THE CEA10 GENE ENCODES A SECRETED MEMBER OF THE MURINE CARCINOEMBRYONIC ANTIGEN FAMILY AND IS EXPRESSED IN THE PLACENTA, GASTROINTESTINAL-TRACT AND BONE-MARROW

Although members of the carcinoembryonic antigen (CEA) family have bee n shown to convey cell adhesion in vitro, their location in some tissu es contradicts such a function. As a basis for investigating their in vivo functions, we are characterizing the mouse CEA family. This paper describes the structure and expression of a new murine family member, cea10. Two full-length cDNA clones were isolated from a mouse colon l ibrary, whose deduced protein sequence comprises two immunoglobulin va riable-like N-domains, directly followed by a short C-terminal domain indicating that this molecule is secreted. Although this domain organi zation suggests a closer relationship to the murine pregnancy-specific glycoproteins (PSG), which form a subgroup within the CEA family, seq uence comparisons place Cea10 within the CEA subgroup. Overlapping cos mid clones containing the complete cea10 locus were mapped and the exo ns determined. No A2-like exon, characteristic for all other members o f the murine CEA family, could be found. Sequences of the promoter and the first exon showed remarkably high similarity to the corresponding regions of bgp1 and bgp2, two other members of the murine CEA subgrou p. Consensus sequences for two transcription factors (USF and an AP-2- like factor) that bind to the human BGP gene promoter were also presen t in the cea10 promoter and possibly convey expression of these genes in epithelial cells. RNase protection assays revealed transcriptional activity of cea10 in the colon and early placenta (10.5-12.5-day embry os) and to a lower extent in the small intestine, cecum, stomach, sali vary glands and bone marrow. As some other CEA family members are dere gulated in tumors, we quantified the expression levels of Cea10 transc ripts in colonic mucosa and in adenomatous polyps of Min/+ mice. No di fferences in the steady-state levels of Cea10 mRNA could be found, sug gesting that the Cea10 protein does not play a role in early tumor dev elopment. Taken together, Cea10 combines characteristic features of bo th CEA and PSG subgroup members in its structure and expression patter n.