title: Immunohistochemical characterization of the out-of frame splice variants GFAP Delta164/Deltaexon 6 in focal lesions associated with chronic epilepsy.
abstract: GFAP Delta164/Deltaexon 6 are two out-of frame splice variants of GFAP. The aim of this study was to investigate the distribution of GFAP Delta164/Deltaexon 6 expressing cells, in focal lesions associated with chronic intractable epilepsy, in light of the increasing interest in the role of specific astrocyte subtypes in epilepsy. Immunocytochemical analysis, using an antibody against Delta164 and Deltaexon6 (GFAP+1), was performed in surgical specimens of patients with hippocampal sclerosis (HS), focal cortical dysplasia type IIB (FCD), cortical tubers of tuberous sclerosis complex (TSC), glioneuronal and glial tumors. Expression of GFAP+1 was also evaluated in developing and adult human control cortex and hippocampus. GFAP+1 immunoreactivity was undetectable in developing human brain. In control human hippocampus and cortex (from young controls) only occasional GFAP+1 positive cells were observed. In contrast, GFAP+1 immunoreactivity was consistently detected in the glial component of the epileptogenic lesions. Balloon cells in FCD and giant cells in TSC, only rarely express GFAP+1. GFAP+1 co-localized with GFAPalpha, but not with GFAPdelta. Co-localization with aquaporin 4 was observed around blood vessels. GFAP+1 immunoreactivity in epilepsy-associated pathologies reveals a specific subpopulation of astrocytes in regions of astrogliosis. Further studies on GFAP+1 positive astrocytes are important to understand whether the expression of this isoform may affect the cytoskeletal integrity and the shape and function of glial cells under pathological conditions. However, while the staining is increased in epilepsy-associated pathologies, GFAP+1 is expressed in a small percentage of astrocytes. Thus, the possible role of this subpopulation of astrocytes in epilepsy is likely minor, compared to astrocytes expressing other GFAP isoforms.
authors.affiliation: Department of (Neuro) Pathology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Boer
authors.forename: J
authors.initials: J
authors.lastname: Middeldorp
authors.forename: W G M
authors.initials: WG
authors.lastname: Spliet
authors.forename: F
authors.initials: F
authors.lastname: Razavi
authors.forename: P C
authors.initials: PC
authors.lastname: van Rijen
authors.forename: J C
authors.initials: JC
authors.lastname: Baayen
authors.forename: E M
authors.initials: EM
authors.lastname: Hol
authors.forename: E
authors.initials: E
authors.lastname: Aronica
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D051401:Aquaporin 4 / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology; D002540:Cerebral Cortex / Q000378:metabolism* / Q000473:pathology; D002908:Chronic Disease; D004827:Epilepsy / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008297:Male; D054220:Malformations of Cortical Development / Q000378:metabolism / Q000473:pathology; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008875:Middle Aged; D016900:Neurofilament Proteins / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D014402:Tuberous Sclerosis / Q000378:metabolism / Q000473:pathology; D055815:Young Adult
chemical_list: C496030:AQP4 protein, human; D051401:Aquaporin 4; D005904:Glial Fibrillary Acidic Protein; C489788:MAP2 protein, human; D008869:Microtubule-Associated Proteins; D016900:Neurofilament Proteins; D020033:Protein Isoforms; C051774:neurofilament protein H