EFFICIENT GENE-TRANSFER INTO ZEBRAFISH SKELETAL-MUSCLE BY INTRAMUSCULAR INJECTION OF PLASMID DNA

The ability of zebrafish skeletal muscles to internalize and express p lasmid DNA was demonstrated using pCMVCAT1, a chloramphenicol acetyltr ansferase (CAT) construct driven by the human cytomegalovirus immediat e early (CMV-IE) promoter. We found that CAT activity was correlated t o the amount of plasmid DNA injected, with maximal expression at 5 mu g of pCMVCAT1. CAT activity was also shown to increase steadily over t he first seven days after injection, with high levels of CAT expressio n persisting up to one year. Intramuscular injection of CAT constructs driven by other viral promoters also resulted in high levels of CAT a ctivity. Histochemical localization using a CAT beta-galactosidase con struct confirmed that only myofibers at the site of injection expresse d beta-galactosidase enzyme. The persistence and strong expression of injected plasmid constructs suggest that zebrafish may be a simple and readily accessible system fur direct muscle injection studies.