SPERM CELLS AS VECTORS FOR INTRODUCING FOREIGN DNA INTO ZEBRAFISH

Mature female zebrafish (Brachydanio rerio) eggs were in-vitro fertilized with zebrafish sperm cells incubated with pUSVCAT plasmid in either circular or linearized form. Analysis of adult pectoral fins showed that 23.33% (21 out of 89) and 37.5% (3 out of 8) of the treated founder fish (P), fertilized with sperms incubated with circular and linearized plasmid DNA, respectively, showed positive hybridization with whole pUSVCAT plasmid P-32 radiolabelled probes. When crossbred to nontransgenic fish, these putative founder transgenics (P) produced transgenic F1 progenies which in turn produced transgenic F2 fry when crossbred with non-transgenics. No expression of the CAT has been detected so far. Sperm-mediated transfer of foreign genes into the zebrafish is therefore possible; however, the nature of the incorporation is not known at the moment. It would appear from the results obtained that the introduced foreign DNA exists extrachromosomally. Although it has been shown that sperms can be used to insert genes into the fish, methods to integrate the introduced gene into the fish genome need to be explored further.