cDNA cloning demonstrates the expression of pregnancy-specific glycoprotein genes, a subgroup of the carcinoembryonic antigen gene family, in fetal liver.

The pregnancy-specific glycoprotein (PSG) genes constitute a subgroup of the carcinoembryonic antigen (CEA) gene family. Here we report the cloning of four cDNAs coding for different members of the PSG family from a human fetal liver cDNA library. They are derived from three closely related genes (PSG1, PSG4 and PSG6). Two of the cDNA clones represent splice variants of PSG1 (PSG1a, PSG1d) differing in their C-terminal domain and 3'-untranslated regions. All encoded proteins show the same domain arrangement (N-RA1-RA2-RB2-C). Transcripts of the genes PSG1 and PSG4 could be detected in placenta by hybridization with gene-specific oligonucleotides. Expression of cDNA in a mouse and monkey cell line shows that the glycosylated PSG1a protein has a Mr of 65-66 kD and is released from the transfected cells. Sequence comparisons in the C-terminal domain and the 3'-untranslated regions of CEA/PSG-like genes suggests a complex splicing pattern to exist for various gene family members and a common evolutionary origin of these regions.