Profiling gene expression in growth-arrested mouse embryos in diapause

Abstract

In many mammalian species, embryonic cell proliferation can be reversibly arrested in an embryonic diapause at the time of embryo implantation. A recent report has identified changes in embryonic gene expression that are associated with, and may halt, embryonic cell proliferation.

Figure 1

The growth of diapausing blastocysts is reversibly arrested before implantation into the uterus. (a) A diapausing blastocyst (arrowhead) is shown in contact with the uterine luminal epithelium (LE). Note the loose fibroblastic morphology of the stroma (S) underlying the luminal epithelium. T, the trophoblast of the blastocyst. (b) Implantation after diapause starts with the luminal epithelium adjacent to the trophoblast of the blastocyst undergoing apoptosis as the trophoblast cells start to invade the uterus. After implantation, the stroma has undergone massive proliferation and differentiation to form the decidua (D).

Figure 2

The time course of events leading to embryo implantation in the mouse. (a) On day 3 after fertilization the uterus is undergoing differentiation and proliferation under control of the ovarian steroid hormones estrogen and progesterone. (b) On day 4 the blastocyst is adjacent to the uterus and the production of leukemia inhibitory factor (LIF) is induced in the endometrial glands by nidatory estrogen. LIF is released into the uterine lumen, where it binds to LIF receptors on the luminal epithelium. LIF binding induces the expression of many genes, including the cell adhesion factors Coch and CD9, as the uterus becomes receptive to the embryo allowing the onset of implantation. Other adhesion molecules, such as E-cadherin, undergo redistribution in their expression. (c) On day 5 the blastocyst has started to invade the uterus and the stroma is undergoing decidualization, accompanied by the expression of prostaglandins (PGEs), which are regulated by Cox-2, and the cytokine interleukin-11 (IL-11), which is essential for decidualization.