Plays a role in the formation and organization of tight junctions during the establishment of polarity in epithelial cells. Component of a complex composed of PALS1, CRB1 and EPB41L5 (By similarity). Within the complex, interacts (via FERM domain) with PALS1 (via HOOK domain) and with CRB1 (via intracellular domain) (By similarity). Interacts with CRB2 (via intracellular domain) (By similarity). Interacts with CRB3 (via intracellular domain) (By similarity). In the retina, expressed at the outer limiting membrane, retinal pigment epithelium, outer nuclear layer and outer plexiform layer (at protein level) (PubMed:17920587). Also detected in the inner segments (at protein level) (PubMed:17920587). Expressed at the basolateral and apical sides of the mesonephric tubules in the kidney (at protein level) (PubMed:17920587). At 10.5 dpc, strongly expressed in the developing neural tube and optic vesicle, as well as in the branchial arches and kidney (PubMed:17920587). In the developing kidney, detected in the mesonephrotic tubules (PubMed:17920587). At 11.5 dpc, expressed along the entire cranial-caudal length of the developing neural tube, including the anterior forebrain and the posterior spinal cord (PubMed:17920587). Always restricted to the ventricular layer, where proliferative cells are located (PubMed:17920587). Conversely, not detected in postmitotic neural compartments (PubMed:17920587). In the developing lung, at 11.5 dpc, expressed in the internal endodermal layer and in particular in the nascent bronchial tips (PubMed:17920587). At 12.5 dpc, expressed in the optic vesicle, detected mainly in the retinal layer (PubMed:17920587). The retinal pigment epithelium shows only background levels (PubMed:17920587). At 15.5 dpc expressed at the basolateral side of the plasma membrane in brain, spinal cord, kidney, testis, intestine, skin, and muscles (PubMed:17920587).