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Mutations in MME cause an autosomal‐recessive Charcot–Marie–Tooth disease type 2
Author(s) -
Higuchi Yujiro,
Hashiguchi Akihiro,
Yuan Junhui,
Yoshimura Akiko,
Mitsui Jun,
Ishiura Hiroyuki,
Tanaka Masaki,
Ishihara Satoshi,
Tanabe Hajime,
Nozuma Satoshi,
Okamoto Yuji,
Matsuura Eiji,
Ohkubo Ryuichi,
Inamizu Saeko,
Shiraishi Wataru,
Yamasaki Ryo,
Ohyagi Yasumasa,
Kira Junichi,
Oya Yasushi,
Yabe Hayato,
Nishikawa Noriko,
Tobisawa Shinsuke,
Matsuda Nozomu,
Masuda Masayuki,
Kugimoto Chiharu,
Fukushima Kazuhiro,
Yano Satoshi,
Yoshimura Jun,
Doi Koichiro,
Nakagawa Masanori,
Morishita Shinichi,
Tsuji Shoji,
Takashima Hiroshi
Publication year - 2016
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.24612
Subject(s) - mutation , exome sequencing , loss function , compound heterozygosity , dementia , atrophy , medicine , gene , genetics , disease , phenotype , pathology , biology
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. Ann Neurol 2016;79:659–672