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Distribution of the integrin β1 subunit on radial cells in the embryonic and adult avian retina

The distribution of the β1 integrin subunit was investigated in the developing and adult chick retina at the light and electron microscopic levels, using two different monoclonal antibodies. Western blotting revealed a single band with a molecular weight of approximately 130 kDa in the retina and in a number of other tissues, indicating the specificity of the antibodies . In the retina, immunoreactivity was detected on radial cells spanning the entire width between the pigment epithelium and the vitreal border. These cells were undifferentiated neuroepithelial cells at early stages and radial Müller glial cells at later stages of development. At all stages, the β1 subunit was concentrated at the vitreal border of the retina around the inner limiting membrane. Mechanical isolation of the inner limiting membrane, as well as immunoelectron microscopy, demonstrated that this immunoreactivity was due to a concentration of the β1 subunit in the endfeet of neuroepithelial and Müller glial cells. Injection of collagenase into the vitreous of live embryos, a procedure that selectively removes the inner limiting membrane, but does not proteolytically degrade the integrin protein, resulted in a redistribution of the integrin immunoreactivity, demonstrating that the integrity of the basal lamina is required for the maintenance of the concentration of the β1 subunit in the endfeet. These results suggest a role for the β1 subunit‐containing integrin heterodimers in the adhesion of neuroepithelial and Müller glial cells to extracellular matrix components of the inner limiting membrane, possibly stabilizing the radial morphology of these cells. J. Comp. Neurol. 424:153–164, 2000. © 2000 Wiley‐Liss, Inc.