Abstract
The intermediate filament network of astrocytes includes Glial fibrillary acidic protein (Gfap) as a major component. Gfap mRNA is alternatively spliced resulting in generation of different protein isoforms where Gfapα is the most predominant isoform. The Gfapδ isoform is expressed in proliferating neurogenic astrocytes of the developing human brain and in the adult human and mouse brain. Here we provide a characterization of mouse Gfapδ mRNA and Gfapδ protein. RT-qPCR analysis showed that Gfapδ mRNA and Gfapα mRNA expression is coordinately increased in the post-natal period. Immunohistochemical staining of developing mouse brain samples showed that Gfapδ is expressed in the sub-ventricular zones in accordance with the described localization in the developing and adult human brain. Immunofluorescence analysis verified incorporation of Gfapδ into the Gfap intermediate filament network and overlap in Gfapδ and Gfapα subcellular localization. Subcellular mRNA localization studies identified different localization patterns of Gfapδ and Gfapα mRNA in mouse primary astrocytes. A larger fraction of Gfapα mRNA showed mRNA localization to astrocyte protrusions compared to Gfapδ mRNA. The differential mRNA localization patterns were dependent on the different 3′-exon sequences included in Gfapδ and Gfapα mRNA. The presented results show that alternative Gfap mRNA splicing results in isoform-specific mRNA localization patterns with resulting different local mRNA concentration ratios which have potential to participate in subcellular region-specific intermediate filament dynamics during brain development, maintenance and in disease.
Highlights
Glial fibrillary acidic protein (Gfap) is a component of the intermediate filaments in astrocytes together with Vimentin and Nestin [1]
By RT-qPCR we examined for Gfapd and Gfapa mRNA accumulation in the protrusion fraction (PF) and compared it to the entire cell represented by the Boyden chamber upper side cell body fraction (CF)
We here describe the characterization of the mouse Gfapd isoform at the levels of mRNA and protein
Summary
Glial fibrillary acidic protein (Gfap) is a component of the intermediate filaments in astrocytes together with Vimentin and Nestin [1]. In humans at gestational week 9–12 Gfap expression starts in the radial glial cells [5,6,7]. Gfap expression increases during the maturation and differentiation of the precursor cells whereas Nestin and Vimentin expression decreases. Increased expression of Gfap, together with Vimentin and Nestin, and enlargement of astrocytes is indicative of reactive gliosis [18]. The differences in Gfap expression can alter the morphology of astrocytes with direct consequences for a variety of astrocyte functions during development and ageing, and have indirect consequences for other CNS cell types [17]
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