HEART TARGETING OF RETROVIRAL EXPRESSION IN AVIAN EMBRYOS - A SPECIES-INDEPENDENT PHENOMENON

A replication-incompetent retroviral vector derived from spleen necros is virus (SNV), in which the viral structural genes gag, pol, and env were replaced with the bacterial beta-galactosidase gene lacZ, was use d to infect embryos from outbred and inbred chicken lines, japanese qu ail and duck between embryonic day 0 and 13. LacZ expression was restr icted to a few organs or cell types, and this distribution was not inf luenced by the different routes of inoculation tested but was specifie d by the age of the embryo at the time of inoculation. Inoculations at EO-EI beneath or onto the blastodisc resulted in lacZ expression in e ctodermal derivatives, i.e. skin and neural structures. From E2 onward s, heart muscle and skin were the preferential targets in all the spec ies or inbred lines tested. Heart muscle was positive in 100% of the e mbryos displaying lacZ+ clones. Skin exhibited on and off periods depe nding on the age at inoculation. No lacZ-positive clones were detected in chick embryos infected after E11. Outbred chick embryos displayed the largest array of organs labelled (heart, skin, liver, gizzard) whi le quail and duck embryos exhibited a more restrictive pattern. These results are of import if the vector is to be used as a tool to map lin eages or to transfer genes into the developing embryo.