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Bhattacharyya N, Chai N, Hafford-Tear NJ, Sadan AN, Szabo A, Zarouchlioti C, Jedlickova J, Leung SK, Liao T, Dudakova L, Skalicka P, Parekh M, Moghul I, Jeffries AR, Cheetham ME, Muthusamy K, Hardcastle AJ, Pontikos N, Liskova P, Tuft SJ, Davidson AE. Deciphering novel TCF4-driven mechanisms underlying a common triplet repeat expansion-mediated disease. PLoS Genet 2024; 20:e1011230. [PMID: 38713708 PMCID: PMC11101122 DOI: 10.1371/journal.pgen.1011230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 05/17/2024] [Accepted: 03/19/2024] [Indexed: 05/09/2024] Open
Abstract
Fuchs endothelial corneal dystrophy (FECD) is an age-related cause of vision loss, and the most common repeat expansion-mediated disease in humans characterised to date. Up to 80% of European FECD cases have been attributed to expansion of a non-coding CTG repeat element (termed CTG18.1) located within the ubiquitously expressed transcription factor encoding gene, TCF4. The non-coding nature of the repeat and the transcriptomic complexity of TCF4 have made it extremely challenging to experimentally decipher the molecular mechanisms underlying this disease. Here we comprehensively describe CTG18.1 expansion-driven molecular components of disease within primary patient-derived corneal endothelial cells (CECs), generated from a large cohort of individuals with CTG18.1-expanded (Exp+) and CTG 18.1-independent (Exp-) FECD. We employ long-read, short-read, and spatial transcriptomic techniques to interrogate expansion-specific transcriptomic biomarkers. Interrogation of long-read sequencing and alternative splicing analysis of short-read transcriptomic data together reveals the global extent of altered splicing occurring within Exp+ FECD, and unique transcripts associated with CTG18.1-expansions. Similarly, differential gene expression analysis highlights the total transcriptomic consequences of Exp+ FECD within CECs. Furthermore, differential exon usage, pathway enrichment and spatial transcriptomics reveal TCF4 isoform ratio skewing solely in Exp+ FECD with potential downstream functional consequences. Lastly, exome data from 134 Exp- FECD cases identified rare (minor allele frequency <0.005) and potentially deleterious (CADD>15) TCF4 variants in 7/134 FECD Exp- cases, suggesting that TCF4 variants independent of CTG18.1 may increase FECD risk. In summary, our study supports the hypothesis that at least two distinct pathogenic mechanisms, RNA toxicity and TCF4 isoform-specific dysregulation, both underpin the pathophysiology of FECD. We anticipate these data will inform and guide the development of translational interventions for this common triplet-repeat mediated disease.
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Affiliation(s)
- Nihar Bhattacharyya
- University College London Institute of Ophthalmology, London, United Kingdom
| | - Niuzheng Chai
- University College London Institute of Ophthalmology, London, United Kingdom
| | | | - Amanda N. Sadan
- University College London Institute of Ophthalmology, London, United Kingdom
| | - Anita Szabo
- University College London Institute of Ophthalmology, London, United Kingdom
| | | | - Jana Jedlickova
- Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Szi Kay Leung
- Faculty of Health and Life Sciences, University of Exeter, Exeter, United Kingdom
| | - Tianyi Liao
- University College London Institute of Ophthalmology, London, United Kingdom
| | - Lubica Dudakova
- Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Pavlina Skalicka
- Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
- Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Mohit Parekh
- University College London Institute of Ophthalmology, London, United Kingdom
| | - Ismail Moghul
- University College London Institute of Ophthalmology, London, United Kingdom
- Moorfields Eye Hospital, London, United Kingdom
| | - Aaron R. Jeffries
- Faculty of Health and Life Sciences, University of Exeter, Exeter, United Kingdom
| | - Michael E. Cheetham
- University College London Institute of Ophthalmology, London, United Kingdom
| | | | - Alison J. Hardcastle
- University College London Institute of Ophthalmology, London, United Kingdom
- Moorfields Eye Hospital, London, United Kingdom
| | - Nikolas Pontikos
- University College London Institute of Ophthalmology, London, United Kingdom
- Moorfields Eye Hospital, London, United Kingdom
| | - Petra Liskova
- Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
- Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Stephen J. Tuft
- University College London Institute of Ophthalmology, London, United Kingdom
- Moorfields Eye Hospital, London, United Kingdom
| | - Alice E. Davidson
- University College London Institute of Ophthalmology, London, United Kingdom
- Moorfields Eye Hospital, London, United Kingdom
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McGoldrick P, Lau A, You Z, Durcan TM, Robertson J. Loss of C9orf72 perturbs the Ran-GTPase gradient and nucleocytoplasmic transport, generating compositionally diverse Importin β-1 granules. Cell Rep 2023; 42:112134. [PMID: 36821445 DOI: 10.1016/j.celrep.2023.112134] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/05/2022] [Accepted: 01/31/2023] [Indexed: 02/24/2023] Open
Abstract
A hexanucleotide (GGGGCC)n repeat expansion in C9orf72 causes amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), eliciting toxic effects through generation of RNA foci, dipeptide repeat proteins, and/or loss of C9orf72 protein. Defects in nucleocytoplasmic transport (NCT) have been implicated as a pathogenic mechanism underlying repeat expansion toxicity. Here, we show that loss of C9orf72 disrupts the Ran-GTPase gradient and NCT in vitro and in vivo. NCT disruption in vivo is enhanced by the presence of compositionally different types of cytoplasmic Importin β-1 granule that exhibit neuronal subtype-specific properties. We show that the abundance of Importin β-1 granules is increased in the context of C9orf72 deficiency, disrupting interactions with nuclear pore complex proteins. These granules appear to associate with the nuclear envelope and are co-immunoreactive for G3BP1 and K63-ubiquitin. These findings link loss of C9orf72 protein to gain-of-function mechanisms and defects in NCT.
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Affiliation(s)
- Philip McGoldrick
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Avenue, Toronto, ON M5T 2S8, Canada.
| | - Agnes Lau
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Avenue, Toronto, ON M5T 2S8, Canada
| | - Zhipeng You
- The Neuro's Early Drug Discovery Unit (EDDU), McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
| | - Thomas M Durcan
- The Neuro's Early Drug Discovery Unit (EDDU), McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
| | - Janice Robertson
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Avenue, Toronto, ON M5T 2S8, Canada; Department of Laboratory Medicine and Pathobiology, 27 King's College Circle, Toronto, ON M5S 1A1, Canada.
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3
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Smeyers J, Banchi EG, Latouche M. C9ORF72: What It Is, What It Does, and Why It Matters. Front Cell Neurosci 2021; 15:661447. [PMID: 34025358 PMCID: PMC8131521 DOI: 10.3389/fncel.2021.661447] [Citation(s) in RCA: 69] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 03/17/2021] [Indexed: 12/11/2022] Open
Abstract
When the non-coding repeat expansion in the C9ORF72 gene was discovered to be the most frequent cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) in 2011, this gene and its derived protein, C9ORF72, were completely unknown. The mutation appeared to produce both haploinsufficiency and gain-of-function effects in the form of aggregating expanded RNAs and dipeptide repeat proteins (DPRs). An unprecedented effort was then unleashed to decipher the pathogenic mechanisms and the functions of C9ORF72 in order to design therapies. A decade later, while the toxicity of accumulating gain-of-function products has been established and therapeutic strategies are being developed to target it, the contribution of the loss of function starts to appear more clearly. This article reviews the current knowledge about the C9ORF72 protein, how it is affected by the repeat expansion in models and patients, and what could be the contribution of its haploinsufficiency to the disease in light of the most recent findings. We suggest that these elements should be taken into consideration to refine future therapeutic strategies, compensating for the decrease of C9ORF72 or at least preventing a further reduction.
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Affiliation(s)
- Julie Smeyers
- Sorbonne Université, Institut du Cerveau - Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hôpital de la Pitié Salpêtrière, DMU Neuroscience 6, Paris, France
- PSL Research university, EPHE, Neurogenetics team, Paris, France
| | - Elena-Gaia Banchi
- Sorbonne Université, Institut du Cerveau - Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hôpital de la Pitié Salpêtrière, DMU Neuroscience 6, Paris, France
| | - Morwena Latouche
- Sorbonne Université, Institut du Cerveau - Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hôpital de la Pitié Salpêtrière, DMU Neuroscience 6, Paris, France
- PSL Research university, EPHE, Neurogenetics team, Paris, France
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4
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Jiang Y, Jiao B, Xiao X, Shen L. Genetics of frontotemporal dementia in China. Amyotroph Lateral Scler Frontotemporal Degener 2021; 22:321-335. [PMID: 33538206 DOI: 10.1080/21678421.2021.1880596] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Backgbround: Frontotemporal dementia (FTD) is the second most common presenile dementia, characterized by prominent behavioral, language, and cognitive impairment, which has a strong genetic component contributing to its pathogenesis. Due to geographical and ethnic variability, the prevalence of the causative genes of FTD may be different. Methods: To explore the genetics of FTD in the Chinese population, we reviewed 97 closely related studies that were searched in PubMed and Web of Science. In this review, we summarized the characteristics of each FTD gene. We also reassessed their pathogenicity and revised some mutations from pathogenic to uncertain significance according to the American College of Medical Genetics and Genomics (ACMG). Results: Thirty-two rare variants in genes of MAPT, GRN, C9orf72, CHCHD10, VCP, and TBK1 were identified in Chinese FTD populations, including 25 pathogenic mutations and seven variants of uncertain significance (VUS). Among them, the frequency of rare variants in the CHCHD10 gene was the highest. Surprisingly, twelve variants reported as pathogenic mutations were revised as VUS by ACMG. The correlations between genes and clinical manifestations were MAPT and frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), GRN and frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP), C9orf72/CHCHD10/TBK1 and amyotrophic lateral sclerosis (ALS)-FTD spectrum, and VCP corresponds inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD). Conclusions: It is necessary to strictly interpret the contributions of genes to diseases by ACMG. MAPT is the most common pathogenic gene for FTD in China.
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Affiliation(s)
- Yaling Jiang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Bin Jiao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China, and
| | - Xuewen Xiao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Lu Shen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China, and.,Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Changsha, China
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5
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Braems E, Swinnen B, Van Den Bosch L. C9orf72 loss-of-function: a trivial, stand-alone or additive mechanism in C9 ALS/FTD? Acta Neuropathol 2020; 140:625-643. [PMID: 32876811 PMCID: PMC7547039 DOI: 10.1007/s00401-020-02214-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/28/2020] [Accepted: 08/13/2020] [Indexed: 12/11/2022]
Abstract
A repeat expansion in C9orf72 is responsible for the characteristic neurodegeneration in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) in a still unresolved manner. Proposed mechanisms involve gain-of-functions, comprising RNA and protein toxicity, and loss-of-function of the C9orf72 gene. Their exact contribution is still inconclusive and reports regarding loss-of-function are rather inconsistent. Here, we review the function of the C9orf72 protein and its relevance in disease. We explore the potential link between reduced C9orf72 levels and disease phenotypes in postmortem, in vitro, and in vivo models. Moreover, the significance of loss-of-function in other non-coding repeat expansion diseases is used to clarify its contribution in C9orf72 ALS/FTD. In conclusion, with evidence pointing to a multiple-hit model, loss-of-function on itself seems to be insufficient to cause neurodegeneration in C9orf72 ALS/FTD.
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Affiliation(s)
- Elke Braems
- Department of Neurosciences, Experimental Neurology, and Leuven Brain Institute (LBI), KU Leuven-University of Leuven, 3000, Leuven, Belgium
- Laboratory of Neurobiology, Experimental Neurology, Center for Brain and Disease Research, VIB, Campus Gasthuisberg, O&N4, Herestraat 49, PB 602, 3000, Leuven, Belgium
| | - Bart Swinnen
- Department of Neurosciences, Experimental Neurology, and Leuven Brain Institute (LBI), KU Leuven-University of Leuven, 3000, Leuven, Belgium
- Laboratory of Neurobiology, Experimental Neurology, Center for Brain and Disease Research, VIB, Campus Gasthuisberg, O&N4, Herestraat 49, PB 602, 3000, Leuven, Belgium
- Department of Neurology, University Hospitals Leuven, 3000, Leuven, Belgium
| | - Ludo Van Den Bosch
- Department of Neurosciences, Experimental Neurology, and Leuven Brain Institute (LBI), KU Leuven-University of Leuven, 3000, Leuven, Belgium.
- Laboratory of Neurobiology, Experimental Neurology, Center for Brain and Disease Research, VIB, Campus Gasthuisberg, O&N4, Herestraat 49, PB 602, 3000, Leuven, Belgium.
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6
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Swinnen B, Robberecht W, Van Den Bosch L. RNA toxicity in non-coding repeat expansion disorders. EMBO J 2020; 39:e101112. [PMID: 31721251 PMCID: PMC6939197 DOI: 10.15252/embj.2018101112] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 09/30/2019] [Accepted: 10/09/2019] [Indexed: 12/11/2022] Open
Abstract
Several neurodegenerative disorders like amyotrophic lateral sclerosis (ALS) and spinocerebellar ataxia (SCA) are caused by non-coding nucleotide repeat expansions. Different pathogenic mechanisms may underlie these non-coding repeat expansion disorders. While gain-of-function mechanisms, such as toxicity associated with expression of repeat RNA or toxicity associated with repeat-associated non-ATG (RAN) products, are most frequently connected with these disorders, loss-of-function mechanisms have also been implicated. We review the different pathways that have been linked to non-coding repeat expansion disorders such as C9ORF72-linked ALS/frontotemporal dementia (FTD), myotonic dystrophy, fragile X tremor/ataxia syndrome (FXTAS), SCA, and Huntington's disease-like 2. We discuss modes of RNA toxicity focusing on the identity and the interacting partners of the toxic RNA species. Using the C9ORF72 ALS/FTD paradigm, we further explore the efforts and different methods used to disentangle RNA vs. RAN toxicity. Overall, we conclude that there is ample evidence for a role of RNA toxicity in non-coding repeat expansion diseases.
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Affiliation(s)
- Bart Swinnen
- Department of NeurosciencesExperimental NeurologyLeuven Brain Institute (LBI)KU Leuven – University of LeuvenLeuvenBelgium
- Laboratory of NeurobiologyVIB, Center for Brain & Disease ResearchLeuvenBelgium
- Department of NeurologyUniversity Hospitals LeuvenLeuvenBelgium
| | - Wim Robberecht
- Department of NeurosciencesExperimental NeurologyLeuven Brain Institute (LBI)KU Leuven – University of LeuvenLeuvenBelgium
- Laboratory of NeurobiologyVIB, Center for Brain & Disease ResearchLeuvenBelgium
- Department of NeurologyUniversity Hospitals LeuvenLeuvenBelgium
| | - Ludo Van Den Bosch
- Department of NeurosciencesExperimental NeurologyLeuven Brain Institute (LBI)KU Leuven – University of LeuvenLeuvenBelgium
- Laboratory of NeurobiologyVIB, Center for Brain & Disease ResearchLeuvenBelgium
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7
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Xiao S, McKeever PM, Lau A, Robertson J. Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels. Acta Neuropathol Commun 2019; 7:161. [PMID: 31651360 PMCID: PMC6813971 DOI: 10.1186/s40478-019-0812-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/17/2019] [Indexed: 12/11/2022] Open
Abstract
A hexanucleotide repeat expansion in a noncoding region of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Reduction of select or total C9orf72 transcript and protein levels is observed in postmortem C9-ALS/FTD tissue, and loss of C9orf72 orthologues in zebrafish and C. elegans results in motor deficits. However, how the reduction in C9orf72 in ALS and FTD might contribute to the disease process remains poorly understood. It has been shown that C9orf72 interacts and forms a complex with SMCR8 and WDR41, acting as a guanine exchange factor for Rab GTPases. Given the known synaptosomal compartmentalization of C9orf72-interacting Rab GTPases, we hypothesized that C9orf72 localization to synaptosomes would be required for the regulation of Rab GTPases and receptor trafficking. This study combined synaptosomal and post-synaptic density preparations together with a knockout-confirmed monoclonal antibody for C9orf72 to assess the localization and role of C9orf72 in the synaptosomes of mouse forebrains. Here, we found C9orf72 to be localized to both the pre- and post-synaptic compartment, as confirmed by both post-synaptic immunoprecipitation and immunofluorescence labelling. In C9orf72 knockout (C9-KO) mice, we demonstrated that pre-synaptic Rab3a, Rab5, and Rab11 protein levels remained stable compared with wild-type littermates (C9-WT). Strikingly, post-synaptic preparations from C9-KO mouse forebrains demonstrated a complete loss of Smcr8 protein levels, together with a significant downregulation of Rab39b and a concomitant upregulation of GluR1 compared with C9-WT mice. We confirmed the localization of Rab39b downregulation and GluR1 upregulation to the dorsal hippocampus of C9-KO mice by immunofluorescence. These results indicate that C9orf72 is essential for the regulation of post-synaptic receptor levels, and implicates loss of C9orf72 in contributing to synaptic dysfunction and related excitotoxicity in ALS and FTD.
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8
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Jiang J, Ravits J. Pathogenic Mechanisms and Therapy Development for C9orf72 Amyotrophic Lateral Sclerosis/Frontotemporal Dementia. Neurotherapeutics 2019; 16:1115-1132. [PMID: 31667754 PMCID: PMC6985338 DOI: 10.1007/s13311-019-00797-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In 2011, a hexanucleotide repeat expansion in the first intron of the C9orf72 gene was identified as the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The proposed disease mechanisms include loss of C9orf72 function and gain of toxicity from the bidirectionally transcribed repeat-containing RNAs. Over the last few years, substantial progress has been made to determine the contribution of loss and gain of function in disease pathogenesis. The extensive body of molecular, cellular, animal, and human neuropathological studies is conflicted, but the predominance of evidence favors gain of toxicity as the main pathogenic mechanism for C9orf72 repeat expansions. Alterations in several downstream cellular functions, such as nucleocytoplasmic transport and autophagy, are implicated. Exciting progress has also been made in therapy development targeting this mutation, such as by antisense oligonucleotide therapies targeting sense transcripts and small molecules targeting nucleocytoplasmic transport, and these are now in phase 1 clinical trials.
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Affiliation(s)
- Jie Jiang
- Department of Cell Biology, Emory University, Atlanta, GA, 30322, USA.
| | - John Ravits
- Department of Neurosciences, University of California at San Diego, La Jolla, CA, 92093, USA.
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Abstract
Purpose of review In this review we highlight recent advances in the human genetics of frontotemporal dementia (FTD). In addition to providing a broad survey of genes implicated in FTD in the last several years, we also discuss variation in genes implicated in both hereditary leukodystrophies and risk for FTD (e.g., TREM2, TMEM106B, CSF1R, AARS2, NOTCH3). Recent findings Over the past five years, genetic variation in approximately 50 genes has been confirmed or suggested to cause or influence risk for FTD and FTD-spectrum disorders. We first give background and discuss recent findings related to C9ORF72, GRN and MAPT, the genes most commonly implicated in FTD. We then provide a broad overview of other FTD-associated genes and go on to discuss new findings in FTD genetics in East Asian populations, including pathogenic variation in CHCHD10, which may represent a frequent cause of disease in Chinese populations. Finally, we consider recent insights gleaned from genome-wide association and genetic pleiotropy studies. Summary Recent genetic discoveries highlight cellular pathways involving autophagy, the endolysosomal system and neuroinflammation, and reveal an intriguing overlap between genes that confer risk for leukodystrophy and FTD.
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Molecular Mechanisms of Neurodegeneration Related to C9orf72 Hexanucleotide Repeat Expansion. Behav Neurol 2019; 2019:2909168. [PMID: 30774737 PMCID: PMC6350563 DOI: 10.1155/2019/2909168] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 08/28/2018] [Accepted: 09/18/2018] [Indexed: 12/11/2022] Open
Abstract
Two clinically distinct diseases, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), have recently been classified as two extremes of the FTD/ALS spectrum. The neuropathological correlate of FTD is frontotemporal lobar degeneration (FTLD), characterized by tau-, TDP-43-, and FUS-immunoreactive neuronal inclusions. An earlier discovery that a hexanucleotide repeat expansion mutation in chromosome 9 open reading frame 72 (C9orf72) gene causes ALS and FTD established a special subtype of ALS and FTLD with TDP-43 pathology (C9FTD/ALS). Normal individuals carry 2–10 hexanucleotide GGGGCC repeats in the C9orf72 gene, while more than a few hundred repeats represent a risk for ALS and FTD. The proposed molecular mechanisms by which C9orf72 repeat expansions induce neurodegenerative changes are C9orf72 loss-of-function through haploinsufficiency, RNA toxic gain-of-function, and gain-of-function through the accumulation of toxic dipeptide repeat proteins. However, many more cellular processes are affected by pathological processes in C9FTD/ALS, including nucleocytoplasmic transport, RNA processing, normal function of nucleolus, formation of membraneless organelles, translation, ubiquitin proteasome system, Notch signalling pathway, granule transport, and normal function of TAR DNA-binding protein 43 (TDP-43). Although the exact molecular mechanisms through which C9orf72 repeat expansions account for neurodegeneration have not been elucidated, some potential therapeutics, such as antisense oligonucleotides targeting hexanucleotide GGGGCC repeats in mRNA, were successful in preclinical trials and are awaiting phase 1 clinical trials. In this review, we critically discuss each proposed mechanism and provide insight into the most recent studies aiming to elucidate the molecular underpinnings of C9FTD/ALS.
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11
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Vatsavayai SC, Nana AL, Yokoyama JS, Seeley WW. C9orf72-FTD/ALS pathogenesis: evidence from human neuropathological studies. Acta Neuropathol 2019; 137:1-26. [PMID: 30368547 DOI: 10.1007/s00401-018-1921-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 10/16/2018] [Accepted: 10/16/2018] [Indexed: 12/11/2022]
Abstract
What are the most important and treatable pathogenic mechanisms in C9orf72-FTD/ALS? Model-based efforts to address this question are forging ahead at a blistering pace, often with conflicting results. But what does the human neuropathological literature reveal? Here, we provide a critical review of the human studies to date, seeking to highlight key gaps or uncertainties in our knowledge. First, we engage the C9orf72-specific mechanisms, including C9orf72 haploinsufficiency, repeat RNA foci, and dipeptide repeat protein inclusions. We then turn to some of the most prominent C9orf72-associated features, such as TDP-43 loss-of-function, TDP-43 aggregation, and nuclear transport defects. Finally, we review potential disease-modifying epigenetic and genetic factors and the natural history of the disease across the lifespan. Throughout, we emphasize the importance of anatomical precision when studying how candidate mechanisms relate to neuronal, regional, and behavioral findings. We further highlight methodological approaches that may help address lingering knowledge gaps and uncertainties, as well as other logical next steps for the field. We conclude that anatomically oriented human neuropathological studies have a critical role to play in guiding this fast-moving field toward effective new therapies.
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Affiliation(s)
- Sarat C Vatsavayai
- Memory and Aging Center, Department of Neurology, University of California, San Francisco, USA
| | - Alissa L Nana
- Memory and Aging Center, Department of Neurology, University of California, San Francisco, USA
| | - Jennifer S Yokoyama
- Memory and Aging Center, Department of Neurology, University of California, San Francisco, USA
| | - William W Seeley
- Memory and Aging Center, Department of Neurology, University of California, San Francisco, USA.
- Department of Pathology, University of California, San Francisco, Box 1207, San Francisco, CA, 94143-1207, USA.
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12
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Liu Y, Wang T, Ji YJ, Johnson K, Liu H, Johnson K, Bailey S, Suk Y, Lu YN, Liu M, Wang J. A C9orf72-CARM1 axis regulates lipid metabolism under glucose starvation-induced nutrient stress. Genes Dev 2018; 32:1380-1397. [PMID: 30366907 PMCID: PMC6217731 DOI: 10.1101/gad.315564.118] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 08/27/2018] [Indexed: 12/11/2022]
Abstract
Liu et al. report here that C9orf72, which is linked to the most common forms of the neurodegenerative diseases amyotrophic lateral sclerosis and frontotemporal dementia, is a key regulator of lipid metabolism under stress. Cells undergo metabolic adaptation during environmental changes by using evolutionarily conserved stress response programs. This metabolic homeostasis is exquisitely regulated, and its imbalance could underlie human pathological conditions. We report here that C9orf72, which is linked to the most common forms of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), is a key regulator of lipid metabolism under stress. Loss of C9orf72 leads to an overactivation of starvation-induced lipid metabolism that is mediated by dysregulated autophagic digestion of lipids and increased de novo fatty acid synthesis. C9orf72 acts by promoting the lysosomal degradation of coactivator-associated arginine methyltransferase 1 (CARM1), which in turn regulates autophagy–lysosomal functions and lipid metabolism. In ALS/FTD patient-derived neurons or tissues, a reduction in C9orf72 function is associated with dysregulation in the levels of CARM1, fatty acids, and NADPH oxidase NOX2. These results reveal a C9orf72–CARM1 axis in the control of stress-induced lipid metabolism and implicates epigenetic dysregulation in relevant human diseases.
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Affiliation(s)
- Yang Liu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Tao Wang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Yon Ju Ji
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Kenji Johnson
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Honghe Liu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Kaitlin Johnson
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Scott Bailey
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Yongwon Suk
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Yu-Ning Lu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Mingming Liu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | - Jiou Wang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
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13
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Liu X, He J, Gao FB, Gitler AD, Fan D. The epidemiology and genetics of Amyotrophic lateral sclerosis in China. Brain Res 2018; 1693:121-126. [PMID: 29501653 PMCID: PMC6486791 DOI: 10.1016/j.brainres.2018.02.035] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 02/20/2018] [Accepted: 02/22/2018] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder associated with loss of motor neurons. Previous knowledge of the disease has been mainly based on studies from Caucasian ALS patients of European descent. Here we review the epidemiological characteristics of ALS among the Chinese population in order to compare the similarities and differences between Chinese ALS cases and those from other countries. We describe a potential lower incidence and prevalence of ALS, a younger age of onset and a lower proportion of familial ALS cases in the Chinese population. Additionally, we highlight potential genetic differences between Chinese and Caucasian ALS patients. Most notably, the frequency of GGGGCC repeat expansions in C9ORF72 in Chinese ALS is significantly lower than in Caucasians. Since some conclusions might not be consistent across all of the studies around China to date, we suggest that it is necessary to carry out a prospective population-based study and large-scale gene sequencing around to better define epidemiological and genetic features of Chinese ALS patients.
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Affiliation(s)
- Xiaolu Liu
- Department of Neurology, Peking University Third Hospital, Beijing 100191, PR China
| | - Ji He
- Department of Neurology, Peking University Third Hospital, Beijing 100191, PR China
| | - Fen-Biao Gao
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Dongsheng Fan
- Department of Neurology, Peking University Third Hospital, Beijing 100191, PR China.
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14
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Mutation screening of NEK1 in Chinese ALS patients. Neurobiol Aging 2018; 71:267.e1-267.e4. [PMID: 30093141 DOI: 10.1016/j.neurobiolaging.2018.06.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 06/12/2018] [Accepted: 06/18/2018] [Indexed: 01/07/2023]
Abstract
NEK1 was recently identified as an amyotrophic lateral sclerosis (ALS) gene through rare variant burden analysis, and its role in ALS in various populations is still unclear. The aim of this study was to determine the frequency and spectrum of NEK1 mutations in an ALS cohort from mainland China. All exons and their flanking intron regions of NEK1 were screened by direct nucleotide sequencing in 377 unrelated ALS patients. These patients were also screened with a massive parallel sequencing gene panel for 24 known ALS genes and C9orf72 hexanucleotide repeat expansion. In totality, we detected 9 variants, comprising 3 novel heterozygous loss-of-function mutations and 6 rare missense variants (MAF < 0.1%) in NEK1. The patient with splice site mutation also carried another probably damaging variant in SOD1. Our study established a NEK1 mutant frequency of 0.8% in Chinese ALS patients, further expanded its spectrum of variants, and highlighted the possibility of coexistence with variants in additional ALS genes in NEK1 loss-of-function carriers.
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15
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McGoldrick P, Zhang M, van Blitterswijk M, Sato C, Moreno D, Xiao S, Zhang AB, McKeever PM, Weichert A, Schneider R, Keith J, Petrucelli L, Rademakers R, Zinman L, Robertson J, Rogaeva E. Unaffected mosaic C9orf72 case: RNA foci, dipeptide proteins, but upregulated C9orf72 expression. Neurology 2017; 90:e323-e331. [PMID: 29282338 PMCID: PMC5798652 DOI: 10.1212/wnl.0000000000004865] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 10/16/2017] [Indexed: 12/11/2022] Open
Abstract
Objective Suggested C9orf72 disease mechanisms for amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration include C9orf72 haploinsufficiency, G4C2/C4G2 RNA foci, and dipeptide repeat (DPR) proteins translated from the G4C2 expansion; however, the role of small expansions (e.g., 30–90 repeats) is unknown and was investigated here. Methods We conducted a molecular and pathology study of a family in which the father (unaffected at age 90) carried a 70-repeat allele in blood DNA that expanded to ≈1,750 repeats in his children, causing ALS. Results Southern blotting revealed different degrees of mosaicism of small and large expansions in the father's tissues from the CNS. Surprisingly, in each mosaic tissue, C9orf72 mRNA levels were significantly increased compared to an ALS-affected daughter with a large expansion. Increased expression correlated with higher levels of the 70-repeat allele (the upregulation was also evident at the protein level). Remarkably, RNA foci and DPR burdens were similar or even significantly increased (in cerebellum) in the unaffected father compared to the daughter with ALS. However, the father did not display TDP-43 pathology and signs of neurodegeneration. Conclusion The presence of RNA foci and DPR pathology was insufficient for disease manifestation and TDP-43 pathology in the mosaic C9orf72 carrier with upregulated C9orf72 expression. It is important to conduct an investigation of similar cases, which could be found among unaffected parents of sporadic C9orf72 patients (e.g., 21% among Finnish patients with ALS). Caution should be taken when consulting carriers of small expansions because disease manifestation could be dependent on the extent of the somatic instability in disease-relevant tissues.
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Affiliation(s)
- Philip McGoldrick
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Ming Zhang
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Marka van Blitterswijk
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Christine Sato
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Danielle Moreno
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Shangxi Xiao
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Ashley B Zhang
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Paul M McKeever
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Anna Weichert
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Raphael Schneider
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Julia Keith
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Leonard Petrucelli
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Rosa Rademakers
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Lorne Zinman
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada
| | - Janice Robertson
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada.
| | - Ekaterina Rogaeva
- From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada.
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16
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Moens TG, Partridge L, Isaacs AM. Genetic models of C9orf72: what is toxic? Curr Opin Genet Dev 2017; 44:92-101. [PMID: 28364657 DOI: 10.1016/j.gde.2017.01.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 01/13/2017] [Accepted: 01/18/2017] [Indexed: 12/11/2022]
Abstract
A hexanucleotide repeat expansion in the gene C9orf72 is the most common genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia. Pathogenesis may occur either due to loss of function of the C9orf72 gene, or a toxic gain of function, via the production of repetitive sense and antisense RNA and/or repetitive dipeptide repeat proteins. Recently, mouse knockouts have suggested that a loss of function of C9orf72 alone is insufficient to lead to neurodegeneration, whilst overexpression of hexanucleotide DNA is sufficient in a wide range of model systems. Additionally, models have now been created to attempt to study the effects of repetitive RNA and dipeptide proteins in isolation and thus determine their relevance to disease.
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Affiliation(s)
- Thomas G Moens
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London WC1N 3BG, UK; Department of Genetics, Evolution and Environment, Institute of Healthy Ageing, University College London, London WC1E 6BT, UK
| | - Linda Partridge
- Department of Genetics, Evolution and Environment, Institute of Healthy Ageing, University College London, London WC1E 6BT, UK; Max Planck Institute for Biology of Ageing, Robert-Koch-Str. 21, 50931 Cologne, Germany
| | - Adrian M Isaacs
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London WC1N 3BG, UK.
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