Global Transcriptomic Analyses Reveal Genes Involved in Conceptus Development During the Implantation Stages in Pigs.

Xupeng Zang,Gengyuan Cai,Zhenfang Wu,Ting Gu,Linjun Hong,Chen Zhou,Zheng Xu,Sixiu Huang,Zhiqian Xu,Qun Hu,Fanming Meng,Yanshe Xie,Enqin Zheng

doi:10.3389/fgene.2021.584995

Abstract

Prenatal mortality remains a significant concern to the pig farming industry around the world. Spontaneous fetal loss ranging from 20 to 45% by term occur after fertilization, with most of the loss happening during the implantation period. Since the factors regulating the high mortality rates of early conceptus during implantation phases are poorly understood, we sought to analyze the overall gene expression changes during this period, and identify the molecular mechanisms involved in conceptus development. This work employed Illumina’s next-generation sequencing (RNA-Seq) and quantitative real-time PCR to analyze differentially expressed genes (DEGs). Soft clustering was subsequently used for the cluster analysis of gene expression. We identified 8236 DEGs in porcine conceptus at day 9, 12, and 15 of pregnancy. Annotation analysis of these genes revealed rRNA processing (GO:0006364), cell adhesion (GO:1904874), and heart development (GO:0007507), as the most significantly enriched biological processes at day 9, 12, and 15 of pregnancy, respectively. In addition, we found various genes, such as T-complex 1, RuvB-like AAA ATPase 2, connective tissue growth factor, integrins, interferon gamma, SLA-1, chemokine ligand 9, PAG-2, transforming growth factor beta receptor 1, and Annexin A2, that play essential roles in conceptus morphological development and implantation in pigs. Furthermore, we investigated the function of PAG-2 in vitro and found that PAG-2 can inhibit trophoblast cell proliferation and migration. Our analysis provides a valuable resource for understanding the mechanisms of conceptus development and implantation in pigs.

Highlights

The implantation period is critical for the development of conceptuses during the early stages of pregnancy in swine
Distribution and identity of the three triplicate samples were analyzed by correlation, with Pearson’s correlation coefficient among transcriptomes across porcine conceptus phases on days 9, 12, and 15 revealing a good correlation of biological replicates (Figure 1)
Our results showed that genes that were highly expressed on day 12 were involved in conceptus development and maternal-uterine recognition, which is consistent with previous studies

Summary

Introduction

The implantation period is critical for the development of conceptuses during the early stages of pregnancy in swine. Genes Involved in Conceptus Development morphology, between days 10 and 12 of gestation, mainly due to extensive cellular migration and reorganization (Mattson et al, 1990). These transformations are mainly manifested as changes in conceptus size and shape, and range from spherical (3 to 10 mm diameter) to tubular (10 to 50 mm long) to filamentous (>100 mm long; Perry and Rowlands, 1962; Anderson, 1978). At gestation day 15, filamentous conceptuses extend from 800 to 1000 mm in length, and start to attach to the uterine luminal epithelium (Bazer and Johnson, 2014). Elongation in the uterine horns, before conceptus implantation, simultaneously create a larger contact between the conceptus and maternal tissues, which is crucial for subsequent conceptus attachment (Keys et al, 1986; Bazer and Johnson, 2014)

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