151
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Orozco D, Tahirovic S, Rentzsch K, Schwenk BM, Haass C, Edbauer D. Loss of fused in sarcoma (FUS) promotes pathological Tau splicing. EMBO Rep 2012; 13:759-64. [PMID: 22710833 DOI: 10.1038/embor.2012.90] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 05/22/2012] [Accepted: 06/01/2012] [Indexed: 01/08/2023] Open
Abstract
A subset of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) patients present pathological redistribution and aggregation of the nuclear protein fused in sarcoma (FUS) in the cytoplasm. Although FUS associates with the spliceosomal complex, no endogenous neuronal splicing targets have been identified. Here we identify Tau mRNA as a physiological splicing target of FUS. In mouse brain, FUS directly binds to Tau pre-mRNA, and knockdown of FUS in hippocampal neurons leads to preferential inclusion of Tau exons 3 and 10. FUS knockdown causes significant growth cone enlargement and disorganization reminiscent of Tau loss of function. These findings suggest that disturbed cytoskeletal function and enhanced expression of the neurodegeneration-associated Tau exon 10 might contribute to FTLD/ALS with FUS inclusions.
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Affiliation(s)
- Denise Orozco
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
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152
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Abstract
Both Alzheimer's disease (AD) and frontotemporal dementia (FTD) are characterized by the deposition of hyperphosphorylated forms of the microtubule-associated protein tau in neurons and/or glia. This unifying pathology led to the umbrella term “tauopathies” for these conditions, also emphasizing the central role of tau in AD and FTD. Generation of transgenic mouse models expressing human tau in the brain has contributed to the understanding of the pathomechanistic role of tau in disease. To reveal the physiological functions of tau in vivo, several knockout mouse strains with deletion of the tau-encoding MAPT gene have been established over the past decade, using different gene targeting constructs. Surprisingly, when initially introduced tau knockout mice presented with no overt phenotype or malformations. The number of publications using tau knockout mice has recently markedly increased, and both behavioural changes and motor deficits have been identified in aged mice of certain strains. Moreover, tau knockout mice have been instrumental in identifying novel functions of tau, both in cultured neurons and in vivo. Importantly, tau knockout mice have significantly contributed to the understanding of the pathophysiological interplay between Aβ and tau in AD. Here, we review the literature that involves tau knockout mice to summarize what we have learned so far from depleting tau in vivo.
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153
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Wu QF, Yang L, Li S, Wang Q, Yuan XB, Gao X, Bao L, Zhang X. Fibroblast Growth Factor 13 Is a Microtubule-Stabilizing Protein Regulating Neuronal Polarization and Migration. Cell 2012; 149:1549-64. [DOI: 10.1016/j.cell.2012.04.046] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 02/08/2012] [Accepted: 04/11/2012] [Indexed: 01/24/2023]
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154
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Cantuti-Castelvetri L, Zhu H, Givogri MI, Chidavaenzi RL, Lopez-Rosas A, Bongarzone ER. Psychosine induces the dephosphorylation of neurofilaments by deregulation of PP1 and PP2A phosphatases. Neurobiol Dis 2012; 46:325-35. [PMID: 22326830 DOI: 10.1016/j.nbd.2012.01.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 01/16/2012] [Accepted: 01/26/2012] [Indexed: 11/25/2022] Open
Abstract
Patients with Krabbe disease, a genetic demyelinating syndrome caused by deficiency of galactosyl-ceramidase and the resulting accumulation of galactosyl-sphingolipids, develop signs of a dying-back axonopathy compounded by a deficiency of large-caliber axons. Here, we show that axonal caliber in Twitcher mice, an animal model for Krabbe disease, is impaired in peripheral axons and is accompanied by a progressive reduction in the abundance and phosphorylation of the three neurofilament (NF) subunits. These changes correlate with an increase in the density of NFs per cross-sectional area in numerous mutant peripheral axons and abnormal increases in the activity of two serine/threonine phosphatases (PP1 and PP2A) in mutant tissue. Similarly, acutely isolated mutant cortical neurons show abnormal phosphorylation of NFs. Psychosine, the neurotoxin accumulated in Krabbe disease, was sufficient to induce abnormal dephosphorylation of NF subunits in a normal motor neuron cell line as well as in acutely isolated normal cortical neurons. This in vitro effect was mediated by PP1 and PP2A, which specifically dephosphorylated NFs. These results demonstrate that the reduced caliber observed in some axons in Krabbe disease involves abnormal dephosphorylation of NFs. We propose that a psychosine-driven pathogenic mechanism through deregulated phosphotransferase activities may be involved in this process.
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155
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Tymanskyj SR, Scales TM, Gordon-Weeks PR. MAP1B enhances microtubule assembly rates and axon extension rates in developing neurons. Mol Cell Neurosci 2012; 49:110-9. [DOI: 10.1016/j.mcn.2011.10.003] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 09/28/2011] [Accepted: 10/07/2011] [Indexed: 11/16/2022] Open
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156
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Long H, Zhu X, Yang P, Gao Q, Chen Y, Ma L. Myo9b and RICS modulate dendritic morphology of cortical neurons. ACTA ACUST UNITED AC 2012; 23:71-9. [PMID: 22250289 DOI: 10.1093/cercor/bhr378] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Regulated growth and branching of dendritic processes is critical for the establishment of neuronal circuitry and normal brain functions. Rho family GTPases, including RhoA, Rac1, and Cdc42, play a prominent role in dendritic development. RhoA inhibits dendritic branching and growth, whereas Rac1/Cdc42 does the opposite. It has been suggested that the activity of RhoA must be kept low to allow dendritic growth. However, how neurons restrict the activation of RhoA for proper dendritic development is not clear. In the present study, we undertook a comprehensive loss-of-function analysis of putative RhoA GTPase-activating proteins (RhoA GAPs) in the cortical neurons. The expression of 16 RhoA GAPs was detected in the developing rat brain, and RNA interference experiments suggest that 2 of them, Myo9b and RICS, are critical regulators of dendritic morphogenesis. Knockdown of either Myo9b or RICS in cultured cortical neurons or developing cortex resulted in decreased dendrite length and number. Inhibition of RhoA/ROCK signaling restores the defects of dendritic morphology induced by knockdown of Myo9b or RICS. These data demonstrate that Myo9b and RICS repress RhoA/Rock signaling and modulate dendritic morphogenesis in cortical neurons, providing evidence for critical physiological function of RhoA GAPs in regulation of dendritic development.
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Affiliation(s)
- Hui Long
- The State Key Laboratory of Medical Neurobiology and Pharmacology Research Center, Shanghai Medical College and Institutes of Brain Science, Fudan University, Shanghai 200032, China
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157
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Stress-activated protein kinase MKK7 regulates axon elongation in the developing cerebral cortex. J Neurosci 2012; 31:16872-83. [PMID: 22090513 DOI: 10.1523/jneurosci.1111-11.2011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The c-Jun NH(2)-terminal protein kinase (JNK), which belongs to the mitogen-activated protein kinase family, plays important roles in a broad range of physiological processes. JNK is controlled by two upstream regulators, mitogen-activated protein kinase kinase (MKK) 7 and MKK4. To elucidate the physiological functions of MKK7, we used Nestin-Cre to generate a novel mouse model in which the mkk7 gene was specifically deleted in the nervous system (Mkk7(flox/flox) Nestin-Cre mice). These mice were indistinguishable from their control littermates in gross appearance during embryogenesis but died immediately after birth without breathing. Histological examination showed that the mutants had severe defects in brain development, including enlarged ventricles, reduced striatum, and minimal axon tracts. Electron microscopy revealed abnormal accumulations of filamentous structures and autophagic vacuoles in Mkk7(flox/flox) Nestin-Cre brain. Further analysis showed that MKK7 deletion decreased numbers of TAG-1-expressing axons and delayed neuronal migration in the cerebrum. Neuronal differentiation was not altered. In utero electroporation studies showed that contralateral projection of axons by layer 2/3 neurons was impaired in the absence of MKK7. Moreover, MKK7 regulated axon elongation in a cell-autonomous manner in vivo, a finding confirmed in vitro. Finally, phosphorylation levels of JNK substrates, including c-Jun, neurofilament heavy chain, microtubule-associated protein 1B, and doublecortin, were reduced in Mkk7(flox/flox) Nestin-Cre brain. Our findings demonstrate that the phenotype of Mkk7(flox/flox) Nestin-Cre mice differs substantially from that of Mkk4(flox/flox) Nestin-Cre mice, and establish that MKK7-mediated regulation of JNK is uniquely critical for both axon elongation and radial migration in the developing brain.
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158
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Human pathologies associated with defective RNA transport and localization in the nervous system. Biol Cell 2012; 99:649-61. [DOI: 10.1042/bc20070045] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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159
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Abstract
The protein tau is the most abundant microtubule associated protein in the central and peripheral nervous system. In the brain, tau plays a role in the assembly and stabilization of microtubules. The function of tau, however, appears to overlap with other microtubule binding proteins. The observation that tau is associated with neurodegenerative diseases has renewed interest in this protein. Various aspects of structure and biochemistry of tau, fibril formation and clinical perspectives, including therapeutic strategies are reviewed in this chapter.
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160
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Blackmore MG. Molecular control of axon growth: insights from comparative gene profiling and high-throughput screening. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2012. [PMID: 23206595 DOI: 10.1016/b978-0-12-398309-1.00004-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Axon regeneration in the mammalian adult central nervous system (CNS) is limited by an intrinsically low capacity for axon growth in many CNS neurons. In contrast, embryonic, peripheral, and many nonmammalian neurons are capable of successful regeneration. Numerous studies have compared mammalian CNS neurons to their counterparts in regenerating systems in an effort to identify candidate genes that control regenerative ability. This review summarizes work using this comparative strategy and examines our current understanding of gene function in axon growth, highlighting the emergence of genome-wide expression profiling and high-throughput screening strategies to identify novel regulators of axon growth.
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Affiliation(s)
- Murray G Blackmore
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin, USA.
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161
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Abstract
Tauopathies are age-related neurodegenerative diseases that are characterized by the presence of aggregates of abnormally phosphorylated tau. As tau was originally discovered as a microtubule-associated protein, it has been hypothesized that neurodegeneration results from a loss of the ability of tau to associate with microtubules. However, tau has been found to have other functions aside from the promotion and stabilization of microtubule assembly. It is conceivable that such functions may be affected by the abnormal phosphorylation of tau and might have consequences for neuronal function or viability. This chapter provides an overview of tau structure, functions, and its involvement in neurodegenerative diseases.
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162
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Sapir T, Frotscher M, Levy T, Mandelkow EM, Reiner O. Tau's role in the developing brain: implications for intellectual disability. Hum Mol Genet 2011; 21:1681-92. [PMID: 22194194 DOI: 10.1093/hmg/ddr603] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Microdeletions encompassing the MAPT (Tau) locus resulting in intellectual disability raised the hypothesis that Tau may regulate early functions in the developing brain. Our results indicate that neuronal migration was inhibited in mouse brains following Tau reduction. In addition, the leading edge of radially migrating neurons was aberrant in spite of normal morphology of radial glia. Furthermore, intracellular mitochondrial transport and morphology were affected. In early postnatal brains, a portion of Tau knocked down neurons reached the cortical plate. Nevertheless, they exhibited far less developed dendrites and a striking reduction in connectivity evident by the size of boutons. Our novel results strongly implicate MAPT as a dosage-sensitive gene in this locus involved in intellectual disability. Furthermore, our results are likely to impact our understanding of other diseases involving Tau.
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Affiliation(s)
- Tamar Sapir
- Department of Molecular Genetics, Weizmann Institute of Science, 76100 Rehovot, Israel
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163
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Growing the growth cone: remodeling the cytoskeleton to promote axon regeneration. Trends Neurosci 2011; 35:164-74. [PMID: 22154154 DOI: 10.1016/j.tins.2011.11.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 09/26/2011] [Accepted: 11/01/2011] [Indexed: 01/04/2023]
Abstract
Axon growth is driven by the movement of a growth cone, a specialized sensory motile structure located at the tip of a growing neurite. Although stalled retraction bulbs have long been recognized as hallmarks of regeneration failure, mechanisms that control the formation and migration of nerve endings are only beginning to be unraveled. Recent studies point to microtubules as key determinants for such processes, and emerging evidence suggests that regulators of actin and microtubule dynamics in the growth cone might serve as attractive targets for controlling both the speed and trajectory of regenerating axons. This review discusses the potential of and recent progress in direct modulation of the growth cone machinery as a novel strategy to promote axon regeneration in the nervous system after injury.
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164
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Deak KL, Horn SR, Rehder CW. The evolving picture of microdeletion/microduplication syndromes in the age of microarray analysis: variable expressivity and genomic complexity. Clin Lab Med 2011; 31:543-64, viii. [PMID: 22118736 DOI: 10.1016/j.cll.2011.08.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several new microdeletion and microduplication syndromes have been discovered in a genotype-first approach. Many of these disorders are caused by nonallelic homologous recombination between blocks of segmental duplication. The authors describe 9 regions for which copy number alteration is proposed to cause an abnormal phenotype. Some of these disorders have been observed in affected individuals and individuals lacking a clearly abnormal phenotype. These deletions and duplications are thought to be contributory, but not always sufficient, to elicit an abnormal outcome. Additional studies are necessary to further evaluate the penetrance and delineate the clinical spectrum associated with many of these newly described disorders.
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Affiliation(s)
- Kristen L Deak
- Department of Pathology, Duke University, Durham, NC, USA
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165
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Bhanot K, Young KG, Kothary R. MAP1B and clathrin are novel interacting partners of the giant cyto-linker dystonin. J Proteome Res 2011; 10:5118-27. [PMID: 21936565 DOI: 10.1021/pr200564g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Dystonin is a large multidomain cytoskeletal-associated protein that plays an essential role in the nervous system. Loss of dystonin results in neuromuscular dysfunction and early death in a mouse mutant called dystonia musculorum. Conserved among related proteins, the plakin domain is a defining feature of all major dystonin isoforms, yet its interactions have not been explored in detail. The purpose of the present study was to identify novel interacting partners of the plakin domain of the neuronal isoform of dystonin (dystonin-a). Newly identified interacting proteins discovered through a pull-down assay were validated using coimmunoprecipitation, coimmunofluorescence, and proximity ligation assays. Microtubule associated protein 1B (MAP1B), a microtubule stabilizing protein, and clathrin heavy chain, the major component of the clathrin triskelion, were identified as interaction partners for dystonin-a. Increased levels of phosphorylated MAP1B suggest a misregulation of MAP1B and a potentially novel component of the dt pathology. This work will further facilitate our understanding of how cytoskeletal proteins can affect and regulate neurodegenerative disorders.
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Affiliation(s)
- Kunal Bhanot
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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166
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Tortosa E, Montenegro-Venegas C, Benoist M, Härtel S, González-Billault C, Esteban JA, Avila J. Microtubule-associated protein 1B (MAP1B) is required for dendritic spine development and synaptic maturation. J Biol Chem 2011; 286:40638-48. [PMID: 21984824 DOI: 10.1074/jbc.m111.271320] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Microtubule-associated protein 1B (MAP1B) is prominently expressed during early stages of neuronal development, and it has been implicated in axonal growth and guidance. MAP1B expression is also found in the adult brain in areas of significant synaptic plasticity. Here, we demonstrate that MAP1B is present in dendritic spines, and we describe a decrease in the density of mature dendritic spines in neurons of MAP1B-deficient mice that was accompanied by an increase in the number of immature filopodia-like protrusions. Although these neurons exhibited normal passive membrane properties and action potential firing, AMPA receptor-mediated synaptic currents were significantly diminished. Moreover, we observed a significant decrease in Rac1 activity and an increase in RhoA activity in the post-synaptic densities of adult MAP1B(+/-) mice when compared with wild type controls. MAP1B(+/-) fractions also exhibited a decrease in phosphorylated cofilin. Taken together, these results indicate a new and important role for MAP1B in the formation and maturation of dendritic spines, possibly through the regulation of the actin cytoskeleton. This activity of MAP1B could contribute to the regulation of synaptic activity and plasticity in the adult brain.
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Affiliation(s)
- Elena Tortosa
- Department of Neuroscience, Centro de Biología Molecular Severo Ochoa CSIC/UAM, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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167
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Cho GW, Noh MY, Kang BY, Ku IW, Park J, Hong YH, Kim MH, Kim SH. Development of a Cellular Tau Enzyme-Linked Immunosorbent Assay Method for Screening GSK-3β Inhibitors. Assay Drug Dev Technol 2011; 9:503-13. [DOI: 10.1089/adt.2010.0343] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Goang-Won Cho
- Department of Neurology, College of Medicine, Hanyang University, Seoul, Korea
- Institute of Biomedical Science, Hanyang University, Seoul, Korea
| | - Min-Young Noh
- Department of Neurology, College of Medicine, Hanyang University, Seoul, Korea
| | - Byung Yong Kang
- Department of Neurology, College of Medicine, Hanyang University, Seoul, Korea
| | - Il-Whea Ku
- Drug Discovery Lab., R&D Center, Jeil Pharmaceutical Co., Ltd., Yongin, Korea
| | - Jiseon Park
- Drug Discovery Lab., R&D Center, Jeil Pharmaceutical Co., Ltd., Yongin, Korea
| | - Yoon-Ho Hong
- Department of Neurology, College of Medicine, Seoul National University, Seoul, Korea
| | - Myung-Hwa Kim
- Drug Discovery Lab., R&D Center, Jeil Pharmaceutical Co., Ltd., Yongin, Korea
| | - Seung Hyun Kim
- Department of Neurology, College of Medicine, Hanyang University, Seoul, Korea
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168
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Corbo CP, Alonso ADC. Therapeutic targets in Alzheimer's disease and related tauopathies. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 98:47-83. [PMID: 21199770 DOI: 10.1016/b978-0-12-385506-0.00002-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Alzheimer's disease is a progressive neurodegenerative disease that is characterized histopathologically by the presence of plaques, mainly composed of Abeta amyloid and the tangles, mainly composed of hyperphosphorylated tau. To date, there is no treatment that can reverse the disease, and all the current therapeutics is directed to cope with the symptoms of the disease. Here we describe the efforts dedicated to attack the plaques and, in more detail, the process of neurofibrillary degeneration, linked to the presence of the hyperphosphorylated microtubule associated protein tau. We have identified the different putative targets for therapeutics and the current knowledge on them.
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Affiliation(s)
- Christopher P Corbo
- College of Staten Island, Program in evelopmental Neuroscience, The Graduate Center, City University of New York (CUNY), Staten Island, New York, USA
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169
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Nakata T, Niwa S, Okada Y, Perez F, Hirokawa N. Preferential binding of a kinesin-1 motor to GTP-tubulin-rich microtubules underlies polarized vesicle transport. ACTA ACUST UNITED AC 2011; 194:245-55. [PMID: 21768290 PMCID: PMC3144414 DOI: 10.1083/jcb.201104034] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The high affinity of KIF5 for microtubules rich in GTP-tubulin results in polarized motor protein accumulation at axonal tips in neurons and may underlie polarized vesicle transport. Polarized transport in neurons is fundamental for the formation of neuronal circuitry. A motor domain–containing truncated KIF5 (a kinesin-1) recognizes axonal microtubules, which are enriched in EB1 binding sites, and selectively accumulates at the tips of axons. However, it remains unknown what cue KIF5 recognizes to result in this selective accumulation. We found that axonal microtubules were preferentially stained by the anti–GTP-tubulin antibody hMB11. Super-resolution microscopy combined with EM immunocytochemistry revealed that hMB11 was localized at KIF5 attachment sites. In addition, EB1, which binds preferentially to guanylyl-methylene-diphosphate (GMPCPP) microtubules in vitro, recognized hMB11 binding sites on axonal microtubules. Further, expression of hMB11 antibody in neurons disrupted the selective accumulation of truncated KIF5 in the axon tips. In vitro studies revealed approximately threefold stronger binding of KIF5 motor head to GMPCPP microtubules than to GDP microtubules. Collectively, these data suggest that the abundance of GTP-tubulin in axonal microtubules may underlie selective KIF5 localization and polarized axonal vesicular transport.
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Affiliation(s)
- Takao Nakata
- Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
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170
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Abstract
While the microtubule-binding capacity of the protein tau has been known for many years, new functions of tau in signaling and cytoskeletal organization have recently emerged. In this review, we highlight these functions and the potential roles of tau in neurodegenerative disease. We also discuss the therapeutic potential of drugs targeting various aspects of tau biology.
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Affiliation(s)
- Meaghan Morris
- Gladstone Institute of Neurological Disease, San Francisco, CA 94158, USA
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171
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172
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Dent EW, Gupton SL, Gertler FB. The growth cone cytoskeleton in axon outgrowth and guidance. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a001800. [PMID: 21106647 DOI: 10.1101/cshperspect.a001800] [Citation(s) in RCA: 402] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Axon outgrowth and guidance to the proper target requires the coordination of filamentous (F)-actin and microtubules (MTs), the dynamic cytoskeletal polymers that promote shape change and locomotion. Over the past two decades, our knowledge of the many guidance cues, receptors, and downstream signaling cascades involved in neuronal outgrowth and guidance has increased dramatically. Less is known, however, about how those cascades of information converge and direct appropriate remodeling and interaction of cytoskeletal polymers, the ultimate effectors of movement and guidance. During development, much of the communication that occurs between environmental guidance cues and the cytoskeleton takes place at the growing tip of the axon, the neuronal growth cone. Several articles on this topic focus on the "input" to the growth cone, the myriad of receptor types, and their corresponding cognate ligands. Others investigate the signaling cascades initiated by receptors and propagated by second messenger pathways (i.e., kinases, phosphatases, GTPases). Ultimately, this plethora of information converges on proteins that associate directly with the actin and microtubule cytoskeletons. The role of these cytoskeletal-associated proteins, as well as the cytoskeleton itself in axon outgrowth and guidance, is the subject of this article.
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Affiliation(s)
- Erik W Dent
- Department of Anatomy, University of Wisconsin-Madison, 53706, USA
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173
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Expression and function of neuronal growth-associated proteins (nGAPs) in PC12 cells. Neurosci Res 2011; 70:85-90. [PMID: 21238513 DOI: 10.1016/j.neures.2011.01.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 01/02/2011] [Accepted: 01/04/2011] [Indexed: 11/21/2022]
Abstract
The growth cone plays crucial roles in neural wiring, synapse formation, and axonal regeneration. Continuous rearrangement of cytoskeletal elements and targeting of transported vesicles to the plasma membrane are essential to growth cone motility; however, the proteins directly involved in these processes and their specific functions are not well established. We recently identified 17 proteins as functional marker proteins of the mammalian growth cone and as neuronal growth-associated proteins in rat cortical neurons (nGAPs; Nozumi et al., 2009). To determine whether these 17 proteins are growth cone markers in other neuronal cell types, we examined their expression and function in PC12D cells. We found that all 17 nGAPs were highly concentrated in the growth cones of PC12D cells, and that knockdown of all of them by RNAi reduced or inhibited neurite outgrowth, indicating that all of the 17 nGAPs may be general growth cone markers. Among them, eight proteins were shown to regulate the amount of F-actin in PC12D growth cones. Two of these nGAP that are cytoskeletal proteins, Cap1 and Sept2, increased the mean growth cone area and the mean neurite length by regulating the amount of F-actin; Sept2 also induced filopodial growth. Taken together, our data suggested that some of the nGAPs were generalized markers of the growth cone in multiple neuronal cell types and some of them, such as Cap1 and Sept2, regulated growth cone morphology through rearrangement of F-actin and thereby controlled neurite outgrowth.
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174
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Abstract
Axons depend critically on axonal transport both for supplying materials and for communicating with cell bodies. This chapter looks at each activity, asking what aspects are essential for axon survival. Axonal transport declines in neurodegenerative disorders, such as Alzheimer's disease, amyotrophic lateral sclerosis, and multiple sclerosis, and in normal ageing, but whether all cargoes are equally affected and what limits axon survival remains unclear. Cargoes can be differentially blocked in some disorders, either individually or in groups. Each missing protein cargo results in localized loss-of-function that can be partially modeled by disrupting the corresponding gene, sometimes with surprising results. The axonal response to losing specific proteins also depends on the rates of protein turnover and on whether the protein can be locally synthesized. Among cargoes with important axonal roles are components of the PI3 kinase, Mek/Erk, and Jnk signaling pathways, which help to communicate with cell bodies and to regulate axonal transport itself. Bidirectional trafficking of Bdnf, NT-3, and other neurotrophic factors contribute to intra- and intercellular signaling, affecting the axon's cellular environment and survival. Finally, several adhesion molecules and gangliosides are key determinants of axon survival, probably by mediating axon-glia interactions. Thus, failure of long-distance intracellular transport can deprive axons of one, few, or many cargoes. This can lead to axon degeneration either directly, through the absence of essential axonal proteins, or indirectly, through failures in communication with cell bodies and nonneuronal cells.
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175
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Hirokawa N. From electron microscopy to molecular cell biology, molecular genetics and structural biology: intracellular transport and kinesin superfamily proteins, KIFs: genes, structure, dynamics and functions. Microscopy (Oxf) 2011; 60 Suppl 1:S63-S92. [PMID: 21844601 DOI: 10.1093/jmicro/dfr051] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
Cells transport and sort various proteins and lipids following synthesis as distinct types of membranous organelles and protein complexes to the correct destination at appropriate velocities. This intracellular transport is fundamental for cell morphogenesis, survival and functioning not only in highly polarized neurons but also in all types of cells in general. By developing quick-freeze electron microscopy (EM), new filamentous structures associated with cytoskeletons are uncovered. The characterization of chemical structures and functions of these new filamentous structures led us to discover kinesin superfamily molecular motors, KIFs. In this review, I discuss the identification of these new structures and characterization of their functions using molecular cell biology and molecular genetics. KIFs not only play significant roles by transporting various cargoes along microtubule rails, but also play unexpected fundamental roles on various important physiological processes such as learning and memory, brain wiring, development of central nervous system and peripheral nervous system, activity-dependent neuronal survival, development of early embryo, left-right determination of our body and tumourigenesis. Furthermore, by combining single-molecule biophysics with structural biology such as cryo-electrom microscopy and X-ray crystallography, atomic structures of KIF1A motor protein of almost all states during ATP hydrolysis have been determined and a common mechanism of motility has been proposed. Thus, this type of studies could be a good example of really integrative multidisciplinary life science in the twenty-first century.
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Affiliation(s)
- Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, Hongo, 7-3-1, Bunkyo-ku, Tokyo, Japan 113-0033.
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176
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Ben-Ari Y, Spitzer NC. Phenotypic checkpoints regulate neuronal development. Trends Neurosci 2010; 33:485-92. [PMID: 20864191 DOI: 10.1016/j.tins.2010.08.005] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 08/22/2010] [Accepted: 08/22/2010] [Indexed: 12/22/2022]
Abstract
Nervous system development proceeds by sequential gene expression mediated by cascades of transcription factors in parallel with sequences of patterned network activity driven by receptors and ion channels. These sequences are cell type- and developmental stage-dependent and modulated by paracrine actions of substances released by neurons and glia. How and to what extent these sequences interact to enable neuronal network development is not understood. Recent evidence demonstrates that CNS development requires intermediate stages of differentiation providing functional feedback that influences gene expression. We suggest that embryonic neuronal functions constitute a series of phenotypic checkpoint signatures; neurons failing to express these functions are delayed or developmentally arrested. Such checkpoints are likely to be a general feature of neuronal development and constitute presymptomatic signatures of neurological disorders when they go awry.
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Affiliation(s)
- Yehezkel Ben-Ari
- Institut de Neurobiologie de la Méditerranée (INMED), Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 901, Parc Scientifique de Luminy, Marseille CEDEX 09, France.
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177
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Montenegro-Venegas C, Tortosa E, Rosso S, Peretti D, Bollati F, Bisbal M, Jausoro I, Avila J, Cáceres A, Gonzalez-Billault C. MAP1B regulates axonal development by modulating Rho-GTPase Rac1 activity. Mol Biol Cell 2010; 21:3518-28. [PMID: 20719958 PMCID: PMC2954117 DOI: 10.1091/mbc.e09-08-0709] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
This article shows a novel function for the MAP1B protein, related to the control of actin dynamics through interaction with Tiam1. Cultured neurons obtained from MAP1B-deficient mice have a delay in axon outgrowth and a reduced rate of axonal elongation compared with neurons from wild-type mice. Here we show that MAP1B deficiency results in a significant decrease in Rac1 and cdc42 activity and a significant increase in Rho activity. We found that MAP1B interacted with Tiam1, a guanosine nucleotide exchange factor for Rac1. The decrease in Rac1/cdc42 activity was paralleled by decreases in the phosphorylation of the downstream effectors of these proteins, such as LIMK-1 and cofilin. The expression of a constitutively active form of Rac1, cdc42, or Tiam1 rescued the axon growth defect of MAP1B-deficient neurons. Taken together, these observations define a new and crucial function of MAP1B that we show to be required for efficient cross-talk between microtubules and the actin cytoskeleton during neuronal polarization.
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178
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Abstract
Recent evidence suggests that glycogen synthase kinase 3 (GSK3) proteins and their upstream and downstream regulators have key roles in many fundamental processes during neurodevelopment. Disruption of GSK3 signalling adversely affects brain development and is associated with several neurodevelopmental disorders. Here, we discuss the mechanisms by which GSK3 activity is regulated in the nervous system and provide an overview of the recent advances in the understanding of how GSK3 signalling controls neurogenesis, neuronal polarization and axon growth during brain development. These recent advances suggest that GSK3 is a crucial node that mediates various cellular processes that are controlled by multiple signalling molecules--for example, disrupted in schizophrenia 1 (DISC1), partitioning defective homologue 3 (PAR3), PAR6 and Wnt proteins--that regulate neurodevelopment.
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Affiliation(s)
- Eun-Mi Hur
- Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Feng-Quan Zhou
- Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
- The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
- Address all correspondence to: Feng-Quan Zhou, Ph.D., 215 Ross Research Building, 720 Rutland Ave, Baltimore, MD 21287. (Phone: 443-2875649, Fax: 410-5026414, )
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179
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Gómez de Barreda E, Dawson HN, Vitek MP, Avila J. Tau deficiency leads to the upregulation of BAF-57, a protein involved in neuron-specific gene repression. FEBS Lett 2010; 584:2265-70. [DOI: 10.1016/j.febslet.2010.03.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 03/17/2010] [Accepted: 03/19/2010] [Indexed: 10/19/2022]
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180
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Fang H, Zhang LF, Meng FT, Du X, Zhou JN. Acute hypoxia promote the phosphorylation of tau via ERK pathway. Neurosci Lett 2010; 474:173-177. [PMID: 20304032 DOI: 10.1016/j.neulet.2010.03.037] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Revised: 03/06/2010] [Accepted: 03/15/2010] [Indexed: 11/15/2022]
Abstract
Tau phosphorylation and hypoxia are both linked to the pathology of Alzheimer's disease. To find out the possible connection between hypoxia and tau phosphorylation, we performed this study to evaluate the level of phosphorylated tau under hypoxic or normal condition. We found in our study that hypoxia promoted the phosphorylation of tau protein via ERK pathway, which suggest hypoxia might be involved in the process of tau pathology.
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Affiliation(s)
- Hui Fang
- Key Laboratory of Brain Function and Diseases, School of Life Science, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, Anhui, China
| | - Li-Feng Zhang
- Key Laboratory of Brain Function and Diseases, School of Life Science, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, Anhui, China
| | - Fan-Tao Meng
- Key Laboratory of Brain Function and Diseases, School of Life Science, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, Anhui, China
| | - Xin Du
- Key Laboratory of Brain Function and Diseases, School of Life Science, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, Anhui, China
| | - Jiang-Ning Zhou
- Key Laboratory of Brain Function and Diseases, School of Life Science, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, Anhui, China.
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181
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Shinoda T, Ito H, Sudo K, Iwamoto I, Morishita R, Nagata KI. Septin 14 is involved in cortical neuronal migration via interaction with Septin 4. Mol Biol Cell 2010; 21:1324-34. [PMID: 20181826 PMCID: PMC2854091 DOI: 10.1091/mbc.e09-10-0869] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Septins are a family of conserved GTP/GDP-binding proteins implicated in a variety of cellular functions. We found that knockdown of Septin 14 or Septin 4 resulted in inhibition of cortical neuronal migration and defective leading process formation. These results suggest a novel function of septin in cortical development. Septins are a family of conserved guanosine triphosphate/guanosine diphosphate-binding proteins implicated in a variety of cellular functions such as cell cycle control and cytokinesis. Although several members of septin family, including Septin 14 (Sept14), are abundantly expressed in nervous tissues, little is known about their physiological functions, especially in neuronal development. Here, we report that Sept14 is strongly expressed in the cortical plate of developing cerebral cortex. Knockdown experiments by using the method of in utero electroporation showed that reduction of Sept14 caused inhibition of cortical neuronal migration. Whereas cDNA encoding RNA interference-resistant Sept14 rescued the migration defect, the C-terminal deletion mutant of Sept14 did not. Biochemical analyses revealed that C-terminal coiled-coil region of Sept14 interacts with Septin 4 (Sept4). Knockdown experiments showed that Sept4 is also involved in cortical neuronal migration in vivo. In addition, knockdown of Sept14 or Sept4 inhibited leading process formation in migrating cortical neurons. These results suggest that Sept14 is involved in neuronal migration in cerebral cortex via interaction with Sept4.
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Affiliation(s)
- Tomoyasu Shinoda
- Department of Molecular Neurobiology, Aichi Human Service Center, Institute for Developmental Research, Kasugai, Aichi 480-0392, Japan
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182
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Nervous-tissue-specific elimination of microtubule-actin crosslinking factor 1a results in multiple developmental defects in the mouse brain. Mol Cell Neurosci 2010; 44:1-14. [PMID: 20170731 DOI: 10.1016/j.mcn.2010.01.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 01/12/2010] [Accepted: 01/29/2010] [Indexed: 12/16/2022] Open
Abstract
The microtubule-actin crosslinking factor 1 (MACF1) is a ubiquitous cytoskeletal linker protein with multiple spliced isoforms expressed in different tissues. The MACF1a isoform contains microtubule and actin-binding regions and is expressed at high levels in the nervous system. Macf1-/- mice are early embryonic lethal and hence the role of MACF1 in the nervous system could not be determined. We have specifically knocked out MACF1a in the developing mouse nervous system using Cre/loxP technology. Mutant mice died within 24-36h after birth of apparent respiratory distress. Their brains displayed a disorganized cerebral cortex with a mixed layer structure, heterotopia in the pyramidal layer of the hippocampus, disorganized thalamocortical and corticofugal fibers, and aplastic anterior and hippocampal commissures. Embryonic neurons showed a defect in traversing the cortical plate. Our data suggest a critical role for MACF1 in neuronal migration that is dependent on its ability to interact with both microfilaments and microtubules.
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183
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Quantitative Analysis of MAP-Mediated Regulation of Microtubule Dynamic Instability In Vitro. Methods Cell Biol 2010; 95:481-503. [DOI: 10.1016/s0091-679x(10)95024-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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184
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Molecular layers underlying cytoskeletal remodelling during cortical development. Trends Neurosci 2010; 33:38-47. [DOI: 10.1016/j.tins.2009.09.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 09/16/2009] [Accepted: 09/28/2009] [Indexed: 11/24/2022]
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185
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Utrera J, Junyent F, de Lemos L, Pallàs M, Camins A, Romero R, Auladell C. Tau hyperphosphorylation and axonal damage induced by N,N-diethyldithiocarbamate (DEDTC) treatment along late postnatal development is followed by a rescue during adulthood. J Neurosci Res 2009; 88:1083-93. [PMID: 19908281 DOI: 10.1002/jnr.22284] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Axonal degeneration has been described as the pathological hallmark of peripheral neuropathies induced by DEDTC. In addition, axonal damage has also been observed in the brain of mice treated daily with DEDTC along postnatal development, though with this experimental model there was observed to be axonal recovery after treatment, during the adulthood. To focus on this axonal dynamic activity, damage-recovery, a key axonal protein, the microtubule associated protein tau, was analyzed in this DEDTC model. Tau is a phosphoprotein and its dynamic site-specific phosphorylation is essential for its proper function; in fact, high levels are correlated with cell dysfunction. Furthermore, the levels of tau phosphorylation are associated with dynamic microtubules during periods of high plasticity. Thus, phosphorylated tau at two sites of phosphorylation, Ser(199) and Ser(396), were evaluated during the second week of postnatal development and throughout adulthood. The results obtained by Western blot made it evident that the levels of p-tau Ser(199) and p-tau Ser(396) were higher in treated mice than in controls. Interestingly, by immunohistochemistry there was shown to be an increase in p-tau-immunolabeling in neuronal soma together with axonal tract alterations in treated animals with respect to controls, and the analyses of GSK3 beta and cdk5 revealed an increase in its activity in DEDTC-treated animals. Nevertheless, in the adult a general decline in p-tau was observed together with a rescue of axonal tract. All these data support the idea that the axonal damage induced by DEDTC treatment along postnatal development is followed by an axonal rescue during adulthood.
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Affiliation(s)
- Juana Utrera
- Departament de Biologia Cellular, Facultat Biologia, Universitat Barcelona, Barcelona, Spain
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186
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Sorting nexin 3, a protein upregulated by lithium, contains a novel phosphatidylinositol-binding sequence and mediates neurite outgrowth in N1E-115 cells. Cell Signal 2009; 21:1586-94. [DOI: 10.1016/j.cellsig.2009.06.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Revised: 06/22/2009] [Accepted: 06/23/2009] [Indexed: 11/19/2022]
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187
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Bisig CG, Chesta ME, Zampar GG, Purro SA, Santander VS, Arce CA. Lack of stabilized microtubules as a result of the absence of major maps in CAD cells does not preclude neurite formation. FEBS J 2009; 276:7110-23. [DOI: 10.1111/j.1742-4658.2009.07422.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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188
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Age-dependent impairment of cognitive and synaptic function in the htau mouse model of tau pathology. J Neurosci 2009; 29:10741-9. [PMID: 19710325 DOI: 10.1523/jneurosci.1065-09.2009] [Citation(s) in RCA: 244] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A hallmark feature of Alzheimer's disease pathology is the presence of neurofibrillary tangles (NFTs), which are intracellular aggregates of conformationally abnormal and hyperphosphorylated tau. The presence of NFTs in the forebrain is associated with impairments of cognitive function, supporting a central role for tau in dementia. The significance of the accumulation of NFTs for neuronal and cognitive function is still obscure. It is possible that NFTs disrupt synaptic transmission and plasticity, leading to memory deficits and cognitive malfunction. To elucidate the relationship between the development of tau pathology and synaptic and cognitive functions, we performed behavioral tests and electrophysiological experiments in the htau mouse. Here we report age-dependent cognitive and physiological impairments in htau mice that preceded neurodegeneration. Twelve-month-old htau mice with moderate tau pathology, but not 4-month-old mice with early-stage tau pathology, presented cognitive deficits in an object recognition memory task in which the visual recognition memory of a novel object was disrupted. Moreover, only 12-month-old htau mice exhibit spatial memory deficits, as indicated by the impaired performance in the Morris water maze. In addition, we report that basal synaptic transmission and induction of long-term potentiation with high-frequency stimulation, but not theta burst stimulation, is perturbed in hippocampal CA1 region of old but not young htau mice. Our results suggest that tau pathology may underlie an age-dependent learning impairment through disruption of synaptic function.
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189
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Golde TE, Petrucelli L, Lewis J. Targeting Abeta and tau in Alzheimer's disease, an early interim report. Exp Neurol 2009; 223:252-66. [PMID: 19716367 DOI: 10.1016/j.expneurol.2009.07.035] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 06/25/2009] [Accepted: 07/23/2009] [Indexed: 12/28/2022]
Abstract
The amyloid beta (Abeta) and tau proteins, which misfold, aggregate, and accumulate in the Alzheimer's disease (AD) brain, are implicated as central factors in a complex neurodegenerative cascade. Studies of mutations that cause early onset AD and promote Abeta accumulation in the brain strongly support the notion that inhibiting Abeta aggregation will prevent AD. Similarly, genetic studies of frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17 MAPT) showing that mutations in the MAPT gene encoding tau lead to abnormal tau accumulation and neurodegeneration. Such genetic studies clearly show that tau dysfunction and aggregation can be central to neurodegeneration, however, most likely in a secondary fashion in relation to AD. Additional pathologic, biochemical, and modeling studies further support the concept that Abeta and tau are prime targets for disease modifying therapies in AD. Treatment strategies aimed at preventing the aggregation and accumulation of Abeta, tau, or both proteins should therefore be theoretically possible, assuming that treatment can be initiated before either irreversible damage is present or downstream, self-sustaining, pathological cascades have been initiated. Herein, we will review recent advances and also potential setbacks with respect to the myriad of therapeutic strategies that are designed to slow down, prevent, or clear the accumulation of either "pathological" Abeta or tau. We will also discuss the need for thoughtful prioritization with respect to clinical development of the preclinically validated modifiers of Abeta and tau pathology. The current number of candidate therapies targeting Abeta is becoming so large that a triage process is clearly needed to insure that resources are invested in a way such that the best candidates for disease modifying therapy are rapidly moved toward clinical trials. Finally, we will discuss the challenges for an appropriate "triage" after potential disease modifying therapies targeting tau and Abeta have entered clinical trials.
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Affiliation(s)
- Todd E Golde
- Department of Neuroscience, College of Medicine, Mayo Clinic, 4500 San Pablo Rd., Jacksonville, FL 32224, USA.
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190
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The microtubule network and neuronal morphogenesis: Dynamic and coordinated orchestration through multiple players. Mol Cell Neurosci 2009; 43:15-32. [PMID: 19660553 DOI: 10.1016/j.mcn.2009.07.012] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2009] [Accepted: 07/27/2009] [Indexed: 11/24/2022] Open
Abstract
Nervous system function and plasticity rely on the complex architecture of neuronal networks elaborated during development, when neurons acquire their specific and complex shape. During neuronal morphogenesis, the formation and outgrowth of functionally and structurally distinct axons and dendrites require a coordinated and dynamic reorganization of the microtubule cytoskeleton involving numerous regulators. While most of these factors act directly on microtubules to stabilize them or promote their assembly, depolymerization or fragmentation, others are now emerging as essential regulators of neuronal differentiation by controlling tubulin availability and modulating microtubule dynamics. In this review, we recapitulate how the microtubule network is actively regulated during the successive phases of neuronal morphogenesis, and what are the specific roles of the various microtubule-regulating proteins in that process. We then describe the specific signaling pathways and inter-regulations that coordinate the different activities of these proteins to sustain neuronal development in response to environmental cues.
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191
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Bullmann T, Holzer M, Mori H, Arendt T. Pattern of tau isoforms expression during development
in vivo. Int J Dev Neurosci 2009; 27:591-7. [DOI: 10.1016/j.ijdevneu.2009.06.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 05/19/2009] [Accepted: 06/09/2009] [Indexed: 01/18/2023] Open
Affiliation(s)
- Torsten Bullmann
- Paul Flechsig Institute of Brain ResearchDepartment of Cellular and Molecular Mechanisms of NeurodegenerationUniversity of LeipzigJahnallee 5904019LeipzigGermany
| | - Max Holzer
- Paul Flechsig Institute of Brain ResearchDepartment of Cellular and Molecular Mechanisms of NeurodegenerationUniversity of LeipzigJahnallee 5904019LeipzigGermany
| | - Hiroshi Mori
- Department of NeuroscienceGraduate School of MedicineOsaka City University1‐4‐3 AsahimachiAbenoku545‐8585OsakaJapan
| | - Thomas Arendt
- Paul Flechsig Institute of Brain ResearchDepartment of Cellular and Molecular Mechanisms of NeurodegenerationUniversity of LeipzigJahnallee 5904019LeipzigGermany
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192
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Vogelaar CF, Gervasi NM, Gumy LF, Story DJ, Raha-Chowdhury R, Leung KM, Holt CE, Fawcett JW. Axonal mRNAs: characterisation and role in the growth and regeneration of dorsal root ganglion axons and growth cones. Mol Cell Neurosci 2009; 42:102-115. [PMID: 19520167 DOI: 10.1016/j.mcn.2009.06.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 05/23/2009] [Accepted: 06/02/2009] [Indexed: 01/30/2023] Open
Abstract
We have developed a compartmentalised culture model for the purification of axonal mRNA from embryonic, neonatal and adult rat dorsal root ganglia. This mRNA was used un-amplified for RT-qPCR. We assayed for the presence of axonal mRNAs encoding molecules known to be involved in axon growth and guidance. mRNAs for beta-actin, beta-tubulin, and several molecules involved in the control of actin dynamics and signalling during axon growth were found, but mRNAs for microtubule-associated proteins, integrins and cell surface adhesion molecules were absent. Quantification of beta-actin mRNA by means of qPCR showed that the transcript is present at the same level in embryonic, newborn and adult axons. Using the photoconvertible reporter Kaede we showed that there is local translation of beta-actin in axons, the rate being increased by axotomy. Knock down of beta-actin mRNA by RNAi inhibited the regeneration of new axon growth cones after in vitro axotomy, indicating that local translation of actin-related molecules is important for successful axon regeneration.
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MESH Headings
- Actins/genetics
- Animals
- Animals, Newborn
- Axons/physiology
- Axotomy
- Cytoskeleton/metabolism
- Embryo, Mammalian/cytology
- Embryo, Mammalian/physiology
- Ganglia, Spinal/cytology
- Ganglia, Spinal/physiology
- Growth Cones/physiology
- Nerve Regeneration/physiology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Rats
- Receptors, Cell Surface/genetics
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Signal Transduction/genetics
- Tissue Culture Techniques
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Affiliation(s)
- Christina F Vogelaar
- Cambridge University Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Robinson Way, Cambridge CB2 0PY, UK
| | - Noreen M Gervasi
- Cambridge University Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Robinson Way, Cambridge CB2 0PY, UK
| | - Laura F Gumy
- Cambridge University Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Robinson Way, Cambridge CB2 0PY, UK
| | - David J Story
- Cambridge University Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Robinson Way, Cambridge CB2 0PY, UK
| | - Ruma Raha-Chowdhury
- Cambridge University Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Robinson Way, Cambridge CB2 0PY, UK
| | - Kin-Mei Leung
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Christine E Holt
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - James W Fawcett
- Cambridge University Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Robinson Way, Cambridge CB2 0PY, UK
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193
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Microtubule assembly, organization and dynamics in axons and dendrites. Nat Rev Neurosci 2009; 10:319-32. [PMID: 19377501 DOI: 10.1038/nrn2631] [Citation(s) in RCA: 762] [Impact Index Per Article: 50.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During the past decade enormous advances have been made in our understanding of the basic molecular machinery that is involved in the development of neuronal polarity. Far from being mere structural elements, microtubules are emerging as key determinants of neuronal polarity. Here we review the current understanding of the regulation of microtubule assembly, organization and dynamics in axons and dendrites. These studies provide new insight into microtubules' function in neuronal development and their potential contribution to plasticity.
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194
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Reiner O, Shmueli A, Sapir T. Neuronal migration and neurodegeneration: 2 sides of the same coin. Cereb Cortex 2009; 19 Suppl 1:i42-8. [PMID: 19346270 DOI: 10.1093/cercor/bhp039] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The human genome contains only about double the number of genes in comparison to the fruit fly. This necessitates efficient recurrent usage of the same molecular components to participate in different processes. When the same proteins are used for different signaling pathways, it may be conceivable that if they go awry the phenotypic consequences may vary to a great extent. The involvement of amyloid beta precursor protein, Presenilin-1, and Tau in the pathogenesis of Alzheimer's disease is well established. Here we are highlighting a second facet of their function, their participation in developmental and adult neuronal migration. We propose that the prevalent and early Anosmia found in Alzheimer's patients may be due in part to malfunctioning of the above-mentioned proteins.
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Affiliation(s)
- Orly Reiner
- Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, Israel
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195
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Reiner O, Sapir T. Polarity regulation in migrating neurons in the cortex. Mol Neurobiol 2009; 40:1-14. [PMID: 19330467 DOI: 10.1007/s12035-009-8065-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Accepted: 03/12/2009] [Indexed: 12/25/2022]
Abstract
The formation of the cerebral cortex requires migration of billions of cells from their birth position to their final destination. A motile cell must have internal polarity in order to move in a specified direction. Locomotory polarity requires the coordinated polymerization of cytoskeletal elements such as microtubules and actin combined with regulated activities of the associated molecular motors. This review is focused on migrating neurons in the developing cerebral cortex, which need to attain internal polarity in order to reach their proper target. The position and dynamics of the centrosome plays an important function in this directed motility. We highlight recent interesting findings connecting polarity proteins with neuronal migration events regulated by the microtubule-associated molecular motor, cytoplasmic dynein.
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Affiliation(s)
- Orly Reiner
- Department of Molecular Genetics, The Weizmann Institute of Science, 76100 Rehovot, Israel.
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196
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Gorlovoy P, Larionov S, Pham TTH, Neumann H. Accumulation of tau induced in neurites by microglial proinflammatory mediators. FASEB J 2009; 23:2502-13. [DOI: 10.1096/fj.08-123877] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Philipp Gorlovoy
- Neural Regeneration UnitInstitute of Reconstructive NeurobiologyUniversity Bonn and Hertie‐FoundationBonnGermany
| | - Sergey Larionov
- Neural Regeneration UnitInstitute of Reconstructive NeurobiologyUniversity Bonn and Hertie‐FoundationBonnGermany
| | - Thao Thi Hien Pham
- Neural Regeneration UnitInstitute of Reconstructive NeurobiologyUniversity Bonn and Hertie‐FoundationBonnGermany
| | - Harald Neumann
- Neural Regeneration UnitInstitute of Reconstructive NeurobiologyUniversity Bonn and Hertie‐FoundationBonnGermany
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Gendron TF, Petrucelli L. The role of tau in neurodegeneration. Mol Neurodegener 2009; 4:13. [PMID: 19284597 PMCID: PMC2663562 DOI: 10.1186/1750-1326-4-13] [Citation(s) in RCA: 312] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Accepted: 03/11/2009] [Indexed: 01/31/2023] Open
Abstract
Since the identification of tau as the main component of neurofibrillary tangles in Alzheimer's disease and related tauopathies, and the discovery that mutations in the tau gene cause frontotemporal dementia, much effort has been directed towards determining how the aggregation of tau into fibrillar inclusions causes neuronal death. As evidence emerges that tau-mediated neuronal death can occur even in the absence of tangle formation, a growing number of studies are focusing on understanding how abnormalities in tau (e.g. aberrant phosphorylation, glycosylation or truncation) confer toxicity. Though data obtained from experimental models of tauopathies strongly support the involvement of pathologically modified tau and tau aggregates in neurodegeneration, the exact neurotoxic species remain unclear, as do the mechanism(s) by which they cause neuronal death. Nonetheless, it is believed that tau-mediated neurodegeneration is likely to result from a combination of toxic gains of function as well as from the loss of normal tau function. To truly appreciate the detrimental consequences of aberrant tau function, a better understanding of all functions carried out by tau, including but not limited to the role of tau in microtubule assembly and stabilization, is required. This review will summarize what is currently known regarding the involvement of tau in the initiation and development of neurodegeneration in tauopathies, and will also highlight some of the remaining questions in need of further investigation.
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Affiliation(s)
- Tania F Gendron
- Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, Florida, USA.
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198
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Denk F, Wade-Martins R. Knock-out and transgenic mouse models of tauopathies. Neurobiol Aging 2009; 30:1-13. [PMID: 17590238 PMCID: PMC2806682 DOI: 10.1016/j.neurobiolaging.2007.05.010] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 05/04/2007] [Accepted: 05/11/2007] [Indexed: 12/26/2022]
Abstract
Tauopathies, characterized by the dysfunction and aggregation of the microtubule-associated protein tau (MAPT), represent some of the most devastating neurodegenerative disorders afflicting the elderly, including Alzheimer's disease and progressive supranuclear palsy. Here we review the range of Mapt knock-out and MAPT transgenic mouse models which have proven successful at providing insights into the molecular mechanisms of neurodegenerative disease. In this overview we highlight several themes, including the insights such models provide into the cellular and molecular mechanisms of tauopathy, the direct relationship between neuropathology and behaviour, and the use of mouse models to help provide a platform for testing novel therapies. Mouse models have helped clarify the relationship between pathological forms of tau, cell death, and the emergence of disease, as well as the interaction between tau and other disease-associated molecules, such as the A beta peptide. Finally, we discuss potential future MAPT genomic DNA models to investigate the importance of alternative splicing of the MAPT locus and its role in sporadic tauopathies.
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Affiliation(s)
- Franziska Denk
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom.
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199
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Allen J, Chilton JK. The specific targeting of guidance receptors within neurons: who directs the directors? Dev Biol 2008; 327:4-11. [PMID: 19121301 DOI: 10.1016/j.ydbio.2008.12.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 11/27/2008] [Accepted: 12/09/2008] [Indexed: 02/04/2023]
Abstract
Guidance molecules present in both axonal and dendritic growth cones mediate neuronal responses to extracellular cues thereby ensuring correct neurite pathfinding and development of the nervous system. Little is known though about the mechanisms employed by neurons to deliver these receptors, specifically and efficiently, to the extending growth cone. A deeper understanding of this process is crucial if guidance receptors are to be manipulated to promote nervous system repair. Studies in other polarised cells, notably epithelial, have elucidated fundamental routes to the intracellular segregation of molecules mediated by endosomal pathways. Due to their extreme complexity and specialisation, neurons appear to have built upon these generic systems to evolve sophisticated trafficking networks. A striking feature is the axon initial segment which acts like a valve to tightly regulate the flux of molecules both entering and leaving the axon. Once in the growth cone, further controls operate to enhance the retention or rejection, as appropriate, of membrane receptors. We discuss the current state of knowledge regarding the intracellular trafficking of axon guidance receptors and how this relates to their developmental roles. We highlight the various facets still to be properly elucidated and by building on existing data regarding neuronal polarity and intracellular sorting mechanisms suggest ways to fill these gaps.
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Affiliation(s)
- James Allen
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Research Way, Plymouth PL6 8BU, UK
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200
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Molecular Mechanisms of Axonal Growth. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 621:1-16. [DOI: 10.1007/978-0-387-76715-4_1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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