The transcription factor GATA6 is essential for early extraembryonic development

The gene coding for the murine transcription factor GATA6 was inactivated b y insertion of a beta-galactosidase marker gene. The analysis of heterozygo te GATA6/lacZ mice shows two inductions of GATA6 expression early in develo pment. It is first expressed at the blastocyst stage in part of the inner c ell mass and in the trophectoderm. The second wave of expression is in pari etal endoderm that form the heart and gut. Inactivation leads to a lethalit y shortly after implantation (5.5 days postcoitum). Chimeric experiments sh ow this to be caused by an indirect effect on the epiblast due to a defect in an extraembryonic tissue.