Expression vectors encoding human growth hormone (hGH) controlled by human muscle-specific promoters: prospects for regulated production of hGH delivered by myoblast transfer or intravenous injection

Abstract

We report here the construction of vectors that produce and secrete human growth hormone (hGH) in a muscle-specific manner. The promoter regions of the genes encoding human skeletal α-actin (HSA) and troponin I slow (HTnI s) were linked to the hGH-encoding gene. These vectors were designated pHSA2000GH and pHTnI s4200GH, respectively. The HSA and HTnIs promoters linked to the cat gene have previously been shown to be necessary and sufficient for developmentally regulated muscle-specific expression. Furthermore, these promoters function in a fibre-type-specific manner in transgenic animals. Transient and stable transfection analyses with pHSA2000GH and pHTnI s4200GH indicated that: ( i) these vectors efficiently synthesized hGH in a muscle-specific manner; ( ii) the myogenic master regulatory gene, myoD, a determinant of cell fate, trans-activated expression of hGH in pluripotential non-muscle cells; and ( iii) these hGH expression vectors were developmentally regulated during myogenic differentiation. These regulated tissue/fibre-type-specific hGH-containing plasmids are suitable vectors for the delivery and stable production of GH in livestock and GH-deficient hosts by either transgenesis, myoblast transfer or liposome-mediated intravenous injection.