Convergent evolution of pregnancy-specific glycoproteins in human and horse.

This research paper discusses the evolution of pregnancy-specific glycoproteins (PSGs) found in horse and human species. Teachers suggest that these proteins have independently evolved in horses from an equine ancestor — not from a common ancestor with rodents and primates. This research contributes to understanding the evolution of PSGs and how they function in maternal-fetal interactions.

Objective of the Research

• The main goal of the study was to investigate the evolutionary lineage of pregnancy-specific glycoproteins (PSGs) in horses and humans.
• The researchers aimed at understanding if these proteins emerged from a common ancestor with rodents and primates or if they evolved independently.
• The team was also keen to understand the implications of the evolution of these PSGs in maternal-fetal interactions.

Methodology

• Researchers analyzed the carcinoembryonic antigen cell adhesion molecule (CEACAM) gene family of the horse, which has a non-invasive epitheliochorial placenta, except for the transient endometrial cups.
• They identified seven genes that encode secreted PSG-like CEACAMs and conducted phylogenetic analyses to understand their evolutionary history.
• The team also assessed the expression of PSG-like genes in non-invasive as well as invasive trophoblast cells, such as purified chorionic girdle cells and endometrial cup cells.

Findings

• The study found that horses possess PSG-like proteins, although they have a non-invasive placenta. This discovery was made upon analyzing the CEACAM gene family of the horse.
• The phylogenetic analysis suggests that these proteins have evolved independently from an equine CEACAM1-like ancestor rather than from a common ancestor shared with rodents and primates.
• The expression of PSG-like genes was discovered in both non-invasive and invasive trophoblast cells, hinting at a similar function to PSGs in other species.
• Chorionic girdle cells, which contain PSG-like proteins, reveal a microenvironment that mirrors the one found in invasive trophoblast cells of species with highly invasive (hemochorial) placentation. This discovery suggests possible convergent evolution of these proteins.
• Moreover, the finding that equine PSG-like CEACAM49 exhibits behavior similar to certain rodent and human PSGs in a functional assay of platelet-fibrinogen binding further supports this idea.

Implications

• This research provides critical insights into the evolution of pregnancy-specific glycoproteins, particularly in species that do not share a common PSG-like ancestor.
• More significantly, it adds to the understanding of the role of PSGs in maternal-fetal interactions, possibly paving the way for improved reproductive health management protocols.