Non-Coding RNA Sequencing of Equine Endometrium During Maternal Recognition of Pregnancy.

Kristin M Klohonatz,Kailee J Reed,Ashley D Cameron,Stephen J Coleman,Jason E Bruemmer,Ted Kalbfleisch,Gerrit J Bouma,Juan F Medrano,Angela Canovas,Alma D Islas-Trejo,Ann M Hess

doi:10.3390/genes10100821

Kristin M Klohonatz, Kailee J Reed + Show 9 more

Open Access

https://doi.org/10.3390/genes10100821

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Abstract

Maternal recognition of pregnancy (MRP) in the mare is not well defined. In a non-pregnant mare, prostaglandin F2α (PGF) is released on day 14 post-ovulation (PO) to cause luteal regression, resulting in loss of progesterone production. Equine MRP occurs prior to day 14 to halt PGF production. Studies have failed to identify a gene candidate for MRP, so attention has turned to small, non-coding RNAs. The objective of this study was to evaluate small RNA (<200 nucleotides) content in endometrium during MRP. Mares were used in a cross-over design with each having a pregnant and non-mated cycle. Each mare was randomly assigned to collection day 11 or 13 PO (n = 3/day) and endometrial biopsies were obtained. Total RNA was isolated and sequencing libraries were prepared using a small RNA library preparation kit and sequenced on a HiSeq 2000. EquCab3 was used as the reference genome and DESeq2 was used for statistical analysis. On day 11, 419 ncRNAs, representing miRNA, snRNA, snoRNA, scaRNA, and vaultRNA, were different between pregnancy statuses, but none on day 13. Equine endometrial ncRNAs with unknown structure and function were also identified. This study is the first to describe ncRNA transcriptome in equine endometrium. Identifying targets of these ncRNAs could lead to determining MRP.

Highlights

Pregnancy in the mare is a process that is still not well defined
There were 8370 non-coding RNAs identified in the equine endometrium on day 11 and 3984 on day 13
Non-coding RNA transcripts, like miRNA, were once considered. These are the first sequence data to investigate small non-coding RNAs (ncRNAs) in equine endometrium during part of the genome’s “junk” DNA, which was believed to be non-functional in terms of transcription

Summary

Introduction

Pregnancy in the mare is a process that is still not well defined. The signal for maternal recognition of pregnancy (MRP) remains a mystery. The equine embryo does not attach to the endometrium until approximately day 35 post-ovulation (PO). The communication between the embryo and the endometrium occurs without any attachment of the two. Genes 2019, 10, 821 cycle, if the endometrium fails to recognize a viable embryo, it produces prostaglandin F2α (PGF). On day 14 PO to cause regression of the corpus luteum (CL) [1,2]. The corpus luteum is necessary during pregnancy to produce progesterone. There may be the presence of a conceptus, but this does not necessarily mean that the mare will be pregnant or undergo maternal recognition of pregnancy (such as with concomitant inflammation/aneuploidy) [3]

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