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Dendritic spine and dendritic field characteristics of layer V pyramidal neurons in the visual cortex of fragile-X knockout mice

Authors

  • Scott A. Irwin,

    1. Neuroscience Program, University of Illinois, Urbana, Illinois
    2. Medical Scholars Program, University of Illinois, Urbana, Illinois
    3. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Madhuri Idupulapati,

    1. Department of Physiology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Molly E. Gilbert,

    1. Department of Psychology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Jennifer B. Harris,

    1. Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Aparna B. Chakravarti,

    1. Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Erica J. Rogers,

    1. Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Ralph A. Crisostomo,

    1. Department of Biology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Brian P. Larsen,

    1. Department of Psychology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Amit Mehta,

    1. Department of Physiology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • C.J. Alcantara,

    1. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Biraju Patel,

    1. Department of Physiology, University of Illinois, Urbana, Illinois
    2. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Rodney A. Swain,

    1. Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
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  • Ivan Jeanne Weiler,

    1. Beckman Institute, University of Illinois, Urbana, Illinois
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  • Ben A. Oostra,

    1. Department of Clinical Genetics, Erasmus University, Rotterdam, The Netherlands
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  • William T. Greenough

    Corresponding author
    1. Neuroscience Program, University of Illinois, Urbana, Illinois
    2. Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois
    3. Department of Psychology, University of Illinois, Urbana, Illinois
    4. Department of Psychiatry, University of Illinois, Urbana, Illinois
    5. Beckman Institute, University of Illinois, Urbana, Illinois
    • University of Illinois at Urbana-Champaign, Beckman Institute, 405 N. Mathews Ave., Urbana, IL 61801.
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Abstract

Fragile-X syndrome is a common form of mental retardation resulting from the inability to produce the fragile-X mental retardation protein. The specific function of this protein is unknown; however, it has been proposed to play a role in developmental synaptic plasticity. Examination of human brain autopsy material has shown that fragile-X patients exhibit abnormalities in dendritic spine structure and number, suggesting a failure of normal developmental dendritic spine maturation and pruning in this syndrome. Similar results using a knockout mouse model have previously been described; however, it was noted in retrospect that the mice used in that study may have carried a mutation for retinal degeneration, which may have affected cell morphology in the visual cortex of those animals. In this study, dendritic spines on layer V pyramidal cells of visual cortices, taken from fragile-X knockout and wild-type control mice without the retinal degeneration mutation and stained using the Golgi-Cox method, were investigated for comparison with the human condition. Quantitative analyses of the lengths, morphologies, and numbers of dendritic spines, as well as amount of dendritic arbor and dendritic branching complexity, were conducted. The fragile-X mice exhibited significantly more long dendritic spines and significantly fewer short dendritic spines than control mice. Similarly, fragile-X mice exhibited significantly more dendritic spines with an immature-like morphology and significantly fewer with a more mature type morphology. However, unlike the human condition, fragile-X mice did not exhibit statistically significant dendritic spine density differences from controls. Fragile-X mice also did not demonstrate any significant differences from controls in dendritic tree complexity or dendritic arbor. Long dendritic spines with immature morphologies are characteristic of early development or a lack of sensory experience. These results are similar to those found in the human condition and further support a role for the fragile-X mental retardation protein specifically in normal dendritic spine developmental processes. They also support the validity of these mice as a model of fragile-X syndrome. © 2002 Wiley-Liss, Inc.

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