Bmp2 and Notch cooperate to pattern the embryonic endocardium.

Area of Science:

• Developmental Biology
• Cardiac Development
• Molecular Cardiology

Background:

• Myocardium-endocardium signaling is crucial for embryonic heart development and regional patterning.
• Congenital heart valve defects arise from disruptions in normal cardiac development.
• Understanding the molecular mechanisms of valve formation is critical for therapeutic development.

Purpose of the Study:

• To investigate the role of bone morphogenetic protein 2 (Bmp2) in chamber endocardial cell differentiation.
• To elucidate the molecular pathways by which myocardial Bmp2 influences endocardial valve development.
• To identify key signaling interactions driving the epithelial-mesenchyme transition in cardiac endocardium.

Main Methods:

• Utilized ectopic Bmp2 expression in mouse embryonic chamber myocardium.
• Analyzed transcriptional changes in adjacent chamber endocardial cells.
• Performed biochemical experiments to investigate protein-ligand interactions (Smad1/5, Notch1, Jag1).

Main Results:

• Ectopic Bmp2 induced a valve tissue transcriptional signature in chamber endocardial cells.
• Bmp2-induced endocardial differentiation required high Notch1 activity and was independent of valve myocardium.
• Bmp2 signaling activated Notch1 via Jag1 transcriptional activation and Smad1/5 interaction with Notch1.

Conclusions:

• Widespread myocardial Bmp2 and endocardial Notch signaling promote presumptive ventricular endocardium differentiation into valve endocardium.
• This study reveals a novel Bmp2-Notch1-Jag1 axis in embryonic valve development.
• Elucidating these molecular underpinnings is essential for addressing congenital heart valve anomalies.