Abstract
Carefully coordinated interaction between the endometrium and embryo is critical for the establishment and maintenance of pregnancy in mammals. By exploring the gene expression dynamics of this tissue during preimplantation development, we may be able to get insight into the genetic mechanisms of reproduction during early pregnancy. Here, we have performed comparative transcriptome profiling of the endometrium in response to spherical (Day 7 to Day 12) and elongated (Day 13 to Day 17) embryos in Finnsheep, Texel and their F1 crosses using RNA sequencing (RNA-seq) approach. A total of 21125 genes were expressed in our dataset of which 554 were significantly (absolute log2 fold change > 2.5; adjusted p-value < 0.01) upregulated in the endometrium with elongated embryos. Highly abundant autosomal genes in the endometrium were associated with biological processes such as facilitation of maternal recognition of pregnancy, trophoblast elongation and implantation (LGALS15, CST3, CST6, and EEF1A1). Several endogenous retroviruses (ERVs) including a novel ERV gene located in a reduced FecL locus potentially associated with sheep prolificacy were expressed in our dataset. Comparative transcriptome profiling of the endometrium having spherical and elongated embryos revealed distinct gene expression patterns. Genes that were upregulated in response to elongated embryos indicated the importance of immune system at the maternal-embryo interface prior to implantation.
Highlights
Prolific breeds of sheep such as native Finnsheep are of high economic importance for global sheep industry
Several tissue biopsies were collected at the slaughterhouse of which ovarian corpus luteum (CL) (Pokharel et al 2020) and the endometrium were employed for RNA sequencing (RNA-seq)
The transition time from spherical to elongated embryo appeared to be very short to classify them into intermediary shape which have been explained by the gene expression results
Summary
Prolific breeds of sheep such as native Finnsheep are of high economic importance for global sheep industry. The outer lining of the endometrium secretes histotroph, a complex mixture of enzymes, growth factors, hormones, transport proteins and other substances that are key to conceptus survival and implantation, pregnancy recognition and placentation (Spencer and Bazer 2004, Forde et al 2013). Despite a large number of pregnancy-related studies in sheep, (Spencer et al 2004, Spencer et al 2007, Mamo et al 2012, Bazer 2013, Raheem 2017), only a handful of experiments have applied whole transcriptome based RNA sequencing (RNA-seq) approaches to the endometrium. We have used RNA sequencing (RNA-seq) approach to compile a list of genes expressed in the endometrium and compared the expression profiles of the endometrium having spherical and elongated forms of embryos during preimplantation development in sheep. The dataset presented in this paper is part of a larger project which aimed to understand the genetic basis of prolificacy in sheep by conducting experiments on two different time points during establishment of pregnancy: follicular growth phase and early pregnancy prior to implantation
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