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Spencer PS. Parkinsonism and motor neuron disorders: Lessons from Western Pacific ALS/PDC. J Neurol Sci 2021; 433:120021. [PMID: 34635325 DOI: 10.1016/j.jns.2021.120021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 08/06/2021] [Accepted: 09/01/2021] [Indexed: 01/16/2023]
Abstract
Recognized worldwide as an unusual "overlap" syndrome, Parkinsonism and motor neuron disease, with or without dementia, is best exemplified by the former high-incidence clusters of Amyotrophic Lateral Sclerosis and Parkinsonism-Dementia Complex (ALS/PDC) in Guam, USA, in the Kii Peninsula of Honshu Island, Japan, and in Papua, Indonesia, on the western side of New Guinea. Western Pacific ALS/PDC is a disappearing neurodegenerative disorder with multiple and sometime overlapping phenotypes (ALS, atypical parkinsonism, dementia) that appear to constitute a single disease of environmental origin, in particular from exposure to genotoxins/neurotoxins in seed of cycad plants (Cycas spp.) formerly used as a traditional source of food (Guam) and/or medicine (Guam, Kii-Japan, Papua-Indonesia). Seed compounds include the principal cycad toxin cycasin, its active metabolite methylazoxymethanol (MAM) and a non-protein amino acid β-N-methylamino-L-alanine (L-BMAA); each reproduces components of ALS/PDC neuropathology when individually administered to laboratory species in single doses perinatally (MAM, L-BMAA) or repeatedly for prolonged periods to young adult animals (L-BMAA). Human exposure to MAM, a potent DNA-alkylating mutagen, also has potential relevance to the high incidence of diverse mutations found among Guamanians with/without ALS/PDC. In sum, seven decades of intensive study of ALS/PDC has revealed field and laboratory approaches leading to discovery of disease etiology that are now being applied to sporadic neurodegenerative disorders such as ALS beyond the Western Pacific region. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.
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Affiliation(s)
- Peter S Spencer
- Department of Neurology, School of Medicine, Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon, USA.
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2
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Marsili L, Mata IF, Kauffman MA. Editorial: Genotype-Phenotype Correlation in Parkinsonian Conditions. Front Neurol 2021; 12:743953. [PMID: 34497580 PMCID: PMC8420997 DOI: 10.3389/fneur.2021.743953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 07/30/2021] [Indexed: 11/15/2022] Open
Affiliation(s)
- Luca Marsili
- Department of Neurology, James J. and Joan A. Gardner Center for Parkinson's Disease and Movement Disorders, University of Cincinnati, Cincinnati, OH, United States
| | - Ignacio F. Mata
- Genomic Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, United States
| | - Marcelo A. Kauffman
- Consultorio y Laboratorio de Neurogenética, Centro Universitario de Neurología José María Ramos Mejía, Buenos Aires, Argentina
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3
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van Rooij J, Mol MO, Melhem S, van der Wal P, Arp P, Paron F, Donker Kaat L, Seelaar H, Miedema SSM, Oshima T, Eggen BJL, Uitterlinden A, van Meurs J, van Kesteren RE, Smit AB, Buratti E, van Swieten JC. Somatic TARDBP variants as a cause of semantic dementia. Brain 2020; 143:3827-3841. [PMID: 33155043 PMCID: PMC7805802 DOI: 10.1093/brain/awaa317] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 07/13/2020] [Accepted: 08/06/2020] [Indexed: 12/12/2022] Open
Abstract
The aetiology of late-onset neurodegenerative diseases is largely unknown. Here we investigated whether de novo somatic variants for semantic dementia can be detected, thereby arguing for a more general role of somatic variants in neurodegenerative disease. Semantic dementia is characterized by a non-familial occurrence, early onset (<65 years), focal temporal atrophy and TDP-43 pathology. To test whether somatic variants in neural progenitor cells during brain development might lead to semantic dementia, we compared deep exome sequencing data of DNA derived from brain and blood of 16 semantic dementia cases. Somatic variants observed in brain tissue and absent in blood were validated using amplicon sequencing and digital PCR. We identified two variants in exon one of the TARDBP gene (L41F and R42H) at low level (1-3%) in cortical regions and in dentate gyrus in two semantic dementia brains, respectively. The pathogenicity of both variants is supported by demonstrating impaired splicing regulation of TDP-43 and by altered subcellular localization of the mutant TDP-43 protein. These findings indicate that somatic variants may cause semantic dementia as a non-hereditary neurodegenerative disease, which might be exemplary for other late-onset neurodegenerative disorders.
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Affiliation(s)
- Jeroen van Rooij
- Department of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Merel O Mol
- Department of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Shamiram Melhem
- Department of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Pelle van der Wal
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Pascal Arp
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Francesca Paron
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
| | - Laura Donker Kaat
- Department of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Harro Seelaar
- Department of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Suzanne S M Miedema
- Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Takuya Oshima
- Department of Biomedical Sciences of Cells and Systems, section Molecular Neurobiology, University of Groningen, University Medical Center Groningen (UMCG), Groningen, The Netherlands
| | - Bart J L Eggen
- Department of Biomedical Sciences of Cells and Systems, section Molecular Neurobiology, University of Groningen, University Medical Center Groningen (UMCG), Groningen, The Netherlands
| | - André Uitterlinden
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Joyce van Meurs
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Ronald E van Kesteren
- Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - August B Smit
- Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Emanuele Buratti
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
| | - John C van Swieten
- Department of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands
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Singh SM, Castellani CA, Hill KA. Postzygotic Somatic Mutations in the Human Brain Expand the Threshold-Liability Model of Schizophrenia. Front Psychiatry 2020; 11:587162. [PMID: 33192734 PMCID: PMC7642466 DOI: 10.3389/fpsyt.2020.587162] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 09/22/2020] [Indexed: 12/11/2022] Open
Abstract
The search for what causes schizophrenia has been onerous. This research has included extensive assessment of a variety of genetic and environmental factors using ever emerging high-resolution technologies and traditional understanding of the biology of the brain. These efforts have identified a large number of schizophrenia-associated genes, some of which are altered by mutational and epi-mutational mechanisms in a threshold liability model of schizophrenia development. The results, however, have limited predictability and the actual cause of the disease remains unknown. This current state asks for conceptualizing the problem differently in light of novel insights into the nature of mutations, the biology of the brain and the fine precision and resolution of emerging technologies. There is mounting evidence that mutations acquired during postzygotic development are more common than germline mutations. Also, the postzygotic somatic mutations including epimutations (PZMs), which often lead to somatic mosaicism, are relatively common in the mammalian brain in comparison to most other tissues and PZMs are more common in patients with neurodevelopmental mental disorders, including schizophrenia. Further, previously inaccessible, detection of PZMs is becoming feasible with the advent of novel technologies that include single-cell genomics and epigenomics and the use of exquisite experimental designs including use of monozygotic twins discordant for the disease. These developments allow us to propose a working hypothesis and expand the threshold liability model of schizophrenia that already encompasses familial genetic, epigenetic and environmental factors to include somatic de novo PZMs. Further, we offer a test for this expanded model using currently available genome sequences and methylome data on monozygotic twins discordant for schizophrenia (MZD) and their parents. The results of this analysis argue that PZMs play a significant role in the development of schizophrenia and explain extensive heterogeneity seen across patients. It also offers the potential to convincingly link PZMs to both nervous system health and disease, an area that has remained challenging to study and relatively under explored.
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Affiliation(s)
- Shiva M. Singh
- Molecular Genetics Unit, Department of Biology, The University of Western Ontario, London, ON, Canada
| | | | - Kathleen A. Hill
- Molecular Genetics Unit, Department of Biology, The University of Western Ontario, London, ON, Canada
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Leija-Salazar M, Pittman A, Mokretar K, Morris H, Schapira AH, Proukakis C. Investigation of Somatic Mutations in Human Brains Targeting Genes Associated With Parkinson's Disease. Front Neurol 2020; 11:570424. [PMID: 33193015 PMCID: PMC7642339 DOI: 10.3389/fneur.2020.570424] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 09/22/2020] [Indexed: 12/25/2022] Open
Abstract
Background: Somatic single nucleotide variant (SNV) mutations occur in neurons but their role in synucleinopathies is unknown. Aim: We aimed to identify disease-relevant low-level somatic SNVs in brains from sporadic patients with synucleinopathies and a monozygotic twin carrying LRRK2 G2019S, whose penetrance could be explained by somatic variation. Methods and Results: We included different brain regions from 26 Parkinson's disease (PD), one Incidental Lewy body, three multiple system atrophy cases, and 12 controls. The whole SNCA locus and exons of other genes associated with PD and neurodegeneration were deeply sequenced using molecular barcodes to improve accuracy. We selected 21 variants at 0.33-5% allele frequencies for validation using accurate methods for somatic variant detection. Conclusions: We could not detect disease-relevant somatic SNVs, however we cannot exclude their presence at earlier stages of degeneration. Our results support that coding somatic SNVs in neurodegeneration are rare, but other types of somatic variants may hold pathological consequences in synucleinopathies.
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Affiliation(s)
- Melissa Leija-Salazar
- Department of Clinical and Movement Neurosciences, University College London Queen Square Institute of Neurology, London, United Kingdom
| | - Alan Pittman
- Genetics Research Centre, Molecular and Clinical Sciences, St George's University of London, London, United Kingdom
| | - Katya Mokretar
- Department of Clinical and Movement Neurosciences, University College London Queen Square Institute of Neurology, London, United Kingdom
| | - Huw Morris
- Department of Clinical and Movement Neurosciences, University College London Queen Square Institute of Neurology, London, United Kingdom
| | - Anthony H. Schapira
- Department of Clinical and Movement Neurosciences, University College London Queen Square Institute of Neurology, London, United Kingdom
| | - Christos Proukakis
- Department of Clinical and Movement Neurosciences, University College London Queen Square Institute of Neurology, London, United Kingdom
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Galet B, Cheval H, Ravassard P. Patient-Derived Midbrain Organoids to Explore the Molecular Basis of Parkinson's Disease. Front Neurol 2020; 11:1005. [PMID: 33013664 PMCID: PMC7500100 DOI: 10.3389/fneur.2020.01005] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/30/2020] [Indexed: 12/20/2022] Open
Abstract
Induced pluripotent stem cell-derived organoids offer an unprecedented access to complex human tissues that recapitulate features of architecture, composition and function of in vivo organs. In the context of Parkinson's Disease (PD), human midbrain organoids (hMO) are of significant interest, as they generate dopaminergic neurons expressing markers of Substantia Nigra identity, which are the most vulnerable to degeneration. Combined with genome editing approaches, hMO may thus constitute a valuable tool to dissect the genetic makeup of PD by revealing the effects of risk variants on pathological mechanisms in a representative cellular environment. Furthermore, the flexibility of organoid co-culture approaches may also enable the study of neuroinflammatory and neurovascular processes, as well as interactions with other brain regions that are also affected over the course of the disease. We here review existing protocols to generate hMO, how they have been used so far to model PD, address challenges inherent to organoid cultures, and discuss applicable strategies to dissect the molecular pathophysiology of the disease. Taken together, the research suggests that this technology represents a promising alternative to 2D in vitro models, which could significantly improve our understanding of PD and help accelerate therapeutic developments.
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Affiliation(s)
- Benjamin Galet
- Molecular Pathophysiology of Parkinson's Disease Group, Paris Brain Institute (ICM), INSERM U, CNRS UMR 7225, Sorbonne University, Paris, France
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Ross JP, Dion PA, Rouleau GA. Exome sequencing in genetic disease: recent advances and considerations. F1000Res 2020; 9:F1000 Faculty Rev-336. [PMID: 32431803 PMCID: PMC7205110 DOI: 10.12688/f1000research.19444.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/30/2020] [Indexed: 12/14/2022] Open
Abstract
Over the past decade, exome sequencing (ES) has allowed significant advancements to the field of disease research. By targeting the protein-coding regions of the genome, ES combines the depth of knowledge on protein-altering variants with high-throughput data generation and ease of analysis. New discoveries continue to be made using ES, and medical science has benefitted both theoretically and clinically from its continued use. In this review, we describe recent advances and successes of ES in disease research. Through selected examples of recent publications, we explore how ES continues to be a valuable tool to find variants that might explain disease etiology or provide insight into the biology underlying the disease. We then discuss shortcomings of ES in terms of variant discoveries made by other sequencing technologies that would be missed because of the scope and techniques of ES. We conclude with a brief outlook on the future of ES, suggesting that although newer and more thorough sequencing methods will soon supplant ES, its results will continue to be useful for disease research.
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Affiliation(s)
- Jay P. Ross
- Department of Human Genetics, McGill University, 3640 University, Montréal, QC, H3A 0C7, Canada
- Montreal Neurological Institute and Hospital, McGill University, 3801 University, Montréal, QC, H3A 2B4, Canada
| | - Patrick A. Dion
- Montreal Neurological Institute and Hospital, McGill University, 3801 University, Montréal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, McGill University, 3801 University, Montréal, QC, H3A 2B4, Canada
| | - Guy A. Rouleau
- Department of Human Genetics, McGill University, 3640 University, Montréal, QC, H3A 0C7, Canada
- Montreal Neurological Institute and Hospital, McGill University, 3801 University, Montréal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, McGill University, 3801 University, Montréal, QC, H3A 2B4, Canada
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Dickerson AS, Hansen J, Thompson S, Gredal O, Weisskopf MG. A mixtures approach to solvent exposures and amyotrophic lateral sclerosis: a population-based study in Denmark. Eur J Epidemiol 2020; 35:241-249. [PMID: 32193761 PMCID: PMC7176306 DOI: 10.1007/s10654-020-00624-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 03/13/2020] [Indexed: 12/14/2022]
Abstract
Studies of occupational solvent exposures and amyotrophic lateral sclerosis (ALS) have been conflicting. We conducted a population-based case-control study of mixed occupational solvent exposures and ALS. Using the Danish National Patient Registry, we identified ALS cases in Denmark from 1982 to 2013, and matched them to 100 controls based on sex and birth year. We estimated cumulative exposures to solvents (benzene, methylene chloride, toluene, trichloroethylene, perchloroethylene, and 1,1,1-trichloroethane) via job exposure matrices and applied them to occupational history from the Danish Pension Fund. Sex-stratified conditional logistic regression analyses revealed higher adjusted odds of ALS for men with exposure to benzene (aOR = 1.20; 95% CI 1.02, 1.41) and methylene chloride (aOR = 1.23; 95% CI 1.07, 1.42). We used weighted quantile sum regression to explore combined solvent exposures and risk of ALS in exposed subjects and found increased odds of 26 to 28% in all exposure lag periods for every one-unit increase in the mixture index in men. Weights of methylene chloride predominated the mixture index in all lag periods. Our study suggests an increased risk of ALS in men exposed to multiple solvents, with the greatest influence being from methylene chloride. These findings highlight the need to utilize mixtures analysis when considering co-occurring exposures.
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Affiliation(s)
- Aisha S Dickerson
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA.
- Environmental and Occupation Medicine and Epidemiology Division of the Department of Environmental Health, Harvard T.H. Chan School of Public Health, 667 Huntington Ave, Boston, MA, 1402-176, USA.
| | - Johnni Hansen
- Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Shiraya Thompson
- Department of Comparative Human Development, University of Chicago, Chicago, IL, USA
| | - Ole Gredal
- National Rehabilitation Center for Neuromuscular Disorders, Copenhagen, Denmark
| | - Marc G Weisskopf
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Environmental and Occupation Medicine and Epidemiology Division of the Department of Environmental Health, Harvard T.H. Chan School of Public Health, 667 Huntington Ave, Boston, MA, 1402-176, USA
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Abstract
Virtually all adults with Down syndrome (DS) show the neuropathological changes of Alzheimer disease (AD) by the age of 40 years. This association is partially due to overexpression of amyloid precursor protein, encoded by APP, as a result of the location of this gene on chromosome 21. Amyloid-β accumulates in the brain across the lifespan of people with DS, which provides a unique opportunity to understand the temporal progression of AD and the epigenetic factors that contribute to the age of dementia onset. This age dependency in the development of AD in DS can inform research into the presentation of AD in the general population, in whom a longitudinal perspective of the disease is not often available. Comparison of the risk profiles, biomarker profiles and genetic profiles of adults with DS with those of individuals with AD in the general population can help to determine common and distinct pathways as well as mechanisms underlying increased risk of dementia. This Review evaluates the similarities and differences between the pathological cascades and genetics underpinning DS and AD with the aim of providing a platform for common exploration of these disorders.
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Affiliation(s)
- Ira T Lott
- Department of Pediatrics and Neurology, School of Medicine, University of California, Irvine, CA, USA.
| | - Elizabeth Head
- Sanders Brown Center on Aging, University of Kentucky, Lexington, KY, USA
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Verheijen BM, Vermulst M, van Leeuwen FW. Somatic mutations in neurons during aging and neurodegeneration. Acta Neuropathol 2018; 135:811-826. [PMID: 29705908 PMCID: PMC5954077 DOI: 10.1007/s00401-018-1850-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Revised: 04/20/2018] [Accepted: 04/21/2018] [Indexed: 12/22/2022]
Abstract
The nervous system is composed of a large variety of neurons with a diverse array of morphological and functional properties. This heterogeneity is essential for the construction and maintenance of a distinct set of neural networks with unique characteristics. Accumulating evidence now indicates that neurons do not only differ at a functional level, but also at the genomic level. These genomic discrepancies seem to be the result of somatic mutations that emerge in nervous tissue during development and aging. Ultimately, these mutations bring about a genetically heterogeneous population of neurons, a phenomenon that is commonly referred to as "somatic brain mosaicism". Improved understanding of the development and consequences of somatic brain mosaicism is crucial to understand the impact of somatic mutations on neuronal function in human aging and disease. Here, we highlight a number of topics related to somatic brain mosaicism, including some early experimental evidence for somatic mutations in post-mitotic neurons of the hypothalamo-neurohypophyseal system. We propose that age-related somatic mutations are particularly interesting, because aging is a major risk factor for a variety of neuronal diseases, including Alzheimer's disease. We highlight potential links between somatic mutations and the development of these diseases and argue that recent advances in single-cell genomics and in vivo physiology have now finally made it possible to dissect the origins and consequences of neuronal mutations in unprecedented detail.
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Affiliation(s)
- Bert M Verheijen
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG, Utrecht, The Netherlands.
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3508 GA, Utrecht, The Netherlands.
| | - Marc Vermulst
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Fred W van Leeuwen
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, 6229 ER, Maastricht, The Netherlands
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