Faculty Profiles - Ishiura Hiroyuki

両側脊髄病変による痙性麻痺の亜急性進行を呈した遅発性Krabbe病の症例(A case of late-onset Krabbe disease which showed subacute progression of spastic paresis with bilateral spinal cord lesions) Reviewed

Mitsutake Akihiko, Matsukawa Takashi, Ishiura Hiroyuki, Mitsui Jun, Taira Kenichiro, Tokushige Shin-ichi, Iwata Atsushi, Terao Yasuo, Shimizu Jun, Sakai Norio, Tsuji Shoji

Neurology and Clinical Neuroscience 6 ( 4 ) 104 - 106 2018.7

Language：English Publisher：(一社)日本神経学会

16歳男。10ヵ月前から走行中に転倒するようになり、次第に歩行障害が進行した。末梢神経障害の所見はなかった。MRI T2強調画像で脳内包から腰髄にかけて両側錐体路に高信号病変を認めた。対称性錐体路病変は遅発性Krabbe病の特徴であり、白血球中galactocerebrosidase活性には著明な低値を認めた。遺伝子解析ではhomozygous c.1901T>C変異を認めた。以上の所見より、遅発性Krabbe病と確定診断した。

DOI： 10.1111/ncn3.12188

SLC4A4 compound heterozygous mutations in exon-intron boundary regions presenting with severe proximal renal tubular acidosis and extrarenal symptoms coexisting with Turner's syndrome: a case report. Reviewed International journal

Shoko Horita, Enver Simsek, Tulay Simsek, Nilgun Yildirim, Hiroyuki Ishiura, Motonobu Nakamura, Nobuhiko Satoh, Atsushi Suzuki, Hiroyuki Tsukada, Tomohito Mizuno, George Seki, Shoji Tsuji, Masaomi Nangaku

BMC medical genetics 19 ( 1 ) 103 - 103 2018.6

Language：English Publishing type：Research paper (scientific journal)

BACKGROUND: Congenital NBCe1A deficiency with the SLC4A4 mutation causes severe proximal renal tubular acidosis, which often comprises extrarenal symptoms, such as intellectual disability and developmental delay, glaucoma, cataract and band keratopathy. To date, almost all mutations have been found to be homozygous mutations located in exons. CASE PRESENTATION: We performed direct nucleotide sequencing analysis of exons and exon-intron boundary regions of the SLC4A4 in a patient presenting with severe renal proximal tubule acidosis, glaucoma and intellectual disability and her parents without these signs. The examination revealed compound heterozygous mutations in exon-intron boundary regions, c.1076 + 3A > C and c.1772 - 2A > T, neither of which have been reported previously. While the former mutation was found in the mother, the latter was found in the father. The transcript of the SLC4A4 gene was almost undetectable, and the patient was also diagnosed with Turner's syndrome. CONCLUSIONS: We identified two novel SLC4A4 mutations, c.1076 + 3A > C and c.1772 - 2A > T. When presented in a compound heterozygous state, these mutations caused a phenotype of severe renal proximal tubular acidosis along with glaucoma and mental retardation. This is the first report of congenital proximal renal tubular acidosis carrying compound heterozygous SLC4A4 mutations in exon-intron boundary regions. We suggest that an mRNA surveillance mechanism, nonsense-mediated RNA decay, following aberrant splicing was the reason that the SLC4A4 transcript was almost undetectable in the proband.

DOI： 10.1186/s12881-018-0612-y

Mutations in COA7 cause spinocerebellar ataxia with axonal neuropathy. Reviewed International journal

Yujiro Higuchi, Ryuta Okunushi, Taichi Hara, Akihiro Hashiguchi, Junhui Yuan, Akiko Yoshimura, Kei Murayama, Akira Ohtake, Masahiro Ando, Yu Hiramatsu, Satoshi Ishihara, Hajime Tanabe, Yuji Okamoto, Eiji Matsuura, Takehiro Ueda, Tatsushi Toda, Sumimasa Yamashita, Kenichiro Yamada, Takashi Koide, Hiroaki Yaguchi, Jun Mitsui, Hiroyuki Ishiura, Jun Yoshimura, Koichiro Doi, Shinichi Morishita, Ken Sato, Masanori Nakagawa, Masamitsu Yamaguchi, Shoji Tsuji, Hiroshi Takashima

Brain : a journal of neurology 141 ( 6 ) 1622 - 1636 2018.6

Language：English Publishing type：Research paper (scientific journal)

Several genes related to mitochondrial functions have been identified as causative genes of neuropathy or ataxia. Cytochrome c oxidase assembly factor 7 (COA7) may have a role in assembling mitochondrial respiratory chain complexes that function in oxidative phosphorylation. Here we identified four unrelated patients with recessive mutations in COA7 among a Japanese case series of 1396 patients with Charcot-Marie-Tooth disease (CMT) or other inherited peripheral neuropathies, including complex forms of CMT. We also found that all four patients had characteristic neurological features of peripheral neuropathy and ataxia with cerebellar atrophy, and some patients showed leukoencephalopathy or spinal cord atrophy on MRI scans. Validated mutations were located at highly conserved residues among different species and segregated with the disease in each family. Nerve conduction studies showed axonal sensorimotor neuropathy. Sural nerve biopsies showed chronic axonal degeneration with a marked loss of large and medium myelinated fibres. An immunohistochemical assay with an anti-COA7 antibody in the sural nerve from the control patient showed the positive expression of COA7 in the cytoplasm of Schwann cells. We also observed mildly elevated serum creatine kinase levels in all patients and the presence of a few ragged-red fibres and some cytochrome c oxidase-negative fibres in a muscle biopsy obtained from one patient, which was suggestive of subclinical mitochondrial myopathy. Mitochondrial respiratory chain enzyme assay in skin fibroblasts from the three patients showed a definitive decrease in complex I or complex IV. Immunocytochemical analysis of subcellular localization in HeLa cells indicated that mutant COA7 proteins as well as wild-type COA7 were localized in mitochondria, which suggests that mutant COA7 does not affect the mitochondrial recruitment and may affect the stability or localization of COA7 interaction partners in the mitochondria. In addition, Drosophila COA7 (dCOA7) knockdown models showed rough eye phenotype, reduced lifespan, impaired locomotive ability and shortened synaptic branches of motor neurons. Our results suggest that loss-of-function COA7 mutation is responsible for the phenotype of the presented patients, and this new entity of disease would be referred to as spinocerebellar ataxia with axonal neuropathy type 3.

DOI： 10.1093/brain/awy104

Intronic pentanucleotide TTTCA repeat insertion in the SAMD12 gene causes familial cortical myoclonic tremor with epilepsy type 1. Reviewed

Cen Z, Jiang Z, Chen Y, Zheng X, Xie F, Yang X, Lu X, Ouyang Z, Wu H, Chen S, Yin H, Qiu X, Wang S, Ding M, Tang Y, Yu F, Li C, Wang T, Ishiura H, Tsuji S, Jiao C, Liu C, Xiao J, Luo W

Brain : a journal of neurology 141 ( 8 ) 2280 - 2288 2018.6

HIV Dementia with a Decreased Cardiac ¹²³I-metaiodobenzylguanidine Uptake Masquerading as Dementia with Lewy Bodies. Reviewed

Kurihara M, Sasaki T, Ishiura H, Tsuji S

Internal medicine (Tokyo, Japan) 57 ( 20 ) 3007 - 3010 2018.5

Optineurin pathology in the spinal cord of amyotrophic lateral sclerosis/parkinsonism-dementia complex patients in Kii Peninsula, Japan. Reviewed International journal

Satoru Morimoto, Hiroyuki Hatsuta, Rie Motoyama, Yasumasa Kokubo, Hiroyuki Ishiura, Shoji Tsuji, Shigeki Kuzuhara, Shigeo Murayama

Brain pathology (Zurich, Switzerland) 28 ( 3 ) 422 - 426 2018.5

Novel De Novo KCND3 Mutation in a Japanese Patient with Intellectual Disability, Cerebellar Ataxia, Myoclonus, and Dystonia Reviewed

Masanori Kurihara, Hiroyuki Ishiura, Takuya Sasaki, Juuri Otsuka, Toshihiro Hayashi, Yasuo Terao, Takashi Matsukawa, Jun Mitsui, Juntaro Kaneko, Kazutoshi Nishiyama, Koichiro Doi, Jun Yoshimura, Shinichi Morishita, Jun Shimizu, Shoji Tsuji

Cerebellum 17 ( 2 ) 237 - 242 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer New York LLC

Spinocerebellar ataxia 19/22 (SCA19/22) is a rare type of autosomal dominant SCA that was previously described in 11 families. We report the case of a 30-year-old Japanese man presenting with intellectual disability, early onset cerebellar ataxia, myoclonus, and dystonia without a family history. MRI showed cerebellar atrophy, and electroencephalograms showed paroxysmal sharp waves during hyperventilation and photic stimulation. Trio whole-exome sequencing analysis of DNA samples from the patient and his parents revealed a de novo novel missense mutation (c.1150G&gt
A, p.G384S) in KCND3, the causative gene of SCA19/22, substituting for evolutionally conserved glycine. The mutation was predicted to be functionally deleterious by bioinformatic analysis. Although pure cerebellar ataxia is the most common clinical feature in SCA19/22 families, extracerebellar symptoms including intellectual disability and myoclonus are reported in a limited number of families, suggesting a genotype–phenotype correlation for particular mutations. Although autosomal recessive diseases are more common in patients with early onset sporadic cerebellar ataxia, the present study emphasizes that such a possibility of de novo mutation should be considered.

DOI： 10.1007/s12311-017-0883-4

Scopus

Frequency and characteristics of the TBK1 gene variants in Japanese patients with sporadic amyotrophic lateral sclerosis. Reviewed International journal

Genki Tohnai, Ryoichi Nakamura, Jun Sone, Masahiro Nakatochi, Daichi Yokoi, Masahisa Katsuno, Hazuki Watanabe, Hirohisa Watanabe, Mizuki Ito, Yuanzhe Li, Yuishin Izumi, Mitsuya Morita, Akira Taniguchi, Osamu Kano, Masaya Oda, Satoshi Kuwabara, Koji Abe, Ikuko Aiba, Koichi Okamoto, Kouichi Mizoguchi, Kazuko Hasegawa, Masashi Aoki, Nobutaka Hattori, Osamu Onodera, Hiroya Naruse, Jun Mitsui, Yuji Takahashi, Jun Goto, Hiroyuki Ishiura, Shinichi Morishita, Jun Yoshimura, Koichiro Doi, Shoji Tsuji, Kenji Nakashima, Ryuji Kaji, Naoki Atsuta, Gen Sobue

Neurobiology of aging 64 158.e15-158.e19 - 158.e19 2018.4

Language：English Publishing type：Research paper (scientific journal)

Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease, and the etiology of sporadic ALS is generally unknown. The TANK-binding kinase 1 (TBK1) gene was identified as an ALS gene contributing to a predisposition toward ALS. To reveal the frequency and characteristics of variants of the TBK1 gene in sporadic ALS patients in Japan, we analyzed the TBK1 gene by exome sequencing in a large Japanese cohort of 713 sporadic ALS patients and 800 controls. We identified known or potentially toxic rare variants of TBK1 gene in 9 patients (1.26%) with sporadic ALS, including 4 novel missense variants (p.V23I, p.H322R, p.R358C, and p.T478I) and 3 loss-of-function variants (p.R357X, p.P378_I379del, and p.T419_G420del). The odds ratio between sporadic ALS patients and controls was 10.2 (p = 0.008, 95% confidence interval = 1.67-62.47). These findings support the contribution of TBK1 to the etiology of sporadic ALS in Japanese patients.

DOI： 10.1016/j.neurobiolaging.2017.12.005

A Homozygous LAMA2 Mutation of c.818G>A Caused Partial Merosin Deficiency in a Japanese Patient. Reviewed

Akatsuki Kubota, Hiroyuki Ishiura, Jun Mitsui, Kaori Sakuishi, Atsushi Iwata, Tomotaka Yamamoto, Ichizo Nishino, Shoji Tsuji, Jun Shimizu

Internal medicine (Tokyo, Japan) 57 ( 6 ) 877 - 882 2018.3

Language：English Publishing type：Research paper (scientific journal)

A complete loss of merosin, which is encoded by LAMA2, causes congenital muscular dystrophy with leukoencephalopathy. Partial merosin deficiency can be caused not only by primarily LAMA2 mutations, but also secondarily by dystroglycanopathy. Although it can be molecularly diagnosed based on a genetic analysis, this method is labor-intensive because of its huge genome size. A 26-year-old male patient presented with mild muscular weakness, joint contractures, and epilepsy. Double immunofluorescence staining of a muscle biopsy specimen showed mislocalization of merosin, and a genetic analysis revealed a homozygous c.818G>A (p.Arg273Lys) mutation in LAMA2. Double immunofluorescence staining and whole exome sequencing were useful for the diagnosis of partial merosin deficiency.

DOI： 10.2169/internalmedicine.9588-17

Clinical and genetic features of Charcot-Marie-Tooth disease 2F and hereditary motor neuropathy 2B in Japan Reviewed

Hajime Tanabe, Yujiro Higuchi, Jun-Hui Yuan, Akihiro Hashiguchi, Akiko Yoshimura, Satoshi Ishihara, Satoshi Nozuma, Yuji Okamoto, Eiji Matsuura, Hiroyuki Ishiura, Jun Mitsui, Ryotaro Takashima, Norito Kokubun, Kengo Maeda, Yuri Asano, Yoko Sunami, Yu Kono, Yasunori Ishigaki, Shosaburo Yanamoto, Jiro Fukae, Hiroshi Kida, Mitsuya Morita, Shoji Tsuji, Hiroshi Takashima

Journal of the Peripheral Nervous System 23 ( 1 ) 40 - 48 2018.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Blackwell Publishing Inc.

Mutations in small heat shock protein beta-1 (HspB1) have been linked to Charcot-Marie-Tooth (CMT) disease type 2F and distal hereditary motor neuropathy type 2B. Only four cases with HSPB1 mutations have been reported to date in Japan. In this study between April 2007 and October 2014, we conducted gene panel sequencing in a case series of 1,030 patients with inherited peripheral neuropathies (IPNs) using DNA microarray, targeted resequencing, and whole-exome sequencing. We identified HSPB1 variants in 1.3% (13 of 1,030) of the patients with IPNs, who exhibited a male predominance. Based on neurological and electrophysiological findings, seven patients were diagnosed with CMT disease type 2F, whereas the remaining six patients were diagnosed with distal hereditary motor neuropathy type 2B. P39L, R127W, S135C, R140G, K141Q, T151I, and P182A mutations identified in 12 patients were described previously, whereas a novel K123* variant with unknown significance was found in 1 patient. Diabetes and impaired glucose tolerance were detected in 6 of the 13 patients. Our findings suggest that HSPB1 mutations result in two phenotypes of inherited neuropathies and extend the phenotypic spectrum of HSPB1-related disorders.

DOI： 10.1111/jns.12252

Scopus

Authors’ reply to the Drs. Finsterer and Zarrouk-Mahjoub's comments for our case report Reviewed

Eisuke Amiya, Hiroyuki Morita, Hiroyuki Ishiura, Shoji Tsuji, Issei Komuro

International Journal of Cardiology 254 262 2018.3

Identification of candidate genes involved in the etiology of sporadic Tourette syndrome by exome sequencing Reviewed

Yosuke Eriguchi, Hitoshi Kuwabara, Aya Inai, Yuki Kawakubo, Fumichika Nishimura, Chihiro Kakiuchi, Mamoru Tochigi, Jun Ohashi, Naoto Aoki, Kayoko Kato, Hiroyuki Ishiura, Jun Mitsui, Shoji Tsuji, Koichiro Doi, Jun Yoshimura, Shinichi Morishita, Takafumi Shimada, Masaomi Furukawa, Tadashi Umekage, Tsukasa Sasaki, Kiyoto Kasai, Yukiko Kano

AMERICAN JOURNAL OF MEDICAL GENETICS PART B-NEUROPSYCHIATRIC GENETICS 174 ( 7 ) 712 - 723 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY

Tourette Syndrome (TS) is a neurodevelopmental disorder characterized by chronic motor and vocal tics. Although there is a large genetic contribution, the genetic architecture of TS remains unclear. Exome sequencing has successfully revealed the contribution of de novo mutations in sporadic cases with neuropsychiatric disorders such as autism and schizophrenia. Here, using exome sequencing, we investigated de novo mutations in individuals with sporadic TS to identify novel risk loci and elucidate the genetic background of TS. Exome analysis was conducted for sporadic TS cases: nine trio families and one quartet family with concordant twins were investigated. Missense mutations were evaluated using functional prediction algorithms, and their population frequencies were calculated based on three public databases. Gene expression patterns in the brain were analyzed using the BrainSpan Developmental Transcriptome. Thirty de novo mutations, including four synonymous and four missense mutations, were identified. Among the missense mutations, one in the rapamycin-insensitive companion of mammalian target of rapamycin (RICTOR)-coding gene (rs140964083: G > A, found in one proband) was predicted to be hazardous. In the three public databases analyzed, variants in the same SNP locus were absent, and variants in the same gene were either absent or present at an extremely low frequency (3/5,008), indicating the rarity of hazardous RICTOR mutations in the general population. The de novo variant of RICTOR may be implicated in the development of sporadic TS, and RICTOR is a novel candidate factor for TS etiology.

DOI： 10.1002/ajmg.b.32559

Structural Basis and Genotype-Phenotype Correlations of INSR Mutations Causing Severe Insulin Resistance Reviewed

Jun Hosoe, Hiroko Kadowaki, Fuyuki Miya, Katsuya Aizu, Tomoyuki Kawamura, Ichiro Miyata, Kenichi Satomura, Takeru Ito, Kazuo Hara, Masaki Tanaka, Hiroyuki Ishiura, Shoji Tsuji, Ken Suzuki, Minaka Takakura, Keith A. Boroevich, Tatsuhiko Tsunoda, Toshimasa Yamauchi, Nobuhiro Shojima, Takashi Kadowaki

DIABETES 66 ( 10 ) 2713 - 2723 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER DIABETES ASSOC

The insulin receptor (INSR) gene was analyzed in four patients with severe insulin resistance, revealing five novel mutations and a deletion that removed exon 2. A patient with Donohue syndrome (DS) had a novel p.V657F mutation in the second fibronectin type III domain (FnIII-2), which contains the - cleavage site and part of the insulin-binding site. The mutant INSR was expressed in Chinese hamster ovary cells, revealing that it reduced insulin proreceptor processing and impaired activation of downstream signaling cascades. Using online databases, we analyzed 82 INSR missense mutations and demonstrated that mutations causing DS were more frequently located in the FnIII domains than those causing the milder type A insulin resistance (P = 0.016). In silico structural analysis revealed that missense mutations predicted to severely impair hydrophobic core formation and stability of the FnIII domains all caused DS, whereas those predicted to produce localized destabilization and to not affect folding of the FnIII domains all caused the less severe Rabson-Mendenhall syndrome. These results suggest the importance of the FnIII domains, provide insight into the molecular mechanism of severe insulin resistance, will aid early diagnosis, and will provide potential novel targets for treating extreme insulin resistance.

DOI： 10.2337/db17-0301

New familial amyotrophic lateral sclerosis with benign progression and myoclonus in lower extremities Reviewed

Togawa J, Ohi T, Yuan JH, Takashima H, Furuya H, Takechi S, Fujitake J, Hayashi S, Ishiura H, Naruse H, Mitsui J, Tsuji S

J. Neurol. Sci. 381 ( Supplement ) 716 2017.10

Clinical and mutational spectrum of Charcot-Marie-Tooth disease type 2Z caused by MORC2 variants in Japan Reviewed

M. Ando, Y. Okamoto, A. Yoshimura, J. -H. Yuan, Y. Hiramatsu, Y. Higuchi, A. Hashiguchi, J. Mitsui, H. Ishiura, S. Fukumura, M. Matsushima, N. Ochi, J. Tsugawa, S. Morishita, S. Tsuji, H. Takashima

EUROPEAN JOURNAL OF NEUROLOGY 24 ( 10 ) 1274 - 1282 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY

Background and purpose: The microrchidia family CW-type zinc finger 2 gene (MORC2) was newly identified as a causative gene of Charcot-Marie-Tooth disease (CMT) type 2Z in 2016. We aimed to describe the clinical and mutational spectrum of patients with CMT harboring MORC2 mutations in Japan.
Methods: We analyzed samples from 781 unrelated patients clinically diagnosed with CMT using deoxyribonucleic acid microarray or targeted resequencing by next-generation sequencing, and samples from 434 mutation-negative patients were subjected to whole-exome sequencing. We extracted MORC2 variants from these whole-exome sequencing data and classified them according to American College of Medical Genetics standards and guidelines.
Results: We identified MORC2 variants in 13 patients. As the second most common causative gene of CMT type 2 after MFN2, MORC2 variants were detected in 2.7% of patients with CMT type 2. The mean age of onset was 10.3 +/- 8.7 years, and the inheritance pattern was mostly sporadic (11/13 patients, 84.6%). The clinical phenotype was typically length-dependent polyneuropathy, and electrophysiological studies revealed sensory-dominant axonal neuropathy. Mental retardation was identified in 4/13 patients (30.8%). p.Arg190Trp, as a mutational hotspot, was observed in eight unrelated families. We also identified two novel probably pathogenic variants, p.Cys345Tyr and p.Ala369Val, and one novel uncertain significance variant, p.Tyr332Cys.
Conclusions: Our study is the largest report of patients harboring MORC2 variants. We revealed a clinical and mutational spectrum of Japanese patients with MORC2 variants. More attention should be paid to cognitive impairment, and the responsible mechanism requires further research for elucidation.

DOI： 10.1111/ene.13360

Clinicopathologic features of myositis patients with CD8-MHC-1 complex pathology Reviewed

Chiseko Ikenaga, Akatsuki Kubota, Masato Kadoya, Kenichiro Taira, Naohiro Uchio, Ayumi Hida, Meiko Hashimoto Maeda, Yu Nagashima, Hiroyuki Ishiura, Kenichi Kaida, Jun Goto, Shoji Tsuji, Jun Shimizu

NEUROLOGY 89 ( 10 ) 1060 - 1068 2017.9

Language：English Publishing type：Research paper (scientific journal) Publisher：LIPPINCOTT WILLIAMS & WILKINS

Objective: To determine the clinical features of myositis patients with the histopathologic finding of CD8-positive T cells invading non-necrotic muscle fibers expressing major histocompatibility complex class 1 (CD8-MHC-1 complex), which is shared by polymyositis (PM) and inclusion body myositis (IBM), in relation to the p62 immunostaining pattern of muscle fibers.
Methods: All 93 myositis patients with CD8-MHC-1 complex who were referred to our hospital from 1993 to 2015 were classified on the basis of the European Neuromuscular Center (ENMC) diagnostic criteria for IBM (Rose, 2013) or PM (Hoogendijk, 2004) and analyzed.
Results: The 93 patients included were 17 patients with PM, 70 patients with IBM, and 6 patients who neither met the criteria for PM nor IBM in terms of muscle weakness distribution (unclassifiable group). For these PM, IBM, and unclassifiable patients, their mean ages at diagnosis were 63, 70, and 64 years; autoimmune disease was present in 7 (41%), 13 (19%), and 4 (67%); hepatitis C virus infection was detected in 0%, 13 (20%), and 2 (33%); and p62 was immunopositive in 0%, 66 (94%), and 2 (33%), respectively. Of the treated patients, 11 of 16 PM patients and 4 of 6 p62-immunonegative patients in the unclassifiable group showed responses to immunotherapy, whereas all 44 patients with IBM and 2 p62-immunopositive patients in the unclassifiable group were unresponsive to immunotherapy.
Conclusions: CD8-MHC-1 complex is present in patients with PM, IBM, or unclassifiable group. The data may serve as an argument for a trial of immunosuppressive treatment in p62-immunonegative patients with unclassifiable myositis.

DOI： 10.1212/WNL.0000000000004333

Clinical and mutational spectrum of Japanese patients with Charcot-Marie-Tooth disease caused by GDAP1 variants Reviewed

A. Yoshimura, J. -H. Yuan, A. Hashiguchi, Y. Hiramatsu, M. Ando, Y. Higuchi, T. Nakamura, Y. Okamoto, K. Matsumura, T. Hamano, N. Sawaura, Y. Shimatani, S. Kumada, Y. Okumura, J. Miyahara, Y. Yamaguchi, S. Kitamura, K. Haginoya, J. Mitsui, H. Ishiura, S. Tsuji, H. Takashima

CLINICAL GENETICS 92 ( 3 ) 274 - 280 2017.9

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY

BackgroundMutations in GDAP1 are responsible for heterogeneous clinical and electrophysiological phenotypes of Charcot-Marie-Tooth disease (CMT), with autosomal dominant or recessive inheritance pattern. The aim of this study is to identify the clinical and mutational spectrum of CMT patients with GDAP1 variants in Japan.
Materials and MethodsFrom April 2007 to October 2014, using three state-of-art technologies, we conducted gene panel sequencing in a cohort of 1,030 patients with inherited peripheral neuropathies (IPNs), and 398 mutation-negative cases were further analyzed with whole-exome sequencing.
ResultsWe identified GDAP1 variants from 10 patients clinically diagnosed with CMT. The most frequent recessive variant in our cohort (5/10), c.740C>T (p.A247V), was verified to be associated with a founder event. We also detected three novel likely pathogenic variants: c.928C>T (p.R310W) and c.546delA (p.E183Kfs*23) in Case 2 and c.376G>A (p.E126K) in Case 8. Nerve conduction study or sural nerve biopsy of all 10 patients indicated axonal type peripheral neuropathy.
ConclusionWe identified GDAP1 variants in approximately 1% of our cohort with IPNs, and established a founder mutation in half of these patients. Our study originally described the mutational spectrum and clinical features of GDAP1-related CMT patients in Japan.

DOI： 10.1111/cge.13002