Transcription factor genes Smad4 and Gata4 cooperatively regulate cardiac valve development. [corrected]

Area of Science:

• Cardiovascular Biology
• Developmental Biology
• Genetics

Background:

• GATA4 is a crucial cardiac transcription factor.
• Mutations in GATA4 are linked to congenital heart defects, specifically atrioventricular septal defects (AVSDs) and valve abnormalities.
• Endocardial cushion development is vital for proper heart formation.

Purpose of the Study:

• To investigate the molecular mechanisms by which GATA4 mutations cause AVSDs and valve abnormalities.
• To elucidate the role of GATA4 and its interaction with SMAD4 in endocardial cushion development.

Main Methods:

• Analysis of human GATA4 missense mutations (G303E, G296S) and their effect on protein interactions.
• In vivo genetic interaction studies using endothelial-specific Gata4 and Smad4 knockout models.
• Assessment of Smad4 deficiency in endocardial cushion development, including valve formation, epithelial-to-mesenchymal transformation, and gene expression (Id2).
• Reporter assays to study the cooperative activation of the Id2 promoter by Gata4 and Smad4.

Main Results:

• Dominant GATA4 mutations (G303E, G296S) impair protein interactions with SMAD4, a key factor in bone morphogenetic protein/transforming growth factor-β (BMP/TGF-β) signaling.
• Endothelial-specific compound haploinsufficiency of Gata4 and Smad4 leads to AVSDs.
• Smad4 deficiency in endocardium results in failed valve formation, acellular endocardial cushions, absent epithelial-to-mesenchymal transformation, reduced proliferation, and loss of Id2 expression.
• Gata4 and Smad4 cooperatively activate the Id2 promoter, and human GATA4 mutations abolish this activity.
• Id2 deficiency in mice can cause AVSDs.

Conclusions:

• GATA4 mutations disrupt endocardial cushion development by impairing GATA4/SMAD4 interactions.
• The GATA4-SMAD4-Id2 signaling axis is critical for heart valve formation and septation.
• Differential effects on GATA4/SMAD4 interactions may contribute to the phenotypic spectrum of GATA4 mutations in congenital heart disease.