Localization of transitin mRNA, a nestin-like intermediate filament family member, in chicken radial glia processes

We have examined the gene expression of two radial glia intermediate filament proteins, transitin and vimentin, in the developing chick CNS. Despite global similarities in their mRNA distributions, marked regional differences are observed. Most notably, we show that transitin mRNA is localized along radial glial processes and is localized to radial glia endfeet, whereas vimentin mRNA is not localized in radial glia. Localization of transitin mRNA is best shown in the diencephalic radial glia, as well as cerebellar Bergmann glia. In addition, in the early embryonic optic tectum, telencephalon, and retina, transitin mRNA is highly localized to radial glia endfeet, which is suggestive of its transport in these cells. These in vivo demonstrations of transitin mRNA localization are confirmed by in situ hybridization analysis of cultured chick brain radial glia, which demonstrates the presence of granular staining for transitin mRNA in glial processes. Transitin mRNA distribution in developing muscle also shows a highly regulated expression pattern, especially along the Z-lines of myofibrils. As further support for the transport and localization of transitin mRNA in radial glia and muscle, we have identified a consensus RNA transport signal in transitin mRNA that is absent from vimentin. These data suggest that the local regulation of transitin protein synthesis may contribute to its function as an intermediate filament protein in radial glia.