A reinforcing HNF4-SMAD4 feed-forward module stabilizes enterocyte identity

Area of Science:

• Molecular biology
• Cell biology
• Genetics

Background:

• Bone morphogenetic protein (BMP)/SMAD signaling is vital for intestinal differentiation.
• The precise molecular mechanisms of BMP pathway involvement in enterocyte differentiation remain unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms by which BMP/SMAD signaling drives enterocyte differentiation.
• To identify key transcription factors and regulatory loops involved in intestinal epithelial cell fate determination.

Main Methods:

• Investigated the roles of HNF4A and HNF4G in enterocyte differentiation using genetic knockout models.
• Analyzed chromatin accessibility and gene expression changes.
• Examined the interaction and co-binding of SMAD4 and HNF4 transcription factors to regulatory elements.

Main Results:

• HNF4A and its paralog HNF4G redundantly activate enhancer chromatin, upregulating differentiation-specific genes.
• Double knockout of HNF4A and HNF4G prevents enterocyte differentiation.
• A reinforcing feed-forward loop between SMAD4 and HNF4 enhances their mutual expression and co-occupies regulatory regions of differentiation genes.
• Disruption of the HNF4-SMAD4 module leads to a loss of enterocyte identity, favoring progenitor and secretory cell fates.

Conclusions:

• The interplay between BMP/SMAD signaling and HNF4 transcription factors, particularly through a feed-forward loop, is essential for establishing and maintaining enterocyte identity.
• This regulatory network provides a framework for understanding intestinal tissue regeneration and homeostasis.