Expression of GFAP splice variants in the rodent central nervous system

Purpose: Astrocytes can be identified in the brain by the expression of glial fibrillary acidic protein (GFAP). GFAP is expressed in the core or cytoskeleton of the astrocyte and its function is to provide stability to the cell processes. The expression of GFAP is altered in many diseases that affect the central nervous system (CNS), including multiple sclerosis, stroke, Alzheimer’s disease and traumatic brain injury. Novel isoforms of GFAP (GFAPe and GFAPκ) have recently been identified and may play an important role in development or disease. GFAPe and GFAPκ differ from GFAPα in the C’ terminal region of the protein and have been associated with destabilising the formation of GFAP polymers. Methods: We have generated polyclonal antibodies against GFAPα, GFAPe and GFAPκ and examined the expression of GFAP splice variants using western blotting and immunohistochemistry in CNS tissues from rats, mice and guinea pigs (N=9). Results: Immunohistochemistry revealed that GFAP splice variants co-localized with regular GFAP, detected using a commercial polyclonal antibody from DakoCytomation. GFAPα, GFAPe and GFAPκ were detectable by western blotting in the majority of tissues examined (cortex, hippocampus, thalamus, brain stem, cerebellum, spinal cord and retina). Western blotting revealed slightly different expression profiles of the splice variants, with GFAPκ weakly expressed in the retinas of rats, mice and guinea pigs and GFAPe strongly expressed in guinea pig retina.Conclusion: This study is the first to demonstrate the protein expression of GFAP splice variants. Future studies will examine what role these splice variants might play in development and disease.