Gene transfer into intact vertebrate embryos

Intact chick embryos at 40 h incubation were transfected in vivo with chimeric vectors expressing chloramphenicol acetyl transferase (CAT) under different promoter sequences. The cationic lipid, dioctadecylamidoglycyl spermine (DOGS) used as the transfecting agent had no noticeable toxic effects on embryonic development. CAT activity was monitored 48 h post-transfection on homogenates of embryos dissected free of all annexes. Of the various constructs tested, those containing the AP-1 response element linked to CAT (TRE-tk-CAT) gave high expression and consistent enzyme responses within groups. Co-transfection experiments in which embryos were exposed simultaneously to a CAT vector containing the cAMP response element and to a vector expressing the catalytic subunit of protein kinase A showed that the promoters of the introduced genes can be regulated by their respective transacting factors. This method may therefore represent a general tool for introducing genes into intact vertebrate embryos at precise developmental times.