Analysis of Gene Expression in the Preimplantation Mouse Embryo Using mRNA Differential Display

Abstract

Preimplantation development is characterized by cell proliferation and differentiation. For example, the outer cells of the morula stage embryo differentiate into the trophectoderm of the blastocyst. The trophectoderm, which is a fluid-transporting epithelium, is the first differentiated cell type present in the preimplantation embryo and ultimately gives rise to extraembryonic tissues. In contrast, the inner cells of the morula generate the inner cell mass in the blastocyst. These cells remain totipotent/pluripotent and give rise to the embryo proper. Although changes in gene expression must underlie these differences in cell lineage, the paucity of biological material has severely hampered efforts to analyze changes in gene expression during preimplantation development. The generation of cDNA libraries to preimplantation embryos at different stages of development, coupled with subtraction hybridization methods (Rothstein et al. 1992), has made some inroads into the systematic identification of genes that are transiently expressed during the two-cell stage. The mRNA differential display method (Liang and Pardee 1992), as adapted for preimplantation mouse embryos (Zimmermann and Schultz 1994), provides an ideal approach to analyze changes in the temporal and spatial pattern of gene expression in the preimplantation embryo.