| 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-β) which differs from the CNStype mRNA (GFAP-β) 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-b? was the major GFAP mRNA species, accounting for at least 75% of total GFAP (α+β) mRNA. GFAP-b? 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-β 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-α and -β mRNAs were differentially regulated by exposure to interferon-γ (10 to 25 units/ml), which caused an increase in GFAP-β 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-γ decreased total GFAP mRNA levels over tenfold, while GFAP-b? levels were unaffected. These data indicate that a second form of the GF AP mRNA is expressed in astrocytes both in vivo and in vitro and provide evidence for independent regulation of these two GFAP mRNA species. © 1995 Wiley-Liss, Inc. |
