Publications by authors named "Takeshi Mizuguchi"

134 Publications

Duplications in the G3 domain or switch II region in HRAS identified in patients with Costello syndrome.

Hum Mutat 2021 Oct 7. Epub 2021 Oct 7.

Department of Medical Genetics, Tohoku University School of Medicine, Sendai, Japan.

Costello syndrome (CS) is an autosomal-dominant disorder characterized by distinctive facial features, hypertrophic cardiomyopathy, skeletal abnormalities, intellectual disability, and predisposition to cancers. Germline variants in HRAS have been identified in patients with CS. Intragenic HRAS duplications have been reported in three patients with a milder phenotype of CS. In this study, we identified two known HRAS variants, p.(Glu63_Asp69dup), p.(Glu62_Arg68dup), and one novel HRAS variant, p.(Ile55_Asp57dup), in patients with CS, including a patient with craniosynostosis. These intragenic duplications are located in the G3 domain and the switch II region. Cells expressing cDNA with these three intragenic duplications showed an increase in ELK-1 transactivation. Injection of wild-type or mutant HRAS mRNAs with intragenic duplications in zebrafish embryos showed significant elongation of the yolk at 11 h postfertilization, which was improved by MEK inhibitor treatment, and a variety of developmental abnormalities at 3 days post fertilization was observed. These results indicate that small in-frame duplications affecting the G3 domain and switch II region of HRAS increase the activation of the ERK pathway, resulting in developmental abnormalities in zebrafish or patients with CS.
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http://dx.doi.org/10.1002/humu.24287DOI Listing
October 2021

Pathogenic variants in the survival of motor neurons complex gene GEMIN5 cause cerebellar atrophy.

Clin Genet 2021 Sep 27. Epub 2021 Sep 27.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.

Cerebellar ataxia is a genetically heterogeneous disorder. GEMIN5 encoding an RNA-binding protein of the survival of motor neuron complex, is essential for small nuclear ribonucleoprotein biogenesis, and it was recently reported that biallelic loss-of-function variants cause neurodevelopmental delay, hypotonia, and cerebellar ataxia. Here, whole-exome analysis revealed compound heterozygous GEMIN5 variants in two individuals from our cohort of 162 patients with cerebellar atrophy/hypoplasia. Three novel truncating variants and one previously reported missense variant were identified: c.2196dupA, p.(Arg733Thrfs*6) and c.1831G > A, p.(Val611Met) in individual 1, and c.3913delG, p.(Ala1305Leufs*14) and c.4496dupA, p.(Tyr1499*) in individual 2. Western blotting analysis using lymphoblastoid cell lines derived from both affected individuals showed significantly reduced levels of GEMIN5 protein. Zebrafish model for null variants p.(Arg733Thrfs*6) and p.(Ala1305Leufs*14) exhibited complete lethality at 2 weeks and recapitulated a distinct dysplastic phenotype. The phenotypes of affected individuals and the zebrafish mutant models strongly suggest that biallelic loss-of-function variants in GEMIN5 cause cerebellar atrophy/hypoplasia.
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http://dx.doi.org/10.1111/cge.14066DOI Listing
September 2021

Biallelic null variants in ZNF142 cause global developmental delay with familial epilepsy and dysmorphic features.

J Hum Genet 2021 Sep 17. Epub 2021 Sep 17.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.

Biallelic variants in ZNF142 at 2q35, which encodes zinc-finger protein 142, cause neurodevelopmental disorder with seizures or dystonia. We identified compound heterozygous null variants in ZNF142, NM_001105537.4:c.[1252C>T];[1274-2A>G],p.[Arg418*];[Glu426*], in Malaysian siblings suffering from global developmental delay with epilepsy and dysmorphism. cDNA analysis showed the marked reduction of ZNF142 transcript level through nonsense-mediated mRNA decay by these novel biallelic variants. The affected siblings present with global developmental delay and epilepsy in common, which were previously described, as well as dysmorphism, which was not recognized. It is important to collect patients with ZNF142 abnormality to define its phenotypic spectrum.
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http://dx.doi.org/10.1038/s10038-021-00978-yDOI Listing
September 2021

Myoclonic Epilepsy with Ragged-red Fibers with Intranuclear Inclusions.

Intern Med 2021 Aug 24. Epub 2021 Aug 24.

Department of Neurology, Tokyo Metropolitan Neurological Hospital (TMNH), Japan.

We herein report a case of myoclonic epilepsy with ragged-red fibers (MERRF) harboring a novel variant in mitochondrial cysteine transfer RNA (MT-TC). A 68-year-old woman presented with progressive myoclonic epilepsy with optic atrophy and peripheral neuropathy. A skin biopsy revealed p62-positive intranuclear inclusions. No mutations were found in the causative genes for diseases known to be related to intranuclear inclusions; however, a novel variant in MT-TC was found. The association between intranuclear inclusions and this newly identified MERRF-associated variant is unclear; however, the rare complication of intranuclear inclusions in a patient with typical MERRF symptoms should be noted for future studies.
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http://dx.doi.org/10.2169/internalmedicine.7767-21DOI Listing
August 2021

Intellectual disability and microcephaly associated with a novel CHAMP1 mutation.

Hum Genome Var 2021 Aug 17;8(1):34. Epub 2021 Aug 17.

Department of Pediatrics, Jichi Medical University, Tochigi, Japan.

Mutations in a number of genes related to chromosomal segregation reportedly cause developmental disorders, e.g., chromosome alignment-maintaining phosphoprotein 1 (CHAMP1). We report on an 8-year-old Japanese girl who presented with a developmental disorder and microcephaly and carries a novel nonsense mutation in CHAMP1. Therefore, CHAMP1 mutation should be considered as a differential diagnosis of global developmental delay and microcephaly.
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http://dx.doi.org/10.1038/s41439-021-00165-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8371100PMC
August 2021

De novo ARF3 variants cause neurodevelopmental disorder with brain abnormality.

Hum Mol Genet 2021 Aug 4. Epub 2021 Aug 4.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, 236-0004, Japan.

An optimal Golgi transport system is important for mammalian cells. The adenosine diphosphate (ADP) ribosylation factors (ARF) are key proteins for regulating cargo sorting at the Golgi network. In this family, ARF3 mainly works at the trans-Golgi network (TGN), and no ARF3-related phenotypes have yet been described in humans. We here report the clinical and genetic evaluations of two unrelated children with de novo pathogenic variants in the ARF3 gene: c.200A > T (p.Asp67Val) and c.296G > T (p.Arg99Leu). Although the affected individuals presented commonly with developmental delay, epilepsy, and brain abnormalities, there were differences in severity, clinical course, and brain lesions. In vitro subcellular localization assays revealed that the p.Arg99Leu mutant localized to Golgi apparatus, similar to the wild-type, whereas the p.Asp67Val mutant tended to show a disperse cytosolic pattern together with abnormally dispersed Golgi localization, similar to that observed in a known dominant negative variant (p.Thr31Asn). Pull-down assays revealed that the p.Asp67Val had a loss-of-function effect and the p.Arg99Leu variant had increased binding of the adaptor protein, Golgi-localized, γ-adaptin ear-containing, ARF-binding protein 1 (GGA1), supporting the gain of function. Furthermore, in vivo studies revealed that p.Asp67Val transfection led to lethality in flies. In contrast, flies expressing p.Arg99Leu had abnormal rough eye, as observed in the gain-of-function variant p.Gln71Leu. These data indicate that two ARF3 variants, the possibly loss-of-function p.Asp67Val and the gain-of-function p.Arg99Leu, both impair the Golgi transport system. Therefore, it may not be unreasonable that they showed different clinical features like diffuse brain atrophy (p.Asp67Val) and cerebellar hypoplasia (p.Arg99Leu).
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http://dx.doi.org/10.1093/hmg/ddab224DOI Listing
August 2021

Gait disturbance in a patient with de novo 1.0-kb SOX2 microdeletion.

Brain Dev 2021 Jul 28. Epub 2021 Jul 28.

Division of Child Neurology, Department of Brain and Neurosciences, Faculty of Medicine, Tottori University, Yonago, Japan.

Background: Sex-determining region Y-box 2 (SOX2) plays an important role in the early embryogenesis of the eye, forebrain, and hypothalamic-pituitary axis. Anophthalmia, microphthalmia, and hormonal abnormalities are commonly observed in patients with SOX2-related disorders. Although gait disturbance, particularly ataxic gait, has recently been observed in several cases, detailed data regarding the clinical course of gait disturbance in SOX2-related disorders are limited.

Case Report: A 9-year-old Japanese boy presented with focal dyskinesia only during walking and running after he started walking at the age of 3 years. He also exhibited intellectual disability and mild dysmorphic features, including microcephaly, micropenis, and short stature associated with hormonal abnormalities. Gait disturbance with involuntary extremity movements only during walking and running was indicative of choreoathetosis and dystonia. Genetic analysis detected a de novo heterozygous 1.0-kb deletion including SOX2 at 3q26.32, as described in a previous technical paper.

Conclusions: SOX2-related disorders should be considered in patients with some anomalies having a differential diagnosis of dyskinesia. Focal dyskinesia only during walking and running may be a characteristic feature of SOX2-related disorders.
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http://dx.doi.org/10.1016/j.braindev.2021.07.007DOI Listing
July 2021

Novel CLTC variants cause new brain and kidney phenotypes.

J Hum Genet 2021 Jul 7. Epub 2021 Jul 7.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Kanagawa, Japan.

Heterozygous variants in CLTC, which encode the clathrin heavy chain protein, cause neurodevelopmental delay of varying severity, and often accompanied by dysmorphic features, seizures, hypotonia, and ataxia. To date, 28 affected individuals with CLTC variants have been reported, although their phenotypes have not been fully elucidated. Here, we report three novel de novo CLTC (NM_001288653.1) variants in three individuals with previously unreported clinical symptoms: c.3662_3664del:p.(Leu1221del) in individual 1, c.2878T>C:p.(Trp960Arg) in individual 2, and c.2430+1G>T:p.(Glu769_Lys810del) in individual 3. Consistent with previous reports, individuals with missense or small in-frame variants were more severely affected. Unreported symptoms included a brain defect (cystic lesions along the lateral ventricles of the brain in individuals 1 and 3), kidney findings (high-echogenic kidneys in individual 1 and agenesis of the left kidney and right vesicoureteral reflux in individual 3), respiratory abnormality (recurrent pneumonia in individual 1), and abnormal hematological findings (anemia in individual 1 and pancytopenia in individual 3). Of note, individual 1 even exhibited prenatal abnormality (fetal growth restriction, cystic brain lesions, high-echogenic kidneys, and a heart defect), suggesting that CLTC variants should be considered when abnormal prenatal findings in multiple organs are detected.
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http://dx.doi.org/10.1038/s10038-021-00957-3DOI Listing
July 2021

Head titubation and irritability as early symptoms of Joubert syndrome with a homozygous NPHP1 variant.

Brain Dev 2021 Sep 2;43(8):863-866. Epub 2021 Jun 2.

Department of Pediatric Neurology, Miyagi Children's Hospital, Japan.

Background: Joubert syndrome is an autosomal recessive or X-linked genetic disease with a cerebellar vermis defect or hypoplasia, hypotonia, ocular dyskinesia, and mental retardation. In neonates, respiratory problems such as apnea and tachypnea are notable.

Case Report: We report a patient Joubert syndrome with a homozygous NPHP1 variant, who had head titubation with irritability, including exaggerated jitteriness and a marked Morrow reflex appeared soon after birth without neonatal respiratory problems. These symptoms decreased gradually and disappeared until 1 year.

Conclusion: Irritability with head titubation may be an early clinical clue for the clinician to suspect Joubert syndrome.
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http://dx.doi.org/10.1016/j.braindev.2021.04.011DOI Listing
September 2021

Missense and truncating variants in CHD5 in a dominant neurodevelopmental disorder with intellectual disability, behavioral disturbances, and epilepsy.

Hum Genet 2021 Jul 4;140(7):1109-1120. Epub 2021 May 4.

CHU Sainte-Justine Research Center, Montreal, QC, H3T 1C5, Canada.

Located in the critical 1p36 microdeletion region, the chromodomain helicase DNA-binding protein 5 (CHD5) gene encodes a subunit of the nucleosome remodeling and deacetylation (NuRD) complex required for neuronal development. Pathogenic variants in six of nine chromodomain (CHD) genes cause autosomal dominant neurodevelopmental disorders, while CHD5-related disorders are still unknown. Thanks to GeneMatcher and international collaborations, we assembled a cohort of 16 unrelated individuals harboring heterozygous CHD5 variants, all identified by exome sequencing. Twelve patients had de novo CHD5 variants, including ten missense and two splice site variants. Three familial cases had nonsense or missense variants segregating with speech delay, learning disabilities, and/or craniosynostosis. One patient carried a frameshift variant of unknown inheritance due to unavailability of the father. The most common clinical features included language deficits (81%), behavioral symptoms (69%), intellectual disability (64%), epilepsy (62%), and motor delay (56%). Epilepsy types were variable, with West syndrome observed in three patients, generalized tonic-clonic seizures in two, and other subtypes observed in one individual each. Our findings suggest that, in line with other CHD-related disorders, heterozygous CHD5 variants are associated with a variable neurodevelopmental syndrome that includes intellectual disability with speech delay, epilepsy, and behavioral problems as main features.
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http://dx.doi.org/10.1007/s00439-021-02283-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8197709PMC
July 2021

ATP6V0A1 encoding the a1-subunit of the V0 domain of vacuolar H-ATPases is essential for brain development in humans and mice.

Nat Commun 2021 04 8;12(1):2107. Epub 2021 Apr 8.

Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan.

Vacuolar H-ATPases (V-ATPases) transport protons across cellular membranes to acidify various organelles. ATP6V0A1 encodes the a1-subunit of the V0 domain of V-ATPases, which is strongly expressed in neurons. However, its role in brain development is unknown. Here we report four individuals with developmental and epileptic encephalopathy with ATP6V0A1 variants: two individuals with a de novo missense variant (R741Q) and the other two individuals with biallelic variants comprising one almost complete loss-of-function variant and one missense variant (A512P and N534D). Lysosomal acidification is significantly impaired in cell lines expressing three missense ATP6V0A1 mutants. Homozygous mutant mice harboring human R741Q (Atp6v0a1) and A512P (Atp6v0a1) variants show embryonic lethality and early postnatal mortality, respectively, suggesting that R741Q affects V-ATPase function more severely. Lysosomal dysfunction resulting in cell death, accumulated autophagosomes and lysosomes, reduced mTORC1 signaling and synaptic connectivity, and lowered neurotransmitter contents of synaptic vesicles are observed in the brains of Atp6v0a1 mice. These findings demonstrate the essential roles of ATP6V0A1/Atp6v0a1 in neuronal development in terms of integrity and connectivity of neurons in both humans and mice.
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http://dx.doi.org/10.1038/s41467-021-22389-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8032687PMC
April 2021

Complete sequencing of expanded SAMD12 repeats by long-read sequencing and Cas9-mediated enrichment.

Brain 2021 05;144(4):1103-1117

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan.

A pentanucleotide TTTCA repeat insertion into a polymorphic TTTTA repeat element in SAMD12 causes benign adult familial myoclonic epilepsy. Although the precise determination of the entire SAMD12 repeat sequence is important for molecular diagnosis and research, obtaining this sequence remains challenging when using conventional genomic/genetic methods, and even short-read and long-read next-generation sequencing technologies have been insufficient. Incomplete information regarding expanded repeat sequences may hamper our understanding of the pathogenic roles played by varying numbers of repeat units, genotype-phenotype correlations, and mutational mechanisms. Here, we report a new approach for the precise determination of the entire expanded repeat sequence and present a workflow designed to improve the diagnostic rates in various repeat expansion diseases. We examined 34 clinically diagnosed benign adult familial myoclonic epilepsy patients, from 29 families using repeat-primed PCR, Southern blot, and long-read sequencing with Cas9-mediated enrichment. Two cases with questionable results from repeat-primed PCR and/or Southern blot were confirmed as pathogenic using long-read sequencing with Cas9-mediated enrichment, resulting in the identification of pathogenic SAMD12 repeat expansions in 76% of examined families (22/29). Importantly, long-read sequencing with Cas9-mediated enrichment was able to provide detailed information regarding the sizes, configurations, and compositions of the expanded repeats. The inserted TTTCA repeat size and the proportion of TTTCA sequences among the overall repeat sequences were highly variable, and a novel repeat configuration was identified. A genotype-phenotype correlation study suggested that the insertion of even short (TTTCA)14 repeats contributed to the development of benign adult familial myoclonic epilepsy. However, the sizes of the overall TTTTA and TTTCA repeat units are also likely to be involved in the pathology of benign adult familial myoclonic epilepsy. Seven unsolved SAMD12-negative cases were investigated using whole-genome long-read sequencing, and infrequent, disease-associated, repeat expansions were identified in two cases. The strategic workflow resolved two questionable SAMD12-positive cases and two previously SAMD12-negative cases, increasing the diagnostic yield from 69% (20/29 families) to 83% (24/29 families). This study indicates the significant utility of long-read sequencing technologies to explore the pathogenic contributions made by various repeat units in complex repeat expansions and to improve the overall diagnostic rate.
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http://dx.doi.org/10.1093/brain/awab021DOI Listing
May 2021

De novo ATP1A3 variants cause polymicrogyria.

Sci Adv 2021 Mar 24;7(13). Epub 2021 Mar 24.

Department of Pediatrics, Tottori Prefectural Central Hospital, Tottori 680-0901, Japan.

Polymicrogyria is a common malformation of cortical development whose etiology remains elusive. We conducted whole-exome sequencing for 124 patients with polymicrogyria and identified de novo variants in eight patients. Mutated causes functional brain diseases, including alternating hemiplegia of childhood (AHC), rapid-onset dystonia parkinsonism (RDP), and cerebellar ataxia, areflexia, pes cavus, optic nerve atrophy, and sensorineural deafness (CAPOS). However, our patients showed no clinical features of AHC, RDP, or CAPOS and had a completely different phenotype: a severe form of polymicrogyria with epilepsy and developmental delay. Detected variants had different locations in and different functional properties compared with AHC-, RDP-, or CAPOS-associated variants. In the developing cerebral cortex of mice, radial neuronal migration was impaired in neurons overexpressing the variant of the most severe patients, suggesting that this variant is involved in cortical malformation pathogenesis. We propose a previously unidentified category of polymicrogyria associated with abnormalities.
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http://dx.doi.org/10.1126/sciadv.abd2368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7990330PMC
March 2021

Variants Associated With X-Linked Intellectual Disability and Congenital Malformation.

Front Cell Dev Biol 2021 3;9:631428. Epub 2021 Mar 3.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.

Background: X-linked intellectual disability (XLID), which occurs predominantly in males, is a relatively common and genetically heterogeneous disorder in which over 100 mutated genes have been reported. The gene at Xp11.23 encodes ovarian tumor deubiquitinase 5 protein, which is a deubiquitinating enzyme member of the ovarian tumor family. LINKage-specific-deubiquitylation-deficiency-induced embryonic defects (LINKED) syndrome, arising from pathogenic variants, was recently reported as a new XLID with additional congenital anomalies.

Methods: We investigated three affected males (49- and 47-year-old brothers [Individuals 1 and 2] and a 2-year-old boy [Individual 3]) from two families who showed developmental delay. Their common clinical features included developmental delay, hypotonia, short stature, and distinctive facial features, such as telecanthus and a depressed nasal bridge. Individuals 1 and 2 showed epilepsy and brain magnetic resonance imaging showed a thin corpus callosum and mild ventriculomegaly. Individual 3 showed congenital malformations, including tetralogy of Fallot, hypospadias, and bilateral cryptorchidism. To identify the genetic cause of these features, we performed whole-exome sequencing.

Results: A hemizygous missense variant, c.878A>T, p.Asn293Ile [NM_017602.4], was identified in one family with Individuals 1 and 2, and another missense variant, c.1210 C>T, p.Arg404Trp, in the other family with Individual 3, respectively. The former variant has not been registered in public databases and was predicted to be pathogenic by multiple prediction tools. The latter variant p.Arg404Trp was previously reported as a pathogenic variant, and Individual 3 showed a typical LINKED syndrome phenotype. However, Individuals 1 and 2, with the novel variant (p.Asn293Ile), showed no cardiac or genitourinary malformations.

Conclusions: Unlike previous reports of LINKED syndrome, which described early lethality with congenital cardiac anomalies, our three cases are still alive. Notably, the adult brothers with the novel missense variant have lived into their forties. This may be indicative of a milder phenotype as a possible genotype-phenotype correlation. These findings imply a possible long-term prognosis for individuals with this new XLID syndrome, and a wider phenotypic variation than initially thought.
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http://dx.doi.org/10.3389/fcell.2021.631428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7965969PMC
March 2021

Mutation-specific pathophysiological mechanisms define different neurodevelopmental disorders associated with SATB1 dysfunction.

Am J Hum Genet 2021 02 28;108(2):346-356. Epub 2021 Jan 28.

Department of Rehabilitation and Development, Randall Children's Hospital at Legacy Emanuel Medical Center, Portland, OR 97227, USA.

Whereas large-scale statistical analyses can robustly identify disease-gene relationships, they do not accurately capture genotype-phenotype correlations or disease mechanisms. We use multiple lines of independent evidence to show that different variant types in a single gene, SATB1, cause clinically overlapping but distinct neurodevelopmental disorders. Clinical evaluation of 42 individuals carrying SATB1 variants identified overt genotype-phenotype relationships, associated with different pathophysiological mechanisms, established by functional assays. Missense variants in the CUT1 and CUT2 DNA-binding domains result in stronger chromatin binding, increased transcriptional repression, and a severe phenotype. In contrast, variants predicted to result in haploinsufficiency are associated with a milder clinical presentation. A similarly mild phenotype is observed for individuals with premature protein truncating variants that escape nonsense-mediated decay, which are transcriptionally active but mislocalized in the cell. Our results suggest that in-depth mutation-specific genotype-phenotype studies are essential to capture full disease complexity and to explain phenotypic variability.
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http://dx.doi.org/10.1016/j.ajhg.2021.01.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7895900PMC
February 2021

Long-read whole-genome sequencing identified a partial MBD5 deletion in an exome-negative patient with neurodevelopmental disorder.

J Hum Genet 2021 Jul 29;66(7):697-705. Epub 2021 Jan 29.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.

Whole-exome sequencing (WES) can detect not only single-nucleotide variants in causal genes, but also pathogenic copy-number variations using several methods. However, there may be overlooked pathogenic variations in the out of target genome regions of WES analysis (e.g., promoters), leaving many patients undiagnosed. Whole-genome sequencing (WGS) can potentially analyze such regions. We applied long-read nanopore WGS and our recently developed analysis pipeline "dnarrange" to a patient who was undiagnosed by trio-based WES analysis, and identified a heterozygous 97-kb deletion partially involving 5'-untranslated exons of MBD5, which was outside the WES target regions. The phenotype of the patient, a 32-year-old male, was consistent with haploinsufficiency of MBD5. The transcript level of MBD5 in the patient's lymphoblastoid cells was reduced. We therefore concluded that the partial MBD5 deletion is the culprit for this patient. Furthermore, we found other rare structural variations (SVs) in this patient, i.e., a large inversion and a retrotransposon insertion, which were not seen in 33 controls. Although we considered that they are benign SVs, this finding suggests that our pipeline using long-read WGS is useful for investigating various types of potentially pathogenic SVs. In conclusion, we identified a 97-kb deletion, which causes haploinsufficiency of MBD5 in a patient with neurodevelopmental disorder, demonstrating that long-read WGS is a powerful technique to discover pathogenic SVs.
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http://dx.doi.org/10.1038/s10038-020-00893-8DOI Listing
July 2021

Neuronal intranuclear inclusion disease presenting with an MELAS-like episode in chronic polyneuropathy.

Neurol Genet 2020 Dec 19;6(6):e531. Epub 2020 Nov 19.

Department of Neurology (T.I., T.O., Y. Saitoh, S.O., Y.T.), National Center Hospital, National Center of Neurology and Psychiatry, Tokyo; Department of Human Genetics (K.S., A.F., H.F., N. Miyake, T.M., N. Matsumoto), Yokohama City University Graduate School of Medicine, Kanagawa; Department of Pathology and Laboratory Medicine (T.S., Y. Saito), National Center Hospital, National Center of Neurology and Psychiatry, Tokyo; Department of Neurology (T.Y.), Iida Municipal Hospital, Shinshu University School of Medicine, Nagano; Department of Medicine (Neurology and Rheumatology) (Y.M., Y. Sekijima), Shinshu University School of Medicine, Nagano; and Department of Neurology and Stroke Medicine (H.F.), Yokohama City University, Japan.

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http://dx.doi.org/10.1212/NXG.0000000000000531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7713717PMC
December 2020

Hemizygous FLNA variant in West syndrome without periventricular nodular heterotopia.

Hum Genome Var 2020 Dec 3;7(1):43. Epub 2020 Dec 3.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa, Yokohama, 236-0004, Japan.

Pathogenic FLNA variants can be identified in patients with seizures accompanied by periventricular nodular heterotopia (PVNH). It is unusual to find FLNA aberrations in epileptic patients without PVNH on brain imaging. We report a boy with cryptogenic West syndrome followed by refractory seizures and psychomotor delay. We performed whole-exome sequencing and identified a de novo missense variant in FLNA. It is noteworthy that this patient showed no PVNH. As no other pathogenic variants were found in epilepsy-related genes, this FLNA variant likely caused West syndrome but with no PVNH.
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http://dx.doi.org/10.1038/s41439-020-00131-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7713383PMC
December 2020

Clinical variations of epileptic syndrome associated with PACS2 variant.

Brain Dev 2021 Feb 23;43(2):343-347. Epub 2020 Nov 23.

Department of Pediatrics, Showa University School of Medicine, Japan.

Background: Recent studies have suggested that two PACS2 pathogenic variants, c.625G > A (p.Glu209Lys) and c.631G > A (p.Glu211Lys), have been causally linked to the characteristic developmental and epileptic encephalopathy, including autistic behaviors, hypotonia, cerebellar dysgenesis and facial dysmorphism. Their seizures appear most difficult to control in neonatal and infant period, but improve after the first year of life. We herein report three patients with the same PACS2 variant, c.625G > A (p.Glu209Lys), showing different characteristics from previous reports.

Case Report: Case 1, a 2-year-old girl, developed frequent tonic convulsions 2 weeks after birth. Brain magnetic resonance imaging showed a decrease in posterior periventricular white matter volume, an enlargement of the inferior horn of lateral ventricles and old subependymal hemorrhage. Epilepsy is now controlled with antiepileptic drugs. Case 2, a 12-year-old girl, developed generalized tonic convulsions 3 days after birth. Although epilepsy had been controlled since the age of 4, she developed Lennox-Gastaut syndrome at 9 years old. Case 3, a 3-year-old girl, developed tonic convulsions 3 days after birth. She now exhibits normal psychomotor development, and epilepsy is controlled without medicine.

Conclusion: PACS2-related epileptic syndrome presents variable phenotypes than previously reported. We think that our findings expand the clinical spectrum of this disease, and provide important information about the differential diagnosis of neonatal-onset epileptic syndrome.
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http://dx.doi.org/10.1016/j.braindev.2020.10.006DOI Listing
February 2021

Novel ACOX1 mutations in two siblings with peroxisomal acyl-CoA oxidase deficiency.

Brain Dev 2021 Mar 21;43(3):475-481. Epub 2020 Nov 21.

Department of Pediatrics, University of Tsukuba Hospital, Japan; Department of Child Health, Faculty of Medicine, University of Tsukuba, Japan.

Peroxisomal acyl-CoA oxidase (ACOX1) deficiency is a rare autosomal recessive single enzyme deficiency characterized by hypotonia, seizures, failure to thrive, developmental delay, and neurological regression starting from approximately 3 years of age. Here, we report two siblings with ACOX1 deficiency born to non-consanguineous Japanese parents. They showed mild global developmental delay from infancy and began to regress at 5 years 10 months and 5 years 6 months of age respectively. They gradually manifested with cerebellar ataxia, dysarthria, pyramidal signs, and dysphasia. Brain MRI revealed T2 high-intensity areas in the cerebellar white matter, bilateral middle cerebellar peduncle, and transverse tracts of the pons, followed by progressive atrophy of these areas. Intriguingly, the ratios of C24:0, C25:0, and C26:0 to C22:0 in plasma, which usually increase in ACOX1 deficiency were within normal ranges in both patients. On the other hand, whole exome sequencing revealed novel compound heterozygous variants in ACOX1: a frameshift variant (c.160delC:p.Leu54Serfs*18) and a missense variant (c.1259 T > C:p.Phe420Ser). The plasma concentration of individual very long chain fatty acids (C24:0, C25:0, and C26:0) was elevated, and we found that peroxisomes in fibroblasts of the patients were larger in size and fewer in number as previously reported in patients with ACOX1 deficiency. Furthermore, the C24:0 β-oxidation activity was dramatically reduced. Our findings suggest that the elevation of individual plasma very long chain fatty acids concentration, genetic analysis including whole exome analysis, and biochemical studies on the patient's fibroblasts should be considered for the correct diagnosis of ACOX1 deficiency.
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http://dx.doi.org/10.1016/j.braindev.2020.10.011DOI Listing
March 2021

Diverse Pathological Findings of Interstitial Lung Disease in a Patient with Dyskeratosis Congenita.

Intern Med 2021 Apr 16;60(8):1257-1263. Epub 2020 Nov 16.

Department of Respiratory Medicine, Kanagawa Cardiovascular and Respiratory Center, Japan.

A 42-year-old man with a history of surgery for tongue cancer was referred to our hospital due to an abnormal chest shadow. High-resolution computed tomography showed lower lobe reticulation. A physical examination revealed nail dystrophy, oral leukoplakia, and reticulated hypopigmentation. Lung biopsy revealed subpleural and perilobular fibrosis, suggestive of usual interstitial pneumonia. However, multiple pathological findings, including homogenous fibrosis and cell infiltration in the centrilobular region, which were compatible with nonspecific interstitial pneumonia, and bronchiolitis were also seen. Genetic testing showed a hemizygous missense mutation in the DKC1 gene, and the patient was diagnosed with dyskeratosis congenita. Although anti-fibrotic therapy was initiated, the patient's respiratory function has continued to decrease.
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http://dx.doi.org/10.2169/internalmedicine.5143-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8112977PMC
April 2021

Pathogenic 12-kb copy-neutral inversion in syndromic intellectual disability identified by high-fidelity long-read sequencing.

Genomics 2021 Jan 4;113(1 Pt 2):1044-1053. Epub 2020 Nov 4.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan. Electronic address:

We report monozygotic twin girls with syndromic intellectual disability who underwent exome sequencing but with negative pathogenic variants. To search for variants that are unrecognized by exome sequencing, high-fidelity long-read genome sequencing (HiFi LR-GS) was applied. A 12-kb copy-neutral inversion was precisely identified by HiFi LR-GS after trio-based variant filtering. This inversion directly disrupted two genes, CPNE9 and BRPF1, the latter of which attracted our attention because pathogenic BRPF1 variants have been identified in autosomal dominant intellectual developmental disorder with dysmorphic facies and ptosis (IDDDFP), which later turned out to be clinically found in the twins. Trio-based HiFi LR-GS together with haplotype phasing revealed that the 12-kb inversion occurred de novo on the maternally transmitted chromosome. This study clearly indicates that submicroscopic copy-neutral inversions are important but often uncharacterized culprits in monogenic disorders and that long-read sequencing is highly advantageous for detecting such inversions involved in genetic diseases.
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http://dx.doi.org/10.1016/j.ygeno.2020.10.038DOI Listing
January 2021

Whole exome sequencing of fetal structural anomalies detected by ultrasonography.

J Hum Genet 2021 May 3;66(5):499-507. Epub 2020 Nov 3.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.

The objective of this study was to evaluate the efficacy of whole exome sequencing (WES) for the genetic diagnosis of cases presenting with fetal structural anomalies detected by ultrasonography. WES was performed on 19 cases with prenatal structural anomalies. Genomic DNA was extracted from umbilical cords or umbilical blood obtained shortly after birth. WES data were analyzed on prenatal phenotypes alone, and the data were re-analyzed after information regarding the postnatal phenotype was obtained. Based solely on the fetal phenotype, pathogenic, or likely pathogenic, single nucleotide variants were identified in 5 of 19 (26.3%) cases. Moreover, we detected trisomy 21 in two cases by WES-based copy number variation analysis. The overall diagnostic rate was 36.8% (7/19). They were all compatible with respective fetal structural anomalies. By referring to postnatal phenotype information, another candidate variant was identified by a postnatal clinical feature that was not detected in prenatal screening. As detailed phenotyping is desirable for better diagnostic rates in WES analysis, we should be aware that fetal phenotype is a useful, but sometimes limited source of information for comprehensive genetic analysis. It is important to amass more data of genotype-phenotype correlations, especially to appropriately assess the validity of WES in prenatal settings.
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http://dx.doi.org/10.1038/s10038-020-00869-8DOI Listing
May 2021

Cerebrospinal fluid abnormalities in developmental and epileptic encephalopathy with a variant.

Neurol Genet 2020 Dec 8;6(6):e527. Epub 2020 Oct 8.

Department of Pediatrics (Y.S., T. Mizuno, K.M.), Tokyo Medical and Dental University, Yushima, Bunkyo-ku; Home Care Clinic for Children Aozora Sumida (H.I.), Higashikomagata, Sumida-ku, Tokyo; Department of Pediatrics (M.K.), Showa University School of Medicine, Hatanodai, Shinagawa-ku, Tokyo; Department of Human Genetics (M.N., T. Mizuguchi, N.M.), Yokohama City University Graduate School of Medicine, Fukuura, Kanazawa-ku, Yokohama; Department of Biochemistry (M.N.), Hamamatsu University School of Medicine, Handayama, Higashi-ku Hamamatsu; and Present Address: Department of Pediatrics (Y.S.), Soka Municipal Hospital, Soka, Soka-Shi, Saitama-Ken, Japan.

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http://dx.doi.org/10.1212/NXG.0000000000000527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7577532PMC
December 2020

Efficient detection of copy-number variations using exome data: Batch- and sex-based analyses.

Hum Mutat 2021 Jan 11;42(1):50-65. Epub 2020 Nov 11.

Department of Genetics, Kuala Lumpur Hospital, Kuala Lumpur, Malaysia.

Many algorithms to detect copy number variations (CNVs) using exome sequencing (ES) data have been reported and evaluated on their sensitivity and specificity, reproducibility, and precision. However, operational optimization of such algorithms for a better performance has not been fully addressed. ES of 1199 samples including 763 patients with different disease profiles was performed. ES data were analyzed to detect CNVs by both the eXome Hidden Markov Model (XHMM) and modified Nord's method. To efficiently detect rare CNVs, we aimed to decrease sequencing biases by analyzing, at the same time, the data of all unrelated samples sequenced in the same flow cell as a batch, and to eliminate sex effects of X-linked CNVs by analyzing female and male sequences separately. We also applied several filtering steps for more efficient CNV selection. The average number of CNVs detected in one sample was <5. This optimization together with targeted CNV analysis by Nord's method identified pathogenic/likely pathogenic CNVs in 34 patients (4.5%, 34/763). In particular, among 142 patients with epilepsy, the current protocol detected clinically relevant CNVs in 19 (13.4%) patients, whereas the previous protocol identified them in only 14 (9.9%) patients. Thus, this batch-based XHMM analysis efficiently selected rare pathogenic CNVs in genetic diseases.
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http://dx.doi.org/10.1002/humu.24129DOI Listing
January 2021

De novo variants in CELF2 that disrupt the nuclear localization signal cause developmental and epileptic encephalopathy.

Hum Mutat 2021 Jan 10;42(1):66-76. Epub 2020 Nov 10.

Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan.

We report heterozygous CELF2 (NM_006561.3) variants in five unrelated individuals: Individuals 1-4 exhibited developmental and epileptic encephalopathy (DEE) and Individual 5 had intellectual disability and autistic features. CELF2 encodes a nucleocytoplasmic shuttling RNA-binding protein that has multiple roles in RNA processing and is involved in the embryonic development of the central nervous system and heart. Whole-exome sequencing identified the following CELF2 variants: two missense variants [c.1558C>T:p.(Pro520Ser) in unrelated Individuals 1 and 2, and c.1516C>G:p.(Arg506Gly) in Individual 3], one frameshift variant in Individual 4 that removed the last amino acid of CELF2 c.1562dup:p.(Tyr521Ter), possibly resulting in escape from nonsense-mediated mRNA decay (NMD), and one canonical splice site variant, c.272-1G>C in Individual 5, also probably leading to NMD. The identified variants in Individuals 1, 2, 4, and 5 were de novo, while the variant in Individual 3 was inherited from her mosaic mother. Notably, all identified variants, except for c.272-1G>C, were clustered within 20 amino acid residues of the C-terminus, which might be a nuclear localization signal. We demonstrated the extranuclear mislocalization of mutant CELF2 protein in cells transfected with mutant CELF2 complementary DNA plasmids. Our findings indicate that CELF2 variants that disrupt its nuclear localization are associated with DEE.
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http://dx.doi.org/10.1002/humu.24130DOI Listing
January 2021

Novel EXOSC9 variants cause pontocerebellar hypoplasia type 1D with spinal motor neuronopathy and cerebellar atrophy.

J Hum Genet 2021 Apr 10;66(4):401-407. Epub 2020 Oct 10.

Department of Human Genetics, Graduate school of medicine, Yokohama City University, Yokohama, Japan.

Pontocerebellar hypoplasia (PCH) is currently classified into 13 subgroups and many gene variants associated with PCH have been identified by next generation sequencing. PCH type 1 is a rare heterogeneous neurodegenerative disorder. The clinical presentation includes early-onset severe developmental delay, progressive motor neuronopathy, and cerebellar and pontine atrophy. Recently two variants in the EXOSC9 gene (MIM: 606180), NM_001034194.1: c.41T>C (p.Leu14Pro) and c.481C>T (p.Arg161*) were identified in four unrelated patients with PCH type 1D (PCH1D) (MIM: 618065). EXOSC9 encodes a component of the exosome complex, which is essential for correct processing and degradation of RNA. We report here two PCH1D families with biallelic EXOSC9 variants: c.239T>G (p.Leu80Arg) and c.484dupA (p.Arg162Lysfs*3) in one family and c.151G>C (p.Gly51Arg) in the other family. Although the patients studied here showed similar clinical features as previously described for PCH1D, relatively greater intellectual development (although still highly restricted) and normal pontine structure were recognized. Our findings expand the clinical consequences of biallelic EXOSC9 variants.
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http://dx.doi.org/10.1038/s10038-020-00853-2DOI Listing
April 2021

Nonsense variants of result in distinct congenital anomalies.

Hum Genome Var 2020 18;7:26. Epub 2020 Sep 18.

Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.

Herein, we report two female cases with novel nonsense mutations of at Xq25, encoding stromal antigen 2, a component of the cohesion complex. Exome analysis identified c.3097 C>T, p.(Arg1033*) in Case 1 (a fetus with multiple congenital anomalies) and c.2229 G>A, p.(Trp743*) in Case 2 (a 7-year-old girl with white matter hypoplasia and cleft palate). X inactivation was highly skewed in both cases.
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http://dx.doi.org/10.1038/s41439-020-00114-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7501222PMC
September 2020

Clinical and genetic characteristics of patients with Doose syndrome.

Epilepsia Open 2020 Sep 23;5(3):442-450. Epub 2020 Jul 23.

Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama Japan.

Objective: To elucidate the genetic background and genotype-phenotype correlations for epilepsy with myoclonic-atonic seizures, also known as myoclonic-astatic epilepsy (MAE) or Doose syndrome.

Methods: We collected clinical information and blood samples from 29 patients with MAE. We performed whole-exome sequencing for all except one MAE case in whom custom capture sequencing identified a variant.

Results: We newly identified four variants: and missense variants and microdeletions at 2q24.2 involving and Xp22.31 involving . Febrile seizures preceded epileptic or afebrile seizures in four patients, of which two patients had gene variants. Myoclonic-atonic seizures occurred at onset in four patients, of which two had variants, and during the course of disease in three patients. Variants were more commonly identified in patients with a developmental delay or intellectual disability (DD/ID), but genetic status was not associated with the severity of DD/ID. Attention-deficit/hyperactivity disorder and autistic spectrum disorder were less frequently observed in patients with variants than in those with unknown etiology.

Significance: MAE patients had genetic heterogeneity, and and emerged as possible candidate causative genes. Febrile seizures prior to epileptic seizures and myoclonic-atonic seizure at onset indicate a genetic predisposition to MAE. Comorbid conditions were not related to genetic predisposition to MAE.
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http://dx.doi.org/10.1002/epi4.12417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7469791PMC
September 2020
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