Gene expression following transfection of fish cells.

Various genes containing different transcriptional regulatory elements (TRE) and the bacterial marker gene coding for chloramphenicol acetyl transferase were transfected into several fish cell lines to evaluate the efficiency of expression in comparison with mammalian cells. The CMV and RSV TRE were the most efficient non-inducible promoters in directing reporter gene expression. RSV and CMV appeared of similar potency in a stable fish cell line. The human HSP-70 promoter showed high potency in a carp and in a trout cell line after thermal induction. This promoter also induced the synthesis of human growth hormone directed by the corresponding cDNA, but not by the gene. RSV TRE was also able to drive the synthesis of bovine growth hormone when attached directly to the cDNA but not to the gene. These data suggest that non-fish gene TRE can be used to express foreign genes in fish cells or transgenic fish; however, in most cases they are relatively inefficient. The data also suggest that the translation and secretion machinery of fish cells can express efficiently foreign genes but that mammalian introns might be not processed properly in some cases.