Hirotomo Saitsu

Yokohama City University, Yokohama, Kanagawa, Japan

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Publications (134)580.09 Total impact

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    ABSTRACT: Homozygous frameshift BRAT1 mutations were found in patients with lethal neonatal rigidity and multifocal seizure syndrome (MIM# 614498). Here, we report on two siblings with compound heterozygous mutations in BRAT1. They had intractable seizures from neonatal period, dysmorphic features and hypertonia. Progressive microcephaly was also observed. Initial electroencephalogram showed a suppression-burst pattern, leading to a diagnosis of Ohtahara syndrome. They both died from pneumonia at 1 year and 3 months, respectively. Whole-exome sequencing of one patient revealed a compound heterozygous BRAT1 mutations (c.176T>C (p.Leu59Pro) and c.962_963del (p.Leu321Profs*81)). We are unable to obtain DNA from another patient. The p.Leu59Pro mutation occurred at an evolutionarily conserved amino acid in a CIDE-N (N-terminal of an cell death-inducing DFF45-like effector) domain, which has a regulatory role in the DNA fragmentation pathway of apoptosis. Our results further support that mutations of BRAT1 could lead to epileptic encephalopathy.Journal of Human Genetics advance online publication, 16 October 2014; doi:10.1038/jhg.2014.91.
    Journal of human genetics. 10/2014;
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    ABSTRACT: Structural variations (SVs), including translocations, inversions, deletions and duplications, are potentially associated with Mendelian diseases and contiguous gene syndromes. Determination of SV-related breakpoints at the nucleotide level is important to reveal the genetic causes for diseases. Whole-genome sequencing (WGS) by next-generation sequencers is expected to determine structural abnormalities more directly and efficiently than conventional methods. In this study, 14 SVs (9 balanced translocations, 1 inversion and 4 microdeletions) in 9 patients were analyzed by WGS with a shallow (5 × ) to moderate read coverage (20 × ). Among 28 breakpoints (as each SV has two breakpoints), 19 SV breakpoints had been determined previously at the nucleotide level by any other methods and 9 were uncharacterized. BreakDancer and Integrative Genomics Viewer determined 20 breakpoints (16 translocation, 2 inversion and 2 deletion breakpoints), but did not detect 8 breakpoints (2 translocation and 6 deletion breakpoints). These data indicate the efficacy of WGS for the precise determination of translocation and inversion breakpoints.Journal of Human Genetics advance online publication, 9 October 2014; doi:10.1038/jhg.2014.88.
    Journal of human genetics. 10/2014;
  • Journal of human genetics. 09/2014;
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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.
    Journal of human genetics. 08/2014;
  • Clinical Genetics 07/2014; · 4.25 Impact Factor
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    ABSTRACT: Static encephalopathy of childhood with neurodegeneration in adulthood (SENDA) is an X-linked dominant neurodegenerative disorder, and is classified as a subtype of neurodegeneration with brain iron accumulation. Recently, de novo heterozygous mutations in WDR45 at Xp11.23 have been reported in patients with SENDA. We report the clinical and neuroradiological findings of a patient with SENDA with a novel c.322del mutation in WDR45. In this patient, characteristic MRI findings were useful for diagnosis. © 2014 The Authors. American Journal of Medical Genetics published by Wiley Periodicals, Inc.
    American Journal of Medical Genetics Part A 07/2014; · 2.30 Impact Factor
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    ABSTRACT: We report on a 1-year-old boy with microcephaly with a simplified gyral pattern, early-onset seizures, congenital hearing loss and a severe developmental delay. Trio-based whole-exome sequencing identified candidate compound heterozygous mutations in two genes: c.163G>T (p.Ala55Ser) and c.874G>A (p.Gly292Arg) in polynucleotide kinase 3'-phosphatase gene (PNKP), and c.195G>A (p.Met65Ile) and c.1210A>C (p.Ser404Arg) in PCDH15. PNKP and PCDH15 mutations have been reported in autosomal recessive microcephaly with early-onset seizures and developmental delay syndrome, and Usher syndrome type 1F, respectively. Our patient showed neurological features similar to reported cases of both syndromes that could be explained by the observed mutations in both PNKP and PCDH15, which therefore appear to be pathogenic in this case.Journal of Human Genetics advance online publication, 26 June 2014; doi:10.1038/jhg.2014.51.
    Journal of human genetics. 06/2014;
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    ABSTRACT: Hypomyelinating leukoencephalopathy is a heterogeneous disorder caused by mutations in several-different genes. Clinical entity of hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) is one of them.
    Brain & development. 06/2014;
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    ABSTRACT: We report on a girl with absent nails, short/absent distal phalanges of the second to fifth fingers and toes, short thumbs, absent halluces, and carpo-tarsal coalition who also had genitourinary malformations. Trio-based whole exome sequencing identified a novel de novo mutation (c.1102A>T, p.Ile368Phe) in the HOXA13 gene. Heterozygous HOXA13 mutations have been previously reported in hand-foot-genital syndrome and Guttmacher syndrome, which are variably associated with small nails, short distal and middle phalanges, short thumbs and halluces, but not absent nails. Considering the molecular data, the phenotype in the present patient was defined as the severe end of hand-foot-genital and Guttmacher syndrome spectrum. Our observation expands the clinical spectrum caused by heterozygous HOXA13 mutations and reinforces the difficulty of differential diagnosis on clinical grounds for the disorders with short distal phalanges, short thumbs, and short halluces. © 2014 Wiley Periodicals, Inc.
    American Journal of Medical Genetics Part A 06/2014; · 2.30 Impact Factor
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    ABSTRACT: Iris hypoplasia (IH) is rare autosomal dominant disorder characterized by a poorly developed iris stroma and malformations of the eyes and umbilicus. This disorder is caused by mutation of the paired-like homeodomain 2 (PITX2) gene. Here, we describe a novel PITX2 mutation (c.205C4T) in an IH family presenting with very mild eye features but with tooth agenesis as the most obvious clinical feature. Human Genome Variation (2014) 1, 14005; doi:10.1038/hgv.2014.5; published online 31 July 2014 Mutations in the PITX2 (paired-like homeodomain 2) gene are associated with three allelic disorders: iris hypoplasia (IH), iridogoniodysgenesis syndrome (IGDS; OMIM 137600) and Axenfeld-Rieger syndrome (ARS; OMIM 180500). 1–3 Various dental abnormalities including tooth agenesis are also found in IH, IGDS and ARS, which are characterized by abnormal development of the anterior segment of the eyes and umbilicus anomalies. 1–4 IH shows the mildest phenotype among the three, characterized by only iris hypoplasia and glaucoma. 1,5 IGDS presents with goniodysgenesis in addition to iris hypoplasia and glaucoma. 2
    Human Genome Variation. 06/2014; 1.
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    ABSTRACT: Recessive mutations in genes of the glycosylphosphatidylinositol (GPI)-anchor synthesis pathway have been demonstrated as causative of GPI deficiency disorders associated with intellectual disability, seizures, and diverse congenital anomalies. We performed whole exome sequencing in a patient with progressive encephalopathies and multiple dysmorphism with hypophosphatasia and identified novel compound heterozygous mutations, c.250G>T (p. Glu84*) and c.1342C>T (p. Arg488Trp), in PIGT encoding a subunit of the GPI transamidase complex. The surface expression of GPI-anchored proteins (GPI-APs) on patient granulocytes was lower than that of healthy controls. Transfection of the Arg488Trp mutant PIGT construct, but not the Glu84* mutant, into PIGT-deficient cells partially restored the expression of GPI-APs DAF and CD59. These results indicate that PIGT mutations caused neurological impairment and multiple congenital anomalies in this patient.
    Neurogenetics 06/2014; · 3.58 Impact Factor
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    ABSTRACT: We performed whole-exome sequencing analysis of patients with genetically unsolved hypomyelinating leukoencephalopathies, identifying 8 patients with TUBB4A mutations and allowing the phenotypic spectrum of TUBB4A mutations to be investigated.METHODS: Fourteen patients with hypomyelinating leukoencephalopathies, 7 clinically diagnosed with hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC), and 7 with unclassified hypomyelinating leukoencephalopathy, were analyzed by whole-exome sequencing. The effect of the mutations on microtubule assembly was examined by mapping altered amino acids onto 3-dimensional models of the αβ-tubulin heterodimer.RESULTS: Six heterozygous missense mutations in TUBB4A, 5 of which are novel, were identified in 8 patients (6/7 patients with H-ABC [the remaining patient is an atypical case] and 2/7 patients with unclassified hypomyelinating leukoencephalopathy). In 4 cases with parental samples available, the mutations occurred de novo. Analysis of 3-dimensional models revealed that the p.Glu410Lys mutation, identified in patients with unclassified hypomyelinating leukoencephalopathy, directly impairs motor protein and/or microtubule-associated protein interactions with microtubules, whereas the other mutations affect longitudinal interactions for maintaining αβ-tubulin structure, suggesting different mechanisms in tubulin function impairment. In patients with the p.Glu410Lys mutation, basal ganglia atrophy was unobserved or minimal although extrapyramidal features were detected, suggesting its functional impairment.CONCLUSIONS: TUBB4A mutations cause typical H-ABC. Furthermore, TUBB4A mutations associate cases of unclassified hypomyelinating leukoencephalopathies with morphologically retained but functionally impaired basal ganglia, suggesting that TUBB4A-related hypomyelinating leukoencephalopathies encompass a broader clinical spectrum than previously expected. Extrapyramidal findings may be a key for consideration of TUBB4A mutations in hypomyelinating leukoencephalopathies.
    Neurology 05/2014; · 8.25 Impact Factor
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    ABSTRACT: Objective De novo SCN8A mutations have been reported in patients with epileptic encephalopathy. Herein we report seven patients with de novo heterozygous SCN8A mutations, which were found in our comprehensive genetic analysis (target capture or whole-exome sequencing) for early onset epileptic encephalopathies (EOEEs).MethodsA total of 163 patients with EOEEs without mutations in known genes, including 6 with malignant migrating partial seizures in infancy (MMPSI), and 60 with unclassified EOEEs, were analyzed by target capture (28 samples) or whole-exome sequencing (135 samples).ResultsWe identified de novo SCN8A mutations in 7 patients: 6 of 60 unclassified EOEEs (10.0%), and one of 6 MMPSI cases (16.7%). The mutations were scattered through the entire gene: four mutations were located in linker regions, two in the fourth transmembrane segments, and one in the C-terminal domain. The type of the initial seizures was variable including generalized tonic–clonic, atypical absence, partial, apneic attack, febrile convulsion, and loss of tone and consciousness. Onset of seizures was during the neonatal period in two patients, and between 3 and 7 months of age in five patients. Brain magnetic resonance imaging (MRI) showed cerebellar and cerebral atrophy in one and six patients, respectively. All patients with SCN8A missense mutations showed initially uncontrollable seizures by any drugs, but eventually one was seizure-free and three were controlled at the last examination. All patients showed developmental delay or regression in infancy, resulting in severe intellectual disability.SignificanceOur data reveal that SCN8A mutations can cause variable phenotypes, most of which can be diagnosed as unclassified EOEEs, and rarely as MMPSI. Together with previous reports, our study further indicates that genetic testing of SCN8A should be considered in children with unclassified severe epilepsy.A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.
    Epilepsia 05/2014; · 3.96 Impact Factor
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    ABSTRACT: We report a female patient who presented with intractable epileptic seizures, profound developmental delay since early infancy, and hyperkinetic movements with hand stereotypies. The patient initially developed focal seizures with multiple foci at 3 months of age. Thereafter, the seizures evolved to frequent episodes of hyperthermia-induced status epilepticus. A novel de novo SCN1A mutation was identified by whole-exome sequence analysis. This case demonstrates that SCN1A mutations may cause movement disorders as an atypical phenotype and the case history of this patient may expand our understanding of the clinical spectrum of SCN1A-associated epileptic encephalopathy. [Published with video sequences].
    Epileptic disorders: international epilepsy journal with videotape 04/2014; · 1.17 Impact Factor
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    ABSTRACT: When an expected mutation in a particular disease-causing gene is not identified in a suspected carrier, it is usually assumed to be due to germline mosaicism. We report here very-low-grade somatic mosaicism in ACTA1 in an unaffected mother of two siblings affected with a neonatal form of nemaline myopathy. The mosaicism was detected by deep resequencing using a next-generation sequencer. We identified a novel heterozygous mutation in ACTA1, c.448A>G (p.Thr150Ala), in the affected siblings. Three-dimensional structural modeling suggested that this mutation may affect polymerization and/or actin's interactions with other proteins. In this family, we expected autosomal dominant inheritance with either parent demonstrating germline or somatic mosaicism. Sanger sequencing identified no mutation. However, further deep resequencing of this mutation on a next-generation sequencer identified very-low-grade somatic mosaicism in the mother: 0.4%, 1.1%, and 8.3% in the saliva, blood leukocytes, and nails, respectively. Our study demonstrates the possibility of very-low-grade somatic mosaicism in suspected carriers, rather than germline mosaicism.
    Neuromuscular disorders : NMD. 04/2014;
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    ABSTRACT: Ohtahara syndrome is a devastating early infantile epileptic encephalopathy caused by mutations in different genes. We describe a patient with Ohtahara syndrome who presented on the first day of life with refractory tonic seizures and a suppression-burst pattern on EEG. The patient developed severe microcephaly, and never achieved any developmental milestones. He died at the age of 5 years. A de novo missense mutation (c. 4007C>A, p.S1336Y) in SCN2A was found. Interestingly, the father has another son with Ohtahara syndrome from a different mother. The half brother carries the same SCN2A mutation, strongly suggesting paternal gonadal mosaicism of the mutation. The broad clinical spectrum of SCN2A mutations now includes Ohtahara syndrome. This is the first report of familial Ohtahara syndrome due to a germline mosaic SCN2A mutation. Somatic mosaicism, including germline, has been described in several epileptic encephalopathies such as Dravet syndrome, KCNQ2 neonatal epileptic encephalopathy, SCN8A epileptic encephalopathy and STXBP1 related Ohtahara syndrome. Mosaicism should be considered as one of the important inheritance patterns when counseling parents with a child with these devastating diseases.
    European journal of paediatric neurology: EJPN: official journal of the European Paediatric Neurology Society 04/2014; · 2.01 Impact Factor
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    ABSTRACT: To investigate the clinical spectrum caused by mutations in PIGA at Xp22.2, which is involved in the biosynthesis of the glycosylphosphatidylinositol (GPI) anchor, among patients with early-onset epileptic encephalopathies (EOEEs). Whole-exome sequencing was performed as a comprehensive genetic analysis for a cohort of 172 patients with EOEEs including early myoclonic encephalopathy, Ohtahara syndrome, and West syndrome, and PIGA mutations were carefully investigated. We identified 4 PIGA mutations in probands showing early myoclonic encephalopathy, West syndrome, or unclassified EOEE. Flow cytometry of blood granulocytes from patients demonstrated reduced expression of GPI-anchored proteins. Expression of GPI-anchored proteins in PIGA-deficient JY5 cells was only partially or hardly restored by transient expression of PIGA mutants with a weak TATA box promoter, indicating a variable loss of PIGA activity. The phenotypic consequences of PIGA mutations can be classified into 2 types, severe and less severe, which correlate with the degree of PIGA activity reduction caused by the mutations. Severe forms involved myoclonus and asymmetrical suppression bursts on EEG, multiple anomalies with a dysmorphic face, and delayed myelination with restricted diffusion patterns in specific areas. The less severe form presented with intellectual disability and treatable seizures without facial dysmorphism. Our study confirmed that PIGA mutations are one genetic cause of EOEE, suggesting that GPI-anchor deficiencies may be an underlying cause of EOEE.
    Neurology 04/2014; · 8.25 Impact Factor
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    ABSTRACT: The conserved oligomeric Golgi (COG) complex is involved in intra-Golgi retrograde trafficking, and mutations in six of its eight subunits have been reported in congenital disorders of glycosylation (CDG). Here we report a patient showing severe acquired microcephaly, psychomotor retardation, seizures, liver dysfunction, hypocupremia, and hypoceruloplasminemia. Analysis of his serum glycoproteins revealed defects in both sialylation and galactosylation of glycan termini. Trio-based whole-exome sequencing identified two heterozygous mutations in COG2: a de novo frameshift mutation [c.701dup (p.Tyr234*)] and a missense mutation [c.1900T>G (p.Trp634Gly)]. Sequencing of cloned reverse-transcription polymerase chain reaction products revealed that both mutations were located on separate alleles, as expected, and that the mutant transcript harboring the frameshift mutation underwent degradation. The c.1900T>G (p.Trp634Gly) mutation is located in a domain highly conserved among vertebrates and was absent from both the public database and our control exomes. Protein expression of COG2, along with COG3 and COG4, was decreased in fibroblasts from the patient. Our data strongly suggest that these compound heterozygous mutations in COG2 are causative of CDG.
    Clinical Genetics 04/2014; · 4.25 Impact Factor
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    ABSTRACT: A 31-year-old woman presented with severe dystonia-parkinsonism. She had nonprogressive psychomotor retardation and cognitive dysfunction from childhood without evidence of dystonia or parkinsonism. At age 30, she then developed severe dystonia and gait disturbance. There was neither dystonia nor parkinsonism before age 30. MRI revealed cerebral atrophy and iron accumulation in the globus pallidus and substantia nigra (figure 1, A-D). The characteristic MRI findings were hyperintensity of the substantia nigra with a central band of hypointensity in T1-weighted axial slices (figure 1, B). Beta-propeller protein-associated neurodegeneration (BPAN) was diagnosed based on MRI findings and identification of a novel heterozygous mutation in the WDR45 gene (NM_007075.3: c.519+1_519+3del) (figure 2). This is a neurodegeneration involving brain iron accumulation (NBIA) characterized by psychomotor retardation from childhood and dystonia-parkinsonism in midadulthood.(1,2) Although we could not analyze the father's gene since he had died, the mother had no mutation in the WDR45 gene (figure 2). Thus, it might be a de novo mutation in the WDR45 gene, as reported previously.(1,2.)
    Neurology: Clinical Practice (Print) 04/2014; 4(2):175-177.
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    ABSTRACT: Rett syndrome (RTT) is a neurodevelopmental disorder mostly caused by MECP2 mutations. We identified a de novo WDR45 mutation, which caused a subtype of neurodegeneration with brain iron accumulation, in a patient showing clinically typical RTT. The mutation (c.830+1G>A) led to aberrant splicing in lymphoblastoid cells. Sequential brain magnetic resonance imaging demonstrated that iron deposition in the globus pallidus and the substantia nigra was observed as early as at 11 years of age. Because the patient showed four of the main RTT diagnostic criteria, WDR45 should be investigated in patients with RTT without MECP2 mutations.Journal of Human Genetics advance online publication, 13 March 2014; doi:10.1038/jhg.2014.18.
    Journal of Human Genetics 03/2014; · 2.37 Impact Factor

Publication Stats

1k Citations
580.09 Total Impact Points

Institutions

  • 2008–2014
    • Yokohama City University
      Yokohama, Kanagawa, Japan
  • 2013
    • Tohoku University
      • Department of Pediatrics
      Sendai, Kagoshima, Japan
    • Tokyo Medical University
      • Division of Pediatrics
      Edo, Tōkyō, Japan
  • 2012–2013
    • Shinshu University
      • Department of Medical Genetics
      Shonai, Nagano, Japan
    • Kitasato University
      • Medical Department
      Edo, Tōkyō, Japan
    • Ljubljana University Medical Centre
      • Institute of Medical Genetics
      Lubliano, Ljubljana, Slovenia
  • 2011–2013
    • Yamagata University
      • Department of Pediatrics
      Ямагата, Yamagata, Japan
  • 2011–2012
    • Kanagawa Children's Medical Center
      Yokohama, Kanagawa, Japan
  • 2008–2011
    • National Center for Child Health and Development
      Edo, Tōkyō, Japan
  • 2005–2010
    • Kyoto University
      • • Congenital Anomaly Research Center
      • • Graduate School of Medicine / Faculty of Medicine
      Kyoto, Kyoto-fu, Japan