Abstract. Selectins have previously been shown to tether a flowing leukocyte to a vessel wall and mediate rolling. Here, we report that an integrin, VLA-4, can also support tethering and rolling. Blood T lymphocytes and or4 integrin-transfected cells can tether in shear flow, and then roll, through binding of the integrin VLA-4 to purified VCAM-1 on the wall of a flow chamber. VLA-4 transfectants showed similar tethering and rolling on TNF-stimulated endothelium. Tethering efficiency, rolling velocity, and resistance to detachment are related to VCAM-1 density. Tethering and rolling did not occur on ICAM-1, fibronectin, or fibronectin fragments, and tethering did not require integrin activation or the presence of an or4 cytoplasmic domain. Arrest of rolling cells on VCAM-1 occurred spontaneously, and/or was triggered by integrin activating agents Mn 2+, phorbol ester, and mAb TS2/16. These agents, and the o~4 cytoplasmic domain, promoted increased resistance to detachment. Together the results show that VLA-4 is a versatile integrin that can mediate tethering, rolling, and firm arrest on VCAM-1. IMMIGRATION of leukocytes at inflammatory sites is regulated by traffic signal molecules that are displayed together on endothelium. These signals are widely held to act on leukocytes in a sequence, as first shown for neutrophils and hypothesized for monocytes and lymphocytes as well (11,14,41,42,62,65,66,72,75). In this model, selectins that bind to carbohydrate ligands allow flowing cells to tether and subsequently roll along the vessel wall. This labile adhesion to the vessel wall brings the cell into proximity with chemoattractants that are released from tissue or displayed on the surface of endothelium. Chemoattractants bind to receptors that couple to G proteins, which transduce signals that activate integrin adhesiveness. Integrins on leukocytes can then bind to Ig superfamily members on endothelium, mediating firm adhesion, and causing arrest of the rolling leukocyte. After directional cues from chemoattractants and using integrins for traction, leukocytes then cross the endothelial lining of the blood vessel and enter the tissue. These three steps, with multiple molecular choices at each step, provide great combinatorial diversity in signals and may explain the selective localization of leukocyte classes and subsets in different inflammatory states. While this paradigm is widely accepted for neutrophils, much remains to be worked out for monocytes, eosinophils, and in particular, for lymphocytes. These latter cells, but not neutrophils, express the integrin VLA-4. VLA-4 (t~4/~l, CD49d/CD29) is an un- usual 131 integrin that functions as both a matrix and cell eptor (27, 32,48,66). As a matrix receptor, it binds to an alternatively spliced domain of fibronectin distinct from the classical cell binding site recognized by VLA-5. As a cell receptor, it binds to domains 1 and 4 of VCAM-I, an Ig superfamily member induced by inflammatory mediators on endothelium. Both VLA-4 and the integrin LFA-1 are important in vivo...

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The contribution to genetic diversity of genomic segmental copy number variations (CNVs) is less well understood than that of single-nucleotide polymorphisms (SNPs). While less frequent than SNPs, CNVs have greater potential to affect phenotype. In this study, we have performed the most comprehensive survey to date of CNVs in mice, analyzing the genomes of 42 Mouse Phenome Consortium priority strains. This microarray comparative genomic hybridization (CGH)-based analysis has identified 2094 putative CNVs, with an average of 10 Mb of DNA in 51 CNVs when individual mouse strains were compared to the reference strain C57BL/6J. This amount of variation results in gene content that can differ by hundreds of genes between strains. These genes include members of large families such as the major histocompatibility and pheromone receptor genes, but there are also many singleton genes including genes with expected phenotypic consequences from their deletion or amplification. Using a whole-genome association analysis, we demonstrate that complex multigenic phenotypes, such as food intake, can be associated with specific copy number changes.