Submitted to: Journal of Molecular Reproduction and Development
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/16/2007
Publication Date: 6/1/2008
Citation: Talbot, N.C., Powell, A.M., Ocon, O.M., Caperna, T.J., Camp, M.J., Garrett, W.M., Ealy, A.D. 2008. Comparison of the interferon-tau expression from primary trophectoderm outgrowths derived from IVP, NT, and parthenogenote bovine blastocysts. Journal of Molecular Reproduction and Development. 75(2):299-308. Interpretive Summary: The cloning of farm animals may prove to be a useful means of reproducing animals of particular value. Also, cloning is important in that it can enable new and novel traits, such as resistance to disease, to be created in farm animals. An evaluation of the expression of interferon-tau (IFN-tau) in cloned bovine embryos was performed in comparison to natural embryos (i.e., resulting from egg and sperm) and embryos made from eggs that had not been fertilized by sperm (parthenogenetic). Bovine IFN-tau is the “maternal recognition of pregnancy” hormone produced by trophectoderm cells of the bovine embryos early in pregnancy before the embryo implants in the uterus. The expression of IFN-tau is essential for bovine embryo survival in the uterus, and may also be essential for formation of the placenta in early pregnancy. The study specifically analyzed the trophectoderm tissue of the bovine embryos via the culturing of this tissue in dishes in an incubator. The results show that trophectoderm cultures derived from cloned bovine embryos produced significantly less IFN-tau in comparison to those derived from natural embryos or even parthenogenetic embryos. It was also found that the trophectoderm of parthenogenetic embryos was less likely to grow in culture since significantly fewer parthenogenetic-derived cultures were produced. The measurement of IFN-tau production from trophectoderm cultures derived from cloned bovine embryos may prove to be a useful measure of the cloned embryos relative health and its ability to successfully develop to a calf that is born alive.
Technical Abstract: Bovine interferon-tau (IFN-tau) is the “maternal recognition of pregnancy” hormone produced by trophectoderm cells of the pre-implantation stage bovine embryo. The expression of IFN-tau is essential for bovine embryo survival in the uterus, and, because somatic cell nuclear transfer (NT) embryos appear to be compromised in this respect, an evaluation of IFN-tau production from NT-embryo-derived primary trophectoderm cultures in comparison to trophectoderm cultured from parthenogenote (P) and in vitro matured, fertilized, and cultured (IVP) bovine embryos was performed. In Exp. 1, the success/failure ratio for primary trophectoderm colony formation was similar for IVP and NT blastocysts [IVP= 155/29 (84%); NT 104/25 (81%)], but was decreased (p< 0.05) for P blastocysts [54/43 (56%)]. Most trophectoderm colonies reached diameters of at least 1 cm within 3-4 wk, and at this time, 72 h conditioned cell culture medium was measured for IFN-tau concentration by antiviral activity assay. The amount of IFN-tau produced by IVP-outgrowths [4311 IU/ml (n=155)] was greater (P<0.05) than that from NT- [626 IU/ml (n=104)], and P- [1595 IU/ml (n= 54)] derived trophectoderm. Differential expression of IFN-' was confirmed by immunoblotting. In Exp. 2, colony formation was again similar for IVP and NT blastocysts [IVP= 70/5 (93%); NT 67/1 (99%)] and less (p< 0.05) for P blastocysts [65/92 (70%)]. Analysis of trophectoderm colony size after 23 days in culture showed a similar relationship with P-derived colonies being significantly smaller in comparison to IVP and NT colonies. A differential expression of IFN-tau was also observed again, but this time as measured over time in culture. Maximal IFN-tau production was found at day-14 of primary culture and diminished to a minimum by the 23rd day. The results show that NT-derived primary bovine trophectoderm cultures produced significantly less IFN-tau in comparison to IVP- and P-derived cultures, and, also, that significantly fewer parthenogenetic-derived cultures were produced. IFN-tau production from primary trophectoderm cultures may prove to be a useful measure of NT reprogramming success.