Genes involved in implantation

The endometrium is normally a hostile environment for an embryo, except for a short phase in each reproductive cycle known as the 'window of receptivi ty'. The precise molecular events involved in this transformation are not w ell understood. Application of state-of-the-art techniques of the 1990s has identified some of the genes involved, which are reviewed here. Mice with a null mutation in either the gene for leukemia inhibitory factor or the in terleukin-11 receptor alpha chain are infertile, owing in both cases to a f ailure of embryo implantation. Both of these genes are expressed in the hum an endometrium with patterns suggesting a role in human fertility. The tech nique of RNA differential display has been applied to a comparison of the e xpression of genes at implantation sites v. interimplantation sites in the mouse uterus on the first day of implantation, and has defined additional g enes whose products may be important for this process. Among these are the calcium-binding protein D9K, the monoclonal nonspecific suppressor factor b eta, and the splicing factor SC35. The major challenge is to determine whet her manipulation of such genes can increase or decrease endometrial recepti vity in humans.