Abstract
The carcinoembryonic antigen (CEA) gene family encodes a large family of glycoproteins. Some are probably involved in the homeostasis/development of epithelial cells and granulocyte activation, while others e.g. the pregnancy-specific glycoproteins, are expressed in the placenta and are essential for a positive outcome of pregnancy. In this paper, we have characterized cea5, a member of the murine CEA gene family. RNase protection and in situ hybridization analyses revealed that Cea5 mRNA is exclusively synthesized in primary and secondary trophoblast giant cells of the placenta only during early stages of development. Full-length Cea5 cDNA was obtained by a reverse transcription-polymerase chain reaction using day 10.5 post-coitum placental RNA. The 1.6-kilobase pair (kb) Cea5 mRNA encodes a secreted glycoprotein with a predicted size of 30 kDa. It is composed of a leader peptide (L), one immunoglobulin (Ig) variable or N, and one Ig constant-like or A domain. This domain organization is unique within the human and murine CEA families. Two overlapping cosmid clones covering 54 kb of the cea5 gene locus were mapped. cea5 consists of three exons (L, N, A/3'-untranslated region exon) located within a 4-kb region. rnCGM2, the rat cea5 counterpart, exhibits the same restricted expression pattern. This together with their exceptional conservation within the rat and murine CEA families and their absence from the human CEA family suggests that cea5 and rnCGM2 are of functional importance for rodent placental development.
Highlights
The carcinoembryonic antigen (CEA)1 family was originally discovered in humans and was named after CEA, the first family member to be discovered and later characterized as a human tumor marker [1]
Expression Pattern of Cea5—To be able to clone Cea5 cDNA, we identified Cea5 mRNA-containing tissues
We used an RNase protection assay, which allows the specific detection of Cea5 mRNA in the presence of mRNAs of other closely related CEA family members
Summary
The carcinoembryonic antigen (CEA) family was originally discovered in humans and was named after CEA, the first family member to be discovered and later characterized as a human tumor marker [1]. For one PSG subgroup member (PSG11), it was shown that an arginine-glycineaspartic acid (RGD) tripeptide-containing motif mediates binding to receptors on promonocytic cell lines [19] This indicates a possible role of PSG in regulating the maternal immune system during pregnancy. CEA gene families exist in both the rat and mouse, in comparison with their human counterparts, they vary at both the sequence level and in their domain structures [22,23,24,25,26,27,28,29,30,31,32]. Sequence analyses indicate that prior to mammalian radiation only one or two
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