Fibronectin (fn) and integrin α5 (itgα5) are both key players in cell adhesion and intracellar signaling, however the specific in vivo role of these proteins has never been analyzed in the vertebrate lens. The results presented here indicate that Fn1 and Itgα5 proteins are essential for the proper development of the lens. The loss of Fn1 protein in the zebrafish embryo results in distinct adhesion defects, defects in lens fiber morphogenesis, and cataracts. These results were phenocopied in zebrafish itga5 mutants, thereby indicating an essential role for Fn1 and Itgα5 during lens development. Furthermore, embryos with reduced levels of ptk2.1 (focal adhesion kinase – FAK) also phenocopied the defective fn1 and itgα5 lens, suggesting that FAK is a major player in the intracellular signaling mediated by Fn1/Itgα5 interactions in the lens. / text