Eomesodermin requires transforming growth factor-beta/activin signaling and binds Smad2 to activate mesodermal genes

Area of Science:

• Developmental Biology
• Molecular Biology
• Gene Regulation

Background:

• The T-box gene Eomesodermin (Eomes) plays critical roles in embryonic mesoderm differentiation across multiple species.
• Eomes is also implicated in cardiac development and T-cell function, highlighting its diverse biological significance.
• The precise molecular mechanisms underlying Eomes-mediated gene activation remain largely unelucidated.

Purpose of the Study:

• To investigate the mechanism of Eomesodermin (Eomes) gene activation during embryonic development.
• To explore the potential for non-cell autonomous function of Eomes protein.
• To identify the specific domains and factors involved in Eomes protein transfer and transcriptional activity.

Main Methods:

• Investigated Eomes protein interactions, specifically with Smad2.
• Utilized a farnesylated red fluorescent protein (CherryF) to block Eomes protein transfer.
• Mapped the Eomes carboxyl-terminal region responsible for intercellular protein transfer.

Main Results:

• Eomesodermin (Eomes) protein interacts with Smad2.
• Eomes exhibits non-cell autonomous activity, transferring between adjacent embryonic cells.
• Blocking Eomes transfer prevents its nuclear accumulation, and the carboxyl terminus (456-692), including a carbohydrate-binding domain, mediates this transfer and is crucial for gene activation.

Conclusions:

• Eomesodermin (Eomes) functions non-cell autonomously through intercellular protein transfer, mediated by its carboxyl terminus.
• This transfer mechanism is essential for Eomes nuclear localization and subsequent gene activation.
• A novel model is proposed where Eomes protein transfer contributes to cellular responses to morphogen gradients.