Placental PAGs: gene origins, expression patterns, and use as markers of pregnancy

Abstract

Pregnancy-associated glycoproteins (PAGs) are abundantly expressed products of the placenta of species within the Cetartiodactyla order (even-toed ungulates). They are restricted to this order and they are particularly numerous in the Bovidae. The PAGs exhibit a range of temporal and spatial expression patterns by the placental trophoblasts and probably represent a group of related proteins that perform a range of distinct functions in the epitheliochorial and synepitheliochorial placental forms. This review presents an overview of the origins of the PAGs, a summary of PAG expression patterns, and their use as markers of pregnancy status. Speculations about their putative role(s) in pregnancy are also presented.Reproduction (2015) 149 R115-R126

Advances in flow cytometry in basic and applied equine andrology

“…Placental expression of pregnancy-associated glycoproteins (PAGs) occurs throughout Cetartiodactyla (Wallace et al, 2015). As with placental lactogens, the number of PAG genes varies and is highest in cattle (Telugu et al, 2009).…”

“…The second round of duplication occurred in ruminants and many of the resultant proteins lack the active site. They are expressed mainly at the surface of binucleate cells and have been ascribed immunomodulatory functions (Wooding et al, 2005;Wallace et al, 2015). A PAG-like gene has been characterized in equids (horse and mountain zebra, Equus zebra), where it is expressed in the trophectoderm of the blastocyst, including girdle cells, and trophoblast of the term placenta (Xie et al, 1997;Green et al, 1999).…”

“…A related protein has been cloned from the cat (Green et al, 1999;Hughes et al, 2003), but its expression pattern is unknown. The equine and feline variants are not glycosylated, however, and are now referred to as pepsin-F (Wallace et al, 2015). It is thought that PAGs proper evolved in the Cetartiodactyla lineage and were derived from an ancestral pepsin-F gene that in turn originated from the pepsin-A gene (Wallace et al, 2015).…”

Markers of pregnancy: how early can we detect pregnancies in cattle usingpregnancy-associated glycoproteins (PAGs) and microRNAs?

“…Although their physiological role is unknown, a large number of distinct PAGs and more than two dozen specific PAG genes have been described. Based on accumulation of PAGs at the junction between uterus and placenta and known proteolytic activity of certain PAGs, it has been hypothesized that PAGs may help process growth factors or may have adhesion actions (Wallace et al, 2015). Based on evidence that PAGs may inhibit certain immune cells, they may also play a role in disguising antigens from the maternal immune system (Perry et al, 2005).…”

Predicting Embryo Presence and Viability

“…13.1 ; (Wooding et al 2005 )). PAGs are members of a relatively large gene family and are abundantly expressed in the placenta of species within the Cetartiodactyla order (even-toed ungulates) and can be detected in circulation and milk (Wallace et al 2015 ). There is signifi cant variation in the spatial and temporal expression of PAGs in species having an epitheliochorial and synepitheliochorial placenta.…”