Apical polarity protein that plays a central role during the epithelial-to-mesenchymal transition (EMT) at gastrulation, when newly specified mesodermal cells move inside the embryo (By similarity). Acts by promoting cell ingression, the process by which cells leave the epithelial epiblast and move inside the embryo to form a new tissue layer (By similarity). The anisotropic distribution of CRB2 and MYH10/myosin-IIB at cell edges define which cells will ingress: cells with high apical CRB2 are probably extruded from the epiblast by neighboring cells with high levels of apical MYH10/myosin-IIB (By similarity). Plays a role in the maintenance of retinal neuroepithelium organization, structural integrity, adhesion, photoreceptor polarity and retinal photoreceptor layer thickness (By similarity). May play a role in determining the length of cone photoreceptor outer segments and proliferation of late-born progenitor cells (By similarity). Also required for maintenance of the apical polarity complex during development of the cortex (By similarity). Inhibits gamma-secretase-dependent cleavage of APP and secretion of amyloid-beta peptide 40 and amyloid-beta peptide 42, and thereby inhibits gamma-secretase-dependent Notch transcription (PubMed:20299451). Associates with the gamma-secretase complex via interaction (via the transmembrane domain) with PSEN1/PS1 (PubMed:20299451). Interacts (via intracellular domain) with EPB41L5 (PubMed:17920587). Interacts with PALS1 (By similarity). O-glucosylation is required for localization at the apical plasma membrane (By similarity). Distributed in a complex anisotropic pattern on apical cell edges: the level of CRB2 on a cell edge is inversely correlated with the level of MYH10/myosin-IIB (By similarity). Expressed in glomeruli, podocytes of the glomerular capillary loops, and parietal glomerular epithelial cells in the kidney (at protein level) (PubMed:29473663, PubMed:27942854). Expressed in retina, fetal eye and brain (PubMed:15851977). Also expressed in kidney, RPE/choroid, and at low levels in lung, placenta, and heart (PubMed:15851977). O-glucosylated by POGLUT1 at Ser-267; consists of an O-glucose trisaccharide, in which the O-glucose is elongated by the addition of two xylose residues. O-glucosylation is required for localization at the plasma membrane. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility may be associated with variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the Crumbs protein family.