Development of animal embryos before zygotic genome activation at the mid blastula transition （MBT） is essentially supported by eggderived maternal products. Nodal proteins are crucial signals for mesoderm and endod...Development of animal embryos before zygotic genome activation at the mid blastula transition （MBT） is essentially supported by eggderived maternal products. Nodal proteins are crucial signals for mesoderm and endoderm induction after the MBT. It remains unclear which maternal factors activate zygotic expression of nodal genes in the ventrotateral blastodermal margin of the zebrafish blastulas. In this study, we show that loss of maternal Eomesodermin a （Eomesa）, a T-box transcription factor, impairs zygotic expression of the nodal genes ndr1 and ndr2 as well as mesodermal and endodermal markers, indicating an involvement in mesendoderm induction. Maternal Eomesa is also required for timely zygotic expression of the transcription factor gene mxtx2, a regulator of nodal gene expression. Eomesa directly binds to the Eomes-binding sites in the promoter or enhancer of ndr1, ndr2, and rnxtx2 to activate their transcrip- tion. Furthermore, human and mouse Nodal genes are also regulated by Eomes. Transfection of zebrafish eomesa into murine embryonic stem cells promotes mesendodermal differentiation with constant higher levels of endogenous Nodal expression, suggesting a conserved function of Eomes. Taken together, our findings reveal a conserved rote of maternal T-box transcription factors in regulating nodal gene expression and mesendoderm induction in vertebrate embryos.展开更多
基金Acknowledgements We thank Drs Alex Schier and Susan Mango （Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA） for discussion and suggestions, Dr David Kimelman （Department of Biochemistry, University of Washington, Seattle, WA, USA） for myc-eomesa construct, and members of the Meng lab for discussion and technical assistance. This work was financially supported by grants from the Major Science Research Programs of China （2011CB943800） and the National Natural Science Foundation of China （31221064）.
文摘Development of animal embryos before zygotic genome activation at the mid blastula transition （MBT） is essentially supported by eggderived maternal products. Nodal proteins are crucial signals for mesoderm and endoderm induction after the MBT. It remains unclear which maternal factors activate zygotic expression of nodal genes in the ventrotateral blastodermal margin of the zebrafish blastulas. In this study, we show that loss of maternal Eomesodermin a （Eomesa）, a T-box transcription factor, impairs zygotic expression of the nodal genes ndr1 and ndr2 as well as mesodermal and endodermal markers, indicating an involvement in mesendoderm induction. Maternal Eomesa is also required for timely zygotic expression of the transcription factor gene mxtx2, a regulator of nodal gene expression. Eomesa directly binds to the Eomes-binding sites in the promoter or enhancer of ndr1, ndr2, and rnxtx2 to activate their transcrip- tion. Furthermore, human and mouse Nodal genes are also regulated by Eomes. Transfection of zebrafish eomesa into murine embryonic stem cells promotes mesendodermal differentiation with constant higher levels of endogenous Nodal expression, suggesting a conserved function of Eomes. Taken together, our findings reveal a conserved rote of maternal T-box transcription factors in regulating nodal gene expression and mesendoderm induction in vertebrate embryos.
