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Tian G, Jaglin XH, Keays DA, Francis F, Chelly J, Cowan NJ. Disease-associated mutations in TUBA1A result in a spectrum of defects in the tubulin folding and heterodimer assembly pathway. Hum Mol Genet 2010; 19:3599-613. [PMID: 20603323 DOI: 10.1093/hmg/ddq276] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Malformations of cortical development are characteristic of a plethora of diseases that includes polymicrogyria, periventricular and subcortical heterotopia and lissencephaly. Mutations in TUBA1A and TUBB2B, each a member of the multigene families that encode alpha- and beta-tubulins, have recently been implicated in these diseases. Here we examine the defects that result from nine disease-causing mutations (I188L, I238V, P263T, L286F, V303G, L397P, R402C, 402H, S419L) in TUBA1A. We show that the expression of all the mutant proteins in vitro results in the generation of tubulin heterodimers in varying yield and that these can co-polymerize with microtubules in vitro. We identify several kinds of defects that result from these mutations. Among these are various defects in the chaperone-dependent pathway leading to de novo tubulin heterodimer formation. These include a defective interaction with the chaperone prefoldin, a reduced efficiency in the generation of productive folding intermediates as a result of inefficient interaction with the cytosolic chaperonin, CCT, and, in several cases, a failure to stably interact with TBCB, one of five tubulin-specific chaperones that act downstream of CCT in the tubulin heterodimer assembly pathway. Other defects include structural instability in vitro, diminished stability in vivo, a compromised ability to co-assemble with microtubules in vivo and a suppression of microtubule growth rate in the neurites (but not the soma) of cultured neurons. Our data are consistent with the notion that some mutations in TUBA1A result in tubulin deficit, whereas others reflect compromised interactions with one or more MAPs that are essential to proper neuronal migration.
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Affiliation(s)
- Guoling Tian
- Department of Biochemistry, NYU Langone Medical Center, New York, NY 10016, USA
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Tian G, Kong XP, Jaglin XH, Chelly J, Keays D, Cowan NJ. A pachygyria-causing alpha-tubulin mutation results in inefficient cycling with CCT and a deficient interaction with TBCB. Mol Biol Cell 2008; 19:1152-61. [PMID: 18199681 DOI: 10.1091/mbc.e07-09-0861] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The agyria (lissencephaly)/pachygyria phenotypes are catastrophic developmental diseases characterized by abnormal folds on the surface of the brain and disorganized cortical layering. In addition to mutations in at least four genes--LIS1, DCX, ARX and RELN--mutations in a human alpha-tubulin gene, TUBA1A, have recently been identified that cause these diseases. Here, we show that one such mutation, R264C, leads to a diminished capacity of de novo tubulin heterodimer formation. We identify the mechanisms that contribute to this defect. First, there is a reduced efficiency whereby quasinative alpha-tubulin folding intermediates are generated via ATP-dependent interaction with the cytosolic chaperonin CCT. Second, there is a failure of CCT-generated folding intermediates to stably interact with TBCB, one of the five tubulin chaperones (TBCA-E) that participate in the pathway leading to the de novo assembly of the tubulin heterodimer. We describe the behavior of the R264C mutation in terms of its effect on the structural integrity of alpha-tubulin and its interaction with TBCB. In spite of its compromised folding efficiency, R264C molecules that do productively assemble into heterodimers are capable of copolymerizing into dynamic microtubules in vivo. The diminished production of TUBA1A tubulin in R264C individuals is consistent with haploinsufficiency as a cause of the disease phenotype.
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Affiliation(s)
- Guoling Tian
- Department of Biochemistry, New York University Medical Center, New York, NY 10016, USA
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Keays DA, Tian G, Poirier K, Huang GJ, Siebold C, Cleak J, Oliver PL, Fray M, Harvey RJ, Molnár Z, Piñon MC, Dear N, Valdar W, Brown SD, Davies KE, Rawlins JNP, Cowan NJ, Nolan P, Chelly J, Flint J. Mutations in alpha-tubulin cause abnormal neuronal migration in mice and lissencephaly in humans. Cell 2007; 128:45-57. [PMID: 17218254 PMCID: PMC1885944 DOI: 10.1016/j.cell.2006.12.017] [Citation(s) in RCA: 324] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 07/25/2006] [Accepted: 12/18/2006] [Indexed: 02/06/2023]
Abstract
The development of the mammalian brain is dependent on extensive neuronal migration. Mutations in mice and humans that affect neuronal migration result in abnormal lamination of brain structures with associated behavioral deficits. Here, we report the identification of a hyperactive N-ethyl-N-nitrosourea (ENU)-induced mouse mutant with abnormalities in the laminar architecture of the hippocampus and cortex, accompanied by impaired neuronal migration. We show that the causative mutation lies in the guanosine triphosphate (GTP) binding pocket of α-1 tubulin (Tuba1) and affects tubulin heterodimer formation. Phenotypic similarity with existing mouse models of lissencephaly led us to screen a cohort of patients with developmental brain anomalies. We identified two patients with de novo mutations in TUBA3, the human homolog of Tuba1. This study demonstrates the utility of ENU mutagenesis in the mouse as a means to discover the basis of human neurodevelopmental disorders.
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Affiliation(s)
- David A. Keays
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Guoling Tian
- Department of Biochemistry, New York University Medical Center, New York, NY10016, USA
| | - Karine Poirier
- Institut Cochin, INSERM Unité 567, CNRS UMR 8104, Université René Descartes – Paris 5, Faculté de Médecine René Descartes, Paris, F-75014, France
| | - Guo-Jen Huang
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Christian Siebold
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - James Cleak
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Peter L. Oliver
- MRC Functional Genetics Unit, South Parks Road, Oxford, OX1 3QX, UK
| | - Martin Fray
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - Robert J. Harvey
- Department of Pharmacology, The School of Pharmacy, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | - Zoltán Molnár
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford, OX1 3QX, UK
| | - Maria C. Piñon
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford, OX1 3QX, UK
| | - Neil Dear
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - William Valdar
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Steve D.M. Brown
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - Kay E. Davies
- MRC Functional Genetics Unit, South Parks Road, Oxford, OX1 3QX, UK
| | - J. Nicholas P. Rawlins
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, OX1 3UD, UK
| | - Nicholas J. Cowan
- Department of Biochemistry, New York University Medical Center, New York, NY10016, USA
| | - Patrick Nolan
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - Jamel Chelly
- Institut Cochin, INSERM Unité 567, CNRS UMR 8104, Université René Descartes – Paris 5, Faculté de Médecine René Descartes, Paris, F-75014, France
| | - Jonathan Flint
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
- Corresponding author
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Fontalba A, Avila J, Zabala JC. Beta-tubulin folding is modulated by the isotype-specific carboxy-terminal domain. J Mol Biol 1995; 246:628-36. [PMID: 7877181 DOI: 10.1016/s0022-2836(05)80112-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
To investigate the contribution of the carboxy-terminal domain in the process of tubulin folding and dimer formation, we constructed a beta 1-beta 3 tubulin chimaera and two truncated carboxy-terminal beta 3-tubulins. The capacity of these altered polypeptides to incorporate into dimers and into microtubules was tested by non-denaturing electrophoresis and co-assembly experiments. The chimaera and the truncated protein with a deletion encompassing the last 12 amino acid residues (beta 3 delta C12) were incorporated into dimers and microtubules, though the level of incorporation was diminished compared to wild-type beta 3-tubulin. However, the level of incorporation of beta 3 delta C12 into subtilisin-digested dimers was similar to the incorporation of wild-type beta 3-tubulin. Since subtilisin deletes the carboxy-terminal region, these results suggest a regulatory role of the carboxy-terminal region in the folding process itself and not in the formation of the dimer.
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Affiliation(s)
- A Fontalba
- Departamento de Biologia Molecular, Facultad de Medicina, Universidad de Cantabria, Spain
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Fackenthal JD, Hutchens JA, Turner FR, Raff EC. Structural analysis of mutations in the Drosophila beta 2-tubulin isoform reveals regions in the beta-tubulin molecular required for general and for tissue-specific microtubule functions. Genetics 1995; 139:267-86. [PMID: 7705629 PMCID: PMC1206324 DOI: 10.1093/genetics/139.1.267] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have determined the lesions in a number of mutant alleles of beta Tub85D, the gene that encodes the testis-specific beta 2-tubulin isoform in Drosophila melanogaster. Mutations responsible for different classes of functional phenotypes are distributed throughout the beta 2-tubulin molecule. There is a telling correlation between the degree of phylogenetic conservation of the altered residues and the number of different microtubule categories disrupted by the lesions. The majority of lesions occur at positions that are evolutionarily highly conserved in all beta-tubulins; these lesions disrupt general functions common to multiple classes of microtubules. However, a single allele B2t6 contains an amino acid substitution within an internal cluster of variable amino acids that has been identified as an isotype-defining domain in vertebrate beta-tubulins. Correspondingly, B2t6 disrupts only a subset of microtubule functions, resulting in misspecification of the morphology of the doublet microtubules of the sperm tail axoneme. We previously demonstrated that beta 3, a developmentally regulated Drosophila beta-tubulin isoform, confers the same restricted morphological phenotype in a dominant way when it is coexpressed in the testis with wild-type beta 2-tubulin. We show here by complementation analysis that beta 3 and the B2t6 product disrupt a common aspect of microtubule assembly. We therefore conclude that the amino acid sequence of the beta 2-tubulin internal variable region is required for generation of correct axoneme morphology but not for general microtubule functions. As we have previously reported, the beta 2-tubulin carboxy terminal isotype-defining domain is required for suprastructural organization of the axoneme. We demonstrate here that the beta 2 variant lacking the carboxy terminus and the B2t6 variant complement each other for mild-to-moderate meiotic defects but do not complement for proper axonemal morphology. Our results are consistent with the hypothesis drawn from comparisons of vertebrate beta-tubulins that the two isotype-defining domains interact in a three-dimensional structure in wild-type beta-tubulins. We propose that the integrity of this structure in the Drosophila testis beta 2-tubulin isoform is required for proper axoneme assembly but not necessarily for general microtubule functions. On the basis of our observations we present a model for regulation of axoneme microtubule morphology as a function of tubulin assembly kinetics.
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Affiliation(s)
- J D Fackenthal
- Department of Biology, Indiana University, Bloomington 47405
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Burns RG. Alpha-, beta-, and gamma-tubulins: sequence comparisons and structural constraints. CELL MOTILITY AND THE CYTOSKELETON 1991; 20:181-9. [PMID: 1773446 DOI: 10.1002/cm.970200302] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Comparison of congruent to 160 alpha-, beta-, and gamma-tubulins, and excluding the highly divergent C-terminal peptide, indicates that the three subclasses have similar tertiary structures. Conserved sequences within or between the subclasses have been identified, together with the locations of known epitopes, chemical modifications, and mutations. Evidence is also reviewed concerning the identity of the GTP-binding sites, about which residues are exposed in the assembled microtubule and at subunit:subunit interfaces. These characteristics constrain the possible tertiary structure of the tubulin subunit.
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Affiliation(s)
- R G Burns
- Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology and Medicine, London, United Kingdom
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