Cdx2 Expression Regulates Trophectoderm Lineage Specification in Mouse Embryos

Abstract

Evaluation of:Deb K, Sivaguru M, Yong HY and Roberts RM: Cdx2 gene expression and trophectoderm lineage specification in mouse embryos. Science 311, 992–996 (2006) [1] . In a variety of animals such as Drosophila and Xenopus, the earliest stages of development are coordinated by the asymmetrical distribution of maternal transcripts and protein in the egg. In these animals, the position of blastomeres formed by embryo division and the expression products they inherit from egg cytoplasm determines their developmental fates. Thus far, attempts to determine whether such a specification system exists within mammalian embryos have yielded conflicting results. A recent report by Deb and colleagues [1] provides some strong evidence that the distribution of Cdx2 products may predetermine the fate of mouse blastomeres at the two-cell embryo stage. Their elegant data suggest that the asymmetrical localization of Cdx2 mRNA and protein in the oocyte and embryo controls the designation of trophectoderm and inner cell mass lineages, and that Cdx2 expression is necessary for proper blastocyst formation.