Mutations in MME cause an autosomal-recessive Charcot-Marie-Tooth disease type 2

Yujiro Higuchi, Akihiro Hashiguchi, Junhui Yuan, Akiko Yoshimura, Jun Mitsui, Hiroyuki Ishiura, Masaki Tanaka, Satoshi Ishihara, Hajime Tanabe, Satoshi Nozuma, Yuji Okamoto, Eiji Matsuura, Ryuichi Ohkubo, Saeko Inamizu, Wataru Shiraishi, Ryo Yamasaki, Yasumasa Ohyagi, Jun Ichi Kira, Yasushi Oya, Hayato YabeNoriko Nishikawa, Shinsuke Tobisawa, Nozomu Matsuda, Masayuki Masuda, Chiharu Kugimoto, Kazuhiro Fukushima, Satoshi Yano, Jun Yoshimura, Koichiro Doi, Masanori Nakagawa, Shinichi Morishita, Shoji Tsuji, Hiroshi Takashima

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Abstract

Objective The objective of this study was to identify new causes of Charcot-Marie-Tooth (CMT) disease in patients with autosomal-recessive (AR) CMT. Methods To efficiently identify novel causative genes for AR-CMT, we analyzed 303 unrelated Japanese patients with CMT using whole-exome sequencing and extracted recessive variants/genes shared among multiple patients. We performed mutation screening of the newly identified membrane metalloendopeptidase (MME) gene in 354 additional patients with CMT. We clinically, genetically, pathologically, and radiologically examined 10 patients with the MME mutation. Results We identified recessive mutations in MME in 10 patients. The MME gene encodes neprilysin (NEP), which is well known to be one of the most prominent beta-amyloid (Aβ)-degrading enzymes. All patients had a similar phenotype consistent with late-onset axonal neuropathy. They showed muscle weakness, atrophy, and sensory disturbance in the lower extremities. All the MME mutations could be loss-of-function mutations, and we confirmed a lack/decrease of NEP protein expression in a peripheral nerve. No patients showed symptoms of dementia, and 1 patient showed no excess Aβ in Pittsburgh compound-B positron emission tomography imaging. Interpretation Our results indicate that loss-of-function MME mutations are the most frequent cause of adult-onset AR-CMT2 in Japan, and we propose that this new disease should be termed AR-CMT2T. A loss-of-function MME mutation did not cause early-onset Alzheimer's disease. Identifying the MME mutation responsible for AR-CMT could improve the rate of molecular diagnosis and the understanding of the molecular mechanisms of CMT.

Original languageEnglish
Pages (from-to)659-672
Number of pages14
JournalAnnals of Neurology
Volume79
Issue number4
DOIs
Publication statusPublished - Apr 1 2016

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All Science Journal Classification (ASJC) codes

  • Neurology
  • Clinical Neurology

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Higuchi, Y., Hashiguchi, A., Yuan, J., Yoshimura, A., Mitsui, J., Ishiura, H., ... Takashima, H. (2016). Mutations in MME cause an autosomal-recessive Charcot-Marie-Tooth disease type 2. Annals of Neurology, 79(4), 659-672. https://doi.org/10.1002/ana.24612