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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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Justin Margret J, Jayasankaran C, Amritkumar P, Azaiez H, Srisailapathy CRS. Unraveling the Genetic Basis of Combined Deafness and Male Infertility Phenotypes through High-Throughput Sequencing in a Unique Cohort from South India. ADVANCED GENETICS (HOBOKEN, N.J.) 2024; 5:2300206. [PMID: 38884051 PMCID: PMC11170077 DOI: 10.1002/ggn2.202300206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 03/15/2024] [Indexed: 06/18/2024]
Abstract
The co-occurrence of sensorineural hearing loss and male infertility has been reported in several instances, suggesting potential shared genetic underpinnings. One such example is the contiguous gene deletion of CATSPER2 and STRC genes, previously associated with deafness-infertility syndrome (DIS) in males. Fifteen males with both hearing loss and infertility from southern India after exclusion for the DIS contiguous gene deletion and the FOXI1 gene mutations are subjected to exome sequencing. This resolves the genetic etiology in four probands for both the phenotypes; In the remaining 11 probands, two each conclusively accounted for deafness and male infertility etiologies. Genetic heterogeneity is well reflected in both phenotypes. Four recessive (TRIOBP, SLC26A4, GJB2, COL4A3) and one dominant (SOX10) for the deafness; six recessive genes (LRGUK, DNAH9, ARMC4, DNAH2, RSPH6A, and ACE) for male infertility can be conclusively ascribed. LRGUK and RSPH6A genes are implicated earlier only in mice models, while the ARMC4 gene is implicated in chronic destructive airway diseases due to primary ciliary dyskinesia. This study would be the first to document the role of these genes in the male infertility phenotype in humans. The result suggests that deafness and infertility are independent events and do not segregate together among the probands.
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Affiliation(s)
- Jeffrey Justin Margret
- Department of Genetics Dr. ALM Post Graduate Institute of Basic Medical Sciences University of Madras Taramani Campus Chennai 600 113 India
- Department of Pediatrics Louisiana State University Health Sciences Center Shreveport LA 71103 USA
| | - Chandru Jayasankaran
- Department of Genetics Dr. ALM Post Graduate Institute of Basic Medical Sciences University of Madras Taramani Campus Chennai 600 113 India
- Department of Personalized Health Care Roche Products India Pvt., Ltd. Bengaluru Karnataka 560 025 India
| | - Pavithra Amritkumar
- Department of Genetics Dr. ALM Post Graduate Institute of Basic Medical Sciences University of Madras Taramani Campus Chennai 600 113 India
- Meenakshi Academy of Higher Education and Research (MAHER) Chennai 600 078 India
| | - Hela Azaiez
- Department of Otolaryngology Carver College of Medicine University of Iowa Iowa City Iowa 52242 USA
| | - C R Srikumari Srisailapathy
- Department of Genetics Dr. ALM Post Graduate Institute of Basic Medical Sciences University of Madras Taramani Campus Chennai 600 113 India
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Ronchi D, Garbellini M, Magri F, Menni F, Meneri M, Bedeschi MF, Dilena R, Cecchetti V, Picciolli I, Furlan F, Polimeni V, Salani S, Pezzoli L, Fortunato F, Bellini M, Piga D, Ripolone M, Zanotti S, Napoli L, Ciscato P, Sciacco M, Mangili G, Mosca F, Corti S, Iascone M, Comi GP. A biallelic variant in COX18 cause isolated Complex IV deficiency associated with neonatal encephalo-cardio-myopathy and axonal sensory neuropathy. Eur J Hum Genet 2023; 31:1414-1420. [PMID: 37468577 PMCID: PMC10689781 DOI: 10.1038/s41431-023-01433-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 07/03/2023] [Accepted: 07/10/2023] [Indexed: 07/21/2023] Open
Abstract
Pathogenic variants impacting upon assembly of mitochondrial respiratory chain Complex IV (Cytochrome c Oxidase or COX) predominantly result in early onset mitochondrial disorders often leading to CNS, skeletal and cardiac muscle manifestations. The aim of this study is to describe a molecular defect in the COX assembly factor gene COX18 as the likely cause of a neonatal form of mitochondrial encephalo-cardio-myopathy and axonal sensory neuropathy. The proband is a 19-months old female displaying hypertrophic cardiomyopathy at birth and myopathy with axonal sensory neuropathy and failure to thrive developing in the first months of life. Serum lactate was consistently increased. Whole exome sequencing allowed the prioritization of the unreported homozygous substitution NM_001297732.2:c.667 G > C p.(Asp223His) in COX18. Patient's muscle biopsy revealed severe and diffuse COX deficiency and striking mitochondrial abnormalities. Biochemical and enzymatic studies in patient's myoblasts and in HEK293 cells after COX18 silencing showed a severe impairment of both COX activity and assembly. The biochemical defect was partially rescued by delivery of wild-type COX18 cDNA into patient's myoblasts. Our study identifies a novel defect of COX assembly and expands the number of nuclear genes involved in a mitochondrial disorder due to isolated COX deficiency.
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Affiliation(s)
- Dario Ronchi
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Manuela Garbellini
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Francesca Magri
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Francesca Menni
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Regional Clinical Center for expanded newborn screening, Milan, Italy
| | - Megi Meneri
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | | | - Robertino Dilena
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, UO Neurofisiopatologia, Milan, Italy
| | - Valeria Cecchetti
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neonatal Intensive Care Unit, Milan, Italy
| | - Irene Picciolli
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neonatal Intensive Care Unit, Milan, Italy
| | - Francesca Furlan
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Regional Clinical Center for expanded newborn screening, Milan, Italy
| | - Valentina Polimeni
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neonatal Intensive Care Unit, Milan, Italy
| | - Sabrina Salani
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Laura Pezzoli
- ASST Papa Giovanni XXIII, Laboratorio di Genetica Medica, Bergamo, Italy
| | - Francesco Fortunato
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Matteo Bellini
- ASST Papa Giovanni XXIII, Laboratorio di Genetica Medica, Bergamo, Italy
| | - Daniela Piga
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Michela Ripolone
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
| | - Simona Zanotti
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
| | - Laura Napoli
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
| | - Patrizia Ciscato
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
| | - Monica Sciacco
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
| | | | - Fabio Mosca
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neonatal Intensive Care Unit, Milan, Italy
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Stefania Corti
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
| | - Maria Iascone
- ASST Papa Giovanni XXIII, Laboratorio di Genetica Medica, Bergamo, Italy
| | - Giacomo Pietro Comi
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy.
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Khodaeian M, Bitarafan F, Garrousi F, Sardehie EA, Pak N, Hosseinpour S, Shakiba M, Falah M, Garshasbi M, Tavasoli AR. Expanding phenotype heterogeneity of NARS2 by presenting subdural hematoma and parenchymal hemorrhage. J Clin Lab Anal 2023; 37:e24983. [PMID: 37950505 PMCID: PMC10749492 DOI: 10.1002/jcla.24983] [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: 01/18/2023] [Revised: 10/12/2023] [Accepted: 10/22/2023] [Indexed: 11/12/2023] Open
Abstract
BACKGROUND NARS2 encodes mitochondrial Asparaginyl-tRNA Synthetase 2, which catalyzes the aminoacylation of tRNA-Asn in the mitochondria. To date, 24 variants have been reported in NARS2 gene in 35 patients. The phenotypic variability of NARS2-associated disorder is broad, ranging from neurodevelopmental disorders to hearing loss. In this study, we report some novel imaging findings in an Iranian patient suffering from epileptic encephalopathy, caused by a previously reported variant, c.500A > G; p.(His167Arg), in NARS2. METHODS The spectrum of clinical manifestations of two Iranian patients was investigated and genetic analysis was performed by Whole-exome sequencing (WES). Additionally, we also reviewed the literature and summarized the phenotypes of previously reported patients with variants in the NARS2 gene. RESULTS Here, we present the phenotypic and genetic features of 2 unrelated Iranian infants presented with neurodevelopmental delay, seizures, hearing impairment, feeding problems, elevated serum lactate levels in addition to subdural hematoma and cerebral parenchymal hemorrhage in the brain magnetic resonance imaging (MRI) of one of the patients. Genetic analysis revealed a biallelic missense variant in NARS2: c.500A > G; p.(His167Arg). We described the subdural hematoma and cerebral parenchymal hemorrhage of the brain for the first time. CONCLUSIONS Our study provides new clinical findings, subdural hematoma, and parenchymal hemorrhage, in NARS2-related disorders. Our findings along with previous studies provide more evidence of the clinical presentation of the disease caused by pathogenic variants in NARS2. Expanding the clinical spectrum increases the diagnostic rate of molecular testing and improves the quality of counseling for at-risk couples.
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Affiliation(s)
| | - Fatemeh Bitarafan
- Department of Medical GeneticsOslo University Hospital and University of Oslo0450OsloNorway
| | | | | | - Neda Pak
- Pediatric Radiology Division, Children's Medical Center, Pediatrics Center of ExcellenceTehran University of Medical SciencesTehranIran
| | - Sareh Hosseinpour
- Myelin Disorders Clinic, Pediatric Neurology Division, Children's Medical Center, Pediatrics Center of ExcellenceTehran University of Medical SciencesTehranIran
| | - Marjan Shakiba
- Department of Pediatric Endocrinology and Metabolism, Mofid Children's HospitalShahid Beheshti University of Medical SciencesTehranIran
| | - Masoumeh Falah
- ENT and Head and Neck Research Center and Department, The Five Senses Health Institute, School of Medicine, Hazrat Rasoul Akram HospitalIran University of Medical SciencesTehranIran
| | - Masoud Garshasbi
- Department of Medical Genetics, Faculty of Medical SciencesTarbiat Modares UniversityTeheranIran
| | - Ali Reza Tavasoli
- Myelin Disorders Clinic, Pediatric Neurology Division, Children's Medical Center, Pediatrics Center of ExcellenceTehran University of Medical SciencesTehranIran
- Department of Neurology, Barrow Neurological InstitutePhoenix Children's HospitalPhoenixArizonaUSA
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Abstract
Hearing loss (HL) is an etiologically heterogeneous disorder that affects around 5% of the world's population. There has been an exponential increase in the identification of genes and variants responsible for hereditary HL over recent years. Iran, a country located in the Middle East, has a high prevalence of consanguineous marriages, so heterogeneous diseases such as HL are more common. Comprehensive studies using different strategies from linkage analysis to next-generation sequencing, especially exome-sequencing, have achieved significant success in identifying possible pathogens in deaf Iranian families. About 12% of non-syndromic autosomal recessive HL genes investigated to date, were first identified in families from Iran. Variations of 56 genes have been observed in families with NSHL in Iran. Variants in GJB2, SLC26A4, MYO15A, MYO7A, CDH23, and TMC1 account for 16.5%, 16.25%, 13.5%, 9.35%, 6.9% and 4.92%, cases of NSHL, respectively. In summary, there are also different diagnostic rates between studies conducted in Iran. In the comprehensive investigations conducted by the Genetic Research Center of the University of Social Welfare and Rehabilitation Sciences over the past 20 years, the overall diagnosis rate is about 80% while there are other studies with lower diagnostic rates which could reflect differences in project designs, sampling, and accuracy and validity of the methods used. Furthermore, there are several syndromic HHLs in Iran including, Waardenburg syndrome, BOR syndrome, Brown-Vialetto-Van Laere syndrome, Wolfram syndrome, among which Pendred and Usher syndromes are well-studied. These results are of importance for further investigation and elucidation of the molecular basis of HHL in Iran.
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