title: Inner cell mass-specific expression of a cell adhesion molecule (PECAM-1/CD31) in the mouse blastocyst.
abstract: Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1 or CD31) is thought to be a vascular-specific protein, but its function has not been clearly defined. Here, we demonstrate by using confocal immunofluorescence microscopy that PECAM-1 is first detected in the mouse blastocyst, which contains no vascular cells, and its expression is restricted to the pluripotent inner cell mass (ICM) cells. Expression is localized to cell-cell borders of the ICM and is detected at the very first signs of blastocoel formation. Consistent with these observations is that embryonic transcripts of PECAM-1 mRNA, as detected by RT-PCR, greatly increase during the morula-to-blastocyst transition and seven of the eight known alternatively spliced isoforms of PECAM-1 are expressed in the blastocyst. The synthesis of PECAM-1 is independent of compaction, cytokinesis, and DNA replication, as it is detected in embryos that are chronologically at the blastocyst stage following culture of 8-cell embryos in Ca2+-free medium, or medium containing cytochalasin D or aphidicolin, respectively. By the late blastocyst stage, PECAM-1 expression is restricted to the pluripotent epiblast, at which point it has a mutually exclusive expression pattern to that of type IV collagen, a basement membrane marker. The reduction in PECAM-1 transcripts in retinoic acid-induced differentiation of F9 teratocarcinoma cells, a model of epiblast-to-primitive endoderm differentiation, confirmed the epiblast-specific expression of PECAM-1. By the egg cylinder stage of development, at which point the epiblast is no longer pluripotent, PECAM-1 is not detected. This ICM-specific pattern of expression suggests a novel developmental role of PECAM-1 that is independent of its function in vascular ontogeny.
authors.affiliation: Division of Cardiology, Joseph Stokes Jr. Research Institute, Philadelphia, Pennsylvania 19104, USA.
authors.forename: P
authors.initials: P
authors.lastname: Robson
authors.forename: P
authors.initials: P
authors.lastname: Stein
authors.forename: B
authors.initials: B
authors.lastname: Zhou
authors.forename: R M
authors.initials: RM
authors.lastname: Schultz
authors.forename: H S
authors.initials: HS
authors.lastname: Baldwin
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D002454:Cell Differentiation; D010064:Embryo Implantation; D047108:Embryonic Development; D005260:Female; D051379:Mice; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis* / Q000235:genetics; D011247:Pregnancy; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D013234:Stem Cells; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D019408:Platelet Endothelial Cell Adhesion Molecule-1; D020033:Protein Isoforms