Endothelial cells use dynamic actin to facilitate lymphocyte transendothelial migration and maintain the monolayer barrier

The vascular endothelium is a highly dynamic structure, and the integrity of its barrier function is tightly regulated. Normally impenetrable to cells, the endothelium actively assists lymphocytes to exit the bloodstream during inflammation. The actin cytoskeleton of the endothelial cell (EC) is known to facilitate transmigration, but the cellular and molecular mechanisms are not well understood. Here we report that actin assembly in the EC, induced by Arp2/3 complex under control of WAVE2, is important for several steps in the process of transmigration. To begin transmigration, ECs deploy actin-based membrane protrusions that create a cup-shaped docking structure for the lymphocyte. We found that docking structure formation involves the localization and activation of Arp2/3 complex by WAVE2. The next step in transmigration is creation of a migratory pore, and we found that endothelial WAVE2 is needed for lymphocytes to follow a transcellular route through an EC. Later, ECs use actin-based protrusions to close the gap behind the lymphocyte, which we discovered is also driven by WAVE2. Finally, we found that ECs in resting endothelial monolayers use lamellipodial protrusions dependent on WAVE2 to form and maintain contacts and junctions between cells

Multilocus ISSR Markers Reveal Two Major Genetic Groups in Spanish and South African Populations of the Grapevine Fungal Pathogen Cadophora luteo-olivacea

Cadophora luteo-olivacea is a lesser-known fungal trunk pathogen of grapevine which has been recently isolated from vines showing decline symptoms in grape growing regions worldwide. In this study, 80 C. luteo-olivacea isolates (65 from Spain and 15 from South Africa) were studied. Inter-simple-sequence repeat-polymerase chain reaction (ISSR-PCR) generated 55 polymorphic loci from four ISSR primers selected from an initial screen of 13 ISSR primers. The ISSR markers revealed 40 multilocus genotypes (MLGs) in the global population. Minimum spanning network analysis showed that the MLGs from South Africa clustered around the most frequent genotype, while the genotypes from Spain were distributed all across the network. Principal component analysis and dendrograms based on genetic distance and bootstrapping identified two highly differentiated genetic clusters in the Spanish and South African C. luteo-olivacea populations, with no intermediate genotypes between these clusters. Movement within the Spanish provinces may have occurred repeatedly given the frequent retrieval of the same genotype in distant locations. The results obtained in this study provide new insights into the population genetic structure of C. luteo-olivacea in Spain and highlights the need to produce healthy and quality planting material in grapevine nurseries to avoid the spread of this fungus throughout different grape growing regions

Phase diagrams of the transverse Ising model with a four-spin interaction

10.1007/s00382-005-0099-zEurophysics Letters734601-60