Publications by authors named "Nobuaki Wakamatsu"

40 Publications

R3HDM1 haploinsufficiency is associated with mild intellectual disability.

Am J Med Genet A 2021 Jun 22;185(6):1776-1786. Epub 2021 Mar 22.

Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Japan.

R3HDM1 (R3H domain containing 1) is an uncharacterized RNA-binding protein that is highly expressed in the human cerebral cortex. We report the first case of a 12-year-old Japanese male with haploinsufficiency of R3HDM1. He presented with mild intellectual disability (ID) and developmental delay. He had a pericentric inversion of 46,XY,inv(2)(p16.1q21.3)dn with breakpoints in intron 19 of R3HDM1 (2q21.3) and the intergenic region (2p16.1). The R3HDM1 levels in his lymphoblastoid cells were reduced to approximately half that of the healthy controls. However, the expression of MIR128-1, in intron 18 of R3HDM1, was not affected via the pericentric inversion. Knockdown of R3HDM1 in mouse embryonic hippocampal neurons suppressed dendritic growth and branching. Notably, the Database of Genomic Variants reported the case of a healthy control with a 488-kb deletion that included both R3HDM1 and MIR128-1. miR-128 has been reported to inhibit dendritic growth and branching in mouse brain neurons, which directly opposes the novel functions of R3HDM1. These findings suggest that deleting both R3HDM1 and MIR128-1 alleviates the symptoms of the disease caused by loss-of-function mutations in R3HDM1 only. Thus, haploinsufficiency of R3HDM1 in the patient may be the cause of the mild ID due to the genetic imbalance between R3HDM1 and MIR128-1.
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http://dx.doi.org/10.1002/ajmg.a.62173DOI Listing
June 2021

Successful treatment of drug-resistant status epilepticus in an adult patient with Mowat-Wilson syndrome: A case report.

Epilepsy Behav Rep 2020 25;14:100410. Epub 2020 Nov 25.

Department of Neurology, Toyohashi Municipal Hospital, Toyohashi, Japan.

Mowat-Wilson syndrome (MWS) is a rare genetic disorder characterized by intellectual disability, distinctive facial features, epilepsy, and multiple anomalies caused by heterozygous loss-of-function mutations in the zinc finger E-box-binding homeobox-2 gene (). Treatment choice is very important as patients with MWS because patients sometimes develop drug-resistant epilepsy. Here, we report the case of a 45-year-old male patient with MWS who developed drug-resistant status epilepticus after a 26-years seizure-free period while taking multiple anti-seizure medications. He showed a characteristic magnetic resonance imaging finding with a focal lesion in his left thalamic pulvinar nucleus, a finding not previously reported in status epilepticus with MWS. We succeeded in controlling seizures in the patient after trying multiple new antiseizure drug combinations. These findings indicate that patients with MWS may develop drug-resistant status epilepticus with age, even after a long-term seizure-free period, which can be managed with anti-seizure medication. Therefore, careful monitoring of seizures is important for the treatment of people with MWS, even in patients who have not experienced seizures for a long time.
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http://dx.doi.org/10.1016/j.ebr.2020.100410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7736901PMC
November 2020

Clinical and molecular genetic characterization of two female patients harboring the Xq27.3q28 deletion with different ratios of X chromosome inactivation.

Hum Mutat 2020 08 19;41(8):1447-1460. Epub 2020 Jun 19.

Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Aichi, Japan.

A heterozygous deletion at Xq27.3q28 including FMR1, AFF2, and IDS causing intellectual disability and characteristic facial features is very rare in females, with only 10 patients having been reported. Here, we examined two female patients with different clinical features harboring the Xq27.3q28 deletion and determined the chromosomal breakpoints. Moreover, we assessed the X chromosome inactivation (XCI) in peripheral blood from both patients. Both patients had an almost overlapping deletion at Xq27.3q28, however, the more severe patient (Patient 1) showed skewed XCI of the normal X chromosome (79:21) whereas the milder patient (Patient 2) showed random XCI. Therefore, deletion at Xq27.3q28 critically affected brain development, and the ratio of XCI of the normal X chromosome greatly affected the clinical characteristics of patients with deletion at Xq27.3q28. As the chromosomal breakpoints were determined, we analyzed a change in chromatin domains termed topologically associated domains (TADs) using published Hi-C data on the Xq27.3q28 region, and found that only patient 1 had a possibility of a drastic change in TADs. The altered chromatin topologies on the Xq27.3q28 region might affect the clinical features of patient 1 by changing the expression of genes just outside the deletion and/or the XCI establishment during embryogenesis resulting in skewed XCI.
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http://dx.doi.org/10.1002/humu.24058DOI Listing
August 2020

Isozyme-Specific Role of SAD-A in Neuronal Migration During Development of Cerebral Cortex.

Cereb Cortex 2019 08;29(9):3738-3751

Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan.

SAD kinases regulate presynaptic vesicle clustering and neuronal polarization. A previous report demonstrated that Sada-/- and Sadb-/- double-mutant mice showed perinatal lethality with a severe defect in axon/dendrite differentiation, but their single mutants did not. These results indicated that they were functionally redundant. Surprisingly, we show that on a C57BL/6N background, SAD-A is essential for cortical development whereas SAD-B is dispensable. Sada-/- mice died within a few days after birth. Their cortical lamination pattern was disorganized and radial migration of cortical neurons was perturbed. Birth date analyses with BrdU and in utero electroporation using pCAG-EGFP vector showed a delayed migration of cortical neurons to the pial surface in Sada-/- mice. Time-lapse imaging of these mice confirmed slow migration velocity in the cortical plate. While the neurites of hippocampal neurons in Sada-/- mice could ultimately differentiate in culture to form axons and dendrites, the average length of their axons was shorter than that of the wild type. Thus, analysis on a different genetic background than that used initially revealed a nonredundant role for SAD-A in neuronal migration and differentiation.
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http://dx.doi.org/10.1093/cercor/bhy253DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7335017PMC
August 2019

Clinical and genetic characterization of a patient with SOX5 haploinsufficiency caused by a de novo balanced reciprocal translocation.

Gene 2018 May 22;655:65-70. Epub 2018 Mar 22.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan; Department of Neurology, Neurology and Stroke Center, Takamatsu Municipal Hospital, Takamatsu, Kagawa, Japan. Electronic address:

Lamb-Shaffer syndrome (OMIM: 616803) is a neurodevelopmental disorder characterized by developmental delay, mild to moderate intellectual disability, speech delay, and mild characteristic facial appearance caused by SOX5 haploinsufficiency on chromosome 12p12.1. There are clinical variabilities among the patients with genomic alterations, such as intragenic deletions, a point mutation, and a chromosomal translocation of t(11;12)(p13;p12.1), in SOX5. We report herein a 5-year-old Japanese male with a de novo balanced reciprocal translocation t(12;20)(p12.1;p12.3) presenting a mild intellectual disability, speech delay, characteristic facial appearance, and autistic features. We determined the translocation breakpoints of the patient to be in intron 4 of SOX5 and the intergenic region in 20p12.3 via FISH and nucleotide sequence analyses. Thus, the present patient has SOX5 haploinsufficiency affecting 2 long forms of SOX5 and is the second reported case of Lamb-Shaffer syndrome caused by a de novo balanced reciprocal translocation. This report confirmed that haploinsufficiency of the 2 long forms of SOX5 presents common clinical features, including mild intellectual disability and autistic features, which could be useful for the clinical diagnosis of Lamb-Shaffer syndrome.
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http://dx.doi.org/10.1016/j.gene.2018.02.049DOI Listing
May 2018

High-dose thiamine prevents brain lesions and prolongs survival of Slc19a3-deficient mice.

PLoS One 2017 30;12(6):e0180279. Epub 2017 Jun 30.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

SLC19A3 deficiency, also called thiamine metabolism dysfunction syndrome-2 (THMD2; OMIM 607483), is an autosomal recessive neurodegenerative disorder caused by mutations in SLC19A3, the gene encoding thiamine transporter 2. To investigate the molecular mechanisms of neurodegeneration in SLC19A3 deficiency and whether administration of high-dose thiamine prevents neurodegeneration, we generated homozygous Slc19a3 E314Q knock-in (KI) mice harboring the mutation corresponding to the human SLC19A3 E320Q, which is associated with the severe form of THMD2. Homozygous KI mice and previously reported homozygous Slc19a3 knock-out (KO) mice fed a thiamine-restricted diet (thiamine: 0.60 mg/100 g food) died within 30 and 12 days, respectively, with dramatically decreased thiamine concentration in the blood and brain, acute neurodegeneration, and astrogliosis in the submedial nucleus of the thalamus and ventral anterior-lateral complex of the thalamus. These findings may bear some features of thiamine-deficient mice generated by pyrithiamine injection and a thiamine-deficient diet, suggesting that the primary cause of THMD2 could be thiamine pyrophosphate (TPP) deficiency. Next, we analyzed the therapeutic effects of high-dose thiamine treatment. When the diet was reverted to a conventional diet (thiamine: 1.71 mg/100 g food) after thiamine restriction, all homozygous KO mice died. In contrast, when the diet was changed to a high-thiamine diet (thiamine: 8.50 mg/100 g food) after thiamine restriction, more than half of homozygous KO mice survived, without progression of brain lesions. Unexpectedly, when the high-thiamine diet of recovered mice was reverted to a conventional diet, some homozygous KO mice died. These results showed that acute neurodegeneration caused by thiamine deficiency is preventable in most parts, and prompt high-dose thiamine administration is critical for the treatment of THMD2. However, reduction of thiamine should be performed carefully to prevent recurrence after recovery of the disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180279PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493381PMC
October 2017

Clinical and molecular genetic characterization of two siblings with trisomy 2p24.3-pter and monosomy 5p14.3-pter.

Am J Med Genet A 2017 Aug 9;173(8):2201-2209. Epub 2017 Jun 9.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

Partial trisomy 2p syndrome is occasionally associated with neural tube defects (NTDs), such as anencephaly, encephalocele, and spina bifida, in addition to common features of intellectual disability, developmental delay, and characteristic facial appearance. The 2p24 region has been reported to be associated with NTDs. Here, we report the cases of 2 siblings with trisomy 2p24.3-pter and monosomy 5p14.3-pter caused by the paternal translocation t(2;5)(p24.3;p14.3). Of the two siblings, the elder sister had spina bifida. We determined the nucleotide sequences of the chromosomal breakpoints and found that the sizes of trisomy 2p and monosomy 5p segments were 18.77 and 17.89 Mb, respectively. NTDs were present in four of seven previously reported patients with trisomy 2p and monosomy 5p as well as in one of the two patients examined in the present study. Although the monosomy 5p of the nine patients were similar in size, the two patients reported here had the smallest size of trisomy 2p. When the clinical features of the nine patients were compared to the present two patients, the elder sister had postaxial polydactyly of the left foot in addition to the characteristic facial appearance and spina bifida, indicating that these features were associated with trisomy 2p24.3-pter. To our knowledge, this is the first study on spina bifida to determine the nucleotide sequences of breakpoints for trisomy 2p24.3-pter and monosomy 5p14.3-pter. Increased gene dosages of dosage-sensitive genes or genes at the trisomy segment (2p24.3) of the presented patients could be associated with NTDs of patients with trisomy 2p.
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http://dx.doi.org/10.1002/ajmg.a.38313DOI Listing
August 2017

The effect of rapamycin, NVP-BEZ235, aspirin, and metformin on PI3K/AKT/mTOR signaling pathway of PIK3CA-related overgrowth spectrum (PROS).

Oncotarget 2017 Jul;8(28):45470-45483

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Japan.

The phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR signaling pathway is critical for cellular growth and metabolism. Recently, mosaic or segmental overgrowth, a clinical condition caused by heterozygous somatic activating mutations in PIK3CA, was established as PIK3CA-related overgrowth spectrum (PROS). In this study, we report a Japanese female diagnosed with PROS, who presented with hyperplasia of the lower extremities, macrodactyly, multiple lipomatosis, and sparse hair. Sequencing and mutant allele frequency analysis of PIK3CA from affected tissues revealed that the patient had a heterozygous mosaic mutation (c.3140A>G [p.H1047R]) in PIK3CA and that there were higher mutant allele frequencies from samples with a larger amount of subcutaneous adipose tissue. We established two fibroblast cell lines from the patient, harboring high and low frequencies of the mosaic mutation, in which AKT and S6 showed higher level of phosphorylation compared with three control fibroblasts, indicating that PI3K/AKT/mTOR signaling is activated. We assessed the therapeutic effects of four compounds (rapamycin, NVP-BEZ235, aspirin, and metformin) on PI3K/AKT/mTOR signaling pathway and cell growth. All four compounds suppressed S6 phosphorylation and inhibited cell growth of the patient-derived fibroblast cell lines. However, only metformin mildly inhibited the growth of the control fibroblast cell lines. Since PROS is a congenital disorder, drugs for therapy should take into consideration the natural growth of children. Thus, metformin is a candidate drug for treating PROS in growing children.
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http://dx.doi.org/10.18632/oncotarget.17566DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5542201PMC
July 2017

Critical involvement of ZEB2 in collagen fibrillogenesis: the molecular similarity between Mowat-Wilson syndrome and Ehlers-Danlos syndrome.

Sci Rep 2017 04 19;7:46565. Epub 2017 Apr 19.

Department of Dermatology, Kochi Medical School, Nankoku 783-8505, Japan.

Mowat-Wilson syndrome (MOWS) is a congenital disease caused by de novo heterozygous loss of function mutations or deletions of the ZEB2 gene. MOWS patients show multiple anomalies including intellectual disability, a distinctive facial appearance, microcephaly, congenital heart defects and Hirschsprung disease. However, the skin manifestation(s) of patients with MOWS has not been documented in detail. Here, we recognized that MOWS patients exhibit many Ehlers-Danlos syndrome (EDS)-like symptoms, such as skin hyperextensibility, atrophic scars and joint hypermobility. MOWS patients showed a thinner dermal thickness and electron microscopy revealed miniaturized collagen fibrils. Notably, mice with a mesoderm-specific deletion of the Zeb2 gene (Zeb2-cKO) demonstrated redundant skin, dermal hypoplasia and miniaturized collagen fibrils similar to those of MOWS patients. Dermal fibroblasts derived from Zeb2-cKO mice showed a decreased expression of extracellular matrix (ECM) molecules, such as collagens, whereas molecules involved in degradation of the ECM, such as matrix metalloproteinases (MMPs), were up-regulated. Furthermore, bleomycin-induced skin fibrosis was attenuated in Zeb2-cKO mice. We conclude that MOWS patients exhibit an EDS-like skin phenotype through alterations of collagen fibrillogenesis due to ZEB2 mutations or deletions.
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http://dx.doi.org/10.1038/srep46565DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5396187PMC
April 2017

Phenotype-genotype correlations of PIGO deficiency with variable phenotypes from infantile lethality to mild learning difficulties.

Hum Mutat 2017 07 20;38(7):805-815. Epub 2017 Apr 20.

Department of Immunoregulation, Research Institute for Microbial Diseases Osaka University, Suita, Osaka, Japan.

Inherited GPI (glycosylphosphatidylinositol) deficiencies (IGDs), a recently defined group of diseases, show a broad spectrum of symptoms. Hyperphosphatasia mental retardation syndrome, also known as Mabry syndrome, is a type of IGDs. There are at least 26 genes involved in the biosynthesis and transport of GPI-anchored proteins; however, IGDs constitute a rare group of diseases, and correlations between the spectrum of symptoms and affected genes or the type of mutations have not been shown. Here, we report four newly identified and five previously described Japanese families with PIGO (phosphatidylinositol glycan anchor biosynthesis class O) deficiency. We show how the clinical severity of IGDs correlates with flow cytometric analysis of blood, functional analysis using a PIGO-deficient cell line, and the degree of hyperphosphatasia. The flow cytometric analysis and hyperphosphatasia are useful for IGD diagnosis, but the expression level of GPI-anchored proteins and the degree of hyperphosphatasia do not correlate, although functional studies do, with clinical severity. Compared with PIGA (phosphatidylinositol glycan anchor biosynthesis class A) deficiency, PIGO deficiency shows characteristic features, such as Hirschsprung disease, brachytelephalangy, and hyperphosphatasia. This report shows the precise spectrum of symptoms according to the severity of mutations and compares symptoms between different types of IGD.
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http://dx.doi.org/10.1002/humu.23219DOI Listing
July 2017

Hearing impairment in a female infant with interstitial deletion of 2q24.1q24.3.

Congenit Anom (Kyoto) 2017 Jul 30;57(4):118-121. Epub 2017 Mar 30.

The Department of Pediatric rehabilitation, Hiroshima Prefectural Hospital, Hiroshima, Japan.

Patients with interstitial deletions in 2q24.1q24.3 are rarely reported. These patients manifest a variety of clinical features in addition to intellectual disability, depending on the size and location of the deletion. We report a female patient with interstitial deletion of 5.5 Mb in 2q24.1q24.3, who showed intrauterine growth retardation, hypotonia, global developmental delay, microcephaly, and characteristic facial appearance. In addition, she had hearing impairment, with no auditory brainstem response. Case of 2q24.1q24.3 deletion with hearing impairment is quite rare. We suspect that hearing impairment is caused by bilateral cochlear nerve deficiency due to cochlear nerve canal stenosis. Further studies are necessary to evaluate hearing impairment as a clinical feature in patients with de novo heterozygous 2q24.1q24.3 deletion.
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http://dx.doi.org/10.1111/cga.12207DOI Listing
July 2017

Novel mutation in HPRT1 causing a splicing error with multiple variations.

Nucleosides Nucleotides Nucleic Acids 2017 Jan 18;36(1):1-6. Epub 2016 Oct 18.

a Department of Child Neurology , National Center Hospital, National Center of Neurology and Psychiatry (NCNP) , Tokyo , Japan.

Lesch-Nyhan disease (LND) is a rare X-linked recessive disorder caused by deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT), encoded by the HPRT1. To date, nearly all types of mutations have been reported in the whole gene; however, duplication mutations are rare. We here report the case of a 9-month-old boy with LND. He showed developmental delay, athetosis, and dystonic posture from early infancy, but no self-injurious behaviors. Hyperuricemia was detected, and his HPRT enzyme activity in erythrocytes was completely deficient. A novel duplication mutation (c.372dupT, c.372_374 TTT > c.372_375 TTTT) was identified in exon 4 of the HPRT1, which causes aberrant splicing. This is the third case of a duplication mutation in the HPRT1 that causes splicing error.
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http://dx.doi.org/10.1080/15257770.2016.1163381DOI Listing
January 2017

De novo inbred heterozygous Zeb2/Sip1 mutant mice uniquely generated by germ-line conditional knockout exhibit craniofacial, callosal and behavioral defects associated with Mowat-Wilson syndrome.

Hum Mol Genet 2015 Nov 28;24(22):6390-402. Epub 2015 Aug 28.

Department of Perinatology, Institute for Developmental Research, Aichi Human Service Center, 713-8 Kagiya-cho, Kasugai, Aichi 480-0392, Japan

Mowat-Wilson syndrome (MOWS) is caused by de novo heterozygous mutation at ZEB2 (SIP1, ZFHX1B) gene, and exhibit moderate to severe intellectual disability (ID), a characteristic facial appearance, epilepsy and other congenital anomalies. Establishing a murine MOWS model is important, not only for investigating the pathogenesis of this disease, but also for identifying compounds that may improve the symptoms. However, because the heterozygous Zeb2 knockout mouse could not be maintained as a mouse line with the inbred C57BL/6 background, it was difficult to use those mice for the study of MOWS. Here, we systematically generated de novo Zeb2 Δex7/+ mice by inducing the Zeb2 mutation in the germ cells using conditional recombination system. The de novo Zeb2 Δex7/+ mice with C57BL/6 background developed multiple defects relevant to MOWS, including craniofacial abnormalities, defective corpus callosum formation and the decreased number of parvalbumin interneurons in the cortex. In behavioral analyses, these mice showed reduced motor activity, increased anxiety and impaired sociability. Notably, during the Barnes maze test, immobile Zeb2 mutant mice were observed over repeated trials. In contrast, neither the mouse line nor the de novo Zeb2 Δex7/+ mice with the closed colony ICR background showed cranial abnormalities or reduced motor activities. These results demonstrate the advantages of using de novo Zeb2 Δex7/+ mice with the C57BL/6 background as the MOWS model. To our knowledge, this is the first time an inducible de novo mutation system has been applied to murine germline cells to produce an animal model of a human congenital disease.
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http://dx.doi.org/10.1093/hmg/ddv350DOI Listing
November 2015

Clinical, biochemical and metabolic characterisation of a mild form of human short-chain enoyl-CoA hydratase deficiency: significance of increased N-acetyl-S-(2-carboxypropyl)cysteine excretion.

J Med Genet 2015 Oct 6;52(10):691-8. Epub 2015 Aug 6.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

Background: Short-chain enoyl-CoA hydratase-ECHS1-catalyses many metabolic pathways, including mitochondrial short-chain fatty acid β-oxidation and branched-chain amino acid catabolic pathways; however, the metabolic products essential for the diagnosis of ECHS1 deficiency have not yet been determined. The objective of this report is to characterise ECHS1 and a mild form of its deficiency biochemically, and to determine the candidate metabolic product that can be efficiently used for neonatal diagnosis.

Methods: We conducted a detailed clinical, molecular genetics, biochemical and metabolic analysis of sibling patients with ECHS1 deficiency. Moreover, we purified human ECHS1, and determined the substrate specificity of ECHS1 for five substrates via different metabolic pathways.

Results: Human ECHS1 catalyses the hydration of five substrates via different metabolic pathways, with the highest specificity for crotonyl-CoA and the lowest specificity for tiglyl-CoA. The patients had relatively high (∼7%) residual ECHS1 enzyme activity for crotonyl-CoA and methacrylyl-CoA caused by the compound heterozygous mutations (c.176A>G, (p.N59S) and c.413C>T, (p.A138V)) with normal mitochondrial complex I-IV activities. Affected patients excrete large amounts of N-acetyl-S-(2-carboxypropyl)cysteine, a metabolite of methacrylyl-CoA.

Conclusions: Laboratory data and clinical features demonstrated that the patients have a mild form of ECHS1 deficiency harbouring defective valine catabolic and β-oxidation pathways. N-Acetyl-S-(2-carboxypropyl) cysteine level was markedly high in the urine of the patients, and therefore, N-acetyl-S-(2-carboxypropyl)cysteine was regarded as a candidate metabolite for the diagnosis of ECHS1 deficiency. This metabolite is not part of current routine metabolic screening protocols, and its inclusion, therefore, holds immense potential in accurate diagnosis.
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http://dx.doi.org/10.1136/jmedgenet-2015-103231DOI Listing
October 2015

Erratum to "the spectrum of ZEB2 mutations causing the Mowat-Wilson syndrome in Japanese populations".

Am J Med Genet A 2015 Jun 21;167(6):1428. Epub 2015 Apr 21.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

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http://dx.doi.org/10.1002/ajmg.a.36911DOI Listing
June 2015

Clinical and biochemical characterization of 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency that causes Leigh-like disease and ketoacidosis.

Mol Genet Metab Rep 2014 16;1:455-460. Epub 2014 Oct 16.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

3-Hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency is an autosomal recessive disorder characterized by episodes of ketoacidosis and a Leigh-like basal ganglia disease, without high concentrations of pyruvate and lactate in the cerebrospinal fluid. Only 4 cases of HIBCH deficiency have been reported. However, clinical-biochemical correlation in HIBCH deficiency by determining the detailed residual enzyme activities has not yet been elucidated. Here, we report a case of two Japanese siblings with HIBCH deficiency carrying a new homozygous missense mutation (c.287C > A, [p.A96D]) at the substrate-binding site. A transfection study using HIBCH expression vectors harboring wild type or 4 reported mutations, including the newly identified mutation (p.A96D, p.Y122C, p.G317E, and p.K74Lfs*13), revealed a correlation between residual HIBCH activities and the severity of the disease. All HIBCH mutants, except p.K74Lfs*13, showed residual enzyme activity and only the patient with p.K74Lfs*13 had congenital anomalies. p.G317E showed only low enzyme activity (~ 3%) of that of wild-type HIBCH. Although p.A96D had approximately 7 times higher enzyme activity than p.G317E, patients with p.A96D died during childhood. These findings are essential for clinical management, genetic counseling, and specific meal and concomitant drug considerations as part of the treatment for patients with HIBCH deficiency.
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http://dx.doi.org/10.1016/j.ymgmr.2014.10.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5121361PMC
October 2014

Hypoxanthine guanine phosphoribosyltransferase (HPRT) deficiencies: HPRT1 mutations in new Japanese families and PRPP concentration.

Nucleosides Nucleotides Nucleic Acids 2014 ;33(4-6):218-22

a Department of Genetics, Institute for Developmental Research , Aichi Human Service Center , Aichi , Japan.

Mutation of hypoxanthine guanine phosphoribosyltransferase (HPRT) gives rise to Lesch-Nyhan syndrome, which is characterized by hyperuricemia, severe motor disability, and self-injurious behavior, or HPRT-related gout with hyperuricemia. Four mutations were detected in two Lesch-Nyhan families and two families with partial deficiency since our last report. A new mutation of G to TT (c.456delGinsTT) resulting in a frameshift (p.Q152Hfs*3) in exon 3 has been identified in one Lesch-Nyhan family. In the other Lesch-Nyhan family, a new point mutation in intron 7 (c.532+5G>T) causing splicing error (exon 7 excluded, p.L163Cfs*4) was detected. In the two partial deficiency cases with hyperuricemia, two missense mutations of p.D20V (c.59A>T) and p.H60R (c.179A>G) were found. An increase of erythrocyte PRPP concentration was observed in the respective phenotypes and seems to be correlated with disease severity.
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http://dx.doi.org/10.1080/15257770.2013.865743DOI Listing
February 2015

The spectrum of ZEB2 mutations causing the Mowat-Wilson syndrome in Japanese populations.

Am J Med Genet A 2014 Aug 8;164A(8):1899-908. Epub 2014 Apr 8.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome characterized by moderate or severe intellectual disability, a characteristic facial appearance, microcephaly, epilepsy, agenesis or hypoplasia of the corpus callosum, congenital heart defects, Hirschsprung disease, and urogenital/renal anomalies. It is caused by de novo heterozygous loss of function mutations including nonsense mutations, frameshift mutations, and deletions in ZEB2 at 2q22. ZEB2 encodes the zinc finger E-box binding homeobox 2 protein consisting of 1,214 amino acids. Herein, we report 13 nonsense and 27 frameshift mutations from 40 newly identified MWS patients in Japan. Although the clinical findings of all the Japanese MWS patients with nonsense and frameshift mutations were quite similar to the previous review reports of MWS caused by nonsense mutations, frameshift mutations and deletions of ZEB2, the frequencies of microcephaly, Hirschsprung disease, and urogenital/renal anomalies were small. Patients harbored mutations spanning the region between the amino acids 55 and 1,204 in wild-type ZEB2. There was no obvious genotype-phenotype correlation among the patients. A transfection study demonstrated that the cellular level of the longest form of the mutant ZEB2 protein harboring the p.D1204Rfs*29 mutation was remarkably low. The results showed that the 3'-end frameshift mutation of ZEB2 causes MWS due to ZEB2 instability.
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http://dx.doi.org/10.1002/ajmg.a.36551DOI Listing
August 2014

Mutations in HADHB, which encodes the β-subunit of mitochondrial trifunctional protein, cause infantile onset hypoparathyroidism and peripheral polyneuropathy.

Am J Med Genet A 2014 May 24;164A(5):1180-7. Epub 2014 Mar 24.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan; Department of Pediatrics, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.

Mitochondrial trifunctional protein (MTP) is a hetero-octamer composed of four α- and four β-subunits that catalyzes the final three steps of mitochondrial β-oxidation of long chain fatty acids. HADHA and HADHB encode the α-subunit and the β-subunit of MTP, respectively. To date, only two cases with MTP deficiency have been reported to be associated with hypoparathyroidism and peripheral polyneuropathy. Here, we report on two siblings with autosomal recessive infantile onset hypoparathyroidism, peripheral polyneuropathy, and rhabdomyolysis. Sequence analysis of HADHA and HADHB in both siblings shows that they were homozygous for a mutation in exon 14 of HADHB (c.1175C>T, [p.A392V]) and the parents were heterozygous for the mutation. Biochemical analysis revealed that the patients had MTP deficiency. Structural analysis indicated that the A392V mutation identified in this study and the N389D mutation previously reported to be associated with hypoparathyroidism are both located near the active site of MTP and affect the conformation of the β-subunit. Thus, the present patients are the second and third cases of MTP deficiency associated with missense HADHB mutation and infantile onset hypoparathyroidism. Since MTP deficiency is a treatable disease, MTP deficiency should be considered when patients have hypoparathyroidism as the initial presenting feature in infancy.
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http://dx.doi.org/10.1002/ajmg.a.36434DOI Listing
May 2014

Clinical characterization and identification of duplication breakpoints in a Japanese family with Xq28 duplication syndrome including MECP2.

Am J Med Genet A 2014 Apr 29;164A(4):924-33. Epub 2014 Jan 29.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

Xq28 duplication syndrome including MECP2 is a neurodevelopmental disorder characterized by axial hypotonia at infancy, severe intellectual disability, developmental delay, mild characteristic facial appearance, epilepsy, regression, and recurrent infections in males. We identified a Japanese family of Xq28 duplications, in which the patients presented with cerebellar ataxia, severe constipation, and small feet, in addition to the common clinical features. The 488-kb duplication spanned from L1CAM to EMD and contained 17 genes, two pseudo genes, and three microRNA-coding genes. FISH and nucleotide sequence analyses demonstrated that the duplication was tandem and in a forward orientation, and the duplication breakpoints were located in AluSc at the EMD side, with a 32-bp deletion, and LTR50 at the L1CAM side, with "tc" and "gc" microhomologies at the duplication breakpoints, respectively. The duplicated segment was completely segregated from the grandmother to the patients. These results suggest that the duplication was generated by fork-stalling and template-switching at the AluSc and LTR50 sites. This is the first report to determine the size and nucleotide sequences of the duplicated segments at Xq28 of three generations of a family and provides the genotype-phenotype correlation of the patients harboring the specific duplicated segment.
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http://dx.doi.org/10.1002/ajmg.a.36373DOI Listing
April 2014

Characterization of the mutant β-subunit of β-hexosaminidase for dimer formation responsible for the adult form of Sandhoff disease with the motor neuron disease phenotype.

J Biochem 2013 Jan 5;153(1):111-9. Epub 2012 Nov 5.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, 713-8 Kamiya-cho, Kasugai, Aichi 480-0392, Japan.

The adult form of Sandhoff disease with the motor neuron disease phenotype is a rare neurodegenerative disorder caused by mutations in HEXB encoding the β-subunit of β-hexosaminidase, yet the properties of mutant β-subunits of the disease have not been fully determined. We identified a novel mutation (H235Y) in the β-sheet of the (β/α)₈-barrel domain, in addition to the previously reported P417L mutation that causes aberrant splicing, in a Japanese patient with the motor neuron disease phenotype. Enzyme assays, gel filtration studies and immunoprecipitation studies with HEK293 cells transiently expressing mutant β-subunits demonstrated that the H235Y mutation abolished both α-β and β-β dimer formation without increasing β-hexosaminidase activity, whereas other reported mutant β-subunits (Y456S, P504S or R533H) associated with the motor neuron disease phenotype formed dimers. Structural analysis suggested that the H235Y mutation in the β-sheet of the (β/α)₈-barrel domain changed the conformation of the β-subunit by causing a clash with the E288 side chain. In summary, H235Y is the first mutation in the β-sheet of the (β/α)₈-barrel domain of the β-subunit that abolishes α-β and β-β dimer formation; the presented patient is the second patient to exhibit the motor neuron disease phenotype with P417L and a non-functional allele of HEXB.
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http://dx.doi.org/10.1093/jb/mvs131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3528005PMC
January 2013

Molecular analysis of X-linked inborn errors of purine metabolism: HPRT1 and PRPS1 mutations.

Nucleosides Nucleotides Nucleic Acids 2011 Dec;30(12):1272-5

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Aichi, Japan.

Mutations of two enzyme genes, HPRT1 encoding hypoxanthine guanine phosphoribosyltransferase (HPRT) and PRPS1 encoding a catalytic subunit (PRS-I) of phosphoribosylpyrophosphate synthetase, cause X-linked inborn errors of purine metabolism. Analyzing these two genes, we have identified three HPRT1 mutations in Lesch-Nyhan families following our last report. One of them, a new mutation involving the deletion of 4224 bp from intron 4 to intron 5 and the insertion of an unknown 28 bp, has been identified. This mutation resulted in an enzyme polypeptide with six amino acids deleted due to abnormal mRNA skipping exon 5. The other HPRT1 mutations, a single base deletion (548delT, 183fs189X), and a point mutation causing a splicing error (532+1G>A, 163fs165X) were detected first in Japanese patients but have been reported in European families. On the other hand, in the analysis of PRPS1, no mutation was identified in any patient.
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http://dx.doi.org/10.1080/15257770.2011.597369DOI Listing
December 2011

MBTPS2 mutation causes BRESEK/BRESHECK syndrome.

Am J Med Genet A 2012 Jan 21;158A(1):97-102. Epub 2011 Nov 21.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

BRESEK/BRESHECK syndrome is a multiple congenital malformation characterized by brain anomalies, intellectual disability, ectodermal dysplasia, skeletal deformities, ear or eye anomalies, and renal anomalies or small kidneys, with or without Hirschsprung disease and cleft palate or cryptorchidism. This syndrome has only been reported in three male patients. Here, we report on the fourth male patient presenting with brain anomaly, intellectual disability, growth retardation, ectodermal dysplasia, vertebral (skeletal) anomaly, Hirschsprung disease, low-set and large ears, cryptorchidism, and small kidneys. These manifestations fulfill the clinical diagnostic criteria of BRESHECK syndrome. Since all patients with BRESEK/BRESHECK syndrome are male, and X-linked syndrome of ichthyosis follicularis with atrichia and photophobia is sometimes associated with several features of BRESEK/BRESHECK syndrome such as intellectual disability, vertebral and renal anomalies, and Hirschsprung disease, we analyzed the causal gene of ichthyosis follicularis with atrichia and photophobia syndrome, MBTPS2, in the present patient and identified an p.Arg429His mutation. This mutation has been reported to cause the most severe type of ichthyosis follicularis with atrichia and photophobia syndrome, including neonatal and infantile death. These results demonstrate that the p.Arg429His mutation in MBTPS2 causes BRESEK/BRESHECK syndrome.
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http://dx.doi.org/10.1002/ajmg.a.34373DOI Listing
January 2012

Identification and characterization of splicing variants of PLEKHA5 (Plekha5) during brain development.

Gene 2012 Jan 20;492(1):270-5. Epub 2011 Oct 20.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Aichi, Japan.

PLEKHA5 (pleckstrin homology domain-containing protein family A, member 5) belongs to the PLEKHA family (PLEKHA1-6); however, the properties of this protein remain poorly characterized. We have identified and characterized two forms of PLEKHA5 mRNA. The long form of PLEKHA5 (L-PLEKHA5) contains 32 exons, encodes 1282 amino acids, and is specifically expressed in the brain; the short form of PLEKHA5 (S-PLEKHA5) is generated by alternative splicing of L-PLEKHA5, contains 26 exons, encodes 1116 amino acids, and is ubiquitously expressed. Both forms of the protein contain putative Trp-Trp (WW) and pleckstrin homology (PH) domains and are located mainly in the cytosol. Developmental and age-dependent expression studies in the mouse brain have shown that Plekha5 is the most abundantly expressed protein at E13.5 with S-Plekha5 dominancy. L-Plekha5 levels increased gradually with the decrease in total Plekha5 levels; moreover, L-Plekha5 became the dominant protein at E17.5, maintaining its dominance throughout adulthood. Protein-lipid overlay assays have indicated that the PH domain of PLEKHA5 specifically interacts with PI3P, PI4P, PI5P, and PI(3,5)P2. These results suggest that the S- to L-conversion of PLEKHA5 (Plekha5) may play an important role in brain development through association with specific phosphoinositides.
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http://dx.doi.org/10.1016/j.gene.2011.10.018DOI Listing
January 2012

Clinical and genomic characterization of siblings with a distal duplication of chromosome 9q (9q34.1-qter).

Am J Med Genet A 2011 Sep 10;155A(9):2274-80. Epub 2011 Aug 10.

Department of Clinical Genetics, Central Hospital, Aichi Human Service Center, Kasugai, Japan.

We report herein on two female siblings exhibiting mild intellectual disability, hypotonia in infancy, postnatal growth retardation, characteristic appearance of the face, fingers, and toes. Their healthy mother had a translocation between 9q34.1 and the 13pter. FISH and array CGH analysis demonstrated that the two children had an additional 8.5 Mb segment of the 9q34.1-qter at 13pter. The clinical features of the present cases were similar to those of previously reported 9q34 duplication cases; however, the present cases did not exhibit other abnormal behaviors, such as autistic features or attention deficit disorders, those are reportedly associated with 9q34 duplications. A 3.0 Mb region (9q34.1-q34.3) within 9q34 duplication in our patients are overlapped with duplication region of previously reported cases and is proposed to be critical for the presentation of several phenotypes associated with 9q34 duplications.
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http://dx.doi.org/10.1002/ajmg.a.34160DOI Listing
September 2011

A wide spectrum of clinical and brain MRI findings in patients with SLC19A3 mutations.

BMC Med Genet 2010 Dec 22;11:171. Epub 2010 Dec 22.

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Aichi, Japan.

Background: SLC19A3 (solute carrier family 19, member 3) is a thiamin transporter with 12 transmembrane domains. Homozygous or compound heterozygous mutations in SLC19A3 cause two distinct clinical phenotypes, biotin-responsive basal ganglia disease and Wernicke's-like encephalopathy. Biotin and/or thiamin are effective therapies for both diseases.

Methods: We conducted on the detailed clinical, brain MRI and molecular genetic analysis of four Japanese patients in a Japanese pedigree who presented with epileptic spasms in early infancy, severe psychomotor retardation, and characteristic brain MRI findings of progressive brain atrophy and bilateral thalami and basal ganglia lesions.

Results: Genome-wide linkage analysis revealed a disease locus at chromosome 2q35-37, which enabled identification of the causative mutation in the gene SLC19A3. A pathogenic homozygous mutation (c.958G > C, [p.E320Q]) in SLC19A3 was identified in all four patients and their parents were heterozygous for the mutation. Administration of a high dose of biotin for one year improved neither the neurological symptoms nor the brain MRI findings in one patient.

Conclusion: Our cases broaden the phenotypic spectrum of disorders associated with SLC19A3 mutations and highlight the potential benefit of biotin and/or thiamin treatments and the need to assess the clinical efficacy of these treatments.
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http://dx.doi.org/10.1186/1471-2350-11-171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3022826PMC
December 2010

Characterization of a de novo balanced t(4;20)(q33;q12) translocation in a patient with mental retardation.

Am J Med Genet A 2010 Dec;152A(12):3057-67

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.

CHD6 is an ATP-dependent chromatin-remodeling enzyme, which has been implicated as a crucial component for maintaining and regulating chromatin structure. CHD6 belongs to the largest subfamily, subfamily III (CHD6-9), of the chromodomain helicase DNA (CHD-binding protein) family of enzymes (CHD1-9). Here we report on a female patient with a balanced translocation t(4;20)(q33;q12) presenting with severe mental retardation and brachydactyly of the toes. We identified the translocation breakpoint in intron 27 of CHD6 at 20q12, while the 4q33 breakpoint was intergenic. Northern blot analysis demonstrated the CHD6 mRNA in the patient's lymphoblastoid cells was decreased to ∼50% of the control cells. To investigate the cellular mechanism of diseases resulting from decreased CHD subfamily III proteins, we knocked down CHD6 or CHD7 by RNA interference in HeLa cells and analyzed chromosome alignment. The both CHD6- and CHD7-knockdown cells showed increased frequency of misaligned chromosomes on metaphase plates. Moreover, an elevated frequency of aneuploidy, the major cause of miscarriages and mental retardation, was observed in patients with CHD6 and CHD7 haploinsufficiency. These results suggest that CHD6 and CHD7 play important roles in chromatin assembly during mitosis and that mitotic delay and/or impaired cell proliferation may be associated with pathogenesis of the diseases caused by CHD6 or CHD7 mutations.
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http://dx.doi.org/10.1002/ajmg.a.33174DOI Listing
December 2010

Genotype-phenotype correlations in Down syndrome identified by array CGH in 30 cases of partial trisomy and partial monosomy chromosome 21.

Eur J Hum Genet 2009 Apr 12;17(4):454-66. Epub 2008 Nov 12.

Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland.

Down syndrome (DS) is one of the most frequent congenital birth defects, and the most common genetic cause of mental retardation. In most cases, DS results from the presence of an extra copy of chromosome 21. DS has a complex phenotype, and a major goal of DS research is to identify genotype-phenotype correlations. Cases of partial trisomy 21 and other HSA21 rearrangements associated with DS features could identify genomic regions associated with specific phenotypes. We have developed a BAC array spanning HSA21q and used array comparative genome hybridization (aCGH) to enable high-resolution mapping of pathogenic partial aneuploidies and unbalanced translocations involving HSA21. We report the identification and mapping of 30 pathogenic chromosomal aberrations of HSA21 consisting of 19 partial trisomies and 11 partial monosomies for different segments of HSA21. The breakpoints have been mapped to within approximately 85 kb. The majority of the breakpoints (26 of 30) for the partial aneuploidies map within a 10-Mb region. Our data argue against a single DS critical region. We identify susceptibility regions for 25 phenotypes for DS and 27 regions for monosomy 21. However, most of these regions are still broad, and more cases are needed to narrow down the phenotypic maps to a reasonable number of candidate genomic elements per phenotype.
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http://dx.doi.org/10.1038/ejhg.2008.214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2986205PMC
April 2009

Molecular analysis of hypoxanthine guanine phosphoribosyltransferase (HPRT) deficiencies: novel mutations and the spectrum of Japanese mutations.

Nucleosides Nucleotides Nucleic Acids 2008 Jun;27(6):570-4

Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai Aichi, Japan.

Inherited mutation of hypoxanthine guanine phosphoribosyltransferase, (HPRT) gives rise to Lesch-Nyhan syndrome or HPRT-related gout. We have identified a number of HPRT mutations in patients manifesting different clinical phenotypes, by analyzing all nine exons of the HPRT gene (HPRT1) from genomic DNA and reverse transcribed mRNA using the PCR technique coupled with direct sequencing. Recently, we detected two novel mutations: a single nucleotide substitution (430C > T) resulting in a nonsense mutation Q144X, and a deletion of HPRT1 exon 1 expressing no mRNA of HPRT. Furthermore, we summarized the spectrum of 56 Japanese HPRT mutations.
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http://dx.doi.org/10.1080/15257770802135869DOI Listing
June 2008

Mowat-Wilson syndrome affecting 3 siblings.

J Child Neurol 2008 Mar 29;23(3):274-8. Epub 2008 Jan 29.

Department of Pediatrics, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo.

We herein report 3 cases of Mowat-Wilson syndrome, characterized by distinct facial features, severe psychomotor retardation, and epilepsy, recurring in 3 siblings from the same parents. The proband was a 15-month-old boy, the youngest of 3 children (2 elder sisters), who was referred to our hospital for the treatment of severe seizures. The clinical features and course of these 3 siblings were compatible with those of previously reported Mowat-Wilson syndrome patients, and all siblings had the same E87X nonsense mutation in ZFHX1B, whereas their mother did not show the mutation. Because Mowat-Wilson syndrome has been caused by de novo mutation in ZFHX1B, germ-line mosaicism should be considered if recurrence in siblings is observed.
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http://dx.doi.org/10.1177/0883073807309231DOI Listing
March 2008