International Mammalian Genome Society

The 13th International Mouse Genome Conference
October 31-November 3, 1999

Table of Contents * Structure * Bioinformatics * Sequence * Mapping * New Tools * Gene Discovery * Developmental * Mutagenesis * Functional Genomics

G24 ICM-Specific Expression of PECAM-1 in the Mouse Blastocyst

Paul Robson1, Paula Stein2, Richard Schultz2, H. Scott Baldwin1. 1Department of Cardiology, Children's Hospital of Philadelphia, Philadelphia, PA, USA; 2Department of Biology, University of Pennsylvania, Philadelphia, PA, USA

PECAM-1 was thought to be a vascular-specific protein but two previous observations lead us to investigate its expression in the mouse blastocyst. Firstly it had been identified in ES cells and secondly PECAM-1 promoter-driven expression of Cre recombinase suggested very early expression in the mouse embryo. Here we show through confocal immunofluorescent microscopy that PECAM-1 is indeed expressed in the mouse blastocyst and it is specific for the cell-cell borders of the inner cell mass (ICM). The protein is first detectable as the blastocoel forms. It is not present at any stage prior to the blastocyst. Its expression however is not dependent on compaction, cytokinesis, or DNA synthesis as pre-blastocyst embryos cultured in Ca-free media, cytochalasin D, or aphidicolin, respectively, do not inhibit PECAM-1 expression. Little is understood of the molecular mechanisms involved in the differentiation events leading to the formation of the ICM. This in part is due to a lack of knowledge of ICM-specific genes that are also not expressed early in the developing mouse embryo. The PECAM-1 gene however fits this expression pattern and therefore will be a useful tool to identify ICM-specific regulatory elements. Promoter analysis is underway to identify ICM-specific as well as endothelial-specific enhancer elements within the mouse PECAM-1 gene.


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