in the developing central nervous system. Currently, they are recognised to have four main functions: to direct neuronal migration, to act as neuronal progenitors, to encourage angiogenesis, and to coordinate the formation of axon tracts in the white matter. In this study, we will investigate the fourth of those functions, as we seek to quantify the number of radial processes crossing the white matter in the developing spinal cord. We will then compare the number of processes between wild-type specimens and animals missing genes encoding for proteins essential for normal axon guidance, specifically Semaphorin6A and PlexinA4. This may help to determine whether these signalling pathways are relevant in the developing spinal cord.
Methods and Materials
We examined cryosections from mouse embryos of age E15.5, which were stained to show the traversing radial glial processes. We used a series of 50μm reference lines spaced 25μm apart to quantify the number of processes at each level.
We showed that there were especially large numbers of glial processes in the lateral columns of white matter in all three phenotypes described. However, we found no link between the number of axons and Semaphorin6A or PlexinA4 deficiency.
Our results support conclusions made by previous studies, that many radial glial cells can be seen in the developing spinal cord at a time when axon tracts are developing, suggesting a possible role for these processes in their development. The fact that they are seen in especially great numbers in the lateral columns may suggest which axon tracts they have a role in guiding the development of.