Gene transfer into zebrafish by sperm nuclear transplantation.

A technique for fertilizing zebrafish eggs by injection of sperm nuclei is described. Eggs that cleave normally can develop into swimming larvae and give rise to fertile adults. If sperm nuclei are preincubated for 20 min with DNA encoding the green fluorescent protein, transgene expression can be detected in all cells of the embryo. The use of condensed sperm nuclei allows injection with a small bore pipette, which is critical for successful injection of the relatively small zebrafish egg. This technique enables the generation of ubiquitously expressing transgenic zebrafish directly by microinjection. Hence, experiments involving transgenic fish can be completed in days, without the need for growing and breeding founders. This technique may also be used to generate transgenic lines, as transgene expression was visible in the offspring of transgenic founders. The method described here is likely to be applicable to other teleosts, such as medaka and salmon.