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Curiel J, Rodríguez Bey G, Takanohashi A, Bugiani M, Fu X, Wolf NI, Nmezi B, Schiffmann R, Bugaighis M, Pierson T, Helman G, Simons C, van der Knaap MS, Liu J, Padiath Q, Vanderver A. TUBB4A mutations result in specific neuronal and oligodendrocytic defects that closely match clinically distinct phenotypes. Hum Mol Genet 2018; 26:4506-4518. [PMID: 28973395 DOI: 10.1093/hmg/ddx338] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/24/2017] [Indexed: 12/16/2022] Open
Abstract
Hypomyelinating leukodystrophies are heritable disorders defined by lack of development of brain myelin, but the cellular mechanisms of hypomyelination are often poorly understood. Mutations in TUBB4A, encoding the tubulin isoform tubulin beta class IVA (Tubb4a), result in the symptom complex of hypomyelination with atrophy of basal ganglia and cerebellum (H-ABC). Additionally, TUBB4A mutations are known to result in a broad phenotypic spectrum, ranging from primary dystonia (DYT4), isolated hypomyelination with spastic quadriplegia, and an infantile onset encephalopathy, suggesting multiple cell types may be involved. We present a study of the cellular effects of TUBB4A mutations responsible for H-ABC (p.Asp249Asn), DYT4 (p.Arg2Gly), a severe combined phenotype with hypomyelination and encephalopathy (p.Asn414Lys), as well as milder phenotypes causing isolated hypomyelination (p.Val255Ile and p.Arg282Pro). We used a combination of histopathological, biochemical and cellular approaches to determine how these different mutations may have variable cellular effects in neurons and/or oligodendrocytes. Our results demonstrate that specific mutations lead to either purely neuronal, combined neuronal and oligodendrocytic or purely oligodendrocytic defects that closely match their respective clinical phenotypes. Thus, the DYT4 mutation that leads to phenotypes attributable to neuronal dysfunction results in altered neuronal morphology, but with unchanged tubulin quantity and polymerization, with normal oligodendrocyte morphology and myelin gene expression. Conversely, mutations associated with isolated hypomyelination (p.Val255Ile and p.Arg282Pro) and the severe combined phenotype (p.Asn414Lys) resulted in normal neuronal morphology but were associated with altered oligodendrocyte morphology, myelin gene expression, and microtubule dysfunction. The H-ABC mutation (p.Asp249Asn) that exhibits a combined neuronal and myelin phenotype had overlapping cellular defects involving both neuronal and oligodendrocyte cell types in vitro. Only mutations causing hypomyelination phenotypes showed altered microtubule dynamics and acted through a dominant toxic gain of function mechanism. The DYT4 mutation had no impact on microtubule dynamics suggesting a distinct mechanism of action. In summary, the different clinical phenotypes associated with TUBB4A reflect the selective and specific cellular effects of the causative mutations. Cellular specificity of disease pathogenesis is relevant to developing targeted treatments for this disabling condition.
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Affiliation(s)
- Julian Curiel
- Center for Neuroscience Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA
| | | | - Asako Takanohashi
- Center for Genetic Medicine Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA.,Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | | | - Xiaoqin Fu
- Center for Neuroscience Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA
| | - Nicole I Wolf
- VU University Medical Center, Amsterdam, The Netherlands
| | - Bruce Nmezi
- Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Raphael Schiffmann
- Institute of Metabolic Disease, Baylor Scott & White Research Institute, Dallas, TX 75204, USA
| | - Mona Bugaighis
- Center for Neuroscience Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA
| | - Tyler Pierson
- Departments of Pediatrics and Neurology, Cedar Sinai Medical Center, Board of Governors Regenerative Medicine Institute, Los Angeles, CA 90048, USA
| | - Guy Helman
- Center for Genetic Medicine Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA.,Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia.,Department of Neurology, Children's National Health System, Washington, DC 20010, USA
| | - Cas Simons
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | | | - Judy Liu
- Center for Neuroscience Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA
| | - Quasar Padiath
- Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Adeline Vanderver
- Center for Genetic Medicine Research, Children's National Health System, Children's Research Institute, Washington, DC 20010, USA.,Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.,Department of Neurology, Children's National Health System, Washington, DC 20010, USA.,Perlman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Hamilton EM, Wolf NI, van der Knaap MS. Reply: A novel TUBB4A mutation suggests that genotype-phenotype correlation of H-ABC syndrome needs to be revisited. Brain 2015; 138:e371. [PMID: 25619510 DOI: 10.1093/brain/awu404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Eline M Hamilton
- 1 Department of Child Neurology and Neuroscience Campus Amsterdam, VU University Medical Centre, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Nicole I Wolf
- 1 Department of Child Neurology and Neuroscience Campus Amsterdam, VU University Medical Centre, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Marjo S van der Knaap
- 1 Department of Child Neurology and Neuroscience Campus Amsterdam, VU University Medical Centre, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands 2 Department of Functional Genomics, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
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