Free Access
Reprod. Nutr. Dev.
Volume 43, Number 6, November-December 2003
Page(s) 497 - 516
Reprod. Nutr. Dev. 43 (2003) 497-516
DOI: 10.1051/rnd:2004004

Chorionic expression of heterogeneous products of the PAG (Pregnancy-Associated Glycoprotein) gene family secreted in vitro throughout embryonic and foetal development in the pig

Bozena Szafranskaa, Grzegorz Panasiewicza, Marta Majewskaa and Jean-Francois Beckersb

a  Department of Animal Physiology, Faculty of Biology, University of Warmia and Mazury, 10-719 Olsztyn-Kortowo, Oczapowskiego Str 1A/222, Poland
b  Departments of Reproductive Physiology, Faculty of Veterinary Medicine, University of Liege, B-40000 Sart-Tilman, Belgium

Received 20 June 2003; accepted 15 September 2003

Abstract - Porcine PAG (pPAG) are placental products of a multigene family that is strongly expressed in the chorionic epithelium (trophoblast and trophectoderm). The objective of this study was to define a pattern of the pPAG proteins, secreted in vitro by chorionic explants harvested on 16-77 days of pregnancy. Trophoblastic and trophectodermal explants were collected from pregnant (PR) gilts ( n = 27) and used for protein in vitro production (8-261 h). Endometrial explants of luteal-phase gilts (E10, n = 4) and pseudopregnant gilts (PsE, n = 2) were used as negative controls for protein immunoblotting. Proteins (PR, E10, PsE) were isolated mainly from incubation media, fractionated, dialysed and separated by SDS-PAGE. Heterogeneous Western blotting with various polyclonal anti-PAG sera raised against bovine or ovine antigens (anti-bPAG, or anti-oPAG) initially identified the pPAG proteins. Such blotting of fractionated chorionic proteins allowed for the isolation of porcine antigens that were employed as immunogens to raise several homologous antisera (anti-pPAG). Crude antisera were adsorbed on endometrial extracts or proteins of non-PR pigs, to remove non-relevant antibodies. The patterns of pPAG proteins secreted in vitro varied throughout pregnancy (35-72 kDa). During implantation, ~43 kDa (Day 16) or ~68.1 kDa (Days 17-25) pPAG proteins were detected. During placentation and as pregnancy advanced (Days 31-77), ~72.3 kDa pPAG proteins were observed. The secretions of parallel multiple smaller proteins (35.4-47.2 kDa), presumably, as forms of processed pPAG precursors, increased with the progress of gestation. In conclusion, the pPAG protein family plays a very important role during implantation, placenta formation and embryonic/foetal development in the pig.

Key words: chorionic glycoproteins / placenta / pPAG gene family / pig / pregnancy / trophectoderm

Corresponding author: Bozena Szafranska

© INRA, EDP Sciences 2003