Deposition of bioactive human epidermal growth factor in the egg white of transgenic hens using an oviduct‐specific minisynthetic promoter

Abstract

Currently, transgenic animals have found a wide range of industrial applications and are invaluable in various fields of basic research. Notably, deposition of transgene-encoded proteins in the egg white (EW) of hens affords optimal production of genetically engineered biomaterials. In the present study, we developed a minisynthetic promoter modulating transgene transcription specifically in the hen's oviduct, and assayed the bioactivity of human epidermal growth factor (hEGF) driven by that promoter, after partial purification of epidermal growth factor (EGF) from transgenic hen eggs. Our minisynthetic promoter driving expression of chicken codon-optimized human epidermal growth factor (cEGF) features 2 consecutive estrogen response elements of the ovalbumin (OV) promoter, ligated with a 3.0 kb OV promoter region carrying OV regulatory elements, and a 5'-UTR. Subsequently, a 3'-UTR carrying the poly-A tail sequence of the OV gene was added after incorporation of the cEGF transgene. Finally, we partially purified cEGF from transgenic hen eggs and evaluated the biofunctional activities thereof in vitro and in vivo. In the in vitro assay, EW-derived hEGF exhibited a proliferative effect on HeLa cells similar to that of commercial hEGF. In the in vivo assay, compared to the nontreated control, transgenic hen egg-derived EGF afforded slightly higher levels of re-epithelialization (via fibroplasia) and neovascularization of wounded skin of miniature pigs than did the commercial material. In conclusion, transgenic hens may be used to produce genetically engineered bioactive biomaterials driven by an oviduct-specific minisynthetic promoter.