43 Impact of Pregnancy Status on the Transcriptome of Peripheral White Blood Cells

Abstract

Abstract Most embryo losses occur in the first trimester of pregnancy in cows, resulting in negative economic impact for dairy production systems. The current scientific paradigm implies the conceptus evades rejection by the maternal immune system. However, the cellular and molecular mechanisms behind the maternal immune response to the growing embryo have not been fully characterized. Hence, this study examined gene expression profiles of peripheral white blood cells (PWBC) from pregnant cows at 21 days after an embryo was transferred, (Bos taurus taurus), and cows that were treated equally but lost the embryo. We investigated the effect of pregnancy status on differential gene expression in PBMCs. We obtained and compared the total transcripts of PWBC from heifers that became pregnant at day 21 (N = 5) or failed to become pregnant after the embryo transfer (N = 5t). The total RNA transcripts, where an average of 96 % of the total reads were successfully mapped to the bovine reference genome. Each sample generates between 32 to 43 million reads. Sequencing data can be accessed by GEO with the accession number GSE210665. There was no need to remove samples in this study. Based on the length and abundance of the reads that cover the bovine genomic, we conclude that deep sequencing is suitable for the experiment outcome. A total of 13.167 genes were tested for differential expression by controlling the false discovery rate (FDR). A positive fold change denotes an overexpression and a negative fold change value a downregulation gene between treatments. After statistical analysis, 682 of these genes present a P-value smaller than 0.01, a total of 302 genes were upregulated, and 382 downregulated. The top 7 expression fold change top upregulated (logFC > 2) genes were COL1A2, LOC100337213, H2AC18, HTRA1, MMP14, CD5L, and LOC100297044. The top 4 downregulated (logFC< − 2) were ADAMDEC1, MYO1A, RPL39, and Histone H4. These data show differentially expressed genes associated with pregnancy status were both upregulated and downregulated as a response to early pregnancy, or a failure to become pregnant after embryo transfer. Our results show that these are key maternal genes for promoting tolerance allowing developing of the embryo. In summary, this study presented the genes related to positive regulation of inflammatory chemokine activity and immune defense response in the maternal PWBC.