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    In certain species, specialized glial cells delineate cell domains in the central nervous system and assist in the elongation of axons by providing mechanical and chemical barriers. We showed previously, that the glial intermediate filament proteins vimentin and glial fibrillary acidic protein are extensively coexpressed in radial glia in the developing hindbrain, and that subsequently, the two proteins define distinct rhombomere domains: vimentin is localized in radial glia at the rhombomere boundaries and glial fibrillary acidic protein expression is restricted to the rhombomere centers (Yoshida and Colman [2000] J. Comp. Neurol. 424:47–57). The present study reveals that vimentin and glial fibrillary acidic protein continue to display distinct expression domains throughout the developing Xenopus central nervous system. Although the precise function of the two intermediate filaments in glial cells has yet to be revealed, the observations presented here suggests that glial intermediate filament proteins demarcate different populations of glial cells during nervous system development and that the existence of different glial populations may define glial boundaries. J. Neurosci. Res. 63:284–289, 2001. © 2001 Wiley-Liss, Inc.
    Rhombomere
    Intermediate Filament Protein
    Hindbrain
    Neuroglia
    GFAP stain
    The glial fibrillary acidic protein (GFAP) gene is alternatively spliced to give GFAP-α, the most abundant isoform, and seven other differentially expressed transcripts including GFAP-δ. GFAP-δ has an altered C-terminal domain that renders it incapable of self-assembly in vitro. When titrated with GFAP-α, assembly was restored providing GFAP-δ levels were kept low (∼10%). In a range of immortalized and transformed astrocyte derived cell lines and human spinal cord, we show that GFAP-δ is naturally part of the endogenous intermediate filaments, although levels were low (∼10%). This suggests that GFAP filaments can naturally accommodate a small proportion of assembly-compromised partners. Indeed, two other assembly-compromised GFAP constructs, namely enhanced green fluorescent protein (eGFP)-tagged GFAP and the Alexander disease–causing GFAP mutant, R416W GFAP both showed similar in vitro assembly characteristics to GFAP-δ and could also be incorporated into endogenous filament networks in transfected cells, providing expression levels were kept low. Another common feature was the increased association of αB-crystallin with the intermediate filament fraction of transfected cells. These studies suggest that the major physiological role of the assembly-compromised GFAP-δ splice variant is as a modulator of the GFAP filament surface, effecting changes in both protein– and filament–filament associations as well as Jnk phosphorylation.
    GFAP stain
    Citations (103)
    Normal, reactive, and neoplastic astrocytes express two types of intermediate filament (IF) proteins, namely glial fibrillary acidic protein (GFAP) and vimentin. Their submicroscopical distribution in vivo is so far unknown. We therefore investigated four malignant gliomas by electron microscopy, applying postembedding double immunogold labeling. The IF proteins were randomly scattered over the same filament bundles, as in previous experiments on glioma cultures. No clustering or preferential intracytoplasmic location of either IF protein was visible. The demonstration of IF proteins within nuclei gives some support to the suggested intranuclear functions of IF proteins.
    Immunogold labelling
    Intermediate Filament Protein
    GFAP stain
    Neuroglia
    Citations (13)
    In certain species, specialized glial cells delineate cell domains in the central nervous system and assist in the elongation of axons by providing mechanical and chemical barriers. We showed previously, that the glial intermediate filament proteins vimentin and glial fibrillary acidic protein are extensively coexpressed in radial glia in the developing hindbrain, and that subsequently, the two proteins define distinct rhombomere domains: vimentin is localized in radial glia at the rhombomere boundaries and glial fibrillary acidic protein expression is restricted to the rhombomere centers (Yoshida and Colman [2000] J. Comp. Neurol. 424:47–57). The present study reveals that vimentin and glial fibrillary acidic protein continue to display distinct expression domains throughout the developing Xenopus central nervous system. Although the precise function of the two intermediate filaments in glial cells has yet to be revealed, the observations presented here suggests that glial intermediate filament proteins demarcate different populations of glial cells during nervous system development and that the existence of different glial populations may define glial boundaries. J. Neurosci. Res. 63:284–289, 2001. © 2001 Wiley-Liss, Inc.
    Rhombomere
    Intermediate Filament Protein
    Hindbrain
    GFAP stain
    Neuroglia