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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] [What about the content of this article? (0)] [Affiliation(s)] [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: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Macintosh J, Perrier S, Pinard M, Tran LT, Guerrero K, Prasad C, Prasad AN, Pastinen T, Thiffault I, Coulombe B, Bernard G. Biallelic pathogenic variants in POLR3D alter tRNA transcription and cause a hypomyelinating leukodystrophy: A case report. Front Neurol 2023; 14:1254140. [PMID: 37915380 PMCID: PMC10616956 DOI: 10.3389/fneur.2023.1254140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 09/28/2023] [Indexed: 11/03/2023] Open
Abstract
RNA polymerase III-related leukodystrophy (POLR3-related leukodystrophy) is a rare, genetically determined hypomyelinating disease arising from biallelic pathogenic variants in genes encoding subunits of RNA polymerase III (Pol III). Here, we describe the first reported case of POLR3-related leukodystrophy caused by biallelic pathogenic variants in POLR3D, encoding the RPC4 subunit of Pol III. The individual, a female, demonstrated delays in walking and expressive and receptive language as a child and later cognitively plateaued. Additional neurological features included cerebellar signs (e.g., dysarthria, ataxia, and intention tremor) and dysphagia, while non-neurological features included hypodontia, hypogonadotropic hypogonadism, and dysmorphic facial features. Her MRI was notable for diffuse hypomyelination with myelin preservation of early myelinating structures, characteristic of POLR3-related leukodystrophy. Exome sequencing revealed the biallelic variants in POLR3D, a missense variant (c.541C > T, p.P181S) and an intronic splice site variant (c.656-6G > A, p.?). Functional studies of the patient's fibroblasts demonstrated significantly decreased RNA-level expression of POLR3D, along with reduced expression of other Pol III subunit genes. Notably, Pol III transcription was also shown to be aberrant, with a significant decrease in 7SK RNA and several distinct tRNA genes analyzed. Affinity purification coupled to mass spectrometry of the POLR3D p.P181S variant showed normal assembly of Pol III subunits yet altered interaction of Pol III with the PAQosome chaperone complex, indicating the missense variant is likely to alter complex maturation. This work identifies biallelic pathogenic variants in POLR3D as a novel genetic cause of POLR3-related leukodystrophy, expanding the molecular spectrum associated with this disease, and proposes altered tRNA homeostasis as a factor in the underlying biology of this hypomyelinating disorder.
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Affiliation(s)
- 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 Centre, Montreal, QC, Canada
| | - Stefanie Perrier
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Maxime Pinard
- Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada
| | - Luan T. Tran
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Kether Guerrero
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Chitra Prasad
- Department of Pediatrics, London Health Sciences Center and Western University, London, ON, Canada
- Medical Genetics Program of Southwestern Ontario, London Health Sciences Center, London, ON, Canada
- Children’s Health Research Institute, London, ON, Canada
| | - Asuri N. Prasad
- Department of Pediatrics, London Health Sciences Center and Western University, London, ON, Canada
- Children’s Health Research Institute, London, ON, Canada
| | - Tomi Pastinen
- Genomic Medicine Center, Children's Mercy Hospital, Kansas City, MO, United States
- University of Missouri Kansas City School of Medicine, Kansas City, MO, United States
- Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO, United States
| | - Isabelle Thiffault
- Genomic Medicine Center, Children's Mercy Hospital, Kansas City, MO, United States
- University of Missouri Kansas City School of Medicine, Kansas City, MO, United States
- Department of Pathology and Laboratory Medicine, Children's Mercy Hospital, Kansas City, MO, United States
| | - Benoit Coulombe
- Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada
- Département de Biochimie et Médecine Moléculaire, Faculté de Médecine, Université de Montréal, 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 Centre, Montreal, QC, Canada
- Department of Pediatrics, McGill University, Montreal, QC, Canada
- Department of Human Genetics, McGill University, Montreal, QC, Canada
- Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Centre, Montreal, QC, Canada
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Pinard M, Dastpeyman S, Poitras C, Bernard G, Gauthier MS, Coulombe B. Riluzole partially restores RNA polymerase III complex assembly in cells expressing the leukodystrophy-causative variant POLR3B R103H. Mol Brain 2022; 15:98. [PMID: 36451185 PMCID: PMC9710144 DOI: 10.1186/s13041-022-00974-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 10/16/2022] [Indexed: 12/12/2022] Open
Abstract
The mechanism of assembly of RNA polymerase III (Pol III), the 17-subunit enzyme that synthesizes tRNAs, 5 S rRNA, and other small-nuclear (sn) RNAs in eukaryotes, is not clearly understood. The recent discovery of the HSP90 co-chaperone PAQosome (Particle for Arrangement of Quaternary structure) revealed a function for this machinery in the biogenesis of nuclear RNA polymerases. However, the connection between Pol III subunits and the PAQosome during the assembly process remains unexplored. Here, we report the development of a mass spectrometry-based assay that allows the characterization of Pol III assembly. This assay was used to dissect the stages of Pol III assembly, to start defining the function of the PAQosome in this process, to dissect the assembly defects driven by the leukodystrophy-causative R103H substitution in POLR3B, and to discover that riluzole, an FDA-approved drug for alleviation of ALS symptoms, partly corrects these assembly defects. Together, these results shed new light on the mechanism and regulation of human nuclear Pol III biogenesis.
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Affiliation(s)
- Maxime Pinard
- grid.511547.30000 0001 2106 1695Translational Proteomics Laboratory, Institut de Recherches Cliniques de Montréal, Montréal, Québec Canada
| | - Samaneh Dastpeyman
- grid.511547.30000 0001 2106 1695Translational Proteomics Laboratory, Institut de Recherches Cliniques de Montréal, Montréal, Québec Canada
| | - Christian Poitras
- grid.511547.30000 0001 2106 1695Translational Proteomics Laboratory, Institut de Recherches Cliniques de Montréal, Montréal, Québec Canada
| | - Geneviève Bernard
- grid.63984.300000 0000 9064 4811Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Neurology and Neurosurgery, McGill University, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Human Genetics, McGill University, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Pediatrics, McGill University, Montreal, Canada ,grid.63984.300000 0000 9064 4811Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montreal, Canada
| | - Marie-Soleil Gauthier
- grid.511547.30000 0001 2106 1695Translational Proteomics Laboratory, Institut de Recherches Cliniques de Montréal, Montréal, Québec Canada
| | - Benoit Coulombe
- grid.511547.30000 0001 2106 1695Translational Proteomics Laboratory, Institut de Recherches Cliniques de Montréal, Montréal, Québec Canada ,grid.14848.310000 0001 2292 3357Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec Canada
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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] [What about the content of this article? (0)] [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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Bai H, Li D, Zheng Y, Jiang X. Case report: Biallelic variants in POLR3B gene lead to 4H leukodystrophy from the study of brother and sister. Medicine (Baltimore) 2022; 101:e30350. [PMID: 36042647 PMCID: PMC9410618 DOI: 10.1097/md.0000000000030350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
INTRODUCTION 4H leukodystrophy, one of POLR3-related leukodystrophy, is a rare hereditary brain white matter disease caused by the pathogenic biallelic variations in POLR3A, POLR3B, or POLR1C. Hypomyelination, hypodontia, and hypogonadotropic hypogonadism is mainly presented in patients with 4H leukodystrophy. PATIENT CONCERNS Here, we reported the brother and the sister with new compound heterozygous (c.1615G>T and c.165-167del) with various degrees of phenotypes including dysbasia, myopia, dental abnormal, and hypogonadotropic hypogonadism. DIAGNOSIS The brother and sister were diagnosed with 4H leukodystrophy. INTERVENTIONS Gonadotrophins treatment of the brother could significantly improve the development of secondary sexual characteristics and genitalia. OUTCOMES This study showed that the same genotype of POLR3B may have variable clinical phenotypes in the brother and sister. CONCLUSION The exploration of molecular functions and genetic counseling are crucial for further diagnosis and treatment of POLR3-related leukodystrophy.
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Affiliation(s)
- Hengzhou Bai
- Andrology, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
- Key Laboratory of Birth Defects and Related Disease of Women and Children (Sichuan University), Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Dingming Li
- Andrology, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
- Key Laboratory of Birth Defects and Related Disease of Women and Children (Sichuan University), Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Yi Zheng
- Andrology, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
- Key Laboratory of Birth Defects and Related Disease of Women and Children (Sichuan University), Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
| | - XiaoHui Jiang
- Andrology, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
- Key Laboratory of Birth Defects and Related Disease of Women and Children (Sichuan University), Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
- *Correspondence: XiaoHui Jiang, Andrology, West China Second University Hospital, Sichuan University, No. 1416, Section 1, Cheng Long Avenue, Chengdu, Sichuan 610011, China (e-mail: )
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Merheb E, Cui MH, DuBois JC, Branch CA, Gulinello M, Shafit-Zagardo B, Moir RD, Willis IM. Defective myelination in an RNA polymerase III mutant leukodystrophic mouse. Proc Natl Acad Sci U S A 2021; 118:e2024378118. [PMID: 34583988 DOI: 10.1073/pnas.2024378118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [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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10
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Oleari R, Massa V, Cariboni A, Lettieri A. The Differential Roles for Neurodevelopmental and Neuroendocrine Genes in Shaping GnRH Neuron Physiology and Deficiency. Int J Mol Sci 2021; 22:9425. [PMID: 34502334 PMCID: PMC8431607 DOI: 10.3390/ijms22179425] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/27/2021] [Accepted: 08/28/2021] [Indexed: 01/19/2023] Open
Abstract
Gonadotropin releasing hormone (GnRH) neurons are hypothalamic neuroendocrine cells that control sexual reproduction. During embryonic development, GnRH neurons migrate from the nose to the hypothalamus, where they receive inputs from several afferent neurons, following the axonal scaffold patterned by nasal nerves. Each step of GnRH neuron development depends on the orchestrated action of several molecules exerting specific biological functions. Mutations in genes encoding for these essential molecules may cause Congenital Hypogonadotropic Hypogonadism (CHH), a rare disorder characterized by GnRH deficiency, delayed puberty and infertility. Depending on their action in the GnRH neuronal system, CHH causative genes can be divided into neurodevelopmental and neuroendocrine genes. The CHH genetic complexity, combined with multiple inheritance patterns, results in an extreme phenotypic variability of CHH patients. In this review, we aim at providing a comprehensive and updated description of the genes thus far associated with CHH, by dissecting their biological relevance in the GnRH system and their functional relevance underlying CHH pathogenesis.
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Affiliation(s)
- Roberto Oleari
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milano, Italy;
| | - Valentina Massa
- Department of Health Sciences, University of Milan, 20142 Milano, Italy;
- CRC Aldo Ravelli for Neurotechnology and Experimental Brain Therapeutics, Department of Health Sciences, University of Milan, 20142 Milano, Italy
| | - Anna Cariboni
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milano, Italy;
| | - Antonella Lettieri
- Department of Health Sciences, University of Milan, 20142 Milano, Italy;
- CRC Aldo Ravelli for Neurotechnology and Experimental Brain Therapeutics, Department of Health Sciences, University of Milan, 20142 Milano, Italy
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11
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Louden ED, Poch A, Kim HG, Ben-Mahmoud A, Kim SH, Layman LC. Genetics of hypogonadotropic Hypogonadism-Human and mouse genes, inheritance, oligogenicity, and genetic counseling. Mol Cell Endocrinol 2021; 534:111334. [PMID: 34062169 DOI: 10.1016/j.mce.2021.111334] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 05/12/2021] [Accepted: 05/24/2021] [Indexed: 12/14/2022]
Abstract
Hypogonadotropic hypogonadism, which may be normosmic (nHH) or anosmic/hyposmic, known as Kallmann syndrome (KS), is due to gonadotropin-releasing hormone deficiency, which results in absent puberty and infertility. Investigation of the genetic basis of nHH/KS over the past 35 years has yielded a substantial increase in our understanding, as variants in 44 genes in OMIM account for ~50% of cases. The first genes for KS (ANOS1) and nHH (GNRHR) were followed by the discovery that FGFR1 variants may cause either nHH or KS. Associated anomalies include midline facial defects, neurologic deficits, cardiac anomalies, and renal agenesis, among others. Mouse models for all but one gene (ANOS1) generally support findings in humans. About half of the known genes implicated in nHH/KS are inherited as autosomal dominant and half are autosomal recessive, whereas only 7% are X-linked recessive. Digenic and oligogenic inheritance has been reported in 2-20% of patients, most commonly with variants in genes that may result in either nHH or KS inherited in an autosomal dominant fashion. In vitro analyses have only been conducted for both gene variants in eight cases and for one gene variant in 20 cases. Rigorous confirmation that two gene variants in the same individual cause the nHH/KS phenotype is lacking for most. Clinical diagnosis is probably best accomplished by targeted next generation sequencing of the known candidate genes with confirmation by Sanger sequencing. Elucidation of the genetic basis of nHH/KS has resulted in an enhanced understanding of this disorder, as well as normal puberty, which makes genetic diagnosis clinically relevant.
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Affiliation(s)
- Erica D Louden
- Section of Reproductive Endocrinology, Infertility, & Genetics, Department of Obstetrics & Gynecology, Department of Neuroscience & Regenerative Medicine, Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA
| | - Alexandra Poch
- Section of Reproductive Endocrinology, Infertility, & Genetics, Department of Obstetrics & Gynecology, Department of Neuroscience & Regenerative Medicine, Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA
| | - Hyung-Goo Kim
- Neurological Disorders Research Center, Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Doha, Qatar
| | - Afif Ben-Mahmoud
- Neurological Disorders Research Center, Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Doha, Qatar
| | - Soo-Hyun Kim
- Molecular and Clinical Sciences Research Institute, St. George's, University of London, Cranmer Terrace, London, SW17 0RE, United Kingdom
| | - Lawrence C Layman
- Section of Reproductive Endocrinology, Infertility, & Genetics, Department of Obstetrics & Gynecology, Department of Neuroscience & Regenerative Medicine, Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA.
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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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13
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Abstract
Transcription in eukaryotic cells is performed by three RNA polymerases. RNA polymerase I synthesises most rRNAs, whilst RNA polymerase II transcribes all mRNAs and many non-coding RNAs. The largest of the three polymerases is RNA polymerase III (Pol III) which transcribes a variety of short non-coding RNAs including tRNAs and the 5S rRNA, in addition to other small RNAs such as snRNAs, snoRNAs, SINEs, 7SL RNA, Y RNA, and U6 spilceosomal RNA. Pol III-mediated transcription is highly dynamic and regulated in response to changes in cell growth, cell proliferation and stress. Pol III-generated transcripts are involved in a wide variety of cellular processes, including translation, genome and transcriptome regulation and RNA processing, with Pol III dys-regulation implicated in diseases including leukodystrophy, Alzheimer's, Fragile X-syndrome and various cancers. More recently, Pol III was identified as an evolutionarily conserved determinant of organismal lifespan acting downstream of mTORC1. Pol III inhibition extends lifespan in yeast, worms and flies, and in worms and flies acts from the intestine and intestinal stem cells respectively to achieve this. Intriguingly, Pol III activation achieved through impairment of its master repressor, Maf1, has also been shown to promote longevity in model organisms, including mice. In this review we introduce the Pol III transcription apparatus and review the current understanding of RNA Pol III's role in ageing and lifespan in different model organisms. We then discuss the potential of Pol III as a therapeutic target to improve age-related health in humans.
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Affiliation(s)
- Yavuz Kulaberoglu
- Department of Genetics Evolution and Environment, Institute of Healthy Ageing, University College London, London, United Kingdom
| | - Yasir Malik
- Faculty of Natural Sciences, University of Kent, Canterbury, United Kingdom
| | - Gillian Borland
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Colin Selman
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Nazif Alic
- Department of Genetics Evolution and Environment, Institute of Healthy Ageing, University College London, London, United Kingdom.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
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14
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Derksen A, Shih HY, Forget D, Darbelli L, Tran LT, Poitras C, Guerrero K, Tharun S, Alkuraya FS, Kurdi WI, Nguyen CTE, Laberge AM, Si Y, Gauthier MS, Bonkowsky JL, Coulombe B, Bernard G. Variants in LSM7 impair LSM complexes assembly, neurodevelopment in zebrafish and may be associated with an ultra-rare neurological disease. Human Genetics and Genomics Advances 2021; 2:100034. [PMID: 35047835 PMCID: PMC8756503 DOI: 10.1016/j.xhgg.2021.100034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 04/28/2021] [Indexed: 11/15/2022] Open
Abstract
Leukodystrophies, genetic neurodevelopmental and/or neurodegenerative disorders of cerebral white matter, result from impaired myelin homeostasis and metabolism. Numerous genes have been implicated in these heterogeneous disorders; however, many individuals remain without a molecular diagnosis. Using whole-exome sequencing, biallelic variants in LSM7 were uncovered in two unrelated individuals, one with a leukodystrophy and the other who died in utero. LSM7 is part of the two principle LSM protein complexes in eukaryotes, namely LSM1-7 and LSM2-8. Here, we investigate the molecular and functional outcomes of these LSM7 biallelic variants in vitro and in vivo. Affinity purification-mass spectrometry of the LSM7 variants showed defects in the assembly of both LSM complexes. Lsm7 knockdown in zebrafish led to central nervous system defects, including impaired oligodendrocyte development and motor behavior. Our findings demonstrate that variants in LSM7 cause misassembly of the LSM complexes, impair neurodevelopment of the zebrafish, and may be implicated in human disease. The identification of more affected individuals is needed before the molecular mechanisms of mRNA decay and splicing regulation are added to the categories of biological dysfunctions implicated in leukodystrophies, neurodevelopmental and/or neurodegenerative diseases.
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15
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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: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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16
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Perrier S, Michell-Robinson MA, Bernard G. POLR3-Related Leukodystrophy: Exploring Potential Therapeutic Approaches. Front Cell Neurosci 2021; 14:631802. [PMID: 33633543 PMCID: PMC7902007 DOI: 10.3389/fncel.2020.631802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 12/28/2020] [Indexed: 12/19/2022] Open
Abstract
Leukodystrophies are a class of rare inherited central nervous system (CNS) disorders that affect the white matter of the brain, typically leading to progressive neurodegeneration and early death. Hypomyelinating leukodystrophies are characterized by the abnormal formation of the myelin sheath during development. POLR3-related or 4H (hypomyelination, hypodontia, and hypogonadotropic hypogonadism) leukodystrophy is one of the most common types of hypomyelinating leukodystrophy for which no curative treatment or disease-modifying therapy is available. This review aims to describe potential therapies that could be further studied for effectiveness in pre-clinical studies, for an eventual translation to the clinic to treat the neurological manifestations associated with POLR3-related leukodystrophy. Here, we discuss the therapeutic approaches that have shown promise in other leukodystrophies, as well as other genetic diseases, and consider their use in treating POLR3-related leukodystrophy. More specifically, we explore the approaches of using stem cell transplantation, gene replacement therapy, and gene editing as potential treatment options, and discuss their possible benefits and limitations as future therapeutic directions.
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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
| | - Mackenzie A. Michell-Robinson
- 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
| | - 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
- Department of Pediatrics, McGill University, Montréal, QC, Canada
- Department of Human Genetics, McGill University, Montréal, QC, Canada
- Department of Specialized Medicine, Division of Medical Genetics, Montréal Children’s Hospital and McGill University Health Centre, Montréal, QC, Canada
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17
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Djordjevic D, Pinard M, Gauthier MS, Smith-Hicks C, Hoffman TL, Wolf NI, Oegema R, van Binsbergen E, Baskin B, Bernard G, Fribourg S, Coulombe B, Yoon G. De novo variants in POLR3B cause ataxia, spasticity, and demyelinating neuropathy. Am J Hum Genet 2021; 108:186-193. [PMID: 33417887 DOI: 10.1016/j.ajhg.2020.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 12/02/2020] [Indexed: 10/22/2022] Open
Abstract
POLR3B encodes the second-largest catalytic subunit of RNA polymerase III, an enzyme involved in transcription. Bi-allelic pathogenic variants in POLR3B are a well-established cause of hypomyelinating leukodystrophy. We describe six unrelated individuals with de novo missense variants in POLR3B and a clinical presentation substantially different from POLR3-related leukodystrophy. These individuals had afferent ataxia, spasticity, variable intellectual disability and epilepsy, and predominantly demyelinating sensory motor peripheral neuropathy. Protein modeling and proteomic analysis revealed a distinct mechanism of pathogenicity; the de novo POLR3B variants caused aberrant association of individual enzyme subunits rather than affecting overall enzyme assembly or stability. We expand the spectrum of disorders associated with pathogenic variants in POLR3B to include a de novo heterozygous POLR3B-related disorder.
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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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Moir RD, Lavados C, Lee J, Willis IM. Functional characterization of Polr3a hypomyelinating leukodystrophy mutations in the S. cerevisiae homolog, RPC160. Gene 2020; 768:145259. [PMID: 33148458 DOI: 10.1016/j.gene.2020.145259] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/23/2020] [Accepted: 10/20/2020] [Indexed: 12/12/2022]
Abstract
Mutations in RNA polymerase III (Pol III) cause hypomeylinating leukodystrophy (HLD) and neurodegeneration in humans. POLR3A and POLR3B, the two largest Pol III subunits, together form the catalytic center and carry the majority of disease alleles. Disease-causing mutations include invariant and highly conserved residues that are predicted to negatively affect Pol III activity and decrease transcriptional output. A subset of HLD missense mutations in POLR3A cluster in the pore region that provides nucleotide access to the Pol III active site. These mutations were engineered at the corresponding positions in the Saccharomyces cerevisiae homolog, Rpc160, to evaluate their functional deficits. None of the mutations caused a growth or transcription phenotype in yeast. Each mutation was combined with a frequently occurring pore mutation, POLR3A G672E, which was also wild-type for growth and transcription. The double mutants showed a spectrum of phenotypes from wild-type to lethal, with only the least fit combinations showing an effect on Pol III transcription. In one slow-growing temperature-sensitive mutant the steady-state level of tRNAs was unaffected, however global tRNA synthesis was compromised, as was the synthesis of RPR1 and SNR52 RNAs. Affinity-purified mutant Pol III was broadly defective in both factor-independent and factor-dependent transcription in vitro across genes that represent the yeast Pol III transcriptome. Thus, the robustness of yeast Rpc160 to single Pol III leukodystrophy mutations in the pore domain can be overcome by a second mutation in the domain.
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Affiliation(s)
- Robyn D Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Christian Lavados
- Graduate Program in Biomedical Science, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - JaeHoon Lee
- Department of Medicine (Cardiology), Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Ian M Willis
- Departments of Biochemistry and Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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20
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Xiong F, Xiong J, Wu YF, Cao L, Huang WS, Chang MX. Time-resolved RNA-seq provided a new understanding of intestinal immune response of European eel (Anguilla anguilla) following infection with Aeromonas hydrophila. Fish Shellfish Immunol 2020; 105:297-309. [PMID: 32707296 DOI: 10.1016/j.fsi.2020.06.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/26/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
No studies systematically examined the intestinal immune response for yellow stage of European eel (Anguilla anguilla) with Aeromonas hydrophila infection by time-resolved RNA-seq. Here, we examined transcriptional profiles of the intestines at three-time points following infection with A. hydrophila. Intraperitoneal injections caused mortalities within 48 h post-injection (hpi), with the survival rate 87.5% at 24 hpi and 83.9% at 48 hpi. The result from KEGG pathway enrichment analysis showed that the immune related "cytosolic DNA-sensing pathway" was significantly enriched at the first and second time points (6 hpi and 18 hpi), with the up-regulated expression of irf3, il1b, tnfaip3, cxcl8a, ap1-2, c-fos, polr3d, polr3g and polr3k both at 6 hpi and 18 hpi, but not at the third time point (36 hpi). According to the KEGG annotation, 326 immune and inflammation-related DEGs were found. The co-expression network of those 326 DEGs revealed the existence of three modules, and tlr1 was found to be in the center of the biggest module which contained massive DEGs from "signal transduction" and "transport and catabolism". The c3 isoforms showed different expression pattern among the three time points, indicating a unique activation of complement systems at 18 hpi. Furthermore, two cathelicidins (aaCATH_1 and aaCATH_2) were highly up-regulated at the first two time points, and the bacterial growth inhibition assay revealed their antibacterial properties against A. hydrophila. Our data indicated the important roles of cytosolic DNA-sensing pathway, as well as transcripts including tlr1, c3, polr and cathelicidins in the intestine of A. anguilla in response to A. hydrophila infection. The present study will provide leads for functional studies of host-pathogen interactions.
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Affiliation(s)
- Fan Xiong
- State Key Laboratory of Freshwater Ecology and Biotechnology, Key Laboratory of Aquaculture Disease Control, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, 430072, China
| | - Jing Xiong
- Engineering Research Center of the Modern Technology for Eel Industry, Ministry of Education PR China, Jimei University, Xiamen, 361021, China
| | - Ya Fang Wu
- Engineering Research Center of the Modern Technology for Eel Industry, Ministry of Education PR China, Jimei University, Xiamen, 361021, China
| | - Lu Cao
- State Key Laboratory of Freshwater Ecology and Biotechnology, Key Laboratory of Aquaculture Disease Control, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, 430072, China; University of Chinese Academy of Sciences, Beijing, China
| | - Wen Shu Huang
- Engineering Research Center of the Modern Technology for Eel Industry, Ministry of Education PR China, Jimei University, Xiamen, 361021, China.
| | - Ming Xian Chang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Key Laboratory of Aquaculture Disease Control, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, 430072, China; Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
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21
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Morales-Rosado JA, Macke EL, Cousin MA, Oliver GR, Dhamija R, Klee EW. Interpretation challenges of novel dual-class missense and splice-impacting variant in POLR3A-related late-onset hereditary spastic ataxia. Mol Genet Genomic Med 2020; 8:e1341. [PMID: 32597037 PMCID: PMC7507001 DOI: 10.1002/mgg3.1341] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 05/04/2020] [Accepted: 05/19/2020] [Indexed: 01/20/2023] Open
Abstract
Background RNA polymerase III (Pol III)‐related disorders are autosomal recessive neurodegenerative disorders caused by variants in POLR3A or POLR3B. Recently, a novel phenotype of adult‐onset spastic ataxia was identified in individuals with the c.1909+22G>A POLR3A variant in compound heterozygosity. Methods Whole‐exome sequencing was performed in the proband and parents. Variants were confirmed by Sanger sequencing. RNA sequencing was performed to evaluate splicing implications. Results A 42‐year‐old female was evaluated for unexplained neurological findings with a slow progressive decline in gait and walking speed since adolescence. WES revealed a novel missense variant (c.3593A>C, p.Lys1198Arg) in exon 27 of POLR3A in compound heterozygosity with the c.1909+22G>A variant. Summary of previously reported clinical features from individuals with pathogenic biallelic alterations in POLR3A and adult‐onset phenotype is consistent with our findings. RNA analysis revealed c.3593A>G drives the production of four RNA transcript products each with different functional impacts. Conclusion The novel dual‐class c.3593A>C variant in POLR3A causes an amino acid substitution and complex disruption of splicing. Our report supports the need to investigate variants near splice junctions for proper interpretation. Current interpretation guidelines need to address best practices for inclusion of predicted or measured transcriptional disruption pending functional activity or reliable transcript abundance estimates.
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Affiliation(s)
- Joel A Morales-Rosado
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Erica L Macke
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Margot A Cousin
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Gavin R Oliver
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Radhika Dhamija
- Department of Clinical Genomics, Mayo Clinic, Scottsdale, AZ, USA.,Department of Neurology, Mayo Clinic, Scottsdale, AZ, USA
| | - Eric W Klee
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.,Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
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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: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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