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Characterization of the endometrial transcriptome in pregnant and non-pregnant sows
Up to 30% of early conceptus losses in the sow occur between 12 and 30 day of gestation and have a major impact on the productivity and profitability of the swine industry. The maternal environment plays a critical role on the ability of the embryo to implant and survive until delivery. The objective of this study was to identify the genes that are differentially expressed between the endometrium of pregnant and non-pregnant sows using next generation RNA sequencing. The endometrial mRNA from three pregnant and four non-pregnant cycling German Landrace gilts was profiled on day 14 after insemination. The RNA-Seq analysis used the Illumina Genome Analyzer II platform. Single-end reads were mapped to the Sus scrofa reference genome Sscrofa10.2/susScr3. In total, 4,921 transcripts pertaining to 4,068 genes were tested and 916 transcripts from 853 genes were found to be differentially expressed (False Discovery Rate adjusted P-value < 0.05). Among these, S100 calcium binding protein A9 and indoleamine 2,3-dioxygenase 1 (IDO1) were over-expressed while C1q, tumor necrosis factor related protein 3 and anterior gradient 2 homolog were under-expressed in pregnant relative to non-pregnant sows. IDO1 has been associated with allogeneic fetal rejection. Functional analysis of the differentially expressed genes using DAVID identified two category clusters (enrichment score > 2 equivalent to average category P-value < 0.01). These categories included immune response processes, graft-versus-host disease, allograft rejection, and antigen processing and presentation pathways. These functional categories confirm the development of embryo-maternal interactions early in the pregnancy. Our results point to maternal pathways that could be key to embryo implantation and survival.
Keywords: RNA-seq, endometrium, swine