Zebrafish epiboly results in the thinning and spreading of the blastoderm to cover the yolk cell and close the blastopore. The extra-embryonic yolk syncytial layer (YSL) tows the blastoderm vegetally during epiboly by means of its tight junction attachments to the enveloping layer (EVL). Claudins are the major transmembrane protein components of tight junctions. Here, we focus on the function of Claudin E (Cldne), which is expressed specifically in the EVL. Morpholino knock-down of cldne produced a highly penetrant epiboly delay. Our analysis suggested that the EVL margin, which is attached to the YSL, was under reduced tension in morphant embryos. We propose that local variation in the strength of EVL-YSL attachment in morphant embryos resulted in slow and uneven advancement of the EVL and blastoderm. Our work is the first to demonstrate that Claudins are important for zebrafish epiboly. Developmental Dynamics 239:715-722,

Despite the great strides have been made in treating diabetes induced vascular endothelial barrier dysfunction, current treatments have shown limited success in reversing vascular pathologies. Increase in endothelial permeability via modification of endothelial junctional proteins, such as vascular endothelial cadherin (VE‐Cadherin), leads to the formation of minute inter‐endothelial gaps, and the infiltration of protein‐rich fluid in the interstitial space. If remained unchecked, the persistent buildup of edema underlying the endothelial lining sets the stage for the serious life‐threatening complications. Hyperglycemia‐induced endothelial dysfunction contributes vascular complications of diabetes. Moreover, wound healing impairment is also increasingly recognized to be a consequence of hyperglycemia‐induced dysfunction of endothelial in type 2 diabetes mellitus (T2DM). Metformin, an oral anti‐hyperglycemic agent, is the first‐line drug in the clinic for patients with T2DM. Clinical studies suggested that the beneficial effect of metformin on the incidence of diabetes complications was not only related to its action on blood glucose normalization. We hypothesized that the metformin prevents high glucose‐induced endothelial barrier dysfunction and accelerates wound healing process in human coronary endothelial cells (HCAE) via preventing the destabilization of VE‐cadherin. Endothelial permeability was evaluated by using Electric Cell‐substrate Impedance Sensing (ECIS) mechanism, a measure of trans‐endothelial electrical resistance (TEER) across the endothelial monolayers using TEER electrodes. Wound healing assay was performed by employing electric signals to both wound and monitor the healing process in endothelial monolayer. Our data show that 25mM glucose concentration increased endothelial permeability and abrogated the wound healing process. Metformin at the dose of 10mM significantly prevented alteration of endothelial barrier function and enhances wound healing process in the presence of high glucose concentration. To investigate the signaling mechanism involved in the protection offered by metformin, we found that metformin prevented myosin light chain kinase (MYLK) phosphorylation and increased in VE‐cadherin expression, suggesting abrogation of increase endothelial contractility and dismantling the junctional proteins in presence of high glucose concentration. In conclusion, our study shows that metformin maintained endothelial barrier function and improved the process of wound healing in endothelial cells exposed to high glucose. Thus, metformin is emerging as a potential therapeutics in improving coronary endothelial barrier function in diabetes mellitus.Support or Funding InformationThis work was supported by funding from CTRE SEED Grant Award to Mohammad Tauseef.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The heterotrimeric G protein α unit Gα13 transmits signals from G protein coupled receptors (GPCRs) to effectors to regulate cell spreading, differentiation, migration, and cell polarity. Both conventional and endothelial cell‐specific Gα13 gene knockouts are embryonically lethal because of impaired vasculogenesis. Here we describe a new pro‐inflammatory function of Gα13 through its displacement from the GPCR protease‐activated receptor 1 (PAR1) to the endothelial adherens junction (AJ) protein VE‐cadherin. H2O2 production induced by multiple mediators (thrombin, LPS or TNFα) induced a shift in Gα13 binding to VE‐cadherin and disassembly of AJs. Gα13/VE‐cadherin interaction activated c‐Src resulting in phosphorylation of VE‐cadherin at Tyr 658, the p120‐ catenin binding site responsible for VE‐cadherin endocytosis from the membrane. Preventing Gα13/VE‐cadherin interaction by Cre recombinase‐mediated Gα13 knockout in mice or an interfering myristoylated peptide derived from VE‐cadherin, inhibited AJ disruption and inflammatory response to sepsis. These studies establish a crucial Gα13 switch mechanism activated by H2O2 generation that mediates Gα13 binding to VE‐cadherin and thereby disrupts AJ integrity. Therefore, blocking Gα13 translocation and Gα13/VE‐cadherin interaction represents a potential anti‐inflammatory target.