The Transcriptome Signature of the Receptive Bovine Uterus Determined at Early Gestation

Abstract

Pregnancy success is critical to the profitability of cattle operations. However, the molecular events driving the uterine tissue towards embryo receptivity are poorly understood. This study aimed to characterize the uterine transcriptome profiles of pregnant (P) versus non-pregnant (NP) cows during early pregnancy and attempted to define a potential set of marker genes that can be valuable for predicting pregnancy outcome. Therefore, beef cows were synchronized (n=51) and artificially inseminated (n=36) at detected estrus. Six days after AI (D6), jugular blood samples and a biopsy from the uterine horn contralateral to the ovary containing the corpus luteum were collected. Based on pregnancy outcome on D30, samples were retrospectively allocated to the following groups: P (n=6) and NP (n=5). Both groups had similar plasma progesterone concentrations on D6. Uterine biopsies were submitted to RNA-Seq analysis in a Illumina platform. The 272,685,768 million filtered reads were mapped to the Bos Taurus reference genome and 14,654 genes were analyzed for differential expression between groups. Transcriptome data showed that 216 genes are differently expressed when comparing NP versus P uterine tissue (Padj≤0.1). More specifically, 36 genes were up-regulated in P cows and 180 are up-regulated in NP cows. Functional enrichment and pathway analyses revealed enriched expression of genes associated with extracellular matrix remodeling in the NP cows and nucleotide binding, microsome and vesicular fraction in the P cows. From the 40 top-ranked genes, the transcript levels of nine genes were re-evaluated using qRT-PCR. In conclusion, this study characterized a unique set of genes, expressed in the uterus 6 days after insemination, that indicate a receptive state leading to pregnancy success. Furthermore, expression of such genes can be used as potential markers to efficiently predict pregnancy success.

Basic and practical aspects of pregnancy establishment in cattle

“…The progesterone-induced changes in the endometrial transcriptome seem to be independent of pregnancy status up to the time of conceptus elongation and maternal recognition of pregnancy on day 15 (Forde et al, 2011), but an embryo-dependent programming of endometrial function has recently been demonstrated already from day 7 in the estrous cycle . Also on day 7, Binelli et al (2015) showed endometrial gene expressions in the uterine horn contralateral to an AI that illustrated the readiness and preparedness of the endometrium to receive an incoming embryo. In addition, pretransfer endometrial biopsies from heifers on day 7 of the estrous cycle revealed differences in gene expression according to pregnancy diagnosis in the following cycle after transfer of in vivo derived embryos (Salilew-Wondim et al, 2010) and in vitro produced embryos (Ponsuksili et al, 2012).…”

“…The hatching is a mutual process, where the embryo is active with collapses and re-expansions, the zona is thinned by secretion of trypsin from the endometrium, and small projections of specialized cellular TE through the zona induce the focal opening(s) through one of which the embryo escapes, aided by TE proteinase secretion (Kirkegaard et al, 2013). In human, an active embryo secretion seems to be essential for establishment of the pregnancy (Brosens et al, 2014).…”

“…On the molecular level, the progesteroneinduced changes in gene expression in the endometrium result in up-or down-regulation of genes involved in processes such as cellular transports, cell cycle, cell growth and differentiation, lipogenesis, metabolism, cell adhesion, signal transduction, biosynthesis and immune response (Bauersachs et al, 2006;Forde et al, 2009Forde et al, , 2011Forde et al, , 2012bSimmons et al, 2009;Binelli et al, 2015). The progesterone-induced changes in the endometrial transcriptome seem to be independent of pregnancy status up to the time of conceptus elongation and maternal recognition of pregnancy on day 15 (Forde et al, 2011), but an embryo-dependent programming of endometrial function has recently been demonstrated already from day 7 in the estrous cycle .…”

63 Effect of Endometrial Biopsy on Uterine Health of Tropically Adapted Beef Cattle

“…In women, endometrial receptivity has been assessed either within a few days prior to the day of ET (Huang et al, 2011) or on the day of ET (Boomsma et al, 2009a). To compare the endometrial transcriptome of cows that would later be determined to be either pregnant or not pregnant, Binelli et al (2015) collected endometrial biopsies on Day 6 after AI from the horn contralateral to the CL.…”

Effect of endometrial biopsy on uterine health in tropically adapted beef cattle

“…The identification of these molecules could be used as a prognostic factor to screen and select recipients with endometrial characteristics that favour receptivity. Salilew-Wondim et al (2010) and recently Binelli et al (2015) described the endometrial gene expression around Day 7 post-oestrus in pregnant and non-pregnant cows. Although different methods for sample collection and platform analysis were used in both studies, they concluded that differences in gene expression exist in the number, types of genes and pathways expressed between pregnant cows with receptive endometrium and non-pregnant cows with non-receptive endometrium at Day 7 post-oestrus.…”