1
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Symonds JD, Park KL, Mignot C, Macleod S, Armstrong M, Ashrafian H, Bernard G, Brown K, Brunklaus A, Callaghan M, Classen G, Cohen JS, Cutcutache I, de Sainte Agathe JM, Dyment D, Elliot KS, Isapof A, Joss S, Keren B, Marble M, McTague A, Osmond M, Page M, Planes M, Platzer K, Redon S, Reese J, Saenz M, Smith-Hicks C, Stobo D, Stockhaus C, Vuillaume ML, Wolf NI, Wakeling EL, Yoon G, Knight JC, Zuberi SM. POLR3B is associated with a developmental and epileptic encephalopathy with myoclonic-atonic seizures and ataxia. Epilepsia 2024. [PMID: 39348199 DOI: 10.1111/epi.18115] [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: 03/29/2024] [Revised: 08/22/2024] [Accepted: 08/22/2024] [Indexed: 10/02/2024]
Abstract
OBJECTIVE POLR3B encodes the second largest subunit of RNA polymerase III, which is essential for transcription of small non-coding RNAs. Biallelic pathogenic variants in POLR3B are associated with an inherited hypomyelinating leukodystrophy. Recently, de novo heterozygous variants in POLR3B were reported in six individuals with ataxia, spasticity, and demyelinating peripheral neuropathy. Three of these individuals had epileptic seizures. The aim of this article is to precisely define the epilepsy phenotype associated with de novo heterozygous POLR3B variants. METHODS We used online gene-matching tools to identify 13 patients with de novo POLR3B variants. We systematically collected genotype and phenotype data from clinicians using two standardized proformas. RESULTS All 13 patients had novel POLR3B variants. Twelve of 13 variants were classified as pathogenic or likely pathogenic as per American College of Medical Genetics (ACMG) criteria. Patients presented with generalized myoclonic, myoclonic-atonic, atypical absence, or tonic-clonic seizures between the ages of six months and 4 years. Epilepsy was classified as epilepsy with myoclonic-atonic seizures (EMAtS) in seven patients and "probable EMAtS" in two more. Seizures were treatment resistant in all cases. Three patients became seizure-free. All patients had some degree of developmental delay or intellectual disability. In most cases developmental delay was apparent before the onset of seizures. Three of 13 cases were reported to have developmental stagnation or regression in association with seizure onset. Treatments for epilepsy that were reported by clinicians to be effective were: sodium valproate, which was effective in five of nine patients (5/9) who tried it; rufinamide (2/3); and ketogenic diet (2/3). Additional features were ataxia/incoordination (8/13); microcephaly (7/13); peripheral neuropathy (4/13), and spasticity/hypertonia (6/13). SIGNIFICANCE POLR3B is a novel genetic developmental and epileptic encephalopathy (DEE) in which EMAtS is the predominant epilepsy phenotype. Ataxia, neuropathy, and hypertonia may be variously observed in these patients.
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Affiliation(s)
- Joseph D Symonds
- Paediatric Neurosciences Research Group, School of Health and Wellbeing, University of Glasgow, Glasgow, UK
- Royal Hospital for Children, Glasgow, UK
| | - Kristen L Park
- Children's Hospital Colorado, Anschutz Medical Campus, University of Colorado, Aurora, Colorado, USA
| | - Cyril Mignot
- Département de Génétique, Groupe Hospitalier Pitié-Salpêtrière-Hôpital Trousseau, Sorbonne Université, Paris, France
| | | | | | - Houman Ashrafian
- Division of Cardiovascular Medicine, John Radcliffe Hospital, Oxford, UK
- Department of Experimental Therapeutics, Radcliffe Department of Medicine, John Radcliffe Hospital, Oxford, UK
| | - Geneviève Bernard
- Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics, McGill University, Montreal, Quebec, Canada
- Department Specialized Medicine, Division of Medical Genetics, McGill University Health Centre, Montreal, Quebec, Canada
- Child Health and Human Development Program, Research, Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Kathleen Brown
- Department of Pediatrics, Section of Genetics and Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Andreas Brunklaus
- Paediatric Neurosciences Research Group, School of Health and Wellbeing, University of Glasgow, Glasgow, UK
- Royal Hospital for Children, Glasgow, UK
| | - Mary Callaghan
- Department of Paediatrics, University Hospital Wishaw, Wishaw, UK
| | - Georg Classen
- Children's Center Bethel, University Bielefeld, Bielefeld, Germany
| | - Julie S Cohen
- Department of Neurology and Developmental Medicine, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | | | | | - David Dyment
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
| | | | - Arnaud Isapof
- Service de Neuropédiatrie, Hôpital Trousseau, Sorbonne Université, Paris, France
| | - Shelagh Joss
- West of Scotland Regional Genetics Service, Queen Elizabeth University Hospitals, Glasgow, UK
| | - Boris Keren
- Department of Genetics, Pitié-Salpêtrière Hospital, APHP. Sorbonne Université, Paris, France
| | - Michael Marble
- Division of Pediatric Genetics, Department of Pediatrics, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, USA
| | - Amy McTague
- Developmental Neurosciences. Zayed Centre for Research into Rare Disease in Children, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Matthew Osmond
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
| | | | - Marc Planes
- Service de Génétique Médicale et Biologie de la Reproduction, CHU de Brest, Brest, France
- Laboratoire de Biologie Médicale Multi-Sites SeqOIA, Paris, France
- Université Brest, Brest, France
| | - Konrad Platzer
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany
| | - Sylvia Redon
- Service de Génétique Médicale et Biologie de la Reproduction, CHU de Brest, Brest, France
- Laboratoire de Biologie Médicale Multi-Sites SeqOIA, Paris, France
- Université Brest, Brest, France
| | - James Reese
- Presbyterian Healthcare System, Albuquerque, New Mexico, USA
| | - Margarita Saenz
- Department of Pediatrics, Section of Genetics and Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Constance Smith-Hicks
- Department of Neurology and Developmental Medicine, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Daniel Stobo
- West of Scotland Regional Genetics Service, Queen Elizabeth University Hospitals, Glasgow, UK
| | - Christian Stockhaus
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany
| | - Marie-Laure Vuillaume
- Laboratoire de Biologie Médicale Multi-Sites SeqOIA, Paris, France
- UMR 1253, iBrain, University of Tours, Tours, France
- Genetics Department, University of Tours, Tours, France
| | - Nicole I Wolf
- Department of Child Neurology, Amsterdam Leukodystrophy Center, Emma's Children's Hospital, Amsterdam UMC, Vrije Universiteit, Amsterdam, The Netherlands
| | - Emma L Wakeling
- North East Thames Regional Genetic Service, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Grace Yoon
- Departments of Paediatrics and Molecular Genetics, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Julian C Knight
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Sameer M Zuberi
- Paediatric Neurosciences Research Group, School of Health and Wellbeing, University of Glasgow, Glasgow, UK
- Royal Hospital for Children, Glasgow, UK
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2
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Rey F, Esposito L, Maghraby E, Mauri A, Berardo C, Bonaventura E, Tonduti D, Carelli S, Cereda C. Role of epigenetics and alterations in RNA metabolism in leukodystrophies. WILEY INTERDISCIPLINARY REVIEWS. RNA 2024; 15:e1854. [PMID: 38831585 DOI: 10.1002/wrna.1854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 04/24/2024] [Accepted: 04/25/2024] [Indexed: 06/05/2024]
Abstract
Leukodystrophies are a class of rare heterogeneous disorders which affect the white matter of the brain, ultimately leading to a disruption in brain development and a damaging effect on cognitive, motor and social-communicative development. These disorders present a great clinical heterogeneity, along with a phenotypic overlap and this could be partially due to contributions from environmental stimuli. It is in this context that there is a great need to investigate what other factors may contribute to both disease insurgence and phenotypical heterogeneity, and novel evidence are raising the attention toward the study of epigenetics and transcription mechanisms that can influence the disease phenotype beyond genetics. Modulation in the epigenetics machinery including histone modifications, DNA methylation and non-coding RNAs dysregulation, could be crucial players in the development of these disorders, and moreover an aberrant RNA maturation process has been linked to leukodystrophies. Here, we provide an overview of these mechanisms hoping to supply a closer step toward the analysis of leukodystrophies not only as genetically determined but also with an added level of complexity where epigenetic dysregulation is of key relevance. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNA RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.
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Affiliation(s)
- Federica Rey
- Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi," Department of Biomedical and Clinical Sciences, University of Milano, Milan, Italy
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Letizia Esposito
- Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi," Department of Biomedical and Clinical Sciences, University of Milano, Milan, Italy
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Erika Maghraby
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
- Department of Biology and Biotechnology "L. Spallanzani" (DBB), University of Pavia, Pavia, Italy
| | - Alessia Mauri
- Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi," Department of Biomedical and Clinical Sciences, University of Milano, Milan, Italy
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Clarissa Berardo
- Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi," Department of Biomedical and Clinical Sciences, University of Milano, Milan, Italy
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Eleonora Bonaventura
- Unit of Pediatric Neurology, COALA Center for Diagnosis and Treatment of Leukodystrophies, V. Buzzi Children's Hospital, Milan, Italy
- Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy
| | - Davide Tonduti
- Unit of Pediatric Neurology, COALA Center for Diagnosis and Treatment of Leukodystrophies, V. Buzzi Children's Hospital, Milan, Italy
- Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy
| | - Stephana Carelli
- Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi," Department of Biomedical and Clinical Sciences, University of Milano, Milan, Italy
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Cristina Cereda
- Center of Functional Genomics and Rare Diseases, Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
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3
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Perrier S, Gauquelin L, Bernard G. Inherited white matter disorders: Hypomyelination (myelin disorders). HANDBOOK OF CLINICAL NEUROLOGY 2024; 204:197-223. [PMID: 39322379 DOI: 10.1016/b978-0-323-99209-1.00014-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/27/2024]
Abstract
Hypomyelinating leukodystrophies are a subset of genetic white matter diseases characterized by insufficient myelin deposition during development. MRI patterns are used to identify hypomyelinating disorders, and genetic testing is used to determine the causal genes implicated in individual disease forms. Clinical course can range from severe, with patients manifesting neurologic symptoms in infancy or early childhood, to mild, with onset in adolescence or adulthood. This chapter discusses the most common hypomyelinating leukodystrophies, including X-linked Pelizaeus-Merzbacher disease and other PLP1-related disorders, autosomal recessive Pelizaeus-Merzbacher-like disease, and POLR3-related leukodystrophy. PLP1-related disorders are caused by hemizygous pathogenic variants in the proteolipid protein 1 (PLP1) gene, and encompass classic Pelizaeus-Merzbacher disease, the severe connatal form, PLP1-null syndrome, spastic paraplegia type 2, and hypomyelination of early myelinating structures. Pelizaeus-Merzbacher-like disease presents a similar clinical picture to Pelizaeus-Merzbacher disease, however, it is caused by biallelic pathogenic variants in the GJC2 gene, which encodes for the gap junction protein Connexin-47. POLR3-related leukodystrophy, or 4H leukodystrophy (hypomyelination, hypodontia, and hypogonadotropic hypogonadism), is caused by biallelic pathogenic variants in genes encoding specific subunits of the transcription enzyme RNA polymerase III. In this chapter, the clinical features, disease pathophysiology and genetics, imaging patterns, as well as supportive and future therapies are discussed for each disorder.
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Affiliation(s)
- Stefanie Perrier
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC, Canada
| | - Laurence Gauquelin
- Division of Pediatric Neurology, Department of Pediatrics, CHUL et Centre Mère-Enfant Soleil du CHU de Québec-Université Laval, Québec, QC, Canada
| | - Geneviève Bernard
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC, Canada; Departments of Pediatrics and Human Genetics, McGill University, Montréal, QC, Canada.
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4
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Watt KE, Macintosh J, Bernard G, Trainor PA. RNA Polymerases I and III in development and disease. Semin Cell Dev Biol 2023; 136:49-63. [PMID: 35422389 PMCID: PMC9550887 DOI: 10.1016/j.semcdb.2022.03.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 03/18/2022] [Accepted: 03/21/2022] [Indexed: 12/18/2022]
Abstract
Ribosomes are macromolecular machines that are globally required for the translation of all proteins in all cells. Ribosome biogenesis, which is essential for cell growth, proliferation and survival, commences with transcription of a variety of RNAs by RNA Polymerases I and III. RNA Polymerase I (Pol I) transcribes ribosomal RNA (rRNA), while RNA Polymerase III (Pol III) transcribes 5S ribosomal RNA and transfer RNAs (tRNA) in addition to a wide variety of small non-coding RNAs. Interestingly, despite their global importance, disruptions in Pol I and Pol III function result in tissue-specific developmental disorders, with craniofacial anomalies and leukodystrophy/neurodegenerative disease being among the most prevalent. Furthermore, pathogenic variants in genes encoding subunits shared between Pol I and Pol III give rise to distinct syndromes depending on whether Pol I or Pol III function is disrupted. In this review, we discuss the global roles of Pol I and III transcription, the consequences of disruptions in Pol I and III transcription, disorders arising from pathogenic variants in Pol I and Pol III subunits, and mechanisms underpinning their tissue-specific phenotypes.
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Affiliation(s)
- Kristin En Watt
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Julia Macintosh
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Geneviève Bernard
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada; Departments of Pediatrics and Human Genetics, McGill University, Montreal, QC, Canada; Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montreal, QC, Canada.
| | - Paul A Trainor
- Stowers Institute for Medical Research, Kansas City, MO, USA; Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA.
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5
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Bergen DJM, Maurizi A, Formosa MM, McDonald GLK, El-Gazzar A, Hassan N, Brandi ML, Riancho JA, Rivadeneira F, Ntzani E, Duncan EL, Gregson CL, Kiel DP, Zillikens MC, Sangiorgi L, Högler W, Duran I, Mäkitie O, Van Hul W, Hendrickx G. High Bone Mass Disorders: New Insights From Connecting the Clinic and the Bench. J Bone Miner Res 2023; 38:229-247. [PMID: 36161343 PMCID: PMC10092806 DOI: 10.1002/jbmr.4715] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 09/05/2022] [Accepted: 09/22/2022] [Indexed: 02/04/2023]
Abstract
Monogenic high bone mass (HBM) disorders are characterized by an increased amount of bone in general, or at specific sites in the skeleton. Here, we describe 59 HBM disorders with 50 known disease-causing genes from the literature, and we provide an overview of the signaling pathways and mechanisms involved in the pathogenesis of these disorders. Based on this, we classify the known HBM genes into HBM (sub)groups according to uniform Gene Ontology (GO) terminology. This classification system may aid in hypothesis generation, for both wet lab experimental design and clinical genetic screening strategies. We discuss how functional genomics can shape discovery of novel HBM genes and/or mechanisms in the future, through implementation of omics assessments in existing and future model systems. Finally, we address strategies to improve gene identification in unsolved HBM cases and highlight the importance for cross-laboratory collaborations encompassing multidisciplinary efforts to transfer knowledge generated at the bench to the clinic. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Dylan J M Bergen
- School of Physiology, Pharmacology, and Neuroscience, Faculty of Life Sciences, University of Bristol, Bristol, UK.,Musculoskeletal Research Unit, Translational Health Sciences, Bristol Medical School, Faculty of Health Sciences, University of Bristol, Bristol, UK
| | - Antonio Maurizi
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Melissa M Formosa
- Department of Applied Biomedical Science, Faculty of Health Sciences, University of Malta, Msida, Malta.,Center for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Georgina L K McDonald
- School of Physiology, Pharmacology, and Neuroscience, Faculty of Life Sciences, University of Bristol, Bristol, UK
| | - Ahmed El-Gazzar
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | - Neelam Hassan
- Musculoskeletal Research Unit, Translational Health Sciences, Bristol Medical School, Faculty of Health Sciences, University of Bristol, Bristol, UK
| | | | - José A Riancho
- Department of Internal Medicine, Hospital U M Valdecilla, University of Cantabria, IDIVAL, Santander, Spain
| | - Fernando Rivadeneira
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Evangelia Ntzani
- Department of Hygiene and Epidemiology, Medical School, University of Ioannina, Ioannina, Greece.,Center for Evidence Synthesis in Health, Policy and Practice, Center for Research Synthesis in Health, School of Public Health, Brown University, Providence, RI, USA.,Institute of Biosciences, University Research Center of loannina, University of Ioannina, Ioannina, Greece
| | - Emma L Duncan
- Department of Twin Research & Genetic Epidemiology, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.,Department of Endocrinology, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - Celia L Gregson
- Musculoskeletal Research Unit, Translational Health Sciences, Bristol Medical School, Faculty of Health Sciences, University of Bristol, Bristol, UK
| | - Douglas P Kiel
- Marcus Institute for Aging Research, Hebrew SeniorLife and Department of Medicine Beth Israel Deaconess Medical Center and Harvard Medical School, Broad Institute of MIT & Harvard, Cambridge, MA, USA
| | - M Carola Zillikens
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Luca Sangiorgi
- Department of Rare Skeletal Diseases, IRCCS Rizzoli Orthopaedic Institute, Bologna, Italy
| | - Wolfgang Högler
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria.,Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK
| | | | - Outi Mäkitie
- Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.,Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Folkhälsan Research Centre, Folkhälsan Institute of Genetics, Helsinki, Finland
| | - Wim Van Hul
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
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6
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Cheng R, Van Bortle K. RNA polymerase III transcription and cancer: A tale of two RPC7 subunits. Front Mol Biosci 2023; 9:1073795. [PMID: 36710885 PMCID: PMC9877311 DOI: 10.3389/fmolb.2022.1073795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 12/19/2022] [Indexed: 01/15/2023] Open
Abstract
RNA polymerase III composition is shaped by the mutually exclusive incorporation of two paralogous subunits, RPC7α and RPC7β, encoded by genes POLR3G and POLR3GL in vertebrates. The expression of POLR3G and POLR3GL is spatiotemporally regulated during development, and multiple reports point to RPC7α-enhanced Pol III activity patterns, indicating that Pol III identity may underly dynamic Pol III transcription patterns observed in higher eukaryotes. In cancer, upregulation of POLR3G, but not POLR3GL, is associated with poor survival outcomes among patients, suggesting differences between RPC7α and RPC7β further influence disease progression and may translate into future biomarkers and therapeutic strategies. Here, we outline our current understanding of Pol III identity and transcription and reexamine the distinct protein characteristics of Pol III subunits RPC7α and RPC7β. Drawing on both structural and genomic studies, we discuss differences between RPC7α and RPC7β and the potential mechanisms by which Pol III identity may establish differential activities during development and disease.
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Affiliation(s)
- Ruiying Cheng
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL, United States
| | - Kevin Van Bortle
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL, United States
- Cancer Center at Illinois, University of Illinois Urbana-Champaign, Urbana, IL, United States
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7
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Abstract
tRNAs are key adaptor molecules that decipher the genetic code during translation of mRNAs in protein synthesis. In contrast to the traditional view of tRNAs as ubiquitously expressed housekeeping molecules, awareness is now growing that tRNA-encoding genes display tissue-specific and cell type-specific patterns of expression, and that tRNA gene expression and function are both dynamically regulated by post-transcriptional RNA modifications. Moreover, dysregulation of tRNAs, mediated by alterations in either their abundance or function, can have deleterious consequences that contribute to several distinct human diseases, including neurological disorders and cancer. Accumulating evidence shows that reprogramming of mRNA translation through altered tRNA activity can drive pathological processes in a codon-dependent manner. This Review considers the emerging evidence in support of the precise control of functional tRNA levels as an important regulatory mechanism that coordinates mRNA translation and protein expression in physiological cell homeostasis, and highlights key examples of human diseases that are linked directly to tRNA dysregulation.
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Affiliation(s)
- Esteban A Orellana
- Stem Cell Program, Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Elisabeth Siegal
- Stem Cell Program, Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, USA
| | - Richard I Gregory
- Stem Cell Program, Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, USA.
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA.
- Harvard Initiative for RNA Medicine, Harvard University, Boston, MA, USA.
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8
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Peng Q, Zhang Y, Xian B, Wu L, Ding J, Ding W, Zhang X, Ding B, Li D, Wu J, Hu X, Lu G. A synonymous variant contributes to a rare Wiedemann-Rautenstrauch syndrome complicated with mild anemia via affecting pre-mRNA splicing. Front Mol Neurosci 2022; 15:1026530. [DOI: 10.3389/fnmol.2022.1026530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 10/11/2022] [Indexed: 11/13/2022] Open
Abstract
Wiedemann-Rautenstrauch syndrome (WDRTS) is an extremely rare autosomal recessive neonatal disorder. Currently, over 50 cases with variable phenotypes of WDRTS have been reported. In our cohort of prenatal and postnatal growth retardation, a female proband was found to have general growth retardation, neurocutaneous syndrome, and anemia. Karyotype test and array-CGH detected no obvious chromosomal aberrations. Trio-based whole-exome sequencing (Trio-WES) identified bi-allelic compound mutations in the coding sequence (CDS) of POLR3A gene (c.3342C > T, p.Ser1114 = and c.3718G > A, p.Gly1240Ser). For the mild anemia phenotype, the underlying causal genetic factors could be attributed to the compound heterozygous mutations in FANCA gene (c.2832dup, p.Ala945CysfsTer6 and c.1902 T > G, p.Asp634Glu). Mini-gene reporter assays revealed that the synonymous variant of POLR3A and the missense variant of FANCA could affect pre-mRNA splicing of each gene. For POLR3A, the synonymous mutation (c.3342C > T, p.Ser1114=) generated three types of aberrant isoforms. Therefore, the female patient was finally diagnosed as WDRTS caused by POLR3A. For FANCA, the missense variant (c.1902 T > G, p.Asp634Glu) disrupted the normal splicing between exon 21 and 22, and produced two types of abnormal isoforms, one carrying the 1902G and the other spliced between exon 21 and 23 to exclude exon 22. Network analysis showed that POLR3A and FANCA could be STRINGed, indicating both proteins might collaborate for some unknown functions. Current investigation would broaden the knowledge for clinicians and genetic counselors and remind them to interpret those synonymous or predicted “benign” variants more carefully.
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9
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Busschers E, Ahmad N, Sun L, Iben JR, Walkey CJ, Rusin A, Yuen T, Rosen CJ, Willis IM, Zaidi M, Johnson DL. MAF1, a repressor of RNA polymerase III-dependent transcription, regulates bone mass. eLife 2022; 11:74740. [PMID: 35611941 PMCID: PMC9212997 DOI: 10.7554/elife.74740] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 04/26/2022] [Indexed: 11/25/2022] Open
Abstract
MAF1, a key repressor of RNA polymerase (pol) III-mediated transcription, has been shown to promote mesoderm formation in vitro. Here, we show that MAF1 plays a critical role in regulating osteoblast differentiation and bone mass. Global deletion of MAF1 (Maf1-/- mice) produced a high bone mass phenotype. However, osteoblasts isolated from Maf1-/- mice showed reduced osteoblastogenesis ex vivo. Therefore, we determined the phenotype of mice overexpressing MAF1 in cells from the mesenchymal lineage (Prx1-Cre;LSL-MAF1 mice). These mice showed increased bone mass. Ex vivo, cells from these mice showed enhanced osteoblastogenesis concordant with their high bone mass phenotype. Thus, the high bone mass phenotype in Maf1-/- mice is likely due to confounding effects from the global absence of MAF1. MAF1 overexpression promoted osteoblast differentiation of ST2 cells while MAF1 downregulation inhibited differentiation, indicating MAF1 enhances osteoblast formation. However, other perturbations used to repress RNA pol III transcription, inhibited osteoblast differentiation. However, decreasing RNA pol III transcription through these perturbations enhanced adipogenesis in ST2 cells. RNA-seq analyzed the basis for these opposing actions on osteoblast differentiation. The different modalities used to perturb RNA pol III transcription resulted in distinct gene expression changes, indicating that this transcription process is highly sensitive and triggers diverse gene expression programs and phenotypic outcomes. Specifically, MAF1 induced genes known to promote osteoblast differentiation. Furthermore, genes that are induced during osteoblast differentiation displayed codon bias. Together, these results reveal a novel role for MAF1 and RNA pol III-mediated transcription in osteoblast fate determination, differentiation, and bone mass regulation.
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Affiliation(s)
- Ellen Busschers
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States
| | - Naseer Ahmad
- Department of Medicine, Ican School of Medicine at Mount Sinai, New York, United States
| | - Li Sun
- Department of Medicine, Ican School of Medicine at Mount Sinai, New York, United States
| | - James R Iben
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, United States
| | - Christopher J Walkey
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States
| | - Aleksandra Rusin
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States
| | - Tony Yuen
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, United States
| | - Clifford J Rosen
- Maine Medical Center Research Institute, Scarborough, United States
| | - Ian M Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, United States
| | - Mone Zaidi
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, United States
| | - Deborah L Johnson
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States
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10
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Saghi M, InanlooRahatloo K, Alavi A, Kahrizi K, Najmabadi H. Intellectual disability associated with craniofacial dysmorphism due to POLR3B mutation and defect in spliceosomal machinery. BMC Med Genomics 2022; 15:89. [PMID: 35436926 PMCID: PMC9014605 DOI: 10.1186/s12920-022-01237-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 04/12/2022] [Indexed: 11/10/2022] Open
Abstract
Background Intellectual disability (ID) is a clinically important disease and a most prevalent neurodevelopmental disorder. The etiology and pathogenesis of ID are poorly recognized. Exome sequencing revealed a homozygous missense mutation in the POLR3B gene in a consanguineous family with three Intellectual disability with craniofacial anomalies patients. POLR3B gene encoding the second largest subunit of RNA polymerase III. Methods We performed RNA sequencing on blood samples to obtain insights into the biological pathways influenced by POLR3B mutation. We applied the results of our RNA-Seq analysis to several gene ontology programs such as ToppGene, Enrichr, KEGG. Results A significant decrease in expression of several spliceosomal RNAs, ribosomal proteins, and transcription factors was detected in the affected, compared to unaffected, family members. Conclusions We hypothesize that POLR3B mutation dysregulates the expression of some important transcription factors, ribosomal and spliceosomal genes, and impairments in protein synthesis and splicing mediated in part by transcription factors such as FOXC2 and GATA1 contribute to impaired neuronal function and concurrence of intellectual disability and craniofacial anomalies in our patients. Our study highlights the emerging role of the spliceosome and ribosomal proteins in intellectual disability. Supplementary Information The online version contains supplementary material available at 10.1186/s12920-022-01237-5.
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Affiliation(s)
- Mostafa Saghi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | | | - Afagh Alavi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Kimia Kahrizi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Hossein Najmabadi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
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11
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Mishra S, Hasan SH, Sakhawala RM, Chaudhry S, Maraia RJ. Mechanism of RNA polymerase III termination-associated reinitiation-recycling conferred by the essential function of the N terminal-and-linker domain of the C11 subunit. Nat Commun 2021; 12:5900. [PMID: 34625550 PMCID: PMC8501072 DOI: 10.1038/s41467-021-26080-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 09/17/2021] [Indexed: 01/06/2023] Open
Abstract
RNA polymerase III achieves high level tRNA synthesis by termination-associated reinitiation-recycling that involves the essential C11 subunit and heterodimeric C37/53. The C11-CTD (C-terminal domain) promotes Pol III active center-intrinsic RNA 3'-cleavage although deciphering function for this activity has been complicated. We show that the isolated NTD (N-terminal domain) of C11 stimulates Pol III termination by C37/53 but not reinitiation-recycling which requires the NTD-linker (NTD-L). By an approach different from what led to current belief that RNA 3'-cleavage activity is essential, we show that NTD-L can provide the essential function of Saccharomyces cerevisiae C11 whereas classic point mutations that block cleavage, interfere with active site function and are toxic to growth. Biochemical and in vivo analysis including of the C11 invariant central linker led to a model for Pol III termination-associated reinitiation-recycling. The C11 NTD and CTD stimulate termination and RNA 3'-cleavage, respectively, whereas reinitiation-recycling activity unique to Pol III requires only the NTD-linker. RNA 3'-cleavage activity increases growth rate but is nonessential.
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Affiliation(s)
- Saurabh Mishra
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Department of Biochemistry, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - Shaina H Hasan
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Mayo Clinic Alix School of Medicine, Scottsdale, AZ, USA
| | - Rima M Sakhawala
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Section on Regulatory RNA, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA
| | - Shereen Chaudhry
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Pfizer (Pearl River Site), 401 N Middletown Rd, Pearl River, NY, USA
| | - Richard J Maraia
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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12
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Defective myelination in an RNA polymerase III mutant leukodystrophic mouse. Proc Natl Acad Sci U S A 2021; 118:2024378118. [PMID: 34583988 DOI: 10.1073/pnas.2024378118] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2021] [Indexed: 01/06/2023] Open
Abstract
RNA polymerase (Pol) III synthesizes abundant short noncoding RNAs that have essential functions in protein synthesis, secretion, and other processes. Despite the ubiquitous functions of these RNAs, mutations in Pol III subunits cause Pol III-related leukodystrophy, an early-onset neurodegenerative disease. The basis of this neural sensitivity and the mechanisms of disease pathogenesis are unknown. Here we show that mice expressing pathogenic mutations in the largest Pol III subunit, Polr3a, specifically in Olig2-expressing cells, have impaired growth and developmental delay, deficits in cognitive, sensory, and fine sensorimotor function, and hypomyelination in multiple regions of the cerebrum and spinal cord. These phenotypes reflect a subset of clinical features seen in patients. In contrast, the gross motor defects and cerebellar hypomyelination that are common features of severely affected patients are absent in the mice, suggesting a relatively mild form of the disease in this conditional model. Our results show that disease pathogenesis in the mice involves defects that reduce both the number of mature myelinating oligodendrocytes and the ability of these cells to produce a myelin sheath of normal thickness. The findings suggest unique sensitivities of oligodendrogenesis and myelination to perturbations of Pol III transcription.
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13
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TAB2 deletions and variants cause a highly recognisable syndrome with mitral valve disease, cardiomyopathy, short stature and hypermobility. Eur J Hum Genet 2021; 29:1669-1676. [PMID: 34456334 DOI: 10.1038/s41431-021-00948-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 05/27/2021] [Accepted: 08/10/2021] [Indexed: 11/08/2022] Open
Abstract
Deletions that include the gene TAB2 and TAB2 loss-of-function variants have previously been associated with congenital heart defects and cardiomyopathy. However, other features, including short stature, facial dysmorphisms, connective tissue abnormalities and a variable degree of developmental delay, have only been mentioned occasionally in literature and thus far not linked to TAB2. In a large-scale, social media-based chromosome 6 study, we observed a shared phenotype in patients with a 6q25.1 deletion that includes TAB2. To confirm if this phenotype is caused by haploinsufficiency of TAB2 and to delineate a TAB2-related phenotype, we subsequently sequenced TAB2 in patients with matching phenotypes and recruited patients with pathogenic TAB2 variants detected by exome sequencing. This identified 11 patients with a deletion containing TAB2 (size 1.68-14.31 Mb) and 14 patients from six families with novel truncating TAB2 variants. Twenty (80%) patients had cardiac disease, often mitral valve defects and/or cardiomyopathy, 18 (72%) had short stature and 18 (72%) had hypermobility. Twenty patients (80%) had facial features suggestive for Noonan syndrome. No substantial phenotypic differences were noted between patients with deletions and those with intragenic variants. We then compared our patients to 45 patients from the literature. All literature patients had cardiac diseases, but syndromic features were reported infrequently. Our study shows that the phenotype in 6q25.1 deletions is caused by haploinsufficiency of TAB2 and that TAB2 is associated not just with cardiac disease, but also with a distinct phenotype, with features overlapping with Noonan syndrome. We propose the name "TAB2-related syndrome".
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14
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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: 29] [Impact Index Per Article: 9.7] [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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15
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Truncating SRCAP variants outside the Floating-Harbor syndrome locus cause a distinct neurodevelopmental disorder with a specific DNA methylation signature. Am J Hum Genet 2021; 108:1053-1068. [PMID: 33909990 PMCID: PMC8206150 DOI: 10.1016/j.ajhg.2021.04.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 03/31/2021] [Indexed: 02/08/2023] Open
Abstract
Truncating variants in exons 33 and 34 of the SNF2-related CREBBP activator protein (SRCAP) gene cause the neurodevelopmental disorder (NDD) Floating-Harbor syndrome (FLHS), characterized by short stature, speech delay, and facial dysmorphism. Here, we present a cohort of 33 individuals with clinical features distinct from FLHS and truncating (mostly de novo) SRCAP variants either proximal (n = 28) or distal (n = 5) to the FLHS locus. Detailed clinical characterization of the proximal SRCAP individuals identified shared characteristics: developmental delay with or without intellectual disability, behavioral and psychiatric problems, non-specific facial features, musculoskeletal issues, and hypotonia. Because FLHS is known to be associated with a unique set of DNA methylation (DNAm) changes in blood, a DNAm signature, we investigated whether there was a distinct signature associated with our affected individuals. A machine-learning model, based on the FLHS DNAm signature, negatively classified all our tested subjects. Comparing proximal variants with typically developing controls, we identified a DNAm signature distinct from the FLHS signature. Based on the DNAm and clinical data, we refer to the condition as “non-FLHS SRCAP-related NDD.” All five distal variants classified negatively using the FLHS DNAm model while two classified positively using the proximal model. This suggests divergent pathogenicity of these variants, though clinically the distal group presented with NDD, similar to the proximal SRCAP group. In summary, for SRCAP, there is a clear relationship between variant location, DNAm profile, and clinical phenotype. These results highlight the power of combined epigenetic, molecular, and clinical studies to identify and characterize genotype-epigenotype-phenotype correlations.
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16
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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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17
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Coulombe B, Derksen A, La Piana R, Brais B, Gauthier MS, Bernard G. POLR3-related leukodystrophy: How do mutations affecting RNA polymerase III subunits cause hypomyelination? Fac Rev 2021; 10:12. [PMID: 33659930 PMCID: PMC7894263 DOI: 10.12703/r/10-12] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Hypomyelinating leukodystrophies are a group of genetic disorders characterized by insufficient myelin deposition during development. A subset of hypomyelinating leukodystrophies, named RNA polymerase III (Pol III or POLR3)-related leukodystrophy or 4H (Hypomyelination, Hypodontia and Hypogonadotropic Hypogonadism) leukodystrophy, was found to be caused by biallelic variants in genes encoding subunits of the enzyme Pol III, including POLR3A, POLR3B, POLR3K, and POLR1C. Pol III is one of the three nuclear RNA polymerases that synthesizes small non-coding RNAs, such as tRNAs, 5S RNA, and others, that are involved in the regulation of essential cellular processes, including transcription, translation and RNA maturation. Affinity purification coupled with mass spectrometry (AP-MS) revealed that a number of mutations causing POLR3-related leukodystrophy impair normal assembly or biogenesis of Pol III, often causing a retention of the unassembled subunits in the cytoplasm. Even though these proteomic studies have helped to understand the molecular defects associated with leukodystrophy, how these mutations cause hypomyelination has yet to be defined. In this review we propose two main hypotheses to explain how mutations affecting Pol III subunits can cause hypomyelination.
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Affiliation(s)
- Benoit Coulombe
- Department of Translational Proteomics, Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, QC, Canada
| | - Alexa Derksen
- Department of Translational Proteomics, Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC, Canada
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada
| | - Roberta La Piana
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
- Department of Diagnostic Radiology, McGill University, Montréal, QC, Canada
| | - Bernard Brais
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
- Department of Human Genetics, McGill University, Montréal, QC, Canada
| | - Marie-Soleil Gauthier
- Department of Translational Proteomics, Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada
| | - Geneviève Bernard
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC, Canada
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada
- Department of Human Genetics, McGill University, Montréal, QC, Canada
- Department of Pediatrics, McGill University, Montréal, QC, Canada
- Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montréal, QC, Canada
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18
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Abstract
In this review, Yeganeh et al. summarize different human diseases that have been linked to defects in the Pol III transcription apparatus or to Pol III products imbalance and discuss the possible underlying mechanisms. RNA polymerase (Pol) III is responsible for transcription of different noncoding genes in eukaryotic cells, whose RNA products have well-defined functions in translation and other biological processes for some, and functions that remain to be defined for others. For all of them, however, new functions are being described. For example, Pol III products have been reported to regulate certain proteins such as protein kinase R (PKR) by direct association, to constitute the source of very short RNAs with regulatory roles in gene expression, or to control microRNA levels by sequestration. Consistent with these many functions, deregulation of Pol III transcribed genes is associated with a large variety of human disorders. Here we review different human diseases that have been linked to defects in the Pol III transcription apparatus or to Pol III products imbalance and discuss the possible underlying mechanisms.
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Affiliation(s)
- Meghdad Yeganeh
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Nouria Hernandez
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
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19
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Schnabel F, Kornak U, Wollnik B. Premature aging disorders: A clinical and genetic compendium. Clin Genet 2020; 99:3-28. [PMID: 32860237 DOI: 10.1111/cge.13837] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/21/2020] [Accepted: 08/24/2020] [Indexed: 12/22/2022]
Abstract
Progeroid disorders make up a heterogeneous group of very rare hereditary diseases characterized by clinical signs that often mimic physiological aging in a premature manner. Apart from Hutchinson-Gilford progeria syndrome, one of the best-investigated progeroid disorders, a wide spectrum of other premature aging phenotypes exist, which differ significantly in their clinical presentation and molecular pathogenesis. Next-generation sequencing (NGS)-based approaches have made it feasible to determine the molecular diagnosis in the early stages of a disease. Nevertheless, a broad clinical knowledge on these disorders and their associated symptoms is still fundamental for a comprehensive patient management and for the interpretation of variants of unknown significance from NGS data sets. This review provides a detailed overview on characteristic clinical features and underlying molecular genetics of well-known as well as only recently identified premature aging disorders and also highlights novel findings towards future therapeutic options.
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Affiliation(s)
- Franziska Schnabel
- Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany
| | - Uwe Kornak
- Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany
| | - Bernd Wollnik
- Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable cells" (MBExC), University of Göttingen, Göttingen, Germany
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20
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Functions of paralogous RNA polymerase III subunits POLR3G and POLR3GL in mouse development. Proc Natl Acad Sci U S A 2020; 117:15702-15711. [PMID: 32576691 DOI: 10.1073/pnas.1922821117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Mammalian cells contain two isoforms of RNA polymerase III (Pol III) that differ in only a single subunit, with POLR3G in one form (Pol IIIα) and the related POLR3GL in the other form (Pol IIIβ). Previous research indicates that POLR3G and POLR3GL are differentially expressed, with POLR3G expression being highly enriched in embryonic stem cells (ESCs) and tumor cells relative to the ubiquitously expressed POLR3GL. To date, the functional differences between these two subunits remain largely unexplored, especially in vivo. Here, we show that POLR3G and POLR3GL containing Pol III complexes bind the same target genes and assume the same functions both in vitro and in vivo and, to a significant degree, can compensate for each other in vivo. Notably, an observed defect in the differentiation ability of POLR3G knockout ESCs can be rescued by exogenous expression of POLR3GL. Moreover, whereas POLR3G knockout mice die at a very early embryonic stage, POLR3GL knockout mice complete embryonic development without noticeable defects but die at about 3 wk after birth with signs of both general growth defects and potential cerebellum-related neuronal defects. The different phenotypes of the knockout mice likely reflect differential expression levels of POLR3G and POLR3GL across developmental stages and between tissues and insufficient amounts of total Pol III in vivo.
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21
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Beauregard-Lacroix E, Salian S, Kim H, Ehresmann S, DʹAmours G, Gauthier J, Saillour V, Bernard G, Mitchell GA, Soucy JF, Michaud JL, Campeau PM. A variant of neonatal progeroid syndrome, or Wiedemann-Rautenstrauch syndrome, is associated with a nonsense variant in POLR3GL. Eur J Hum Genet 2019; 28:461-468. [PMID: 31695177 DOI: 10.1038/s41431-019-0539-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Revised: 10/08/2019] [Accepted: 10/13/2019] [Indexed: 12/19/2022] Open
Abstract
Neonatal progeroid syndrome, also known as Wiedemann-Rautenstrauch syndrome, is a rare condition characterized by severe growth retardation, apparent macrocephaly with prominent scalp veins, and lipodystrophy. It is caused by biallelic variants in POLR3A, a gene encoding for a subunit of RNA polymerase III. All variants reported in the literature lead to at least a partial loss-of-function (when considering both alleles together). Here, we describe an individual with several clinical features of neonatal progeroid syndrome in whom exome sequencing revealed a homozygous nonsense variant in POLR3GL (NM_032305.2:c.358C>T; p.(Arg120Ter)). POLR3GL also encodes a subunit of RNA polymerase III and has recently been associated with endosteal hyperostosis and oligodontia in three patients with a phenotype distinct from the patient described here. Given the important role of POLR3GL in the same complex as the protein implicated in neonatal progeroid syndrome, the nature of the variant identified, our RNA studies suggesting nonsense-mediated decay, and the clinical overlap, we propose POLR3GL as a gene causing a variant of neonatal progeroid syndrome and therefore expand the phenotype associated with POLR3GL variants.
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Affiliation(s)
- Eliane Beauregard-Lacroix
- Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Smrithi Salian
- CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada
| | - Hyunyun Kim
- CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada
| | - Sophie Ehresmann
- CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada
| | - Guylaine DʹAmours
- Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Julie Gauthier
- CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada.,Medical Biological Unit, Molecular Diagnostic Laboratory, Sainte-Justine University Hospital Center, Montreal, QC, Canada.,Integrated Centre for Pediatric Clinical Genomics, Génome Québec and Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Virginie Saillour
- Medical Biological Unit, Molecular Diagnostic Laboratory, Sainte-Justine University Hospital Center, Montreal, QC, Canada.,Integrated Centre for Pediatric Clinical Genomics, Génome Québec and Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Geneviève Bernard
- Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics, McGill University, Montreal, QC, Canada.,Division of Medical Genetics, Department of Specialized Medicine, McGill University Health Center, Montreal, QC, Canada.,Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Grant A Mitchell
- Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada.,CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada.,Integrated Centre for Pediatric Clinical Genomics, Génome Québec and Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Jean-François Soucy
- Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada.,Medical Biological Unit, Molecular Diagnostic Laboratory, Sainte-Justine University Hospital Center, Montreal, QC, Canada.,Integrated Centre for Pediatric Clinical Genomics, Génome Québec and Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Jacques L Michaud
- Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada.,CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada.,Integrated Centre for Pediatric Clinical Genomics, Génome Québec and Sainte-Justine University Hospital Center, Montreal, QC, Canada
| | - Philippe M Campeau
- Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada. .,CHU Sainte Justine Research Center, Université de Montréal, Montreal, QC, Canada.
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