Fish transgene expression by direct injection into fish muscle.

The ability of a promoter sequence to drive expression of a reporter gene can be determined by direct injection of copies of the cloned sequence into fish muscle, followed by biopsy of muscle from the site of injection. We describe a set of experiments in which copies of the constructs FV1 and FV2, both comprising a carp beta-actin promoter sequence spliced to the bacterial reporter gene CAT, were injected into the muscle of tilapia fish )Oreochromis niloticus) of between 5 and 8 cm body length. The site of injection was carefully determined so that biopsy samples could be recovered from the injection site 24 hours, 48 hours, and 7 days after injection. Biopsy samples of muscle were homogenized and used for CAT assays. CAT activity was successfully detected in many of the muscle samples.