Expression of exogenous genes transferred into the avian limb in ovo

We report on a simple method of direct gene transfer which allows the ectopic expression of proteins and the study of mesoderm-specific genes in the chick embryo. We microinjected into the avian embryonic limb several plasmids containing reporter genes under the control of various promoter sequences, including a minimal chicken muscle acetylcholine receptor a-subunit promoter [Klarsfeld, A., Daubas, A., Bourachot, B. and Changeux, J.P., Mel. Cell. Biol., 7 (1987) 951-955]. Gene expression is detectable for 3 days, is reproducible, is restricted to the site of injection, and correlates with the amount of DNA injected. Our observations indicate that it is possible to transfer and express genes in ectodermal and mesodermal cells of the chick limb by direct DNA injection and that the method can be used to analyze promoter sequences in vivo during specific windows of development.