MEKK4 regulates developmental EMT in the embryonic heart

Area of Science:

• Developmental biology
• Molecular signaling
• Cardiovascular science

Background:

• Congenital heart malformations are common birth defects, highlighting gaps in understanding heart development.
• Molecular mechanisms regulating cardiogenesis are not fully defined, hindering repair strategies.
• The role of MEKK4 (MAP kinase kinase kinase 4) in embryonic development and heart formation is largely unknown.

Purpose of the Study:

• To investigate the function of MEKK4 in cardiovascular development and cardiogenesis.
• To determine MEKK4's role in epithelial to mesenchymal transformation (EMT) during heart development.

Main Methods:

• Detected MEKK4 transcripts in developing heart tissues, including myocardium, endocardium, and cardiac cushion cells undergoing EMT.
• Utilized an in vitro assay with a kinase-inactive MEKK4 (MEKK4(KI)) to assess its effect on EMT.
• Employed ventricular explants with constitutively active MEKK4 to evaluate its sufficiency in inducing mesenchymal cell outgrowth.

Main Results:

• MEKK4 transcripts are present in key cell populations during early heart development.
• Kinase-inactive MEKK4 (MEKK4(KI)) inhibited mesenchyme production in an in vitro EMT assay.
• Active MEKK4 alone could not induce mesenchymal cell outgrowth in ventricular explants lacking normal EMT.

Conclusions:

• MEKK4 plays a critical role in cardiovascular development.
• MEKK4's kinase activity is necessary but not sufficient for developmental EMT.
• Understanding MEKK4's function provides insights into signaling pathways controlling heart formation and defects.