Loss of EMG1 function results in pre-implantation arrest. (A) E2.5 embryos collected from Emg1+/- intercross. These embryos are indistinguishable from each other, despite the presence Emg1-/- mutations among these progeny (labeled by arrows). (B) E2.5 Emg-/- embryos (indicated by arrows) display the similar BrdU incorporation as Emg1+/+ or Emg1+/- littermates. (C) E3.5 embryos collected from Emg1+/- intercross, showing that Emg1-/- embryos arrest at the morula stage (labeled by asterisks), and fail to form an inner cell mass, trophectoderm cell layer and blastocoel cavity as wild-type or Emg1+/- embryos. (D) Immunofluoresence with anti-E-cadherin antibody, showing that Emg-/- morulae exhibit the same organized pattern of E-cadherin along the cell boundaries as wild-type littermates. (E) In vitro culture of E3.5 embryos from Emg1+/- intercross. None of Emg1-/- embryos develop into blastocyst (indicated by asterisks). (F) Whole mount TUNEL assay shows the high levels of apoptosis in E3.5 Emg1-/- embryos after 24-hour culture. Few TUNEL-positive cells (indicated by arrows) are detected in wild-type littermate. (G) BrdU labeling assay to demonstrate the lack of cell proliferation in the cultured mutant embryos. Green: BrdU; Blue: Dapi. Scale bar in A-C and E-F, 100μm.