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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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Szasz J, Yaffe MB, Sternlicht H. Site-directed mutagenesis of alpha-tubulin. Reductive methylation studies of the Lys 394 region. Biophys J 1993; 64:792-802. [PMID: 8097117 PMCID: PMC1262393 DOI: 10.1016/s0006-3495(93)81440-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Previous studies have implicated at least two regions in alpha-tubulin that are important for the regulation of microtubule assembly. These regions include a cluster of basic residues consisting of Arg 390, His 393, and Lys 394 and the highly acidic carboxyl terminus. Lys 394 is highly reactive to HCHO and NaCNBH3. The reductive methylation of Lys 394 by these reagents is thought to be responsible for the profound inhibitory effects of low concentrations of HCHO on microtubule assembly (cf. Szasz J., M. B. Yaffe, M. Elzinga, G. S. Blank, and H. Sternlicht. 1986. Biochemistry. 25:4572-4582). In this study we reexamined the basis for this inhibition. Lys 394 in a human keratinocyte alpha-tubulin (k alpha 1) was replaced by a glutamic acid residue using site-directed mutagenesis. The mutant K394E was synthesized in vitro using rabbit reticulocyte lysates, and its ability to coassemble with bovine brain microtubule protein (MTP) before and after reaction with HCHO and NaCNBH3 was compared with that of wild-type. No differences in the coassemblies of the unmethylated proteins were detected suggesting that Lys 394 is not essential for microtubule assembly. However, methylated K394E prepared at low HCHO concentrations (< 1 mM) incorporated into microtubules to a greater extent (approximately 30-40%) than methylated wild-type. This result is consistent with the hypothesis that methylation of Lys 394 interferes with microtubule assembly. However, the extent of protection afforded by the replacement of Lys 394 with Glu 394 was less than half as large as that predicted from the earlier studies. We tentatively conclude that another residue(s) besides Lys 394 contributes significantly to the assembly-inhibition observed with low concentrations of HCHO. Since this residue(s) is less reactive than Lys 394, it would have to inhibit assembly substoichiometrically when methylated. Potential candidates for this residue include bulk lysyl residue(s), a lysyl residue(s) with intermediate reactivity toward HCHO, and the NH2-termini. The NH2-termini are especially attractive candidates since they appear to have a structural role in microtubule assembly.
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Affiliation(s)
- J Szasz
- Department of Pharmacology, Case Western Reserve School of Medicine, Cleveland, Ohio 44106
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