Novel Phosphodiesterase 2A functions in the lymphatic and blood vasculature

• Applicant: Professorin Dr. Maike Frye
• Subject Area: Cell Biology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439891283

Endothelial cells (ECs) comprise the inner layer of the blood and lymphatic vasculature. To guarantee blood and lymph flow without adverse leakage, lymphatic and blood endothelial barrier function is tightly controlled via cell-cell junctions, cell-matrix adhesions, and the actin cytoskeleton through both common and divergent mechanisms. We have recently uncovered a selective role for the phosphodiesterase 2A (PDE2A) during lymphatic junctional maturation via a PDE2A/cyclic guanosine monophosphate (cGMP)/p38/NOTCH axis. In short, we found that deletion of endothelial Pde2a in mouse embryos resulted in severe lymphatic dysplasia, while blood vessels were unaltered. In the absence of PDE2A, human lymphatic ECs (LECs) failed to form mature junctions and induce cell cycle arrest. Unexpectedly, cGMP levels were increased in PDE2A-deficient LECs, which was associated with enhanced p38 phosphorylation and reduced NOTCH signaling. Concordantly, exogenous NOTCH activation via its ligand Delta-like 4 was able to restore junctional maturation in PDE2A-deficient LECs. Recently uncovered findings show now that (i) PDE2A is also expressed in postnatal lymphatics, and lymphatic-specific deletion of Pde2a results in abnormal valve formation in mesenteric collecting lymphatics, consistent with its enrichment in those valves; and (ii) endothelial-specific loss of Pde2a in mouse embryos leads to severe cardiac defects, mirroring those seen in Pde2a global knockout embryos. Surprisingly, others have demonstrated that cardiomyocyte (CM)-specific deletion of Pde2a does not perturb cardiac development, despite the well-known function of PDE2A to regulate cardiac contraction in the adult heart. Hence, the impact of endothelial PDE2A on cardiac development may be far larger than anticipated. To further explore these exciting findings, we here aim to analyze the precise role of endothelial PDE2A in the lymphatic vasculature after birth and in the heart. We will explore its distinct functions in lymphatic and cardiac ECs, focusing on novel signaling mechanisms and their interactions with neighboring cells. For the first aim, we will study how Pde2a/PDE2A deletion affects lymphatic morphology, organ-specific functions, and disease models associated with lymphatic dysfunction by combining in vivo confocal and intravital imaging and single-cell RNA sequencing (scRNAseq), with in vitro cultures of organ-specific LECs. For the second aim, we will investigate effects of endothelial Pde2a/PDE2A deletion on cardiac development, CM function, and cardiac electrophysiological performance via scRNAseq, co-cultures of human lymphatic ECs with CMs, and engineered heart tissues. Additionally, we will test the rescue of cardiac function in endothelial Pde2a-deficient mice through adeno-associated virus-mediated PDE2A overexpression. In summary, our objective is to develop PDE2A-based targeted strategies for LECs and cardiac ECs to address and treat lymphatic and cardiac dysfunctions.

• DFG Programme: Research Grants