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 59-UTR. Subsequently, a 39-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.-Park, T.

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Biological bases for sexual differences in the brain exist in a wide range of vertebrate species, including chickens. Recently, the dogma of hormonal dependence for the sexual differentiation of the brain has been challenged. We examined whether sexually dimorphic gene expression in the brain precedes gonadal differentiation. Using the Affymetrix GeneChip Chicken Genome Array, we identified 42 female- and 167 male-enhanced genes that were differentially expressed in sex-specific brains from stage 29 chicken embryos. To confirm the efficacy of the microarray, and to investigate the stage-specific expression patterns of the identified genes, we used quantitative real-time PCR analysis. Our real-time PCR results for the differentially expressed genes agreed well with our microarray results. Thus, we postulate that these genes have potential roles in the sexual differentiation of neural function and development in chickens.

Chicken oviductal epithelium produces large quantities of egg white protein in daily cycles. In this study, we cultured and characterized oviductal epithelial cells (OECs) from juvenile (10-wk-old) chickens and from actively laying (30-wk-old) hens. The juvenile OECs were maintained over passage 25 and were positive for toluidine blue, lectin-ConA, HPA, UEA-1, WFA, WGA, anti-OVA, anti-ESR1, and anti-PGR, whereas the adult OECs were cultured over passage 6 and were positive for toluidine blue, periodic acid-Schiff, lectin-ConA, WFA, WGA, anti-OVA, anti-ESR1, and anti-PGR. To investigate the optimal concentration of steroid hormones for inducing egg white protein genes in vitro, we examined the effects of estrogen, diethylstilbestrol, progesterone, and corticosterone on OECs. Results showed that oviduct-specific levels of avidin, ovalbumin, ovomucin, lysozyme, ESR1, and PGR gene expression were significantly elevated in steroid hormone-treated OECs compared with those of untreated cells (P < 0.05). Ovalbumin protein was also secreted into culture medium from hormone-treated OECs. In addition, to examine the application of OECs for avian transgenesis, we introduced human thrombopoietin (THPO)-expressing lentiviral vector controlled by a 3.5-kb ovalbumin promoter into cultured OECs, and THPO expression was significantly induced with diethylstilbestrol or progesterone in juvenile OECs (P < 0.05) and in adult OECs (P < 0.05). In conclusion, these data demonstrate the potential of cultured OECs as a model system for providing a better understanding of the regulation of gene expression and for the production of an avian transgenic bioreactor.