Maternal Eomesodermin regulates zygotic nodal gene expression for mesendoderm induction in zebrafish embryos

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Embryonic development before midblastula transition (MBT) relies on maternal factors.
• Nodal proteins are critical for mesoderm and endoderm induction post-MBT.
• The maternal regulators of zygotic nodal gene expression in zebrafish remain largely unknown.

Purpose of the Study:

• To identify maternal factors that activate zygotic nodal gene expression in zebrafish.
• To elucidate the role of Eomesodermin a (Eomesa) in mesendoderm induction.
• To investigate the conserved function of Eomesa in Nodal gene regulation.

Main Methods:

• Loss-of-function analysis of maternal Eomesa in zebrafish.
• Analysis of zygotic expression of nodal genes (ndr1, ndr2) and mesendodermal markers.
• Chromatin immunoprecipitation to assess Eomesa binding to gene regulatory regions.
• In vitro studies using murine embryonic stem cells.

Main Results:

• Loss of maternal Eomesa disrupts zygotic expression of ndr1, ndr2, and mesendodermal markers.
• Maternal Eomesa is required for the timely expression of mxtx2, a nodal gene regulator.
• Eomesa directly binds to regulatory elements of ndr1, ndr2, and mxtx2 to drive transcription.
• Eomesa promotes mesendodermal differentiation in murine stem cells, maintaining Nodal expression.

Conclusions:

• Maternal Eomesa is a key regulator of nodal gene expression and mesendoderm induction in zebrafish.
• Eomesa's function in regulating Nodal signaling and mesendoderm formation is conserved across vertebrates.
• This study reveals a conserved role for maternal T-box transcription factors in early vertebrate development.