Infection of cultured embryo cells of the Pacific oyster, Crassostrea gigas, by pantropic retroviral vectors

The inability to stably introduce and express foreign genes has hampered ba sic research in molluscan species. We cultured cells from dissociated embry os of the Pacific oyster, Crassostrea gigas, and infected these primary cul tures with pantropic: retroviral vectors containing the envelope glycoprote in of vesicular stomatitis virus. Luciferase transgene expression mediated by different heterologous promoters was demonstrated for at least 9 d after infection of the cells. Surprisingly, the promoter reproducibly mediating the highest level of luciferase expression was the retroviral promoter (U3 region of long terminal repeat) from the Moloney murine leukemia virus. The infection efficiency using a low multiplicity of infection (0.05) was esti mated by quantitative polymerase chain reaction to be between 0.1-0.5%. Thi s system will facilitate studies of gene expression and regulation and shou ld be widely applicable to other molluscan species.