OC7 Pregnancy‐Associated Glycoprotein (PAG) Cloning and Expression in Pre‐implantational Ovine Conceptuses

Pregnancy-associated glycoproteins (PAGs) are a multigene family, related to aspartic proteinases, expressed in the placenta of artiodactyls. PAGs cloned from ruminants can be classified into two main groups. The PAG I group, a rapidly-evolving group expressed in the binucleate cells of the trophectoderm, and the PAG II group, with more ancient origin and expressed throughout trophectoderm. The aim of this study was to identify first PAG transcripts to be expressed around implantation in sheep. Day 14 (n = 4) and 17 (n = 12) ovine conceptuses were used for reverse transcription–polymerase chain reaction (RT-PCR) performed on RNA extracted from conceptuses pooled on each day of recovery. PCR products were analysed by restriction digest and subcloned. Similar sequences were aligned and the consensus sequence was checked for identity/similarity in the Gene Bank. A single PAG was detected on day 14, ovPAG2, the only PAG cloned in ovine from the PAG II group. On day 17, three more PAG were identified, one similar to ovPAG1 and two unknown named as ovPAG10 (DQ377958) and ovPAG11 (DQ377959), which were close to each other (95% nt, 91% aa) and other PAG I group members. Phylogenetic analysis as well as a conserved site for propeptide cleavage situated these new PAGs into the PAG I group. In summary, ovPAG2 is expressed at day 14 of pregnancy and as well at day 17, together with ovPAG1 and two unknown PAG transcripts, probably belonging to the PAGI group. These early PAGs might play an important role at the beginning of implantation.