Global analysis of differential gene expression within the porcine conceptus transcriptome as it transitions through spherical, ovoid, and tubular morphologies during the initiation of elongation

Authors: WALSH, SOPHIE - University Of Nebraska; Miles, Jeremy; Keel, Brittney; Rempel, Lea; Wright, Elane; Lindholm-Perry, Amanda; Oliver, William; PANNIER, ANGELA - University Of Nebraska

Submitted to: Molecular Reproduction and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2021
Publication Date: 1/12/2022
Citation: Walsh, S.C., Miles, J.R., Keel, B.N., Rempel, L.A., Wright-Johnson, E.C., Lindholm-Perry, A.K., Oliver, W.T., Pannier, A.K. 2022. Global analysis of differential gene expression within the porcine conceptus transcriptome as it transitions through spherical, ovoid, and tubular morphologies during the initiation of elongation. Molecular Reproduction and Development. Article 23553. https://doi.org/10.1002/mrd.23553.
DOI: https://doi.org/10.1002/mrd.23553

Interpretive Summary: Adequate embryo elongation during early gestation plays a critical role for successful pregnancy outcomes in the pig. Alterations in the signaling of critical molecular factors, such as embryonic gene expression, can result in deficiencies in embryo elongation leading directly to embryonic loss as well as delayed elongation. To identify fine temporal resolution of differential gene expression during the initiation of elongation, an RNA-seq transcriptomic study was performed to compare divergent gene expression among distinct morphologies (spherical, ovoid or tubular) of embryos from litters with homogenic embryonic morphologies as well as transitional stage morphologies from litters with heterogenic embryonic morphologies. This study demonstrated dramatic changes in transcriptomes from these distinct and transitional populations of embryos, particularly during the initial transition of the embryo from spherical to ovoid morphologies. Specifically, this study highlights the importance of changes in genes and associated pathways involved in trophectoderm remodeling, prostaglandin and steroid hormone signaling, and cell adhesion and structural remodeling within the embryos. The information gained from this study can be used to further elucidate mechanisms essential to the successful initiation of pig embryo elongation.

Technical Abstract: This study aimed to identify transcriptome differences between distinct or transitional stage spherical, ovoid, and tubular porcine blastocysts throughout the initiation of elongation. We performed a global transcriptome analysis of differential gene expression using RNA-Seq with high temporal resolution between spherical, ovoid, and tubular stage blastocysts at specific sequential stages of development from litters containing conceptus populations of distinct or transitional blastocysts. After RNA-Seq analysis, significant differentially expressed genes (DEGs) and pathways were identified between distinct morphologies or sequential development stages. Overall, 1898 significant DEGs were identified between distinct spherical and ovoid morphologies, with 311 total DEGs between developmental stages throughout this first morphological transition, while 15 were identified between distinct ovoid and tubular, with eight total throughout these second morphological transition developmental stages. The high quantity of DEGs and pathways between conceptus stages throughout the spherical to ovoid transition suggests the importance of gene regulation during this first morphological transition for initiating elongation. Further, extensive DEG coverage of known elongation signaling pathways was illustrated from spherical to ovoid, and regulation of lipid signaling and membrane/ECM remodeling across these early conceptus stages were implicated as essential to this process, providing novel insights into potential mechanisms governing this rapid morphological change.