Epithelial and endothelial cells form selective barriers between compartments of different composition. To perform this function, they have a specialised intercellular junctional complex (tight and adherens junctions, desmosomes and gap junctions). Assembly and disassembly of the junctional complex is tightly regulated during physiological conditions, but is disturbed in pathological situations such as wounds, inflammation, neovascularisation or transformation. Our research interest is to understand the molecular mechanisms through which tight junctions regulate paracellular permeability, cell proliferation and gene expression as well as to find out whether and how the tight junction signalling pathways interact with related signalling pathways triggered by cell-cell and cell-extracellular matrix interactions. Our findings will be used not only to understand physiologically complex processes ranging from tubulogenesis of epithelial and endothelial cells to the development of the eye but also to develop therapeutic tools to reverse pathological conditions such as tumorigenesis and proliferative or degenerative eye diseases.