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

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 ( ) gene. MTMR2 is a ubiquitously expressed catalytically active 3-phosphatase, which in vitro dephosphorylates the...

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Published in:	Proceedings of the National Academy of Sciences - PNAS 2021-03, Vol.118 (10), p.1
Main Authors:	Guerrero-Valero, Marta, Grandi, Federica, Cipriani, Silvia, Alberizzi, Valeria, Di Guardo, Roberta, Chicanne, Gaetan, Sawade, Linda, Bianchi, Francesca, Del Carro, Ubaldo, De Curtis, Ivan, Pareyson, Davide, Parman, Yesim, Schenone, Angelo, Haucke, Volker, Payrastre, Bernard, Bolino, Alessandra
Format:	Article
Language:	eng
Subjects:	Actomyosin Biological Sciences Charcot-Marie-Tooth disease Children Cytoskeleton Demyelination Fibers Lipid turnover Lipids Mutation Myelin Myosin Neuropathy Phenotypes Phosphoinositides RhoA protein Signaling Synthesis
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Summary:	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 ( ) gene. MTMR2 is a ubiquitously expressed catalytically active 3-phosphatase, which in vitro dephosphorylates the 3-phosphoinositides PtdIns3 and PtdIns(3,5) , with a preference for PtdIns(3,5) 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) 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) 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.
ISSN:	0027-8424 1091-6490