Pregnancy-associated glycoproteins (PAGs) are structurally related to thepepsins, thought to be restricted to the hoofed (ungulate) mammals andcharacterized by being expressed specifically in the outer epithelial celllayer (chorion/trophectoderm) of the placenta. By cloning expressed genes fromovine and bovine placental cDNA libraries, the inventors estimate that cattle,sheep, and most probably all ruminant Artiodactyla, possess possibly 100 ormore PAG genes, many of which are placentally expressed. The PAGs are highlydiverse in sequence, with regions of hypervariability confined largely tosurface-exposed loops. Selected PAG that are products of the invasivebinucleate cells, expressed highly in early pregnancy at the time oftrophoblast invasion and expressed weakly, if at all, in late gestation areuseful in the early diagnosis of pregnancy. In a preferred embodiment, theinvention relates to immunoassays for detecting these PAGs.
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