Crb apical polarity proteins maintain zebrafish retinal cone mosaics via intercellular binding of their extracellular domains

Dev Cell. 2012 Jun 12;22(6):1261-74. doi: 10.1016/j.devcel.2012.03.007. Epub 2012 May 10.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Cell Membrane / genetics
  • Cell Membrane / metabolism
  • Cell Polarity / genetics
  • Cell Polarity / physiology
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary
  • Retinal Cone Photoreceptor Cells / cytology
  • Retinal Cone Photoreceptor Cells / metabolism*
  • Retinal Cone Photoreceptor Cells / physiology
  • Zebrafish / genetics
  • Zebrafish / metabolism
  • Zebrafish / physiology*
  • Zebrafish Proteins / chemistry
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism*


  • Crb2a protein, zebrafish
  • Membrane Proteins
  • Zebrafish Proteins
  • crb2b protein, zebrafish