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Specific expression of ezrin, a cytoskeletal-membrane linker protein, in a subset of chick retinotectal and sensory projections

Authors

  • Masakazu Takahashi,

    1. Division of Molecular Neurobiology, National Institute for Basic Biology, and
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  • Masahito Yamagata,

    1. Division of Molecular Neurobiology, National Institute for Basic Biology, and
    2. Department of Molecular Biomechanics, Graduate University for Advanced Studies, Okazaki 444-8585, Japan
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  • Masaharu Noda

    1. Division of Molecular Neurobiology, National Institute for Basic Biology, and
    2. Department of Molecular Biomechanics, Graduate University for Advanced Studies, Okazaki 444-8585, Japan
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Dr Masaharu Noda, Division of Molecular Neurobiology, National Institute for Basic Biology, Myodaiji-cho, Okazaki 444–8585, Japan. E-mail: madon@nibb.ac.jp

Abstract

Lamina-specific neuronal connections are a fundamental feature in many parts of the vertebrate central nervous system. In the chick, the optic tectum is the primary visual centre, and it has a multilaminated structure consisting of 15 laminae, of which only three or four receive retinal projections. Each of the retinorecipient laminae establishes synaptic connections selectively from one of a few subsets of retinal ganglion cells (RGCs). We have generated a series of monoclonal antibodies that appear to stain only one of the retinorecipient laminae. One of these, TB4, stained lamina F which receives inputs from a subpopulation of ≈ 10–20% of RGCs which express the presynaptic acetylcholine receptor β2-subunit. TB4 recognized a single 79-kDa protein on immunoblotting. cDNA cloning and immunochemical analysis revealed that the TB4 antigen molecule was ezrin, a cytoskeletal-membrane linker molecule belonging to the ezrin-radixin-moesin family. Unilateral enucleation of the eye, both prior to and after the establishment of retinotectal projections, attenuated the lamina-selective staining with TB4 in the contralateral tectum, suggesting that ezrin is anterogradely transported from RGCs to lamina F. Ezrin was thus expressed in a subset of RGCs that project to lamina F. Similar subset-selective expression and resultant lamina-selective distribution of ezrin were also observed in the lamina-specific central projections from the dorsal root ganglia. The staining pattern with TB4 in the dorsal root ganglia and spinal cord indicated that high expression of ezrin was restricted in cutaneous sensory neurons, but not in muscle sensory neurons. Since ezrin modulates cell morphology and cell adhesion profiles by linking membrane proteins with the cytoskeleton, it was suggested that ezrin is involved in the formation and/or maintenance of lamina-specific connections for neuronal subpopulations in the visual and somatosensory systems.

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