Identification of novel pregnancy-associated glycoproteins (PAG) expressed by the peri-implantation conceptus of domestic ruminants.

Pregnancy-associated glycoproteins (PAG) are a multigene family, related to aspartic proteinases, expressed in the placenta of artiodactyls. Ruminant PAG expression varies spatially as well as temporally during gestation. The aim of this study was the identification of novel PAG expressed around implantation in domestic ruminants and to study their phylogenetic relationships. Day 12, 14, 17 (ovine); day 15, 18 (bovine); and day 12, 14, 15, 16, 18 (caprine) conceptuses were used for reverse transcription-polymerase chain reaction (RT-PCR) performed on RNA extracted from conceptuses pooled on each day of recovery. In ovine, a single PAG was detected on day 14, ovPAG2, from the PAG II group. On day 17, three more PAG were identified. One of them similar to ovPAG1 and two unknown named as ovPAG10 and ovPAG11, apparently from the PAG I group. In bovine, PAG expression was detected by day 15 and two transcripts were identified on day 18. One, boPAG2, from the PAG II group and other was previously unknown, boPAG22, closest to boPAG2. In goats, PAG expression was not detected on non-elongated conceptuses (days 12, 14 and 15). Two different transcripts were identified in both day 16 and 18 elongated conceptuses, one similar to caPAG2, from the PAG II group, whereas the other, caPAG12, apparently from the PAG I group, was previously unknown. Interestingly, the three new early PAG identified in sheep and goats are clustered together within the PAG I group. In summary, a complement of new PAGs expressed at implantation in domestic ruminants has been cloned.