The core transcriptome of mammalian placentas and the divergence of expression with placental shape

Abstract

Introduction The placenta is arguably the most anatomically variable organ in mammals even though its primary function is conserved. Method Using RNA-Seq, we measured the expression profiles of 55 term placentas of 14 species of mammals representing all major eutherian superordinal clades and marsupials, and compared the evolution of expression across clades. Results We identified a set of 115 core genes which is expressed (FPKM ≥ 10) in all eutherian placentas, including genes with immune-modulating properties (ANXA2, ANXA1, S100A11, S100A10, and LGALS1), cell-cell interactions (LAMC1, LUM, and LGALS1), invasion (GRB2 and RALB) and syncytialization (ANXA5 and ANXA1). We also identified multiple pre-eclampsia associated genes which are differentially expressed in Homo sapiens when compared to the other 13 species. Multiple genes are significantly associated with placenta morphology, including EREG and WNT5A which are both associated with placental shape. Discussion 115 genes are important for the core functions of the placenta in all eutherian species analyzed. The molecular functions and pathways enriched in the core placenta align with the evolutionarily conserved functionality of the placenta.

Assessment of the cellular localisation of the annexin A2/S100A10 complex in human placenta

“…Although the placenta is anatomically variable across mammalian species, a core transcriptome of around 115 genes can be identified that are critical to the function of the placenta across species (Armstrong et al 2017 ). Predominant amongst these are members of the annexin family, AnxA2, AnxA1 and AnxA5, arguing for the evolutionary importance of annexins (Armstrong et al 2017 ). Annexins are also known as ‘placental anti-coagulant proteins’ and they have been estimated to constitute up to 2% of the total placental membrane proteins (Buhl et al 1991 ).…”

Transcriptomic analysis of primate placentas and novel rhesus trophoblast cell lines informs investigations of human placentation

“…Approximately 14% (N=61/447) of the genes we identified as upregulated in human were previously annotated in other comparative studies as specifically expressed or upregulated in human placenta compared to many distantly-related species (Hou et al 2012;Armstrong et al 2017). However, since these studies relied on the comparison of placental gene expression across numerous distantly-related species, they were limited in the number of orthologous genes eligible for differential expression comparison.…”

The placenta goes viral: Retroviruses control gene expression in pregnancy

“…The mammalian placenta shows great diversity across species in its morphology and tissue organization, mechanisms of implantation and invasion, and physiological regulation [ 2 , 3 ]. Even trophoblast cells, the cellular building blocks of the placenta, bear little morphological or molecular resemblance across species [ 4 ]. Current theories suggest that life history changes and/or parent–offspring conflicts over maternal resources promoted rapid evolution of the placenta [ 5 , 6 ].…”