title: Glial fibrillary acidic protein mRNA isotypes: expression in vitro and in vivo.
abstract: Glial fibrillary acidic protein (GFAP) and its mRNA, primarily expressed in astrocytes, are also expressed in peripheral nervous system Schwann cells as well as in certain non-neural tissues. Schwann cells express a GFAP mRNA (GFAP-beta) which differs from the CNS-type mRNA (GFAP-alpha) by the presence of an extended 5' untranslated region. We have developed a polymerase chain reaction assay which allows distinction of these two GFAP mRNAs, as well as quantitative analysis of their levels. In the cultured rat Schwannoma cell line RT4-D6, GFAP-beta was the major GFAP mRNA species, accounting for at least 75% of total GFAP (alpha + beta) mRNA. GFAP-beta was also detected in primary rat astrocyte cultures, where it constituted approximately 5% of the total GFAP mRNA, as well as in RNA samples prepared from normal rat cerebral cortex, and from hamster and human brain. In rat cortex, the temporal expression of GFAP-beta mRNA paralleled that of total GFAP mRNA, with plateau levels reached between postnatal days 15 and 20. In astrocyte cultures, the relative levels of GFAP-alpha and -beta mRNAs were differentially regulated by exposure to interferon-gamma (10 to 25 units/ml), which caused an increase in GFAP-beta levels while at the same time no change or a small decrease in total GFAP levels. In rat brain cortical slices, 4 hr exposure to 25 units/ml interferon-gamma decreased total GFAP mRNA levels over tenfold, while GFAP-beta levels were unaffected. These data indicate that a second form of the GFAP mRNA is expressed in astrocytes both in vivo and in vitro and provide evidence for independent regulation of these two GFAP mRNA species.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D018076:DNA, Complementary; D015870:Gene Expression; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics*; D066298:In Vitro Techniques; D009457:Neuroglia / Q000502:physiology*; D017933:Peripheral Nervous System / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D005904:Glial Fibrillary Acidic Protein; D012333:RNA, Messenger