51
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Tisi MA, Xie Y, Yeo TT, Longo FM. Downregulation of LAR tyrosine phosphatase prevents apoptosis and augments NGF-induced neurite outgrowth. ACTA ACUST UNITED AC 2000. [DOI: 10.1002/(sici)1097-4695(200003)42:4<477::aid-neu8>3.0.co;2-b] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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52
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Sun Q, Bahri S, Schmid A, Chia W, Zinn K. Receptor tyrosine phosphatases regulate axon guidance across the midline of the Drosophila embryo. Development 2000; 127:801-12. [PMID: 10648238 DOI: 10.1242/dev.127.4.801] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neural receptor-linked protein tyrosine phosphatases (RPTPs) are required for guidance of motoneuron and photoreceptor growth cones in Drosophila. These phosphatases have not been implicated in growth cone responses to specific guidance cues, however, so it is unknown which aspects of axonal pathfinding are controlled by their activities. Three RPTPs, known as DLAR, DPTP69D, and DPTP99A, have been genetically characterized thus far. Here we report the isolation of mutations in the fourth neural RPTP, DPTP10D. The analysis of double mutant phenotypes shows that DPTP10D and DPTP69D are necessary for repulsion of growth cones from the midline of the embryonic central nervous system. Repulsion is thought to be triggered by binding of the secreted protein Slit, which is expressed by midline glia, to Roundabout (Robo) receptors on growth cones. Robo repulsion is downregulated by the Commissureless (Comm) protein, allowing axons to cross the midline. Here we show that the Rptp mutations genetically interact with robo, slit and comm. The nature of these interactions suggests that DPTP10D and DPTP69D are positive regulators of Slit/Roundabout repulsive signaling. We also show that elimination of all four neural RPTPs converts most noncrossing longitudinal pathways into commissures that cross the midline, indicating that tyrosine phosphorylation controls the manner in which growth cones respond to midline signals.
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Affiliation(s)
- Q Sun
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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53
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54
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55
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Van Den Maagdenberg AM, Bächner D, Schepens JT, Peters W, Fransen JA, Wieringa B, Hendriks WJ. The mouse Ptprr gene encodes two protein tyrosine phosphatases, PTP-SL and PTPBR7, that display distinct patterns of expression during neural development. Eur J Neurosci 1999; 11:3832-44. [PMID: 10583472 DOI: 10.1046/j.1460-9568.1999.00802.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The protein tyrosine phosphatases PTP-SL and PTPBR7 differ only in the length of their N-terminal domain. We show here that PTP-SL and PTPBR7 are isoforms derived from a single gene (Ptprr) through developmentally regulated use of alternative promoters. Isoform-specific reverse transcriptase-polymer chain reaction (RT-PCR) and RNA in situ hybridization experiments reveal that PTPBR7 is expressed during early embryogenesis in spinal ganglia cells as well as in developing Purkinje cells. Post-natally, PTPBR7 is expressed in various regions of the adult mouse brain, but expression in Purkinje cells has ceased and is replaced by the PTP-SL-specific transcript. In transient transfection experiments it is confirmed that PTPBR7 is a type I transmembrane protein tyrosine phosphatase (PTPase). PTP-SL, however, appears to be a cytosolic membrane-associated PTPase that is located at perinuclear vesicular structures that partly belong to the endosomal compartment. Thus, during maturation of Purkinje cells, a gene-promoter switch results in the replacement of a receptor-type PTPase by a cytosolic vesicle-associated isoform.
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Affiliation(s)
- A M Van Den Maagdenberg
- Department of Cell Biology, Institute of Ceullular Signalling, University of Nijmegen, The Netherlands
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56
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Ledig MM, Haj F, Bixby JL, Stoker AW, Mueller BK. The receptor tyrosine phosphatase CRYPalpha promotes intraretinal axon growth. J Cell Biol 1999; 147:375-88. [PMID: 10525542 PMCID: PMC2174224 DOI: 10.1083/jcb.147.2.375] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/1999] [Accepted: 09/01/1999] [Indexed: 01/06/2023] Open
Abstract
Retinal ganglion cell axons grow towards the optic fissure in close contact with the basal membrane, an excellent growth substratum. One of the ligands of receptor tyrosine phosphatase CRYPalpha is located on the retinal and tectal basal membranes. To analyze the role of this RPTP and its ligand in intraretinal growth and guidance of ganglion cell axons, we disrupted ligand- receptor interactions on the retinal basal membrane in culture. Antibodies against CRYPalpha strongly reduced retinal axon growth on the basal membrane, and induced a dramatic change in morphology of retinal growth cones, reducing the size of growth cone lamellipodia. A similar effect was observed by blocking the ligand with a CRYPalpha ectodomain fusion protein. These effects did not occur, or were much reduced, when axons were grown either on laminin-1, on matrigel or on basal membranes with glial endfeet removed. This indicates that a ligand for CRYPalpha is located on glial endfeet. These results show for the first time in vertebrates that the interaction of a receptor tyrosine phosphatase with its ligand is crucial not only for promotion of retinal axon growth but also for maintenance of retinal growth cone lamellipodia on basal membranes.
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Affiliation(s)
- Matthias M. Ledig
- Max-Planck-Institut für Entwicklungsbiologie, Physikalische Biologie, D-72076 Tübingen, Germany
| | - Fawaz Haj
- Institute of Child Health, Neural Development Unit, University College London, London WC1N 1EH, United Kingdom
| | - John L. Bixby
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami School of Medicine, Miami, Florida 33101
| | - Andrew W. Stoker
- Institute of Child Health, Neural Development Unit, University College London, London WC1N 1EH, United Kingdom
| | - Bernhard K. Mueller
- Max-Planck-Institut für Entwicklungsbiologie, Physikalische Biologie, D-72076 Tübingen, Germany
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57
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Abstract
Analysis of axon guidance mechanisms in vertebrates, Caenorhabditis elegans, and Drosophila melanogaster has led to the identification of several signaling pathways, many of which are strikingly conserved in function. Recent studies indicate that several axon guidance mechanisms are highly conserved in all animals, whereas others, though still conserved in a general sense, show strong evolutionary divergence at a detailed mechanistic level.
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Affiliation(s)
- A Chisholm
- Sinsheimer Laboratories Department of Biology University of California Santa Cruz, California 96054, USA.
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58
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Wang J, Bixby JL. Receptor tyrosine phosphatase-delta is a homophilic, neurite-promoting cell adhesion molecular for CNS neurons. Mol Cell Neurosci 1999; 14:370-84. [PMID: 10588391 DOI: 10.1006/mcne.1999.0789] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Appropriate regulation of tyrosine phosphorylation is essential for axon growth and guidance; evidence from invertebrates indicates that receptor-type tyrosine phosphatases (RPTPs) are required for correct axon growth during CNS development. One vertebrate RPTP, PTP-delta, is highly expressed in brain and has a cell adhesion molecule-like extracellular domain (ECD) comprising three immunoglobulin repeats and eight fibronectin type III repeats. Using fluorescent beads (Covaspheres) coated with the PTP-delta ECD, as well as insect cells expressing PTP-delta on their surfaces, we show that PTP-delta is a homophilic cell adhesion molecule. A variety of chick neurons adhere strongly to an Fc fusion protein containing the PTP-delta ECD. Additionally, substrate-bound PTP-delta ECD fusion protein strongly promotes neurite outgrowth from forebrain neurons; this effect is separable from its effect on adhesion. Our results indicate that PTP-delta is a neurite-promoting cell adhesion molecule for CNS neurons.
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MESH Headings
- Animals
- Baculoviridae/genetics
- CHO Cells
- Catalytic Domain
- Cell Adhesion/physiology
- Cell Adhesion Molecules, Neuronal/chemistry
- Cell Adhesion Molecules, Neuronal/genetics
- Cell Adhesion Molecules, Neuronal/metabolism
- Chick Embryo
- Cloning, Molecular
- Cricetinae
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Enzymologic
- Humans
- Molecular Sequence Data
- Neurites/enzymology
- Neurons/cytology
- Neurons/enzymology
- Neurons/ultrastructure
- Prosencephalon/cytology
- Protein Binding/physiology
- Protein Structure, Tertiary
- Protein Tyrosine Phosphatases/chemistry
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/metabolism
- RNA, Messenger/analysis
- Receptor-Like Protein Tyrosine Phosphatases, Class 2
- Recombinant Fusion Proteins/genetics
- Sequence Homology, Amino Acid
- Transfection
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Affiliation(s)
- J Wang
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Florida 33101, USA
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59
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Haj F, McKinnell I, Stoker A. Retinotectal ligands for the receptor tyrosine phosphatase CRYPalpha. Mol Cell Neurosci 1999; 14:225-40. [PMID: 10493824 DOI: 10.1006/mcne.1999.0785] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The cell adhesion molecule-like tyrosine phosphatase CRYPalpha is localized on retinal axons and their growth cones. We present evidence that two isoforms of this type IIa phosphatase, CRYPalpha1 and CRYPalpha2, have extracellular ligands along the developing retinotectal pathway. Using alkaline phosphatase fusion proteins containing the CRYPalpha1 ectodomain, we detect a prominent ligand on basement membranes of the early retina, optic stalk, and chiasm. A second ligand is observed in the endfeet region of radial processes in the developing stratum opticum, the site of initial retinal axon invasion. This latter ligand binds CRYPalpha2 preferentially. Further ligand interactions are detected for both CRYPalpha protein isoforms in retinorecipient tectal laminae and on retinal fibers themselves. CRYPalpha thus has cell- and matrix-associated ligands along the entire retinotectal projection. Moreover, these ligands appear to be heterotypic and interact with CRYPalpha through both its immunoglobulin and fibronectin type III regions. The anteroposterior levels of the ligands are relatively uniform within the retina and tectum, suggesting that the CRYPalpha protein within retinal axons does not directly recognise topographically graded guidance cues. We propose that CRYPalpha may have a permissive role in promoting retinal axon growth across the eye and tectum and that its functions are modulated temporally and spatially by isoform-specific interactions with cell- and matrix-associated ligands.
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Affiliation(s)
- F Haj
- Institute of Child Health, University College London, 30 Guilford Street, London, WC1N 1EH, United Kingdom
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60
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Abstract
One of the most important mechanisms of eukaryotic signalling is protein phosphorylation on tyrosine residues, which plays a pivotal role in development by regulating cell proliferation, differentiation and migration. Cellular phosphotyrosine (P.Tyr) levels are regulated by the antagonistic activities of the protein-tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs). We have good insight into the function of PTKs at the molecular level and into the role of PTK-mediated signalling in development. Intuitively, PTPs and PTKs are equally important in development. Over the past decade, much emphasis has been placed on elucidation of the function of PTPs, which has led to good insights into the mechanism of PTP-mediated dephosphorylation. Although still relatively little is known about the role of PTPs in cell signalling and development, evidence is now emerging that several PTPs are crucial for proper development. Here I will introduce PTP-mediated signalling and discuss recent findings regarding the function of PTPs in development.
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Affiliation(s)
- J den Hertog
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands.
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61
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The supporting-cell antigen: a receptor-like protein tyrosine phosphatase expressed in the sensory epithelia of the avian inner ear. J Neurosci 1999. [PMID: 10366616 DOI: 10.1523/jneurosci.19-12-04815.1999] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
After noise- or drug-induced hair-cell loss, the sensory epithelia of the avian inner ear can regenerate new hair cells. Few molecular markers are available for the supporting-cell precursors of the hair cells that regenerate, and little is known about the signaling mechanisms underlying this regenerative response. Hybridoma methodology was used to obtain a monoclonal antibody (mAb) that stains the apical surface of supporting cells in the sensory epithelia of the inner ear. The mAb recognizes the supporting-cell antigen (SCA), a protein that is also found on the apical surfaces of retinal Müller cells, renal tubule cells, and intestinal brush border cells. Expression screening and molecular cloning reveal that the SCA is a novel receptor-like protein tyrosine phosphatase (RPTP), sharing similarity with human density-enhanced phosphatase, an RPTP thought to have a role in the density-dependent arrest of cell growth. In response to hair-cell damage induced by noise in vivo or hair-cell loss caused by ototoxic drug treatment in vitro, some supporting cells show a dramatic decrease in SCA expression levels on their apical surface. This decrease occurs before supporting cells are known to first enter S-phase after trauma, indicating that it may be a primary rather than a secondary response to injury. These results indicate that the SCA is a signaling molecule that may influence the potential of nonsensory supporting cells to either proliferate or differentiate into hair cells.
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62
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Qiu L, Kelso MJ, Hansen C, West ML, Fairlie DP, Parsons PG. Anti-tumour activity in vitro and in vivo of selective differentiating agents containing hydroxamate. Br J Cancer 1999; 80:1252-8. [PMID: 10376979 PMCID: PMC2362353 DOI: 10.1038/sj.bjc.6690493] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A series of hydroxamates, which are not metalloprotease inhibitors, have been found to be selectively toxic to a range of transformed and human tumour cells without killing normal cells (fibroblasts, melanocytes) at the same concentrations. Within 24 h of treatment, drug action is characterized by morphological reversion of tumour cells to a more normal phenotype (dendritic morphology), and rapid and reversible acetylation of histone H4 in both tumour and normal cells. Two hydroxamates inhibited growth of xenografts of human melanoma cells in nude mice; resistance did not develop in vivo or in vitro. A third hydroxamate, trichostatin A, was active in vitro but became inactivated and had no anti-tumour activity in vivo. Development of dendritic morphology was found to be dependent upon phosphatase activity, RNA and protein synthesis. Proliferating hybrid clones of sensitive and resistant cells remained sensitive to ABHA, indicating a dominant-negative mechanism of sensitivity. Histone H4 hyperacetylation suggests that these agents act at the chromatin level. This work may lead to new drugs that are potent, and selective anti-tumour agents with low toxicity to normal cells.
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Affiliation(s)
- L Qiu
- Queensland Cancer Fund Laboratories, Queensland Institute of Medical Research, Herston, Australia
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63
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Drosopoulos NE, Walsh FS, Doherty P. A soluble version of the receptor-like protein tyrosine phosphatase kappa stimulates neurite outgrowth via a Grb2/MEK1-dependent signaling cascade. Mol Cell Neurosci 1999; 13:441-9. [PMID: 10383829 DOI: 10.1006/mcne.1999.0758] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Receptor-like protein tyrosine phosphatase kappa (RPTPkappa) is expressed in the nervous system in a manner consistent with a role in axonal growth and guidance. The extracellular domain of RPTPkappa shares structural features with cell adhesion molecules and can support homophilic adhesion. In the present study we produced a soluble Fc-chimeric protein containing the full extracellular domain of RPTPkappa. Following affinity capture, the RPTPkappa-Fc was shown to promote the aggregation of Covasphere beads, confirming its homophilic binding activity. When added to cultures of cerebellar neurons as a soluble molecule, the RPTPkappa chimera stimulated neurite outgrowth. The neurite outgrowth response was substantially inhibited by a cell-permeable peptide inhibitor of Grb2 and by PD 098059, a drug that has been used to inhibit MEK1 activation in a wide range of cell types. These results demonstrate that RPTPkappa can stimulate neurite outgrowth and provide evidence that this might involve the coupling of Grb2 to a MAPK signal transduction cascade.
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Affiliation(s)
- N E Drosopoulos
- Molecular Neurobiology Group, Guy's, King's and St Thomas's School of Medicine, Kings College London, Fourth Floor Hodgkin Building, Guy's Campus, London, SE1 9RT, United Kingdom
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64
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Wills Z, Bateman J, Korey CA, Comer A, Van Vactor D. The tyrosine kinase Abl and its substrate enabled collaborate with the receptor phosphatase Dlar to control motor axon guidance. Neuron 1999; 22:301-12. [PMID: 10069336 DOI: 10.1016/s0896-6273(00)81091-0] [Citation(s) in RCA: 256] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Genetic analysis of growth cone guidance choice points in Drosophila identified neuronal receptor protein tyrosine phosphatases (RPTPs) as key determinants of axon pathfinding behavior. We now demonstrate that the Drosophila Abl tyrosine kinase functions in the intersegmental nerve b (ISNb) motor choice point pathway as an antagonist of the RPTP Dlar. The function of Abl in this pathway is dependent on an intact catalytic domain. We also show that the Abl phosphoprotein substrate Enabled (Ena) is required for choice point navigation. Both Abl and Ena proteins associate with the Dlar cytoplasmic domain and serve as substrates for Dlar in vitro, suggesting that they play a direct role in the Dlar pathway. These data suggest that Dlar, Abl, and Ena define a phosphorylation state-dependent switch that controls growth cone behavior by transmitting signals at the cell surface to the actin cytoskeleton.
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Affiliation(s)
- Z Wills
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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65
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Haworth K, Shu KK, Stokes A, Morris R, Stoker A. The expression of receptor tyrosine phosphatases is responsive to sciatic nerve crush. Mol Cell Neurosci 1998; 12:93-104. [PMID: 9790732 DOI: 10.1006/mcne.1998.0707] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Given the importance of phosphotyrosine signaling in growth cone dynamics, we have examined the embryonic and adult expression of receptor-like protein tyrosine phosphatases in sensory neurons and studied their responsiveness to nerve lesions in young adult animals. The phosphatases LAR, PTPsigma, and PTPalpha are expressed in most neurons of E14 and E18 rat embryo dorsal root ganglia, while BEM-1 is expressed in a more restricted subset of these neurons. These phosphatases continue to be expressed in young adult animals, suggesting that they have roles in mature as well as in developing dorsal root ganglia neurons. After an experimental sciatic nerve crush, the expression of the phosphatase genes was significantly and differentially altered in these neurons. PTPsigma mRNA was increased by 50% after 3 days, while LAR and PTPalpha expression dropped by 50 and 20%, respectively. BEM-1 mRNA levels were unaltered. These data show that mRNA levels of specific tyrosine phosphatase genes are highly responsive to nerve damage and may be reset to a new and potentially optimal pattern of expression more conducive for nerve regeneration. We propose that tyrosine phosphatases are not only involved in primary axonogenesis but can also now be implicated in the molecular control of adult nerve repair.
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Affiliation(s)
- K Haworth
- Department of Human Anatomy, University of Oxford, Oxford, OX1 3QX, UK
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