PS1-15. Shearing During Early Mid-Gestation Modifies Placental Gene Expression.

Abstract

Shearing ewes before parturition is a common husbandry practice in the US, providing a more sanitary environment for lambing. We previously reported that shearing fall-bred pregnant ewes on day 50 of gestation improves umbilical blood flow and fetal development (measured by Doppler ultrasonography). Moreover, day 50 shearing improved lamb birth and weaning weights in multiples (twins and triplets) by an average of 0.45 kg and 2.52 kg, respectively. Therefore, the goal of this study was to identify if shearing resulted in differentially expressed genes in the placenta. Briefly, twenty-eight Polypay ewes were randomly assigned to two treatments: shorn (S) and sham-shorn (Control, C) and divided in singleton (S: n = 4; C: n = 4), twins (S: n = 5; C: n = 5) and triplets (S: n = 5; C: n = 5). At birth placentas were collected and the largest cotyledon closest to the umbilicus was dissected and rinsed with phosphate-buffered saline solution. A 2.5 ´ 2.5 cm2 of cotyledonary tissue was snap-frozen in liquid nitrogen and stored at -80 °C. Total RNA was isolated from the samples and subjected to RNA sequencing. After quality control, the reads were mapped to the sheep reference genome using STAR aligner, and differentially expressed genes (DEGs) were identified using DESeq2. Transcriptomics analysis revealed 566 genes were downregulated, and 114 were upregulated in the placenta of S ewes (P ≤ 0.05 and |Log2FC| > 1). Functional over-representation analysis of DEGs was performed using DAVID to retrieve biological processes and KEGG pathways. Shearing upregulated genes related with steroidogenesis (HSD3B1), protein digestion and absorption (LOC101105540) and chemotaxis proteins and pathways, including placental prolactin related protein 1 and 3-like genes (LOC101109921 and LOC101109654), which are members of the ruminant placenta prolactin/growth hormone family. Placental prolactin related protein 1 and 3-like genes are specifically expressed in trophoblast binucleate cells of the ruminant placenta that aid in pregnancy maintenance and may aid in fetal growth. Prostaglandin E synthase 3 gene (LOC114118052) related with local vasodilation was also upregulated. Our findings suggest that shearing plays a role in placental gene expression potentially contributing to the phenotypical effects previously reported.