title: Crb apical polarity proteins maintain zebrafish retinal cone mosaics via intercellular binding of their extracellular domains.
abstract: Cone photoreceptors are assembled by unknown mechanisms into geometrically regular mosaics in many vertebrate species. The formation and maintenance of photoreceptor mosaics are speculated to require differential cell-cell adhesion. However, the molecular basis for this theory has yet to be identified. The retina and many other tissues express Crumbs (Crb) polarity proteins. The functions of the extracellular domains of Crb proteins remain to be understood. Here we report cell-type-specific expression of the crb2a and crb2b genes at the cell membranes of photoreceptor inner segments and Müller cell apical processes in the zebrafish retina. We demonstrate that the extracellular domains of Crb2a and Crb2b mediate a cell-cell adhesion function, which plays an essential role in maintaining the integrity of photoreceptor layer and cone mosaics. Because Crb proteins are expressed in many types of epithelia, the Crb-based cell-cell adhesion may underlie cellular patterning in other epithelium-derived tissues as well.
authors.affiliation: Department of Ophthalmology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Zou
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Wang
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Wei
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C513141:Crb2a protein, zebrafish; D008565:Membrane Proteins; D029961:Zebrafish Proteins; C513142:crb2b protein, zebrafish