Dysregulation of myelin synthesis and actomyosin function underlies aberrant myelin in CMT4B1 neuropathy

Marta Guerrero-Valero, Federica Grandi, Silvia Cipriani, Valeria Alberizzi, Roberta Di Guardo, Gaetan Chicanne, Linda Sawade, Francesca Bianchi, Ubaldo Del Carro, Ivan De Curtis, Davide Pareyson, Yesim Parman, Angelo Schenone, Volker Haucke, Bernard Payrastre, Alessandra Bolino

Research output: Contribution to journalArticlepeer-review

Abstract

Charcot-Marie-Tooth type 4B1 (CMT4B1) is a severe autosomal recessive demyelinating neuropathy with childhood onset, caused by loss-of-function mutations in the myotubularin-related 2 (MTMR2) gene. MTMR2 is a ubiquitously expressed catalytically active 3-phosphatase, which in vitro dephosphorylates the 3-phosphoinositides PtdIns3P and PtdIns(3,5)P2, with a preference for PtdIns(3,5)P2 A hallmark of CMT4B1 neuropathy are redundant loops of myelin in the nerve termed myelin outfoldings, which can be considered the consequence of altered growth of myelinated fibers during postnatal development. How MTMR2 loss and the resulting imbalance of 3'-phosphoinositides cause CMT4B1 is unknown. Here we show that MTMR2 by regulating PtdIns(3,5)P2 levels coordinates mTORC1-dependent myelin synthesis and RhoA/myosin II-dependent cytoskeletal dynamics to promote myelin membrane expansion and longitudinal myelin growth. Consistent with this, pharmacological inhibition of PtdIns(3,5)P2 synthesis or mTORC1/RhoA signaling ameliorates CMT4B1 phenotypes. Our data reveal a crucial role for MTMR2-regulated lipid turnover to titrate mTORC1 and RhoA signaling thereby controlling myelin growth.

Original languageEnglish
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number10
DOIs
Publication statusPublished - Mar 9 2021

Keywords

  • Charcot-Marie-Tooth neuropathies
  • myelin
  • myotubularin
  • phosphoinositides
  • Schwann cells

ASJC Scopus subject areas

  • General

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