Somatic Mutations in the MTOR gene cause focal cortical dysplasia type IIb
Mitsuko Nakashima MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
These authors contributed equally to this work.
Search for more papers by this authorHirotomo Saitsu MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
These authors contributed equally to this work.
Search for more papers by this authorNobuyuki Takei PhD
Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
Search for more papers by this authorJun Tohyama MD, PhD
Department of Child Neurology, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorMitsuhiro Kato MD, PhD
Department of Pediatrics, Showa University School of Medicine, Tokyo, Japan
Search for more papers by this authorHiroki Kitaura DDS, PhD
Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
Search for more papers by this authorMasaaki Shiina MD, PhD
Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorHiroshi Shirozu MD, PhD
Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorHiroshi Masuda MD
Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorKeisuke Watanabe PhD
Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
Search for more papers by this authorChihiro Ohba MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorYoshinori Tsurusaki PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorNoriko Miyake MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorYingjun Zheng MD, PhD
Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
Search for more papers by this authorTatsuhiro Sato PhD
Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
Search for more papers by this authorHirohide Takebayashi MD, PhD
Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
Search for more papers by this authorKazuhiro Ogata MD, PhD
Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorShigeki Kameyama MD, PhD
Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorAkiyoshi Kakita MD, PhD
Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
These are co-last authors.
Search for more papers by this authorCorresponding Author
Naomichi Matsumoto MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
These are co-last authors.
Address correspondence to Dr Naomichi Matsumoto, Department of Human Genetics, Yokohama City University Graduate School of Medicine, 3–9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan. E-mail: [email protected]Search for more papers by this authorMitsuko Nakashima MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
These authors contributed equally to this work.
Search for more papers by this authorHirotomo Saitsu MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
These authors contributed equally to this work.
Search for more papers by this authorNobuyuki Takei PhD
Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
Search for more papers by this authorJun Tohyama MD, PhD
Department of Child Neurology, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorMitsuhiro Kato MD, PhD
Department of Pediatrics, Showa University School of Medicine, Tokyo, Japan
Search for more papers by this authorHiroki Kitaura DDS, PhD
Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
Search for more papers by this authorMasaaki Shiina MD, PhD
Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorHiroshi Shirozu MD, PhD
Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorHiroshi Masuda MD
Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorKeisuke Watanabe PhD
Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
Search for more papers by this authorChihiro Ohba MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorYoshinori Tsurusaki PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorNoriko Miyake MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorYingjun Zheng MD, PhD
Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
Search for more papers by this authorTatsuhiro Sato PhD
Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
Search for more papers by this authorHirohide Takebayashi MD, PhD
Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
Search for more papers by this authorKazuhiro Ogata MD, PhD
Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Search for more papers by this authorShigeki Kameyama MD, PhD
Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
Search for more papers by this authorAkiyoshi Kakita MD, PhD
Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
These are co-last authors.
Search for more papers by this authorCorresponding Author
Naomichi Matsumoto MD, PhD
Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
These are co-last authors.
Address correspondence to Dr Naomichi Matsumoto, Department of Human Genetics, Yokohama City University Graduate School of Medicine, 3–9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan. E-mail: [email protected]Search for more papers by this authorAbstract
Objective
Focal cortical dysplasia (FCD) type IIb is a cortical malformation characterized by cortical architectural abnormalities, dysmorphic neurons, and balloon cells. It has been suggested that FCDs are caused by somatic mutations in cells in the developing brain. Here, we explore the possible involvement of somatic mutations in FCD type IIb.
Methods
We collected a total of 24 blood-brain paired samples with FCD, including 13 individuals with FCD type IIb, 5 with type IIa, and 6 with type I. We performed whole-exome sequencing using paired samples from 9 of the FCD type IIb subjects. Somatic MTOR mutations were identified and further investigated using all 24 paired samples by deep sequencing of the entire gene's coding region. Somatic MTOR mutations were confirmed by droplet digital polymerase chain reaction. The effect of MTOR mutations on mammalian target of rapamycin (mTOR) kinase signaling was evaluated by immunohistochemistry and Western blotting analyses of brain samples and by in vitro transfection experiments.
Results
We identified four lesion-specific somatic MTOR mutations in 6 of 13 (46%) individuals with FCD type IIb showing mutant allele rates of 1.11% to 9.31%. Functional analyses showed that phosphorylation of ribosomal protein S6 in FCD type IIb brain tissues with MTOR mutations was clearly elevated, compared to control samples. Transfection of any of the four MTOR mutants into HEK293T cells led to elevated phosphorylation of 4EBP, the direct target of mTOR kinase.
Interpretation
We found low-prevalence somatic mutations in MTOR in FCD type IIb, indicating that activating somatic mutations in MTOR cause FCD type IIb. Ann Neurol 2015;78:375–386
Supporting Information
Additional Supporting Information can be found in the online version of this article.
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Supplementary Information |
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