Project description:Interferon tau (IFNT), a Type I IFN similar to alpha IFNs (IFNA), is the pregnancy recognition signal, produced by the ruminant conceptus. To elucidate specific effects of bovine IFNT and of other conceptus-derived factors, endometrial gene expression changes during early pregnancy were compared to gene expression changes after intrauterine application of human IFNA2. In study one, endometrial tissue samples were obtained on days (D) 12, 15, and 18 post-mating from nonpregnant or pregnant heifers. In study two, heifers were treated from D14 to D16 of the estrous cycle with an intrauterine device releasing IFNA2 or placebo lipid extrudates or PBS only as controls. Endometrial biopsies were collected after flushing the uterus. All samples from both experiments were analyzed with an Affymetrix Bovine Genome Array. Study one revealed differential gene expression between pregnant and nonpregnant endometria on D15 and D18. In study two, IFNA2 treatment resulted in differential gene expression in the bovine endometrium. Comparison of the datasets from both studies identified genes that were differentially expressed in response to IFNA2 but not in response to pregnancy on D15 or D18. Vice versa, genes were found as differentially expressed during pregnancy but not after IFNA2 treatment. In study three, spatiotemporal alterations in expression of selected genes were determined in uteri from nonpregnant and early pregnant heifers using in situ hybridization. The findings of this study suggest differential effects of bovine IFNT compared to human IFNA2 and that some pregnancy-specific changes in the endometrium are elicited by conceptus-derived factors other than IFNT. Study I: Early pregnancy; day 12 of pregnancy (n=5 heifers), day 15 of pregnancy (n=3), day 18 of pregnancy (n=4), day 12 cyclic controls (n=5), day 15 cyclic controls (n=3), day 18 cyclic controls (n=4). Study II: Treatment with human interferon alpha (IFNA); IFNA treatment group (IFNA, n=3 heifers), placebo group (PLAC, n=3 heifers), control group (CONT, n=3 heifers).

Project description:In cattle, maternal recognition of pregnancy occurs on Day 16 via secretion of interferon tau (IFNT) by the conceptus. The endometrium can distinguish between embryos with different developmental competencies. In eutherian mammals, X-chromosome inactivation (XCI) is required to ensure an equal transcriptional level of most X-linked genes for both male and female embryos in adult tissues, but this process is markedly different in cattle than mice. We examined how sexual dimorphism affected conceptus gene expression and amino acid composition as well as the endometrial transcriptome during the peri-implantation period of pregnancy. Of the 5132 genes were differently expressed on Day 19 in male compared to female conceptuses, 2.7% were located on the X-chromosome. Concentrations of specific amino acids were higher in the uterine luminal fluid with male compared to female conceptuses, while female conceptuses had higher expression of specific amino acid transporters (SLC6A19 and SLC1A35). Of note, the endometrial transcriptome was not different in cattle gestating a male or a female conceptus. These data support the hypothesis that, far from being a blastocyst specific phenomenon, XCI is incomplete before and during implantation in cattle. Despite differences in gene expression and amino acid utilization in male versus female conceptuses, the sex of the conceptus itself does not elicit a different response in the endometrium. Following a synchronized estrous cycle, all heifers observed in standing estrus (=Day 0, n=30) were inseminated with semen from a proven sire. All samples were recovered at slaughter on Day 19 following estrus corresponding to the initiation of implantation in cattle, flushed with 10 ml of PBS and the presence of a conceptus was observed under a stereo-microscope (n=24). Each conceptus was dissected into 4 pieces, 3 containing only trophectoderm cells and one containing the embryonic disc along with associated trophectoderm cells, and immediately snap-frozen in liquid nitrogen along with the corresponding intercaruncular endometrium from the uterine horn ipsilateral to the corpus luteum. DNA was extracted from each conceptus with phenol/chloroform treatment and finally re-suspended in 200 Î¼L of milliQ water. Two microliters of each sample were used to perform embryo sexing by PCR amplification of sex-specific polymorphic fragments in the amelogenin gene. N=5 samples of intercaruncular endometirum and the corresponding trophectoderm only sample were anaylsed for gene expression.

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