Expression of Emg1 in pre-implantation embryos. (A) Whole mount RNA in situ hybridization of mouse pre-implantation embryos. Asterisks indicate the E2.5 morulae, and arrows indicate the blastocysts. Hybridization with Emg1 sense probe is presented as a control. (B) High magnification showing that a stronger Emg1 signal is detected within the inside cells at the morula stage. (C) High magnification demonstrating that the inner cell mass of the mouse blastocyst is strongly stained with Emg1 antisense probe (arrow indicates), whereas the trophectoderm has a very low level of Emg1 (arrowhead). (D) Whole mount X-gal staining of zygotes and 2-cell embryos either from the cross of wild-type males with Emg1+/- females or from Emg1+/- males with wild-type females. Only the embryos from the breeding of wild-type males with Emg1+/- females show LacZ signals. (E) X-gal staining of morulae and blastocysts collected from the breeding of wild-type males with Emg1+/- females, shows wide-spread LacZ signals in the 8-cell morula and in the ICM of Emg1+/-. In Emg1+/+ morulae or blastocysts, only a few cells are weakly stained for LacZ, probably reflecting a low level of residual maternally transmitted LacZ protein in these cells. Scale bar in A-D, 50μm, and in E, 100μm.