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MK Manglapus, T Claudepierre, N Marengi, DD Hunter, WJ Brunken; Disruption of the Laminin B2 Chain Alters the Structure of the Photoreceptor Synapse . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2694.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Laminin isoforms containing the ß 2 chain are important in the development and stabilization of photoreceptor synapses. We hypothesize that these laminins are coupled to elements of the cytomatrix, thereby stabilizing pre- and post-synaptic components. To test this hypothesis, we examined the distribution of selected synaptic components in the outer plexiform layer (OPL) of mice lacking the laminin ß 2 chain. Methods: Standard immunohistochemisty was used to determine the expression pattern of several synaptic proteins in the OPL of the adult mouse retina, including: bassoon, kinesin, mGluR6, calbindin, α PKC, and Go α. Confocal microscopy and deconvolution microscopy provided high resolution, 3D reconstruction of photoreceptor synapses. Results: Bassoon, a cytomatrix protein is localized to the ribbon synapse in both rods and cones. In wild type retinae, bassoon immunoreactivity (IR) appears as arc-shaped structures. In knockout retinae, bassoon staining is de-localized and diffuse, with few arc-shaped ribbons, indicating a disruption of the triad synapse. Visualization of the ribbon synapse with kinesin shows similar results. In wild type retina, the metabotropic glutamate receptor (mGluR6) is expressed on the tips of invaginating biopolar dendrites and are restricted to descrete spots in close apposition to bassoon IR. In ß 2 knock out retinae, the tight association between mGluR6 and bassoon is disrupted. Moreover, the subcellular distribution of mGluR6 is changed such that receptor IR is found throughout the OPL and INL. We have identified several putative laminin receptors including integrins α 2, α 3, α 6, ß 3, ß 4, and ß 5; all are expressed in the OPL. Conclusion: There are profound pre- and post-synaptic disruptions in the photoreceptor synapse in the laminin ß 2 chain knock out mouse. These results suggest that the laminin ß 2 chain interacts with a complex of proteins involved in the development and/or maintenance of the photoreceptor synapse. Several candidate transmembrane receptors for the laminin ß 2 chain have been identified and include the integrins. We are currently isolating elements of this complex.
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