Seizures induce widespread upregulation of cystatin B, the gene mutated in progressive myoclonus epilepsy, in rat forebrain neurons

Authors

  • Elena D'amato,

    1. Department of Medical Genetics, University of Helsinki, FIN-00014 Helsinki, Finland, and Folkhälsan Institute of Genetics, FIN-00280 Helsinki, Finland
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    • *E.D. and Z.K. have contributed equally to this work.
  • Zaal Kokaia,

    1. Section of Restorative Neurology, Wallenberg Neuroscience Center, University Hospital, SE-221 85 Lund, Sweden
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    • *E.D. and Z.K. have contributed equally to this work.
  • Avtandil Nanobashvili,

    1. Section of Restorative Neurology, Wallenberg Neuroscience Center, University Hospital, SE-221 85 Lund, Sweden
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  • Mati Reeben,

    1. Program for Molecular Neurobiology, Institute of Biotechnology, Viikki Biocentre, University of Helsinki, FIN-00014 Helsinki, Finland
    2. Department of Neuroscience and Neurology, University of Kuopio, and Kuopio University Hospital, FIN-70211 Kuopio, Finland
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  • Anna-Elina Lehesjoki,

    1. Department of Medical Genetics, University of Helsinki, FIN-00014 Helsinki, Finland, and Folkhälsan Institute of Genetics, FIN-00280 Helsinki, Finland
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  • Mart Saarma,

    1. Program for Molecular Neurobiology, Institute of Biotechnology, Viikki Biocentre, University of Helsinki, FIN-00014 Helsinki, Finland
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  • Olle Lindvall

    1. Section of Restorative Neurology, Wallenberg Neuroscience Center, University Hospital, SE-221 85 Lund, Sweden
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: Dr Z. Kokaia, as above.
E-mail: zaza.kokaia@neurol.lu.se

Abstract

Loss of function mutations in the gene encoding the cysteine protease inhibitor, cystatin B (CSTB), are responsible for the primary defect in human progressive myoclonus epilepsy (EPM1). CSTB inhibits the cathepsins B, H, L and S by tight reversible binding, but little is known regarding its localization and physiological function in the brain and the relation between the depletion of the CSTB protein and the clinical symptoms in EPM1. We have analysed the expression of mRNA and protein for CSTB in the adult rat brain using in situ hybridization and immunocytochemistry. In the control brains, the CSTB gene was differentially expressed with the highest levels in the hippocampal formation and reticular thalamic nucleus, and moderate levels in amygdala, thalamus, hypothalamus and cortical areas. Detectable levels of CSTB were found in virtually all forebrain neurons but not in glial cells. Following 40 rapidly recurring seizures evoked by hippocampal kindling stimulations, CSTB mRNA expression showed marked bilateral increases in the dentate granule cell layer, CA1 and CA4 pyramidal layers, amygdala, and piriform and parietal cortices. Maximum levels were detected at 6 or 24 h, and expression had reached control values at 1 week post-seizures. The changes of mRNA expression were accompanied by transient elevations (at 6–24 h) of CSTB protein in the same brain areas. These findings demonstrate that seizure activity leads to rapid and widespread increases of the synthesis of CSTB in forebrain neurons. We propose that the upregulation of CSTB following seizures may counteract apoptosis by binding cysteine proteases.

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