Expression Of Exogenous Protein In The Egg Yolk Of Transgenic Chickens

Using transgenic chickens as bioreactor to synthesize pharmaceutical proteins have a great prospect. The recombinant proteins target into yolk is a desirable method, it is of significance to explore its molecular mechanism. In chickens, maternal IgY is specifically transported and deposited into egg yolk from the maternal blood circulation mediated by Fc receptors. By using this mechanism, we aimed to develop a transgene chicken bioreactor product recombinant proteins in egg yolk. In this study, weconstructed a lentivirus vector expressing eGFP marker-gene fused with chicken IgY heavy chain constant region CHI-4, under the control of the ubiquitous cytomegalovirus (CMV) promoter. The concentrated viral vector was injected into the blood vessels and subgerminal cavityof chicken embryos at HH stage13-14. eGFP expression was observed in different tissues of the embryos, including the gonads. When we detected the blood genome DNA by PCR,81.8%(36/44) were eGFP-positive. The eGFP-IgY recombinant protein was expressed in the egg yolk of young laying hens demonstrated by western blot analysis. However, we found the transgene expression was subject to silencing, since the fusion proteins cannot be detected in the egg afterwards. In addition, the eGFP expression in adult chicken tissues was observed in breast muscle and heart merely. In conclusion, we obtained a higher transgenic efficiency than our former report by using a novel method of injecting lentiviral vector into embryonic blood vessel. The fusion protein was transported into the yolk initially but become epigenetic silencing in egg and most tissues later, indicating that the transgene was unstable in vivo.