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Ling D, Xie W, Mao X, Yang S, Pang H, Yang P, Shen P, Tang Y. Compound heterozygous B3GALNT2 mutations in a fetus with encephalocele: A case report. Clin Case Rep 2024; 12:e8691. [PMID: 38585583 PMCID: PMC10997814 DOI: 10.1002/ccr3.8691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 02/08/2024] [Accepted: 02/22/2024] [Indexed: 04/09/2024] Open
Abstract
An encephalocele is a congenital malformation characterized by protrusion of the intracranial contents through a cranial defect. We report that a fetus of a pregnant mother who had two consecutive pregnancies with ultrasound-detected encephalocele carried compound heterozygous variants in B3GALNT2 NM_152490.5:c.[1423C > T (p.Gln475Ter)]; [261-2A > G] of maternal and paternal origins, respectively, as confirmed by exome sequencing followed by Sanger sequencing validation. The present case implies that mutations in B3GALNT2, a well-known dystroglycanopathy causative gene, may result in a phenotype of neural tube defect, providing new insights into the clinical spectrum of B3GALNT2-related disorders. Our study may contribute to prenatal screening/diagnosis and genetic counseling of congenital brain malformations.
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Affiliation(s)
- Dandan Ling
- Clinical Research Center For Placental Medicine In Hunan ProvinceChangsha CityChina
- Department of ObstetricsHunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
| | - Wanqin Xie
- Clinical Research Center For Placental Medicine In Hunan ProvinceChangsha CityChina
- NHC key labratory of birth defects for research and prevention, Hunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
| | - Xiao Mao
- Clinical Research Center For Placental Medicine In Hunan ProvinceChangsha CityChina
- NHC key labratory of birth defects for research and prevention, Hunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
| | - Shengzhi Yang
- Department of PediatricsHunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
| | - Haiyan Pang
- Department of Reproductive MedicineAffiliated Hospital of Weifang Medical UniversityWeifangChina
| | - Ping Yang
- Clinical Research Center For Placental Medicine In Hunan ProvinceChangsha CityChina
- Department of ObstetricsHunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
| | - Ping Shen
- Clinical Research Center For Placental Medicine In Hunan ProvinceChangsha CityChina
- Department of ObstetricsHunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
| | - Yabing Tang
- Clinical Research Center For Placental Medicine In Hunan ProvinceChangsha CityChina
- Department of ObstetricsHunan Provincial Maternal and Child Health Care HospitalChangsha CityChina
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2
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Lee HF, Chi CS. Congenital disorders of glycosylation and infantile epilepsy. Epilepsy Behav 2023; 142:109214. [PMID: 37086590 DOI: 10.1016/j.yebeh.2023.109214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 04/01/2023] [Accepted: 04/04/2023] [Indexed: 04/24/2023]
Abstract
Congenital disorders of glycosylation (CDG) are a group of rare inherited metabolic disorders caused by defects in various defects of protein or lipid glycosylation pathways. The symptoms and signs of CDG usually develop in infancy. Epilepsy is commonly observed in CDG individuals and is often a presenting symptom. These epilepsies can present across the lifespan, share features of refractoriness to antiseizure medications, and are often associated with comorbid developmental delay, psychomotor regression, intellectual disability, and behavioral problems. In this review, we discuss CDG and infantile epilepsy, focusing on an overview of clinical manifestations and electroencephalographic features. Finally, we propose a tiered approach that will permit a clinician to systematically investigate and identify CDG earlier, and furthermore, to provide genetic counseling for the family.
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Affiliation(s)
- Hsiu-Fen Lee
- Department of Post-Baccalaureate Medicine, College of Medicine, National Chung Hsing University, 145, Xingda Rd., Taichung 402, Taiwan; Division of Pediatric Neurology, Children's Medical Center, Taichung Veterans General Hospital, 1650, Taiwan Boulevard Sec. 4, Taichung 407, Taiwan.
| | - Ching-Shiang Chi
- Division of Pediatric Neurology, Children's Medical Center, Taichung Veterans General Hospital, 1650, Taiwan Boulevard Sec. 4, Taichung 407, Taiwan.
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3
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Expanding the Phenotype of B3GALNT2-Related Disorders. Genes (Basel) 2022; 13:genes13040694. [PMID: 35456500 PMCID: PMC9024883 DOI: 10.3390/genes13040694] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 04/13/2022] [Indexed: 11/16/2022] Open
Abstract
Dystroglycanopathies are a group of congenital muscular dystrophies (CMDs) that include a broad phenotypic spectrum ranging from late-onset limb-girdle muscular dystrophy to severe muscle–eye–brain disease, Walker–Warburg syndrome, and Fukuyama congenital muscular dystrophy. In addition to clinical heterogeneity, CMDs are characterized by genetic heterogeneity. To date, 18 genes have been associated with CMDs. One of them is B3GALNT2, which encodes the β-1,3-N-acetylgalactosaminyltransferase 2 that glycosylates α-dystroglycan. In this study, using exome sequencing, we identify a homozygous frameshift variant in B3GALNT2 due to a mixed uniparental disomy of chromosome 1 in a 7-year-old girl with global developmental delay, severely delayed active language development, and autism spectrum disorder but without any symptoms of muscular dystrophy. In addition to this case, we also provide an overview of all previously reported cases, further expanding the phenotypic spectrum.
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4
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Wu WJ, Sun SZ, Li BG. Congenital muscular dystrophy caused by beta1,3-N-acetylgalactosaminyltransferase 2 gene mutation: Two case reports. World J Clin Cases 2022; 10:1056-1066. [PMID: 35127920 PMCID: PMC8790464 DOI: 10.12998/wjcc.v10.i3.1056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 08/20/2021] [Accepted: 12/23/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Mutations in the beta1,3-N-acetylgalactosaminyltransferase 2 (B3GALNT2) gene can lead to impaired glycosylation of α-dystroglycan, which, in turn, causes congenital muscular dystrophy (CMD). The clinical phenotypes of CMD are broad, and there are only a few reports of CMD worldwide.
CASE SUMMARY This report describes the cases of two children with CMD caused by B3GALNT2 gene mutation. The main manifestations of the two cases were abnormal walking posture, language development delay, and abnormal development of the white matter. Case 2 also had unreported symptoms of meningocele and giant arachnoid cyst. Both cases had compound heterozygous mutations of the B3GALNT2 gene, each containing a truncated mutation and a missense mutation, and three of the four loci had not been reported. Nineteen patients with CMD caused by B3GALNT2 gene mutation were found in the literature. Summary and analysis of the characteristics of CMD caused by B3GALNT2 gene mutation showed that 100% of the cases had nervous system involvement. Head magnetic resonance imaging often showed abnormal manifestations, and more than half of the children had eye and muscle involvement; some of the gene-related symptoms were self-healing.
CONCLUSION B3GALNT2 gene can be used as one of the candidate genes for screening CMD, cognitive development retardation, epilepsy, and multiple brain developmental malformations in infants.
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Affiliation(s)
- Wen-Juan Wu
- Department of Neurology, Hebei Children's Hospital, Hebei Children's Hospital Affiliated to Hebei Medical University, Shijiazhuang 050031, Hebei Province, China
| | - Su-Zhen Sun
- Department of Neurology, Hebei Children's Hospital, Hebei Children's Hospital Affiliated to Hebei Medical University, Shijiazhuang 050031, Hebei Province, China
| | - Bao-Guang Li
- Department of Neurology, Hebei Children's Hospital, Hebei Children's Hospital Affiliated to Hebei Medical University, Shijiazhuang 050031, Hebei Province, China
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5
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Mohamadian M, Rastegar M, Pasamanesh N, Ghadiri A, Ghandil P, Naseri M. Clinical and Molecular Spectrum of Muscular Dystrophies (MDs) with Intellectual Disability (ID): a Comprehensive Overview. J Mol Neurosci 2021; 72:9-23. [PMID: 34727324 DOI: 10.1007/s12031-021-01933-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 10/18/2021] [Indexed: 12/22/2022]
Abstract
Muscular dystrophies encompass a wide and heterogeneous subset of hereditary myopathies that manifest by the structural or functional abnormalities in the skeletal muscle. Some pathogenic mutations induce a dysfunction or loss of proteins that are critical for the stability of muscle cells, leading to progressive muscle degradation and weakening. Several studies have well-established cognitive deficits in muscular dystrophies which are mainly due to the disruption of brain-specific expression of affected muscle proteins. We provide a comprehensive overview of the types of muscular dystrophies that are accompanied by intellectual disability by detailed consulting of the main libraries. The current paper focuses on the clinical and molecular evidence about Duchenne, congenital, limb-girdle, and facioscapulohumeral muscular dystrophies as well as myotonic dystrophies. Because these syndromes impose a heavy burden of psychological and financial problems on patients, their families, and the health care community, a thorough examination is necessary to perform timely psychological and medical interventions and thus improve the quality of life.
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Affiliation(s)
- Malihe Mohamadian
- Cancer Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran, 616476515.
| | - Mandana Rastegar
- Department of Molecular Medicine, Birjand University of Medical Sciences, Birjand, Iran
| | - Negin Pasamanesh
- Zanjan Metabolic Diseases Research Center, Zanjan University of Medical Sciences, Zanjan, Iran
| | - Ata Ghadiri
- Department of Immunology, Medical School, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Pegah Ghandil
- Diabetes Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.,Department of Medical Genetics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Mohsen Naseri
- Cellular and Molecular Research Center, Birjand University of Medical Sciences, Birjand, Iran
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6
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Aygün N, Elwell AL, Liang D, Lafferty MJ, Cheek KE, Courtney KP, Mory J, Hadden-Ford E, Krupa O, de la Torre-Ubieta L, Geschwind DH, Love MI, Stein JL. Brain-trait-associated variants impact cell-type-specific gene regulation during neurogenesis. Am J Hum Genet 2021; 108:1647-1668. [PMID: 34416157 PMCID: PMC8456186 DOI: 10.1016/j.ajhg.2021.07.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 07/23/2021] [Indexed: 12/21/2022] Open
Abstract
Interpretation of the function of non-coding risk loci for neuropsychiatric disorders and brain-relevant traits via gene expression and alternative splicing quantitative trait locus (e/sQTL) analyses is generally performed in bulk post-mortem adult tissue. However, genetic risk loci are enriched in regulatory elements active during neocortical differentiation, and regulatory effects of risk variants may be masked by heterogeneity in bulk tissue. Here, we map e/sQTLs, and allele-specific expression in cultured cells representing two major developmental stages, primary human neural progenitors (n = 85) and their sorted neuronal progeny (n = 74), identifying numerous loci not detected in either bulk developing cortical wall or adult cortex. Using colocalization and genetic imputation via transcriptome-wide association, we uncover cell-type-specific regulatory mechanisms underlying risk for brain-relevant traits that are active during neocortical differentiation. Specifically, we identified a progenitor-specific eQTL for CENPW co-localized with common variant associations for cortical surface area and educational attainment.
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Affiliation(s)
- Nil Aygün
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Angela L Elwell
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dan Liang
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Michael J Lafferty
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kerry E Cheek
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kenan P Courtney
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jessica Mory
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ellie Hadden-Ford
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Oleh Krupa
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Luis de la Torre-Ubieta
- Neurogenetics Program, Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Center for Autism Research and Treatment, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Psychiatry and Biobehavioral Sciences, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Daniel H Geschwind
- Neurogenetics Program, Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Center for Autism Research and Treatment, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Psychiatry and Biobehavioral Sciences, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Michael I Love
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jason L Stein
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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7
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Bigotti MG, Brancaccio A. High degree of conservation of the enzymes synthesizing the laminin-binding glycoepitope of α-dystroglycan. Open Biol 2021; 11:210104. [PMID: 34582712 PMCID: PMC8478517 DOI: 10.1098/rsob.210104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The dystroglycan (DG) complex plays a pivotal role for the stabilization of muscles in Metazoa. It is formed by two subunits, extracellular α-DG and transmembrane β-DG, originating from a unique precursor via a complex post-translational maturation process. The α-DG subunit is extensively glycosylated in sequential steps by several specific enzymes and employs such glycan scaffold to tightly bind basement membrane molecules. Mutations of several of these enzymes cause an alteration of the carbohydrate structure of α-DG, resulting in severe neuromuscular disorders collectively named dystroglycanopathies. Given the fundamental role played by DG in muscle stability, it is biochemically and clinically relevant to investigate these post-translational modifying enzymes from an evolutionary perspective. A first phylogenetic history of the thirteen enzymes involved in the fabrication of the so-called 'M3 core' laminin-binding epitope has been traced by an overall sequence comparison approach, and interesting details on the primordial enzyme set have emerged, as well as substantial conservation in Metazoa. The optimization along with the evolution of a well-conserved enzymatic set responsible for the glycosylation of α-DG indicate the importance of the glycosylation shell in modulating the connection between sarcolemma and surrounding basement membranes to increase skeletal muscle stability, and eventually support movement and locomotion.
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Affiliation(s)
- Maria Giulia Bigotti
- School of Translational Health Sciences, Research Floor Level 7, Bristol Royal Infirmary, Upper Maudlin Street, Bristol BS2 8HW, UK,School of Biochemistry, University Walk, University of Bristol, Bristol BS8 1TD, UK
| | - Andrea Brancaccio
- School of Biochemistry, University Walk, University of Bristol, Bristol BS8 1TD, UK,Institute of Chemical Sciences and Technologies ‘Giulio Natta’ (SCITEC) - CNR, Largo F.Vito 1, 00168, Rome, Italy
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8
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Kutluk G, Kadem N, Bektas O, Eroglu HN. A Rare Cause of Autism Spectrum Disorder: Megaconial Muscular Dystrophy. Ann Indian Acad Neurol 2020; 23:694-696. [PMID: 33623274 PMCID: PMC7887486 DOI: 10.4103/aian.aian_98_19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 03/14/2019] [Indexed: 12/27/2022] Open
Abstract
Megaconial congenital muscular dystrophy (OMIM 602541) is defined by early-onset hypotonia, mildly elevated serum creatine kinase (CK) levels, muscle wasting, cardiomyopathy, psychomotor developmental delay and intellectual disability. The disease is caused by loss-of-function mutations in Choline kinase beta gene (CHKB) and has specific muscle biopsy findings. Here we investigate two patients with weakness of proximal muscles and generalized muscle atrophy, skin changes, agressiveness, social communication and empathy difficulties. Both patients had mildly elevated serum CK levels. Whole exome sequencing (WES) performed for both patients and homozygous c.818+1G>A and homozygous c.1031+1G>A variants were detected in patient 1 and patient 2, respectively. We would like to draw the attention of autism spectrum disorder in early diagnosis of congenital muscular dystrophies.
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Affiliation(s)
- Gultekin Kutluk
- Antalya Training and Research Hospital, Pediatric Neurology Clinic, Ankara, Turkey
| | - Naz Kadem
- Antalya Training and Research Hospital, Pediatrics Clinic, Ankara, Turkey
| | - Omer Bektas
- Ankara University Faculty of Medicine, Department of Pediatric Neurology, Ankara, Turkey
| | - Hatice Nur Eroglu
- Antalya Training and Research Hospital, Pediatrics Clinic, Ankara, Turkey
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9
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Chen XY, Song DY, Fan YB, Tan DD, Chang XZ, Xiao JX, Toda T, Xiong H. Novel mutations in B3GALNT2 gene causing α-dystroglycanopathy in Chinese patients. Chin Med J (Engl) 2020; 134:1483-1485. [PMID: 33290285 PMCID: PMC8213326 DOI: 10.1097/cm9.0000000000001283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- Xiao-Yu Chen
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Dan-Yu Song
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Yan-Bin Fan
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Dan-Dan Tan
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Xing-Zhi Chang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Jiang-Xi Xiao
- Department of Medical Imaging, Peking University First Hospital, Beijing 100034, China
| | - Tatsushi Toda
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
| | - Hui Xiong
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
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10
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Congenital hearing impairment associated with peripheral cochlear nerve dysmyelination in glycosylation-deficient muscular dystrophy. PLoS Genet 2020; 16:e1008826. [PMID: 32453729 PMCID: PMC7274486 DOI: 10.1371/journal.pgen.1008826] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 06/05/2020] [Accepted: 05/04/2020] [Indexed: 02/06/2023] Open
Abstract
Hearing loss (HL) is one of the most common sensory impairments and etiologically and genetically heterogeneous disorders in humans. Muscular dystrophies (MDs) are neuromuscular disorders characterized by progressive degeneration of skeletal muscle accompanied by non-muscular symptoms. Aberrant glycosylation of α-dystroglycan causes at least eighteen subtypes of MD, now categorized as MD-dystroglycanopathy (MD-DG), with a wide spectrum of non-muscular symptoms. Despite a growing number of MD-DG subtypes and increasing evidence regarding their molecular pathogeneses, no comprehensive study has investigated sensorineural HL (SNHL) in MD-DG. Here, we found that two mouse models of MD-DG, Largemyd/myd and POMGnT1-KO mice, exhibited congenital, non-progressive, and mild-to-moderate SNHL in auditory brainstem response (ABR) accompanied by extended latency of wave I. Profoundly abnormal myelination was found at the peripheral segment of the cochlear nerve, which is rich in the glycosylated α-dystroglycan–laminin complex and demarcated by “the glial dome.” In addition, patients with Fukuyama congenital MD, a type of MD-DG, also had latent SNHL with extended latency of wave I in ABR. Collectively, these findings indicate that hearing impairment associated with impaired Schwann cell-mediated myelination at the peripheral segment of the cochlear nerve is a notable symptom of MD-DG. Hearing loss (HL) is one of the most common sensory impairments and heterogeneous disorders in humans. Up to 60% of HL cases are caused by genetic factors, and approximately 30% of genetic HL cases are syndromic. Although 400–700 genetic syndromes are associated with sensorineural HL (SNHL), caused due to problems in the nerve pathways from the cochlea to the brain, only about 45 genes are known to be associated with syndromic HL. Muscular dystrophies (MDs) are neuromuscular disorders characterized by progressive degeneration of skeletal muscle accompanied by non-muscular symptoms. MD-dystroglycanopathy (MD-DG), caused by aberrant glycosylation of α-dystroglycan, is an MD subtype with a wide spectrum of non-muscular symptoms. Despite a growing number of MD-DG subtypes (at least 18), no comprehensive study has investigated SNHL in MD-DG. Here, we found that hearing impairment was associated with abnormal myelination of the peripheral segment of the cochlear nerve caused by impaired dystrophin–dystroglycan complex in two mouse models (type 3 and 6) of MD-DG and in patients (type 4) with MD-DG. This is the first comprehensive study investigating SNHL in MD-DG. Our findings may provide new insights into understanding the pathogenic characteristics and mechanisms underlying inherited syndromic hearing impairment.
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11
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Nakane T, Angata K, Sato T, Kaji H, Narimatsu H. Identification of mammalian glycoproteins with type-I LacdiNAc structures synthesized by the glycosyltransferase B3GALNT2. J Biol Chem 2019; 294:7433-7444. [PMID: 30898876 DOI: 10.1074/jbc.ra118.006892] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 03/04/2019] [Indexed: 11/06/2022] Open
Abstract
The type-I LacdiNAc (LDN; GalNAcβ1-3GlcNAc) has rarely been observed in mammalian cells except in the O-glycan of α-dystroglycan, in contrast to type-II LDN structures (GalNAcβ1-4GlcNAc) in N- and O-glycans that are present in many mammalian glycoproteins, such as pituitary and hypothalamic hormones. Although a β1,3-N-acetylgalactosaminyltransferase 2 (B3GALNT2; type-I LDN synthase) has been cloned, the function of type-I LDN in mammalian cells is still unclear, as its carrier protein(s) has not been identified. In this study, using HeLa cells, we demonstrate that inhibition of Golgi-resident glycosyltransferase increases the abundance of B3GALNT2-synthesized type-I LDN structures, recognized by Wisteria floribunda agglutinin (WFA). Using isotope-coded glycosylation site-specific tagging (IGOT)-LC/MS analysis of Lec8 Chinese hamster cells lacking galactosylation and of cells transfected with the B3GALNT2 gene, we identified the glycoproteins that carry B3GALNT2-generated type-I LDN in their N-glycans. Our results further revealed that LDN presence on low-density lipoprotein receptor-related protein 1 and nicastrin depends on B3GALNT2, indicating the occurrence of type-I LDN in vivo in mammalian cells. Our analysis also uncovered that most of the identified glycoproteins localize to intracellular organelles, particularly to the endoplasmic reticulum. Whereas B4GALNT3 and B4GALNT4 synthesized LDN on extracellular glycoproteins, B3GALNT2 primarily transferred LDN to intracellular glycoproteins, thereby clearly delineating proteins that carry type-I or type-II LDNs. Taken together, our results indicate the presence of mammalian glycoproteins carrying type-I LDN on N-glycans and suggest that type-I and type-II LDNs have different roles in vivo.
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Affiliation(s)
- Takahiro Nakane
- From the Glycoscience and Glycotechnology Research Group, Biotechnology Research Institute for Drug Discovery, Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan and.,Doctoral Program in Clinical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki 305-8575, Japan
| | - Kiyohiko Angata
- From the Glycoscience and Glycotechnology Research Group, Biotechnology Research Institute for Drug Discovery, Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan and
| | - Takashi Sato
- From the Glycoscience and Glycotechnology Research Group, Biotechnology Research Institute for Drug Discovery, Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan and
| | - Hiroyuki Kaji
- From the Glycoscience and Glycotechnology Research Group, Biotechnology Research Institute for Drug Discovery, Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan and
| | - Hisashi Narimatsu
- From the Glycoscience and Glycotechnology Research Group, Biotechnology Research Institute for Drug Discovery, Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan and .,Doctoral Program in Clinical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki 305-8575, Japan
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