CRB2 (Crumbs homolog 2), like its homologs CRB1 and CRB3, is similar to the Drosophila crumbs protein and is expressed in retina, brain and kidney. Along with other proteins, the Crumbs proteins form a complex that help set up cell polarity in developing neuroepithelial cells. At the onset of neural specification, embryonic stem cells (ESCs) upregulate CRB2, which then localizes apically in neural rosettes. Gain- and loss-of-function studies of CRB2 have shown that CRB2 is essential for the stabilization of other polarity proteins. Unlike CRB1, mutations in CRB2 do not appear to play a role in retinitis pigmentosa or in Leber congenital amaurosis.