Mitsuhiro Kato

Yamagata University, Ямагата, Yamagata, Japan

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Publications (110)486.45 Total impact

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    ABSTRACT: TUBA1A mutations cause a wide spectrum of lissencephaly and brain malformations. Here, we report two patients with severe cortical dysgeneses, one with an extremely thin cerebral parenchyma apparently looking like hydranencephaly and the other with lissencephaly accompanied by marked hydrocephalus, both harbouring novel de novo missense mutations of TUBA1A. To elucidate how the various TUBA1A mutations affect the severity of the phenotype, we examined the capacity of the mutant protein to incorporate into the endogenous microtubule network in transfected COS7 cells by measuring line density using line extraction in an immunofluorescence study. The mutants responsible for severe phenotypes were found to incorporate extensively into the network. To determine how each mutant alters the microtubule stability, we examined cold-induced microtubule depolymerisation in fibroblasts. The depolymerisation of patients' fibroblasts occurred earlier than that of control fibroblasts, suggesting that microtubules bearing mutated tubulins are unstable. Both mutations are predicted to participate in lateral interactions of microtubules. Our data suggest that the TUBA1A mutations disrupting lateral interactions have pronounced dominant-negative effects on microtubule dynamics that are associated with the severe end of the lissencephaly spectrum.
    Full-text · Article · Oct 2015 · Scientific Reports
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    ABSTRACT: Objective: Recent studies have elucidated causative roles for genetic abnormalities in early-onset epileptic encephalopathies (EOEE). Accompanying characteristic features, in addition to seizures, have also been suggested to provide important clues for an early and accurate genetic diagnosis of affected patients. In this study, we investigated the underlying genetic causes in patients with EOEE associated with infantile movement disorders. Methods: We examined 11 patients with EOEE and involuntary movements (nine with West syndrome and two with nonsyndromic epileptic encephalopathy). All showed severe developmental delay, cognitive impairment, and involuntary movements such as chorea, ballism, dyskinesia or myoclonus, and hand stereotypies. We performed whole-exome sequencing of 10 patients, while the other patient underwent high-resolution melting analysis of candidate EOEE genes. Results: We identified mutations in CDKL5, SCN2A, SETD5, ALG13, and TBL1XR1 in seven patients with West syndrome, and in SCN1A and GRIN1 in the two patients with unclassified epileptic encephalopathy. All mutations were validated as de novo events. The genetic cause was undetermined in the remaining two patients. Conclusions: We found pathogenic mutations in seven genes, in nine of 11 patients with EOEE and involuntary movements. Although the results of our study are preliminary because of the small number of patients, they nevertheless suggest that specific accompanying phenotypes such as hyperkinetic movements or hand stereotypies could be important in narrowing the disease spectrum and identifying causative genetic abnormalities.
    No preview · Article · Oct 2015 · Brain & development
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    ABSTRACT: The voltage-gated Kv2.1 potassium channel encoded by KCNB1 produces the major delayed rectifier potassium current in pyramidal neurons. Recently, de novo heterozygous missense KCNB1 mutations have been identified in three patients with epileptic encephalopathy and a patient with neurodevelopmental disorder. However, the frequency of KCNB1 mutations in infantile epileptic patients and their effects on neuronal activity are yet unknown. We searched whole exome sequencing data of a total of 437 patients with infantile epilepsy, and found novel de novo heterozygous missense KCNB1 mutations in two patients showing psychomotor developmental delay and severe infantile generalized seizures with high-amplitude spike-and-wave electroencephalogram discharges. The mutation located in the channel voltage sensor (p.R306C) disrupted sensitivity and cooperativity of the sensor, while the mutation in the channel pore domain (p.G401R) selectively abolished endogenous Kv2 currents in transfected pyramidal neurons, indicating a dominant-negative effect. Both mutants inhibited repetitive neuronal firing through preventing production of deep interspike voltages. Thus KCNB1 mutations can be a rare genetic cause of infantile epilepsy, and insufficient firing of pyramidal neurons would disturb both development and stability of neuronal circuits, leading to the disease phenotypes.
    Full-text · Article · Oct 2015 · Scientific Reports
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    Full-text · Dataset · Aug 2015
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    Full-text · Dataset · Aug 2015
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    Full-text · Dataset · Aug 2015
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    ABSTRACT: KCNT1 mutations have been found in epilepsy of infancy with migrating focal seizures (EIMFS; also known as migrating partial seizures in infancy), autosomal dominant nocturnal frontal lobe epilepsy, and other types of early onset epileptic encephalopathies (EOEEs). We performed KCNT1-targeted next-generation sequencing (207 samples) and/or whole-exome sequencing (229 samples) in a total of 362 patients with Ohtahara syndrome, West syndrome, EIMFS, or unclassified EOEEs. We identified nine heterozygous KCNT1 mutations in 11 patients: nine of 18 EIMFS cases (50%) in whom migrating foci were observed, one of 180 West syndrome cases (0.56%), and one of 66 unclassified EOEE cases (1.52%). KCNT1 mutations occurred de novo in 10 patients, and one was transmitted from the patient's mother who carried a somatic mosaic mutation. The mutations accumulated in transmembrane segment 5 (2/9, 22.2%) and regulators of K(+) conductance domains (7/9, 77.8%). Five of nine mutations were recurrent. Onset ages ranged from the neonatal period (<1 month) in five patients (5/11, 45.5%) to 1-4 months in six patients (6/11, 54.5%). A generalized attenuation of background activity on electroencephalography was seen in six patients (6/11, 54.5%). Our study demonstrates that the phenotypic spectrum of de novo KCNT1 mutations is largely restricted to EIMFS. Wiley Periodicals, Inc. © 2015 International League Against Epilepsy.
    Full-text · Article · Jul 2015 · Epilepsia
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    ABSTRACT: The older of two siblings began to have spasms and partial seizures at 1 month of age. Head magnetic resonance imaging showed an abnormal area in the left temporo-parieto-occipital region. Interictal electroencephalogram (EEG) showed a suppression-burst pattern. Adrenocorticotropic hormone stopped the spasms, but the seizures continued. Clonazepam, carbamazepine, zonisamide, and clobazam were ineffective. She underwent focal resection at age 8 months. Postoperatively, the seizures disappeared. Histopathologically, the lesion appeared to be focal cortical dysplasia type IIa. The younger sibling had spasms from birth. Head magnetic resonance imaging showed left hemi-megalencephaly. Interictal EEG showed a suppression-burst pattern. Phenobarbital, valproic acid, and zonisamide were ineffective. He underwent hemispherotomy at age 2 months and became seizure free. The histopathological features were consistent with those of hemi-megalencephaly. The siblings' EEG and clinical courses had some similarities. These siblings' conditions may have the same genetic background. © 2015 Japan Pediatric Society.
    No preview · Article · Jun 2015 · Pediatrics International
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    Mitsuhiro Kato
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    ABSTRACT: Neuronal migration disorders are human (or animal) diseases that result from a disruption in the normal movement of neurons from their original birth site to their final destination during early development. As a consequence, the neurons remain somewhere along their migratory route, their location depending on the pathological mechanism and its severity. The neurons form characteristic abnormalities, which are morphologically classified into several types, such as lissencephaly, heterotopia, and cobblestone dysplasia. Polymicrogyria is classified as a group of malformations that appear secondary to post-migration development; however, recent findings of the underlying molecular mechanisms reveal overlapping processes in the neuronal migration and post-migration development stages. Mutations of many genes are involved in neuronal migration disorders, such as LIS1 and DCX in classical lissencephaly spectrum, TUBA1A in microlissencephaly with agenesis of the corpus callosum, and RELN and VLDLR in lissencephaly with cerebellar hypoplasia. ARX is of particular interest from basic and clinical perspectives because it is critically involved in tangential migration of GABAergic interneurons in the forebrain and its mutations cause a variety of phenotypes ranging from hydranencephaly or lissencephaly to early-onset epileptic encephalopathies, including Ohtahara syndrome and infantile spasms or intellectual disability with no brain malformations. The recent advances in gene and genome analysis technologies will enable the genetic basis of neuronal migration disorders to be unraveled, which, in turn, will facilitate genotype-phenotype correlations to be determined.
    Preview · Article · May 2015 · Frontiers in Neuroscience
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    ABSTRACT: 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. We collected a total of 24 blood-brain paired samples with FCD, including 13 individuals with FCD Type IIb, five with Type IIa, and six with Type I. We performed whole exome sequencing using paired samples from nine 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 PCR. The effect of MTOR mutations on mTOR kinase signaling was evaluated by immunohistochemistry and western blot analyses of brain samples and by in vitro transfection experiments. We identified four lesion-specific somatic MTOR mutations in six of 13 (46%) individuals with FCD Type IIb showing mutant allele rates of 1.11-9.31%. Functional analyses showed that phosphorylation of ribosomal protein S6 in FCD Type IIb brain tissues with MTOR mutations was clearly elevated compared with 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. We found low-prevalence somatic mutations in MTOR in FCD Type IIb, indicating that activating somatic mutations in MTOR cause FCD Type IIb. This article is protected by copyright. All rights reserved. © 2015 American Neurological Association.
    No preview · Article · May 2015 · Annals of Neurology
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    ABSTRACT: Objective Recently, de novo mutations in GRIN1 have been identified in patients with nonsyndromic intellectual disability and epileptic encephalopathy. Whole exome sequencing (WES) analysis of patients with genetically unsolved epileptic encephalopathies identified four patients with GRIN1 mutations, allowing us to investigate the phenotypic spectrum of GRIN1 mutations.Methods Eighty-eight patients with unclassified early onset epileptic encephalopathies (EOEEs) with an age of onset <1 year were analyzed by WES. The effect of mutations on N-methyl-d-aspartate (NMDA) receptors was examined by mapping altered amino acids onto three-dimensional models.ResultsWe identified four de novo missense GRIN1 mutations in 4 of 88 patients with unclassified EOEEs. In these four patients, initial symptoms appeared within 3 months of birth, including hyperkinetic movements in two patients (2/4, 50%), and seizures in two patients (2/4, 50%). Involuntary movements, severe developmental delay, and intellectual disability were recognized in all four patients. In addition, abnormal eye movements resembling oculogyric crises and stereotypic hand movements were observed in two and three patients, respectively. All the four patients exhibited only nonspecific focal and diffuse epileptiform abnormality, and never showed suppression-burst or hypsarrhythmia during infancy. A de novo mosaic mutation (c.1923G>A) with a mutant allele frequency of 16% (in DNA of blood leukocytes) was detected in one patient. Three mutations were located in the transmembrane domain (3/4, 75%), and one in the extracellular loop near transmembrane helix 1. All the mutations were predicted to impair the function of the NMDA receptor.SignificanceClinical features of de novo GRIN1 mutations include infantile involuntary movements, seizures, and hand stereotypies, suggesting that GRIN1 mutations cause encephalopathy resulting in seizures and movement disorders.
    No preview · Article · Apr 2015 · Epilepsia
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    ABSTRACT: We describe a novel mutation in DCX in a family in which a proband boy had classical lissencephaly and his mother had extremely mild subcortical band heterotopia. No factors that would make the mother's symptoms milder, such as somatic mosaicism or skewed X chromosome inactivation, were observed. From this family, we conclude that a DCX mutation causes a pleiotropic phenotype in the female even if X chromosome inactivation pattern is not skewed, and the novel missense mutation in DCX produced relatively mild dysfunction of the doublecortin protein. © 2015 Japan Pediatric Society.
    No preview · Article · Apr 2015 · Pediatrics International
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    ABSTRACT: Whole-exome sequencing (WES) is a useful method to identify disease-causing mutations, however, often no candidate mutations are identified using commonly available targeted probe sets. In a recent analysis, we also could not find candidate mutations for 20.9% (9/43) of our pedigrees with congenital neurological disorder using pre-designed capture probes (SureSelect V4 or V5). One possible cause for this lack of candidates is that standard WES cannot sequence all protein-coding sequences (CDS) due to capture probe design and regions of low coverage, which account for approximately 10% of all CDS regions. In this study, we combined a selective circularization-based target enrichment method (HaloPlex) with a hybrid capture method (SureSelect V5; WES), and achieved a more complete coverage of CDS regions (~97% of all CDS). We applied this approach to 7 (SureSelect V5) out of 9 pedigrees with no candidates through standard WES analysis and identified novel pathogenic mutations in one pedigree. The application of this effective combination of targeted enrichment methodologies can be expected to aid in the identification of novel pathogenic mutations previously missed by standard WES analysis.
    Full-text · Article · Mar 2015 · Scientific Reports
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    ABSTRACT: Chromosome 1p32-p31 deletion syndrome involving the Nuclear factor I/A (NFIA) gene is characterized by corpus callosum hypoplasia or defects and urinary tract defects. Herein we report on a case resembling the 1p32-p31 deletion syndrome carrying a de novo truncating mutation (c.1094delC; p.Pro365Hisfs*32) in the NFIA gene, confirming that haploinsufficiency of the NFIA gene is a major determinant of this syndrome. Chromosome 1p32-p31 deletion syndrome (OMIM #613735) involving the Nuclear factor I/A (NFIA) gene is characterized by corpus callosum hypoplasia or defects, hydrocephalus or ven-tricular enlargement and urinary tract defects. 1 Only six cases of this contiguous gene-deletion syndrome have been reported in the literature. 1–5 Additionally, Lu et al. 1 reported two patients showing a similar phenotype, but with balanced translocations breakpoints in the NFIA gene. 6 These authors also demonstrated ventricular enlargement, callosal agenesis and urinary tract defects in homozygous Nfia − / − mice and heterozygous Nfia +/ − mice.
    Full-text · Article · Feb 2015

  • No preview · Article · Feb 2015 · Pediatric Neurology
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    ABSTRACT: Recent progress in genetic analysis reveals that a significant proportion of cryptogenic epileptic encephalopathies are single-gene disorders. Mutations in numerous genes for early-onset epileptic encephalopathies have been rapidly identified, including in SPTAN1, which encodes α-II spectrin. The aim of this review is to delineate SPTAN1 encephalopathy as a distinct clinical syndrome. To date, a total of seven epileptic patients with four different in-frame SPTAN1 mutations have been identified. The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability. Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition. A milder variant is characterized by generalized epilepsy with pontocerebellar atrophy. Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes. The last two spectrin repeats are required for α/β spectrin heterodimer associations and the mutations can alter heterodimer formation between the two spectrins. From these data we suggest that SPTAN1 encephalopathy is a distinct clinical syndrome owing to specific SPTAN1 mutations. It is important that this syndrome is recognized by pediatric neurologists to enable proper diagnostic work-up for patients.Journal of Human Genetics advance online publication, 29 January 2015; doi:10.1038/jhg.2015.5.
    No preview · Article · Jan 2015 · Journal of Human Genetics
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    ABSTRACT: Megalencephaly capillary malformation (MCAP) is a syndrome involving brain overgrowth, characterized by megalencephaly, capillary malformations, asymmetric growth, polymicrogyria, polydactyly, and syndactyly. Cerebellar tonsillar herniation (CTH) and ventriculomegaly are also observed in over half the patients with this syndrome. Early sudden death has been reported in MCAP, but its causes and the surgical strategies for its prevention remain unclear. Here, we report on a patient with MCAP who died suddenly at 5 months of age. He presented with progressive macrocephaly and hypotonia. MRI performed at 4 months of age showed tight posterior fossa, bilateral perisylvian polymicrogyria, enlargement of the straight sinus, and a thickened corpus callosum. However, since the patient did not exhibit capillary malformation, polydactyly, or syndactyly, a definitive diagnosis of MCAP could not be made. He died suddenly while asleep at home 1 month later. The sudden death of MCAP patients was previously attributed to CTH, convulsion, or arrhythmia. In this case, progressive cerebellar enlargement appeared to be the underlying cause. After the patient's death, using his preserved DNA, a missense mutation in the AKT3 gene was identified. Vakt murine thymoma viral oncogene homologue (AKT) is a serine-threonine kinase that functions in the mammalian target of rapamycin (mTOR) pathway and plays an important role in cell proliferation. Accurate early diagnosis, including imaging and genetic analyses, and the recognition and treatment of critical conditions are required to prevent the sudden death of patients with MCAP.
    No preview · Article · Nov 2014 · Child s Nervous System
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    ABSTRACT: Sturge-Weber syndrome (SWS) is a neurocutaneous disorder characterized by capillary malformation (port-wine stains), and choroidal and leptomeningeal vascular malformations. Previously, the recurrent somatic mutation c.548G>A (p.R183Q) in the G-α q gene (GNAQ) was identified as causative in SWS and non-syndromic port-wine stain patients using whole-genome sequencing. In this study, we investigated somatic mutations in GNAQ by next-generation sequencing. We first performed targeted amplicon sequencing of 15 blood-brain-paired samples in sporadic SWS and identified the recurrent somatic c.548G>A mutation in 80% of patients (12 of 15). The percentage of mutant alleles in brain tissues of these 12 patients ranged from 3.6 to 8.9%. We found no other somatic mutations in any of the seven GNAQ exons in the remaining three patients without c.548G>A. These findings suggest that the recurrent somatic GNAQ mutation c.548G>A is the major determinant genetic factor for SWS and imply that other mutated candidate gene(s) may exist in SWS.Journal of Human Genetics advance online publication, 6 November 2014; doi:10.1038/jhg.2014.95.
    Full-text · Article · Nov 2014 · Journal of Human Genetics
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    ABSTRACT: Kinesins are a large superfamily of molecular motors. They move along microtubule filaments and are powered by the hydrolysis of ATP. This transport system is essential for neuronal function and survival. KIF1A belongs to the kinesin 3 family and involves in the anterograde transport of synaptic vesicle precursors along axons. Several studies confirmed that KIF1A mutations cause spastic paraplegia and sensory neuropathy in an autosomal-recessive fashion. A missense mutation in the KIF1A gene (p.Thr99Met) has been reported in a patient with intellectual disability (ID), axial hypotonia and peripheral spasticity. Mild atrophy of the cerebellar vermis was found on magnetic resonance imaging. The mutation was heterozygous and de novo. We identified the second patient with the p.T99M mutation in the KIF1A gene by whole-exome sequencing. He showed severe ID, spasticity, optic atrophy, neurogenic bladder, growth failure and progressive cerebellar atrophy. The p.T99M mutation may be a common recurrent mutation. We suppose that this specific mutation of KIF1A shows a novel neurodegenerative syndrome.Journal of Human Genetics advance online publication, 25 September 2014; doi:10.1038/jhg.2014.80.
    No preview · Article · Sep 2014 · Journal of Human Genetics
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    ABSTRACT: Recently, de novo mutations in TBL1XR1 were found in two patients with autism spectrum disorders. Here, we report on a Japanese girl presenting with West syndrome, Rett syndrome-like and autistic features. Her initial development was normal until she developed a series of spasms at 5 months of age. Electroencephalogram at 7 months showed a pattern of hypsarrhythmia, which led to a diagnosis of West syndrome. Stereotypic hand movements appeared at 8 months of age, and autistic features such as deficits in communication, hyperactivity and excitability were observed later, at 4 years and 9 months. Whole exome sequencing of the patient and her parents revealed a de novo TBL1XR1 mutation [c.209 G>A (p.Gly70Asp)] occurring at an evolutionarily conserved amino acid in an F-box-like domain. Our report expands the clinical spectrum of TBL1XR1 mutations to West syndrome with Rett-like features, together with autistic features.Journal of Human Genetics advance online publication, 7 August 2014; doi:10.1038/jhg.2014.71.
    Full-text · Article · Aug 2014 · Journal of Human Genetics

Publication Stats

3k Citations
486.45 Total Impact Points

Institutions

  • 1998-2015
    • Yamagata University
      • Department of Pediatrics
      Ямагата, Yamagata, Japan
  • 2005
    • Kanagawa Children's Medical Center
      Yokohama, Kanagawa, Japan
  • 2002-2004
    • University of Chicago
      • Department of Human Genetics
      Chicago, Illinois, United States
    • Yamagata Prefectural Central Hospital
      Ямагата, Yamagata, Japan
  • 1993
    • Tottori University
      • Institute of Neurological Sciences
      Tottori, Tottori-ken, Japan