AKAP12 regulates vascular integrity in zebrafish

Area of Science:

• Vascular biology
• Endothelial cell biology
• Molecular mechanisms of vascular integrity

Background:

• Endothelial integrity is vital for controlling vascular permeability and preventing leakage.
• Impaired endothelial integrity results in conditions like hemorrhage, edema, and inflammation.
• The precise molecular mechanisms regulating vascular integrity remain incompletely understood.

Purpose of the Study:

• To investigate the role of A-kinase anchoring protein 12 (AKAP12) in maintaining endothelial integrity during vascular development.
• To elucidate the molecular mechanisms by which AKAP12 influences endothelial cell-cell adhesion.

Main Methods:

• Utilized zebrafish (Danio rerio) embryos with AKAP12 depletion (morphants) to study vascular development in vivo.
• Performed time-lapse imaging to observe interendothelial cell-cell adhesions in live zebrafish embryos.
• Employed cultured endothelial cells to examine the expression of cell adhesion molecules and cytoskeletal regulators following AKAP12 depletion.
• Assessed the functional impact of PAK2 and AF6 expression levels on endothelial integrity and hemorrhage.

Main Results:

• Zebrafish akap12 morphants exhibited severe hemorrhages, indicative of compromised vascular integrity.
• Time-lapse analysis revealed disorganized interendothelial cell-cell adhesions as a likely cause of hemorrhage in akap12 morphants.
• AKAP12 depletion led to reduced expression of PAK2 (an actin regulator) and AF6 (an adhesion molecule connector) in endothelial cells.
• Depletion of PAK2 or AF6 alone phenocopied the effects of AKAP12 depletion, causing impaired cell-cell adhesion.
• Overexpression of PAK2 and AF6 rescued the hemorrhage phenotype in akap12 morphants.

Conclusions:

• A-kinase anchoring protein 12 (AKAP12) plays an essential role in maintaining endothelial integrity during vascular development.
• AKAP12 maintains endothelial integrity by regulating the expression of PAK2 and AF6, which are critical for interendothelial cell-cell adhesions.
• Disruption of the AKAP12-PAK2-AF6 pathway leads to impaired vascular integrity and hemorrhage.