Spatiotemporal expression of pregnancy‐specific glycoprotein gene rnCGM1 in rat placenta

Abstract

As a basis towards a better understanding of the role of the pregnancy-specific glycoprotein (PSG) family in the maintenance of pregnancy, detailed investigations are described on the expression of a recently identified rat PSG gene (rnCGMl) at the mRNA and protein levels. Using specific oligonucleotide primers, rnCGMl transcripts were identified after reverse transcription, polymerase chain reaction, and hybridization with a radiolabelled, internal oligonucleotide. Transcripts were only found in significant amounts in placenta. In situ hybridization visualized rnCGM1 transcripts at day 14 post coitum (P.c.), in secondary trophoblast giant cells and in the spongiotrophoblast. Only those secondary giant cells lining the maternal decidua were positive. In contrast, primary giant cells did not contain rnCGMl mRNA. At day 18 P.c., rnCGMl transcripts were almost exclusively detectable in the spongiotrophoblast. No rnCGMl transcripts were found in rat embryos of these two developmental stages. Rabbit antisera were generated against the amino-terminal immunoglobulin variable-like domain and against a synthetic peptide containing the last 13 carboxy-terminal amino acids of rnCGMI. Both antisera recognized a 124 kDa protein in day 18 rat placental extracts as identified by Western blot analysis. The anti-peptide antiserum recognized a 116 kDa protein in the serum of a 14 day p.c. pregnant rat that is absent from the sera of non-pregnant females. Taken together, these results confirm exclusive expression of rnCGMl in the rat trophoblast, but unlike human PSG, negligible or no expression is found in other organs, such as fetal liver or salivary glands, indicating a more specialized function of rnCGM1. Its spatiotemporal expression pattern is conducive with a potential role of PSG in protecting the fetus against the maternal immune system andlor in regulating the invasive growth of trophoblast cells. 0 1993 Wiley-Liss, Inc.

The Cea10 Gene Encodes A Secreted Member of the Murine Carcinoembryonic Antigen Family and is Expressed in the Placenta, Gastrointestinal Tract and Bone Marrow

“…On the other hand, simi- At present, the function of CealO is completely obscure. This is also true for the PSGs, which also represent secreted members of the CEA family, although roles in trophoblast invasion or specific suppression of the maternal immune system during pregnancy have been discussed for PSGs [52]. CealO lacks, however, the ArgGlyAsp-related amino acid sequence motif, presumed to be functionally important, which is present in most human and murine PSGs and is known to be involved in interaction of certain extracellular matrix proteins with their cellular integrin receptors [55].…”

Mouse pregnancy-specific glycoproteins: tissue-specific expression and evidence of association with maternal vasculature

“…They are synthesised in the syncytiotrophoblast of the human placenta and in the giant cells and spongiotrophoblast of the rodent placenta (Lei et al 1992, Rebstock et al 1993, Kromer et al 1996, Zhou et al 1997. The PSG family belongs to the carcinoembryonic antigen (CEA) family, which also includes the CEA-related adhesion molecules (CEACAMs), and is part of the immunoglobulin (Ig) superfamily (Brummendorf & Rathjen 1994).…”

“…Membrane-anchored CEACAMs are widely expressed during embryonic development and in adult tissues, and are implicated in multiple aspects of cell signalling, tissue homeostasis and disease, including carcinogenesis and regulation of immune and metabolic functions (Han et al 2001, Zebhauser et al 2005. PSGs and some CEACAMs are expressed almost exclusively in trophoblasts of the haemochorial placenta of rodents and primates, suggesting potential functional convergence between these otherwise divergent gene families (Rebstock et al 1993, Zhou & Hammarstrom 2001.…”

Spatiotemporal Expression of C-CAM in the Rat Placenta

“…C-CAM is a member of the CEA gene family, which comprises several structurally related proteins (Thompson et al 1991), and it has previously been demonstrated that rat placenta expresses proteins belonging to the PSG subgroup of the CEA family (Rebstock et al 1993;Ogilvie et al 1989). However, antibodies recognizing rat PSGs gave a completely different spatiotemporal staining pattern, demonstrating that the antibodies against C-CAM did not crossreact with PSG.…”

“…It is well known that pregnancy-specific glycoproteins (PSGs) which, like C-CAM, belong to the CEA gene family, are expressed at high levels in placentae of both humans and rodents (Rebstock et al 1993;Ogilvie et al 1989). Because there can be considerable immunological crossreactivity among different members of the CEA family, it was important to demonstrate that the staining observed with anti-C-CAM antibodies indeed reflected expression of C-CAM and not of PSG.…”