STRINGENT REGULATION OF HUMAN GROWTH-HORMONE EXPRESSION IN CULTURED MURINE C2CL2 MYOBLASTS BY THE E. COLI LAC REPRESSOR

Gene transfer techniques can be used to encode the production of a pol ypeptide product, such as human growth hormone (hGH), that is missing in an acquired or inherited disease state such as growth hormone defic iency. In one model system, engineered C2C12 myoblasts are injected in tramuscularly into a mouse and subsequently secrete hGH into the circu lation. In this regard, a gene-expression regulatory system that funct ions in myoblasts would be of interest. We demonstrate that the Escher ichia coli lac operon system can be used to stringently regulate the e xpression of hGH in engineered C2C12 myoblasts in tissue culture. A DN A segment encoding hGH was linked to a DNA segment containing an SV40 enhancer and promoter. The latter components were positioned between t wo synthetic lac operators. Lac repressor expression was driven by a s imian cytomegalovirus promoter. In transient co-transfection assays, h GH expression from cultured C2C12 myoblasts could be modulated up to 6 0-fold (P=0.002) with the inducing agent, isopropyl-beta-D-thiogalacto side (IPTG). In the absence of IPTG, hGH expression was almost fully r epressed. These results show that the components of the E, coli lac op eron provide a stringent regulatory system for use in myoblasts. The s ystem might prove to be useful for the regulation of transferred genes in animals.