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Ahmed AN, Rawlins LE, Khan N, Jan Z, Ubeyratna N, Voutsina N, Azeem A, Khan S, Baple EL, Crosby AH, Saleha S. Expanding the genetic spectrum of hereditary motor sensory neuropathies in Pakistan. BMC Neurol 2024; 24:394. [PMID: 39415096 PMCID: PMC11481789 DOI: 10.1186/s12883-024-03882-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 09/25/2024] [Indexed: 10/18/2024] Open
Abstract
BACKGROUND Hereditary motor and sensory neuropathy (HMSN) refers to a group of inherited progressive peripheral neuropathies characterized by reduced nerve conduction velocity with chronic segmental demyelination and/or axonal degeneration. HMSN is highly clinically and genetically heterogeneous with multiple inheritance patterns and phenotypic overlap with other inherited neuropathies and neurodegenerative diseases. Due to this high complexity and genetic heterogeneity, this study aimed to elucidate the genetic causes of HMSN in Pakistani families using Whole Exome Sequencing (WES) for variant identification and Sanger sequencing for validation and segregation analysis, facilitating accurate clinical diagnosis. METHODS Families from Khyber Pakhtunkhwa with at least two members showing HMSN symptoms, who had not previously undergone genetic analysis, were included. Referrals for genetic investigations were based on clinical features suggestive of HMSN by local neurologists. WES was performed on affected individuals from each family, with Sanger sequencing used to validate and analyze the segregation of identified variants among family members. Clinical data including age of onset were assessed for variability among affected individuals, and the success rate of genetic diagnosis was compared with existing literature using proportional differences and Cohen's h. RESULTS WES identified homozygous pathogenic variants in GDAP1 (c.310 + 4 A > G, p.?), SETX (c.5948_5949del, p.(Asn1984Profs*30), IGHMBP2 (c.1591 C > A, p.(Pro531Thr) and NARS1 (c.1633 C > T, p.(Arg545Cys) as causative for HMSN in five out of nine families, consistent with an autosomal recessive inheritance pattern. Additionally, in families with HMSN, a SETX variant was found to cause cerebellar ataxia, while a NARS1 variant was linked to intellectual disability. Based on American College of Medical Genetics and Genomics criteria, the GDAP1 variant is classified as a variant of uncertain significance, while variants in SETX and IGHMBP2 are classified as pathogenic, and the NARS1 variant is classified as likely pathogenic. The age of onset ranged from 1 to 15 years (Mean = 5.13, SD = 3.61), and a genetic diagnosis was achieved in 55.56% of families with HMSN, with small effect sizes compared to previous studies. CONCLUSIONS This study expands the molecular genetic spectrum of HMSN and HMSN plus type neuropathies in Pakistan and facilitates accurate diagnosis, genetic counseling, and clinical management for affected families.
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Affiliation(s)
- Asif Naveed Ahmed
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, 26000, Pakistan
| | - Lettie E Rawlins
- Medical Research, RILD Wellcome Wolfson Centre (Level 4), Royal Devon and Exeter NHS Foundation Trust, Exeter, Devon, EX2 5DW, UK.
- Peninsula Clinical Genetics Service, Royal Devon & Exeter Hospital (Heavitree), Exeter, UK.
| | - Niamat Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, 26000, Pakistan
| | - Zakir Jan
- Department of Neurology, Pakistan Institute of Medical Science, Islamabad, 44000, Pakistan
| | - Nishanka Ubeyratna
- Medical Research, RILD Wellcome Wolfson Centre (Level 4), Royal Devon and Exeter NHS Foundation Trust, Exeter, Devon, EX2 5DW, UK
| | - Nikol Voutsina
- Medical Research, RILD Wellcome Wolfson Centre (Level 4), Royal Devon and Exeter NHS Foundation Trust, Exeter, Devon, EX2 5DW, UK
| | - Arfa Azeem
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, 26000, Pakistan
| | - Saadullah Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, 26000, Pakistan
| | - Emma L Baple
- Medical Research, RILD Wellcome Wolfson Centre (Level 4), Royal Devon and Exeter NHS Foundation Trust, Exeter, Devon, EX2 5DW, UK
| | - Andrew H Crosby
- Medical Research, RILD Wellcome Wolfson Centre (Level 4), Royal Devon and Exeter NHS Foundation Trust, Exeter, Devon, EX2 5DW, UK
| | - Shamim Saleha
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, 26000, Pakistan.
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Armirola-Ricaurte C, Morant L, Adant I, Hamed SA, Pipis M, Efthymiou S, Amor-Barris S, Atkinson D, Van de Vondel L, Tomic A, de Vriendt E, Zuchner S, Ghesquiere B, Hanna M, Houlden H, Lunn MP, Reilly MM, Rasic VM, Jordanova A. Biallelic variants in COX18 cause a mitochondrial disorder primarily manifesting as peripheral neuropathy. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.07.03.24309787. [PMID: 39006432 PMCID: PMC11245062 DOI: 10.1101/2024.07.03.24309787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Defects in mitochondrial dynamics are a common cause of Charcot-Marie-Tooth disease (CMT), while primary deficiencies in the mitochondrial respiratory chain (MRC) are rare and atypical for this etiology. This study aims to report COX18 as a novel CMT-causing gene. This gene encodes an assembly factor of mitochondrial Complex IV (CIV) that translocates the C-terminal tail of MTCO2 across the mitochondrial inner membrane. Exome sequencing was performed in four affected individuals. The patients and available family members underwent thorough neurological and electrophysiological assessment. The impact of one of the identified variants on splicing, protein levels, and mitochondrial bioenergetics was investigated in patient-derived lymphoblasts. The functionality of the mutant protein was assessed using a Proteinase K protection assay and immunoblotting. Neuronal relevance of COX18 was assessed in a Drosophila melanogaster knockdown model. Exome sequencing coupled with homozygosity mapping revealed a homozygous splice variant c.435-6A>G in COX18 in two siblings with early-onset progressive axonal sensory-motor peripheral neuropathy. By querying external databases, we identified two additional families with rare deleterious biallelic variants in COX18 . All affected individuals presented with axonal CMT and some patients also exhibited central nervous system symptoms, such as dystonia and spasticity. Functional characterization of the c.435-6A>G variant demonstrated that it leads to the expression of an alternative transcript that lacks exon 2, resulting in a stable but defective COX18 isoform. The mutant protein impairs CIV assembly and activity, leading to a reduction in mitochondrial membrane potential. Downregulation of the COX18 homolog in Drosophila melanogaster displayed signs of neurodegeneration, including locomotor deficit and progressive axonal degeneration of sensory neurons. Our study presents genetic and functional evidence that supports COX18 as a newly identified gene candidate for autosomal recessive axonal CMT with or without central nervous system involvement. These findings emphasize the significance of peripheral neuropathy within the spectrum of primary mitochondrial disorders and the role of mitochondrial CIV in the development of CMT. Our research has important implications for the diagnostic workup of CMT patients.
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Figueiredo FB, Tomaselli PJ, Hallak J, Mattiello-Sverzut AC, Covaleski APPM, Sobreira CFDR, de Paula Gouvêa S, Marques W. Genetic diversity in hereditary axonal neuropathy: Analyzing 53 Brazilian children. J Peripher Nerv Syst 2024; 29:97-106. [PMID: 38375759 DOI: 10.1111/jns.12617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 01/24/2024] [Accepted: 01/31/2024] [Indexed: 02/21/2024]
Abstract
BACKGROUND AND AIMS The genetic epidemiology of inherited neuropathies in children remains largely unknown. In this study, we specifically investigated the genetic profile of a Brazilian cohort of pediatric patients with pure or complex axonal neuropathies, a crucial knowledge in the near future for establishing treatment priorities and perspectives for this group of patients. METHODS Fifty-three pediatric patients who were assessed prior to reaching the age of 20, and who had clinical diagnoses of axonal hereditary neuropathy or presented with axonal neuropathy as the primary clinical feature, were included in the study. The recruitment of these cases took place from January 1, 2018, to December 31, 2020. The diagnosis was based on clinical and electrophysiological data. A molecular assessment was made using target-gene panel or whole-exome sequencing. Subsequently, segregation analysis was performed on available family members, and all candidate variants found were confirmed through Sanger. RESULTS A molecular diagnosis was reached in 68% of the patients (n = 36/53), considering only pathogenic and probably pathogenic variants. Variants in MFN2 (n = 15) and GJB1 (n = 3) accounted for half of the genetically confirmed patients (50%; n = 18/36). The other 18 genetically diagnosed patients had variants in several less common genes. INTERPRETATION Apart from MFN2 and GJB1 genes, universally recognized as a frequent cause of axonal neuropathies in most studied population, our Brazilian cohort of children with axonal neuropathies showed an important genetic heterogeneity, probably reflecting the multi ethnicity of the Brazilian population. Diagnostic, counseling, and future interventions should consider this characteristic.
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Affiliation(s)
- Fernanda Barbosa Figueiredo
- Neuroscience and Behavior Sciences Department, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Pedro José Tomaselli
- Neuroscience and Behavior Sciences Department, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Jaime Hallak
- Neuroscience and Behavior Sciences Department, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
- National Institute of Sciences and Technology-INCT-Translational Medicine-CNPq/FAPESP, Ribeirao Preto, Brazil
| | | | | | | | - Silmara de Paula Gouvêa
- Neuroscience and Behavior Sciences Department, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Wilson Marques
- Neuroscience and Behavior Sciences Department, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
- National Institute of Sciences and Technology-INCT-Translational Medicine-CNPq/FAPESP, Ribeirao Preto, Brazil
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Cavalcanti EBU, Leal RDCC, Marques Junior W, Nascimento OJMD. Charcot-Marie-Tooth disease: from historical landmarks in Brazil to current care perspectives. ARQUIVOS DE NEURO-PSIQUIATRIA 2023; 81:913-921. [PMID: 37611635 PMCID: PMC10631856 DOI: 10.1055/s-0043-1770348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Accepted: 03/16/2023] [Indexed: 08/25/2023]
Abstract
Hereditary motor and sensory neuropathy, also known as Charcot-Marie-Tooth disease (CMT), traditionally refers to a group of genetic disorders in which neuropathy is the main or sole feature. Its prevalence varies according to different populations studied, with an estimate between 1:2,500 to 1:10,000. Since the identification of PMP22 gene duplication on chromosome 17 by Vance et al., in 1989, more than 100 genes have been related to this group of disorders, and we have seen advances in the care of patients, with identification of associated conditions and better supportive treatments, including clinical and surgical interventions. Also, with discoveries in the field of genetics, including RNA interference and gene editing techniques, new treatment perspectives begin to emerge. In the present work, we report the most import landmarks regarding CMT research in Brazil and provide a comprehensive review on topics such as frequency of different genes associated with CMT in our population, prevalence of pain, impact on pregnancy, respiratory features, and development of new therapies.
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Affiliation(s)
| | | | - Wilson Marques Junior
- Universidade de São Paulo, Faculdade de Medicina de Ribeirão Preto, Departamento de Neurologia, Ribeirão Preto SP, Brazil.
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Sutinen A, Nguyen GTT, Raasakka A, Muruganandam G, Loris R, Ylikallio E, Tyynismaa H, Bartesaghi L, Ruskamo S, Kursula P. Structural insights into Charcot-Marie-Tooth disease-linked mutations in human GDAP1. FEBS Open Bio 2022; 12:1306-1324. [PMID: 35509130 PMCID: PMC9249340 DOI: 10.1002/2211-5463.13422] [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] [Received: 02/28/2022] [Revised: 04/25/2022] [Accepted: 05/03/2022] [Indexed: 11/11/2022] Open
Abstract
Charcot-Marie-Tooth disease (CMT) is the most common inherited peripheral polyneuropathy in humans, and its different subtypes are linked to mutations in dozens of different genes. Mutations in ganglioside-induced differentiation-associated protein 1 (GDAP1) cause two types of CMT, demyelinating CMT4A and axonal CMT2K. The GDAP1-linked CMT genotypes are mainly missense point mutations. Despite clinical profiling and in vivo studies on the mutations, the etiology of GDAP1-linked CMT is poorly understood. Here, we describe the biochemical and structural properties of the Finnish founding CMT2K mutation H123R as well as CMT2K-linked R120W, both of which are autosomal dominant mutations. The disease variant proteins retain close to normal structure and solution behaviour, but both present a significant decrease in thermal stability. Using GDAP1 variant crystal structures, we identify a side chain interaction network between helices ⍺3, ⍺6, and ⍺7, which is affected by CMT mutations, as well as a hinge in the long helix ⍺6, which is linked to structural flexibility. Structural analysis of GDAP1 indicates that CMT may arise from disruption of specific intra- and intermolecular interaction networks, leading to alterations in GDAP1 structure and stability, and eventually, insufficient motor and sensory neuron function.
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Affiliation(s)
- Aleksi Sutinen
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Finland
| | - Giang Thi Tuyet Nguyen
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Finland
| | - Arne Raasakka
- Department of Biomedicine, University of Bergen, Norway
| | - Gopinath Muruganandam
- VIB-VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium.,Structural Biology Brussels, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Belgium
| | - Remy Loris
- VIB-VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium.,Structural Biology Brussels, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Belgium
| | - Emil Ylikallio
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Finland.,Clinical Neurosciences, Helsinki University Hospital, Neurology, Finland
| | - Henna Tyynismaa
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Finland
| | | | - Salla Ruskamo
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Finland
| | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Finland.,Department of Biomedicine, University of Bergen, Norway
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Uchôa Cavalcanti EB, Santos SCDL, Martins CES, de Carvalho DR, Rizzo IMPDO, Freitas MCDNB, da Silva Freitas D, de Souza FS, Junior AM, do Nascimento OJM. Charcot-Marie-Tooth disease: Genetic profile of patients from a large Brazilian neuromuscular reference center. J Peripher Nerv Syst 2021; 26:290-297. [PMID: 34190362 DOI: 10.1111/jns.12458] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/15/2021] [Accepted: 06/23/2021] [Indexed: 11/28/2022]
Abstract
This study aimed to describe the clinical, genetic, and epidemiological features of Charcot-Marie-Tooth disease (CMT) in Brazilian patients from a tertiary center, and to compare our data with previously published findings. This retrospective observational study conducted between February 2015 and July 2020 evaluated 503 patients (94 families and 192 unrelated individuals), diagnosed with CMT. Clinical and neurophysiological data were obtained from electronic medical records and blood samples were used for genetic analyses. Multiplex ligation-dependent probe amplification was used to assess duplications/deletions in PMP22. Sanger sequencing of GJB1 was performed in cases of suspected demyelinating CMT. Targeted gene panel sequencing was used for the remaining negative demyelinating cases and all axonal CMT cases. The first decade of life was the most common period of disease onset. In all, 353 patients had demyelinating CMT, 39 had intermediate CMT, and 111 had axonal CMT. Pathogenic or likely pathogenic variants were identified in 197 index cases. The most common causative genes among probands were PMP22 (duplication) (n = 116, 58.88%), GJB1 (n = 23, 11.67%), MFN2 (n = 12, 6.09%), GDAP1 (n = 7, 3.55%), MPZ (n = 6, 3.05%), PMP22 (point mutation) (n = 6, 3.05%), NEFL (n = 3, 1.52%), SBF2 (n = 3, 1.52%), and SH3TC2 (n = 3, 1.52%). Other identified variants were ≤1% of index cases. This study provides further data on the frequency of CMT subtypes in a Brazilian clinical-based population and highlights the importance of rarer and previously undiagnosed variants in clinical practice.
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