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Ruan DD, Ruan XL, Wang RL, Lin XF, Zhang YP, Lin B, Li SJ, Wu M, Chen Q, Zhang JH, Cheng Q, Zhang YW, Lin F, Luo JW, Zheng Z, Li YF. Clinical phenotype and genetic function analysis of a family with hypomyelinating leukodystrophy-7 caused by POLR3A mutation. Sci Rep 2024; 14:7638. [PMID: 38561452 PMCID: PMC10985069 DOI: 10.1038/s41598-024-58452-6] [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: 09/06/2023] [Accepted: 03/29/2024] [Indexed: 04/04/2024] Open
Abstract
Hypomyelinating leukodystrophy (HLD) is a rare genetic heterogeneous disease that can affect myelin development in the central nervous system. This study aims to analyze the clinical phenotype and genetic function of a family with HLD-7 caused by POLR3A mutation. The proband (IV6) in this family mainly showed progressive cognitive decline, dentin dysplasia, and hypogonadotropic hypogonadism. Her three old brothers (IV1, IV2, and IV4) also had different degrees of ataxia, dystonia, or dysarthria besides the aforementioned manifestations. Their brain magnetic resonance imaging showed bilateral periventricular white matter atrophy, brain atrophy, and corpus callosum atrophy and thinning. The proband and her two living brothers (IV2 and IV4) were detected to carry a homozygous mutation of the POLR3A (NM_007055.4) gene c. 2300G > T (p.Cys767Phe), and her consanguineous married parents (III1 and III2) were p.Cys767Phe heterozygous carriers. In the constructed POLR3A wild-type and p.Cys767Phe mutant cells, it was seen that overexpression of wild-type POLR3A protein significantly enhanced Pol III transcription of 5S rRNA and tRNA Leu-CAA. However, although the mutant POLR3A protein overexpression was increased compared to the wild-type protein overexpression, it did not show the expected further enhancement of Pol III function. On the contrary, Pol III transcription function was frustrated (POLR3A, BC200, and tRNA Leu-CAA expression decreased), and MBP and 18S rRNA expressions were decreased. This study indicates that the POLR3A p.Cys767Phe variant caused increased expression of mutated POLR3A protein and abnormal expression of Pol III transcripts, and the mutant POLR3A protein function was abnormal.
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Affiliation(s)
- Dan-Dan Ruan
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Xing-Lin Ruan
- Department of Neurology, Fujian Medical University Union Hospital, Fuzhou, 350001, China
| | - Ruo-Li Wang
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
- Fujian Provincial Key Laboratory of Emergency Medicine, Fujian Provincial Institute of Emergency Medicine, Fujian Emergency Medical Center, Fuzhou, 350001, China
| | - Xin-Fu Lin
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
- Pediatrics Department, Fujian Provincial Hospital, Fuzhou, 350001, China
| | - Yan-Ping Zhang
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Bin Lin
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Shi-Jie Li
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Min Wu
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Qian Chen
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Jian-Hui Zhang
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
| | - Qiong Cheng
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China
- Department of Neurology, Fujian Provincial Hospital, Fuzhou, 350001, China
| | - Yi-Wu Zhang
- Department of Neurology, Youxi County General Hospital, Sanming, 365100, China
| | - Fan Lin
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China.
- Department of Geriatric Medicine, Fujian Provincial Center for Geriatrics, Fujian Provincial Hospital, Fuzhou, 350001, China.
| | - Jie-Wei Luo
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China.
| | - Zheng Zheng
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China.
- Department of Neurology, Fujian Provincial Hospital, Fuzhou, 350001, China.
| | - Yun-Fei Li
- Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University, Fuzhou, 350001, China.
- Department of Neurology, Fujian Provincial Hospital, Fuzhou, 350001, China.
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2
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Shih HY, Raas Q, Bonkowsky JL. Progress in leukodystrophies with zebrafish. Dev Growth Differ 2024; 66:21-34. [PMID: 38239149 DOI: 10.1111/dgd.12907] [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: 09/01/2023] [Revised: 12/11/2023] [Accepted: 12/21/2023] [Indexed: 01/31/2024]
Abstract
Inherited leukodystrophies are genetic disorders characterized by abnormal white matter in the central nervous system. Although individually rare, there are more than 400 distinct types of leukodystrophies with a cumulative incidence of 1 in 4500 live births. The pathophysiology of most leukodystrophies is poorly understood, there are treatments for only a few, and there is significant morbidity and mortality, suggesting a critical need for improvements in this field. A variety of animal, cell, and induced pluripotent stem cell-derived models have been developed for leukodystrophies, but with significant limitations in all models. Many leukodystrophies lack animal models, and extant models often show no or mixed recapitulation of key phenotypes. Zebrafish (Danio rerio) have become increasingly used as disease models for studying leukodystrophies due to their early onset of disease phenotypes and conservation of molecular and neurobiological mechanisms. Here, we focus on reviewing new zebrafish disease models for leukodystrophy or models with recent progress. This includes discussion of leukodystrophy with vanishing white matter disease, X-linked adrenoleukodystrophy, Zellweger spectrum disorders and peroxisomal disorders, PSAP deficiency, metachromatic leukodystrophy, Krabbe disease, hypomyelinating leukodystrophy-8/4H leukodystrophy, Aicardi-Goutières syndrome, RNASET2-deficient cystic leukoencephalopathy, hereditary diffuse leukoencephalopathy with spheroids-1 (CSF1R-related leukoencephalopathy), and ultra-rare leukodystrophies. Zebrafish models offer important potentials for the leukodystrophy field, including testing of new variants in known genes; establishing causation of newly discovered genes; and early lead compound identification for therapies. There are also unrealized opportunities to use humanized zebrafish models which have been sparsely explored.
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Affiliation(s)
- Hung-Yu Shih
- Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah, USA
- Department of Biological Sciences, Utah Tech University, Saint George, Utah, USA
- Center for Precision & Functional Genomics, Utah Tech University, Saint George, Utah, USA
| | - Quentin Raas
- Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah, USA
- Laboratory of Translational Research for Neurological Disorders, Imagine Institute, Université de Paris, INSERM UMR 1163, Paris, France
| | - Joshua L Bonkowsky
- Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah, USA
- Center for Personalized Medicine, Primary Children's Hospital, Salt Lake City, Utah, USA
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Michell-Robinson MA, Watt KEN, Grouza V, Macintosh J, Pinard M, Tuznik M, Chen X, Darbelli L, Wu CL, Perrier S, Chitsaz D, Uccelli NA, Liu H, Cox TC, Müller CW, Kennedy TE, Coulombe B, Rudko DA, Trainor PA, Bernard G. Hypomyelination, hypodontia and craniofacial abnormalities in a Polr3b mouse model of leukodystrophy. Brain 2023; 146:5070-5085. [PMID: 37635302 PMCID: PMC10690025 DOI: 10.1093/brain/awad249] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 06/23/2023] [Accepted: 07/06/2023] [Indexed: 08/29/2023] Open
Abstract
RNA polymerase III (Pol III)-related hypomyelinating leukodystrophy (POLR3-HLD), also known as 4H leukodystrophy, is a severe neurodegenerative disease characterized by the cardinal features of hypomyelination, hypodontia and hypogonadotropic hypogonadism. POLR3-HLD is caused by biallelic pathogenic variants in genes encoding Pol III subunits. While approximately half of all patients carry mutations in POLR3B encoding the RNA polymerase III subunit B, there is no in vivo model of leukodystrophy based on mutation of this Pol III subunit. Here, we determined the impact of POLR3BΔ10 (Δ10) on Pol III in human cells and developed and characterized an inducible/conditional mouse model of leukodystrophy using the orthologous Δ10 mutation in mice. The molecular mechanism of Pol III dysfunction was determined in human cells by affinity purification-mass spectrometry and western blot. Postnatal induction with tamoxifen induced expression of the orthologous Δ10 hypomorph in triple transgenic Pdgfrα-Cre/ERT; R26-Stopfl-EYFP; Polr3bfl mice. CNS and non-CNS features were characterized using a variety of techniques including microCT, ex vivo MRI, immunofluorescence, immunohistochemistry, spectral confocal reflectance microscopy and western blot. Lineage tracing and time series analysis of oligodendrocyte subpopulation dynamics based on co-labelling with lineage-specific and/or proliferation markers were performed. Proteomics suggested that Δ10 causes a Pol III assembly defect, while western blots demonstrated reduced POLR3BΔ10 expression in the cytoplasm and nucleus in human cells. In mice, postnatal Pdgfrα-dependent expression of the orthologous murine mutant protein resulted in recessive phenotypes including severe hypomyelination leading to ataxia, tremor, seizures and limited survival, as well as hypodontia and craniofacial abnormalities. Hypomyelination was confirmed and characterized using classic methods to quantify myelin components such as myelin basic protein and lipids, results which agreed with those produced using modern methods to quantify myelin based on the physical properties of myelin membranes. Lineage tracing uncovered the underlying mechanism for the hypomyelinating phenotype: defective oligodendrocyte precursor proliferation and differentiation resulted in a failure to produce an adequate number of mature oligodendrocytes during postnatal myelinogenesis. In summary, we characterized the Polr3bΔ10 mutation and developed an animal model that recapitulates features of POLR3-HLD caused by POLR3B mutations, shedding light on disease pathogenesis, and opening the door to the development of therapeutic interventions.
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Affiliation(s)
- Mackenzie A Michell-Robinson
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Kristin E N Watt
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Vladimir Grouza
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, QC H3A 2B4, Canada
| | - Julia Macintosh
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Maxime Pinard
- Translational Proteomics Research Unit, Montreal Clinical Research Institute, Montréal, QC H2W 1R7, Canada
| | - Marius Tuznik
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, QC H3A 2B4, Canada
| | - Xiaoru Chen
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Lama Darbelli
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Chia-Lun Wu
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Stefanie Perrier
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
| | - Daryan Chitsaz
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
| | - Nonthué A Uccelli
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
| | - Hanwen Liu
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, QC H3A 2B4, Canada
| | - Timothy C Cox
- Department of Oral and Craniofacial Sciences, School of Dentistry, and Pediatrics, School of Medicine, University of Missouri – Kansas City, Kansas City, MO 64108, USA
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Timothy E Kennedy
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
| | - Benoit Coulombe
- Translational Proteomics Research Unit, Montreal Clinical Research Institute, Montréal, QC H2W 1R7, Canada
- Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, QC H3C 3J7, Canada
| | - David A Rudko
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, QC H3A 2B4, Canada
- Department of Biomedical Engineering, McGill University, Montréal, QC H3A 2B4, Canada
| | - Paul A Trainor
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Department of Anatomy and Cell Biology, The University of Kansas School of Medicine, Kansas City, KS 66160, USA
| | - Geneviève Bernard
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 1A1, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC H4A 3J1, Canada
- Department of Pediatrics, McGill University, Montréal, QC H4A 3J1, Canada
- Department of Human Genetics, McGill University, Montréal, QC H4A 0C7, Canada
- Department of Specialized Medicine, Division of Medical Genetics, Montreal Children’s Hospital and McGill University Health Centre, Montréal, QC H4A 3J1, Canada
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4
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Haneda A, Hoots JK, Hagy HA, Lacy M. Case report: neuropsychological assessment in a patient with 4H leukodystrophy. Clin Neuropsychol 2023:1-18. [PMID: 37974060 DOI: 10.1080/13854046.2023.2279697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 10/31/2023] [Indexed: 11/19/2023]
Abstract
Objective: POLR3-HLD or 4H leukodystrophy is an autosomal recessive disorder characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, and caused by variants in POLR3A, POLR3B, POLR1C, or POLR3K genes. Neurological and non-neurological clinical features and disease severity vary. While previous studies reference variable cognition, this is the first report of 4H detailing a comprehensive neuropsychological assessment. Method: The current study presents a 20-year-old, English-speaking, right-handed, non-Hispanic White female with 12 years of education with genetically confirmed 4H POLR3B-related leukodystrophy without hormonal replacement treatment. Results: At age 4, developmental delays, ataxia, hearing loss, and abnormal dentition were present. Imaging, endocrinology, and neurologic examinations revealed hypomyelination, reduced cerebellar volume, delayed bone age density, osteopenia, and evidence of adrenarche without signs of true puberty. Neuropsychological assessment at age 20 revealed global cognitive impairment with intellectual, attention, verbal memory retrieval, construction, executive (e.g. processing speed, sustained attention) and math computation deficits, along with behavioral dysregulation. Conclusion: We present the first detailed neuropsychological assessment of a patient with 4H leukodystrophy. The neuropsychological assessment revealed cognitive and behavioral dysexecutive deficits aligning with hypomyelination observed on imaging. Further longitudinal studies are needed to shed light on the neurobehavioral presentation associated with this disorder to assist care providers, patients, and their families.
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Affiliation(s)
- Aya Haneda
- Department of Psychology, Roosevelt University, Chicago, IL, USA
- University of Chicago Medical Center, Department of Psychiatry and Behavioral Neuroscience, Chicago, IL, USA
| | - Jennifer K Hoots
- University of Chicago Medical Center, Department of Psychiatry and Behavioral Neuroscience, Chicago, IL, USA
- Department of Psychology, University of Illinois Chicago, Chicago, IL, USA
| | - Hannah A Hagy
- University of Chicago Medical Center, Department of Psychiatry and Behavioral Neuroscience, Chicago, IL, USA
- Loyola University, Chicago, IL, USA
| | - Maureen Lacy
- University of Chicago Medical Center, Department of Psychiatry and Behavioral Neuroscience, Chicago, IL, USA
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5
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Hamdan Z, Alasmar D. Uncertain significance mutation in the POLR3B gene in a Syrian boy with leukodystrophy: a case report. Ann Med Surg (Lond) 2023; 85:4126-4130. [PMID: 37554900 PMCID: PMC10406027 DOI: 10.1097/ms9.0000000000001033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/20/2023] [Indexed: 08/10/2023] Open
Abstract
UNLABELLED 4H leukodystrophy, one of the POLR3-related leukodystrophy, is a rare hereditary brain white matter disease with characteristic clinical presentation and imaging findings. Hypomyelination, hypodontia, and hypogonadotropic hypogonadism is mainly presented in patients with 4H leukodystrophy. CASE PRESENTATION A 4-year-old boy presented in the neurologic clinic with delayed psychomotor development and progressive neurologic symptoms that started from the age of 20 months. Physical examination revealed ataxic features and a global development delay. The MRI was significant for hypomyelination. The most common causes of leukodystrophy were rolled out. He was referred to an inherited metabolic disease specialist under suspect of inborn metabolic errors because of laboratory analysis, which showed elevated levels of lactic acid, pyruvate, 4-Hydroxy-Phenylactic acid, 3-Hydroxy propionic acid, and decreased levels of PCO2, HCO3, total CO2, 25-Hydroxyvitamin D. These results were unspecific and mitochondrial disease was highly suspected. However, the genetic study was requested to get a defined diagnosis and treatment; the whole exon sequencing result showed a homozygous variant of uncertain significance mutation; related to an amino acid change from Ile to Thr at position 1002 in the POLR3B gene, which helped us to reveal the final diagnosis, and the genetic counseling were recommended for the next pregnancies. CONCLUSION POLR3-related Leukodystrophy is a very rare disease. The early diagnosis should be raised depending on clinical history and MRI findings after other conditions were rolled out, and the confirmed diagnosis depends on the genetic study.
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Affiliation(s)
| | - Diana Alasmar
- Pediatric Department, Damascus University Damascus, Syria
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Winters SJ. Hypogonadism in Males With Genetic Neurodevelopmental Syndromes. J Clin Endocrinol Metab 2022; 107:e3974-e3989. [PMID: 35913018 DOI: 10.1210/clinem/dgac421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Indexed: 11/19/2022]
Abstract
Genetic syndromes that affect the nervous system may also disrupt testicular function, and the mechanisms for these effects may be interrelated. Most often neurological signs and symptoms predominate and hypogonadism remains undetected and untreated, while in other cases, a thorough evaluation of a hypogonadal male reveals previously unrecognized ataxia, movement disorder, muscle weakness, tremor, or seizures, leading to a syndromic diagnosis. Androgen deficiency in patients with neurological diseases may aggravate muscle weakness and fatigue and predispose patients to osteoporosis and obesity. The purpose of this mini review is to provide a current understanding of the clinical, biochemical, histologic, and genetic features of syndromes in which male hypogonadism and neurological dysfunction may coexist and may be encountered by the clinical endocrinologist.
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Affiliation(s)
- Stephen J Winters
- Division of Endocrinology, Metabolism & Diabetes, University of Louisville, Louisville, KY, USA
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Martin S, Allan KC, Pinkard O, Sweet T, Tesar PJ, Coller J. Oligodendrocyte differentiation alters tRNA modifications and codon optimality-mediated mRNA decay. Nat Commun 2022; 13:5003. [PMID: 36008413 PMCID: PMC9411196 DOI: 10.1038/s41467-022-32766-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 08/15/2022] [Indexed: 11/08/2022] Open
Abstract
Oligodendrocytes are specialized cells that confer neuronal myelination in the central nervous system. Leukodystrophies associated with oligodendrocyte deficits and hypomyelination are known to result when a number of tRNA metabolism genes are mutated. Thus, for unknown reasons, oligodendrocytes may be hypersensitive to perturbations in tRNA biology. In this study, we survey the tRNA transcriptome in the murine oligodendrocyte cell lineage and find that specific tRNAs are hypomodified in oligodendrocytes within or near the anticodon compared to oligodendrocyte progenitor cells (OPCs). This hypomodified state may be the result of differential expression of key modification enzymes during oligodendrocyte differentiation. Moreover, we observe a concomitant relationship between tRNA hypomodification and tRNA decoding potential; observing oligodendrocyte specific alterations in codon optimality-mediated mRNA decay and ribosome transit. Our results reveal that oligodendrocytes naturally maintain a delicate, hypersensitized tRNA/mRNA axis. We suggest this axis is a potential mediator of pathology in leukodystrophies and white matter disease when further insult to tRNA metabolism is introduced.
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Affiliation(s)
- Sophie Martin
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Kevin C Allan
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Otis Pinkard
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Thomas Sweet
- Center for Proteomics and Bioinformatics, Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Paul J Tesar
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Jeff Coller
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Department of Biology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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Lata E, Choquet K, Sagliocco F, Brais B, Bernard G, Teichmann M. RNA Polymerase III Subunit Mutations in Genetic Diseases. Front Mol Biosci 2021; 8:696438. [PMID: 34395528 PMCID: PMC8362101 DOI: 10.3389/fmolb.2021.696438] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/21/2021] [Indexed: 12/24/2022] Open
Abstract
RNA polymerase (Pol) III transcribes small untranslated RNAs such as 5S ribosomal RNA, transfer RNAs, and U6 small nuclear RNA. Because of the functions of these RNAs, Pol III transcription is best known for its essential contribution to RNA maturation and translation. Surprisingly, it was discovered in the last decade that various inherited mutations in genes encoding nine distinct subunits of Pol III cause tissue-specific diseases rather than a general failure of all vital functions. Mutations in the POLR3A, POLR3C, POLR3E and POLR3F subunits are associated with susceptibility to varicella zoster virus-induced encephalitis and pneumonitis. In addition, an ever-increasing number of distinct mutations in the POLR3A, POLR3B, POLR1C and POLR3K subunits cause a spectrum of neurodegenerative diseases, which includes most notably hypomyelinating leukodystrophy. Furthermore, other rare diseases are also associated with mutations in genes encoding subunits of Pol III (POLR3H, POLR3GL) and the BRF1 component of the TFIIIB transcription initiation factor. Although the causal relationship between these mutations and disease development is widely accepted, the exact molecular mechanisms underlying disease pathogenesis remain enigmatic. Here, we review the current knowledge on the functional impact of specific mutations, possible Pol III-related disease-causing mechanisms, and animal models that may help to better understand the links between Pol III mutations and disease.
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Affiliation(s)
- Elisabeth Lata
- Bordeaux University, Inserm U 1212, CNRS UMR 5320, ARNA laboratory, Bordeaux, France
| | - Karine Choquet
- Department of Genetics, Harvard Medical School, Boston, MA, United States
| | - Francis Sagliocco
- Bordeaux University, Inserm U 1212, CNRS UMR 5320, ARNA laboratory, Bordeaux, France
| | - Bernard Brais
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Geneviève Bernard
- Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics, McGill University, Montreal, QC, Canada
- Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montreal, QC, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Martin Teichmann
- Bordeaux University, Inserm U 1212, CNRS UMR 5320, ARNA laboratory, Bordeaux, France
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Combined Genome, Transcriptome and Metabolome Analysis in the Diagnosis of Childhood Cerebellar Ataxia. Int J Mol Sci 2021; 22:ijms22062990. [PMID: 33804237 PMCID: PMC8002209 DOI: 10.3390/ijms22062990] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 03/11/2021] [Accepted: 03/13/2021] [Indexed: 12/30/2022] Open
Abstract
Ataxia in children is a common clinical sign of numerous neurological disorders consisting of impaired coordination of voluntary muscle movement. Its most common form, cerebellar ataxia, describes a heterogeneous array of neurologic conditions with uncountable causes broadly divided as acquired or genetic. Numerous genetic disorders are associated with chronic progressive ataxia, which complicates clinical management, particularly on the diagnostic stage. Advances in omics technologies enable improvements in clinical practice and research, so we proposed a multi-omics approach to aid in the genetic diagnosis and molecular elucidation of an undiagnosed infantile condition of chronic progressive cerebellar ataxia. Using whole-exome sequencing, RNA-seq, and untargeted metabolomics, we identified three clinically relevant mutations (rs141471029, rs191582628 and rs398124292) and an altered metabolic profile in our patient. Two POLR1C diagnostic variants already classified as pathogenic were found, and a diagnosis of hypomyelinating leukodystrophy was achieved. A mutation on the MMACHC gene, known to be associated with methylmalonic aciduria and homocystinuria cblC type, was also found. Additionally, preliminary metabolome analysis revealed alterations in our patient’s amino acid, fatty acid and carbohydrate metabolism. Our findings provided a definitive genetic diagnosis reinforcing the association between POLR1C mutations and hypomyelinating leukodystrophy and highlighted the relevance of multi-omics approaches to the disease.
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