Disruption of <i>Mtmr2</i> produces CMT4B1-like neuropathy with myelin outfolding and impaired spermatogenesis

  • Alessandra Bolino
    1Dulbecco Telethon Institute, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Annalisa Bolis
    1Dulbecco Telethon Institute, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Stefano Carlo Previtali
    2Department of Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Giorgia Dina
    2Department of Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Simona Bussini
    1Dulbecco Telethon Institute, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Gabriele Dati
    3Department of Biological and Technological Research, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Stefano Amadio
    2Department of Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Ubaldo Del Carro
    2Department of Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Dolores D. Mruk
    4Population Council, Center for Biomedical Research, The Rockefeller University, New York, NY 10021
  • Maria Laura Feltri
    3Department of Biological and Technological Research, San Raffaele Scientific Institute, 20132 Milan, Italy
  • C. Yan Cheng
    4Population Council, Center for Biomedical Research, The Rockefeller University, New York, NY 10021
  • Angelo Quattrini
    2Department of Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
  • Lawrence Wrabetz
    3Department of Biological and Technological Research, San Raffaele Scientific Institute, 20132 Milan, Italy

Description

<jats:p>Mutations in MTMR2, the myotubularin-related 2 gene, cause autosomal recessive Charcot-Marie-Tooth (CMT) type 4B1, a demyelinating neuropathy with myelin outfolding and azoospermia. MTMR2 encodes a ubiquitously expressed phosphatase whose preferred substrate is phosphatidylinositol (3,5)-biphosphate, a regulator of membrane homeostasis and vesicle transport. We generated Mtmr2-null mice, which develop progressive neuropathy characterized by myelin outfolding and recurrent loops, predominantly at paranodal myelin, and depletion of spermatids and spermatocytes from the seminiferous epithelium, which leads to azoospermia. Disruption of Mtmr2 in Schwann cells reproduces the myelin abnormalities. We also identified a novel physical interaction in Schwann cells, between Mtmr2 and discs large 1 (Dlg1)/synapse-associated protein 97, a scaffolding molecule that is enriched at the node/paranode region. Dlg1 homologues have been located in several types of cellular junctions and play roles in cell polarity and membrane addition. We propose that Schwann cell–autonomous loss of Mtmr2–Dlg1 interaction dysregulates membrane homeostasis in the paranodal region, thereby producing outfolding and recurrent loops of myelin.</jats:p>

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