A NOVEL GLIAL FIBRILLARY ACIDIC PROTEIN MESSENGER-RNA LACKING EXON-1

Glial fibrillary acidic protein (GFAP) is the major intermediate filam ent protein in the mature astrocytes. We have assayed for the presence of GFAP mRNA gene in mouse tissues outside the nervous system. Nuclea se S1 protection experiments show that RNAs lacking exon 1 are transcr ibed in bone marrow. From a mouse bone marrow cDNA library we isolated GFAP cDNAs which start in the 3' part of intron 1 and contain all the dowstream GFAP exons. The new GFAP mRNAs, which we call GFAP gamma mR NAs, are already present in the brain at embryonic day 15 and in adult forebrain and cerebellum. Their presence in astrocytic cell lines sug gests that astrocytes may be the site of in vivo expression of these m RNAs. In addition we have detected GFAP gamma mRNAs in mouse spleen. F uthermore in human an analogous GFAP mRNA containing the 3' part of in tron 1 and lacking the exon 1 is also present in adult brain. These re sults suggest a new regulation of the GFAP gene expression.