Studies of genes expressed in the brain and regulated by transforming growth factor beta

Human S-protein is a serum glycoprotein that binds the activated complement complex, mediates coagulation, and also functions as a cell adhesion protein through interactions with its integrin receptor. A cDNA clone for human S-protein was isolated from a lambda gt11 cDNA library of mRNA from HepG2 hepatocellular carcinoma cell line. The cDNA clone in lambda was subcloned into pUC18 for Southern and Northern blot experiments. Hybridization with {dollar}sp{lcub}32{rcub}{dollar}P-radiolabeled human S-protein cDNA revealed a single copy gene encoding S-protein in the human and mouse genome. A 1.6 Kb mRNA for S-protein was detected in mRNA from mouse liver and brain. S-protein is known to be regulated by transforming growth factor {dollar}beta{dollar}, although the mouse brain-derived glial cells, SFME, are not induced by the growth factor to express S-protein mRNA.; Transforming growth factor {dollar}beta{dollar} promotes the differentiation of serum-free mouse embryo cells (SFME) into astroblasts that express the astrocyte-specific marker glial fibrillary acidic protein (GFAP). In order to find other genes induced by TGF {dollar}beta{dollar}, a cDNA library made from mRNA of SFME grown in the presence of TGF {dollar}beta{dollar} for 48 hours was differentially screened using cDNA probes made from mRNA of SFME grown with and without TGF {dollar}beta{dollar}. After screening approximately 10,000 clones, 14 clones were detected by the TGF {dollar}beta{dollar}(+) probe but not by the TGF {dollar}beta{dollar}({dollar}-{dollar}) probe. Sequencing of one clone revealed that it was a full length copy of cystatin C cDNA.; Other growth factors do not induce cystatin C, including nerve growth factor, basic fibroblast growth factor and platelet-derived growth factor. Hydrocortisone at 10{dollar}sp{lcub}-7{rcub}{dollar} M does induce cystatin C in SFME at comparable levels of TGF {dollar}beta{dollar}. When transcription is inhibited for 8 hours, cystatin C mRNA is stable in the presence of TGF {dollar}beta{dollar} compared to its observable decay when TGF {dollar}beta{dollar} is not present. Also, a 4 Kb RNA species is detected by Northern blot experiments and is induced by TGF {dollar}beta{dollar} in SFME. This message may be the primary cystatin C transcript, which may suggest regulation of cystatin C in the nucleus.