Endometrial gene expression and cow fertility. Bos taurus

Profitable milk production in dairy cows requires good reproductive performance. Calving interval is a trait used to measure reproductive efficiency. Here we used a novel lactating Holstein cow model with genetic and phenotypic divergence in calving interval. Cows had similar genetic merit for milk production traits, but either very good genetic merit for fertility (Fert+; n = 7) or very poor genetic merit for fertility (Fert-; n = 6). We sequenced the transcriptome of endometrial biopsies collected on day 7 of the estrous cycle, a crucial stage for establishment of pregnancy. Significant differential expression (FDR adjusted p < 0.1) of 403 genes was found between the Fert+ and Fert- animals. A standard over-representation analysis resulted in 12 lowly populated canonical pathways; however a novel in-depth analysis revealed a core of eighteen genes both differentially expressed and highly abundant. Almost all of these genes were related to actin-related and cytoskeletal components of the endometrium; fundamental cell-structure differences existed between Fert+ and Fert- phenotypes. We also present results indicating inflammation-related genes are down-regulated, and that multiple ion transporters and gated-voltage channels were up-regulated, in Fert+ cows. These three topics are discussed in terms of the uterus and in the context of fertility during early embryo development. Transcriptomic data analysis is complex; we use a method that filters those genes that may be of greatest importance to the tissue at the timepoint of sampling. Our findings support the utility of this approach, as well as highlighting clear physiological differences in our animal model. Overall design: 14 samples total; 7 Fert+ ('high fertility'), 7 Fert- ('low fertility'); no controls; Fert+, Fert- differential gene expression analysis