Abstract
Radial glial cells play an essential role during corticogenesis through their function as neural precursors and guides of neuronal migration. Both reelin and neuregulin1 (NRG1) maintain the radial glial scaffold; they also induce expression of Brain Lipid Binding Protein (BLBP), a well known marker of radial glia. Although radial glia in normal ferrets express both vimentin and BLBP, this coexpression diverges at P3; vimentin is expressed in the radial glial processes, while BLBP appears in cells detached from the ventricular zone. Our lab developed a model of cortical dysplasia in the ferret, resulting in impaired migration of neurons into the cortical plate and disordered radial glia. This occurs after exposure to the antimitotic methylazoxymethanol (MAM) on the 24th day of development (E24). Ferrets treated with MAM on E24 result in an overall decrease of BLBP expression; radial glia that continue to express BLBP, however, show only mild disruption compared with the strongly disrupted vimentin expressing radial glia. When E24 MAM-treated organotypic slices are exposed to reelin or NRG1, the severely disrupted vimentin+ radial glial processes are repaired but the slightly disordered BLBP+ processes are not. The realignment of vimentin+ processes was linked with an increase of their BLBP expression. BLBP expressing radial glia are distinguished by being both less affected by MAM treatment and by attempts at repair. We further investigated the effects induced by reelin and found that signaling was mediated via VLDLR/Dab1/Pi3K activation while NRG1 signaling was mediated via erbB3/erbB4/Pi3K. We then tested whether radial glial repair correlated with improved neuronal migration. Repairing the radial glial scaffold is not sufficient to restore neuronal migration; although reelin improves migration of neurons toward the cortical plate signaling through ApoER2/Dab1/PI3K activation, NRG1 does not.
Highlights
The developing cerebral cortex contains a transient elongated population, the radial glial cells, which play an essential role through their function as guides of neuronal migration and neural precursors [1,2]
These cells, seen at postanal day 14 (P14), express vimentin and show an elongated process oriented toward the pia; interestingly, their cell bodies are in the cortical plate (Figure 2H,L)
We show here that severely disrupted dyplasic brains can be repaired by specific application of reelin or NRG1
Summary
The developing cerebral cortex contains a transient elongated population, the radial glial cells, which play an essential role through their function as guides of neuronal migration and neural precursors [1,2]. Fietz et al [19] proposed that outer subventricular progenitors have a fundamental role in cortical expansion of gyrencephalic brains in ferrets as well as in humans. These distinctions emphasize that it is important to involve more complex mammals like ferrets in developmental studies as fundamental processes can differ between species These distinctions emphasize that it is important to involve more complex mammals like ferrets in developmental studies as fundamental processes can differ between species (e.g. [15])
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