Corticospinal neurons exhibit a novel pattern of cytoskeletal gene expression after injury

Corticospinal neurons exhibit a novel pattern of cytoskeletal gene expression after injury We examined changes in the expression of major cytoskeletal protein mRNAs in adult hamster corticospinal neurons after axotomy. While a number of studies had determined that peripheral neurons exhibit major alterations in cytoskeletal gene expression after axotomy, no previous studies had addressed the question of whether or not intrinsic mammalian CNS neurons, which do not have the ability to successfully regenerate axons after injury, alter their expression of tubulin and neurofilament genes after injury. In the present study we used in situ hybridization methods to examine this issue. 35S‐labeled cDNA probe for the low molecular weight neurofilament protein (NF‐L) mRNA and an α‐tubulin mRNA species (Mα1) were used for in situ hybridizations of sections of the sensorimotor cortex obtained 2, 7, and 14 days after unilateral axotomy of the corticospinal tract in the caudal medulla. Film as well as emulsion autoradiography showed dramatic decreases in both α‐tubulin and NF‐L mRNA levels within axotomized neurons in layer Vb of the sensorimotor cortex. Tubulin mRNA levels were decreased as early as 2 days after injury whereas NF‐L mRNA levels were not decreased until later times. Ribosomal RNA (rRNA) levels in axotomized corticospinal neurons were also examined using in situ hybridization with a 35S‐labeled rDNA probe. These studies showed only a slight decrease in rRNA levels in corticospinal neurons at 14 days after axotomy. Immunoblotting experiments of total protein from corticospinal axons in the medulla were performed to assess whether the axonal composition immediately proximal to the injury site reflected changes in cell body gene expression. Both α‐tubulin and NF‐L levels were found to decrease in corticospinal axons by 28 days after injury. These findings, to our knowledge, are the first to demonstrate that a class of mammalian CNS neurons have an intrinsically different cytoskeletal response to axonal injury than do PNS neurons. The failure to up‐regulate tubulin gene expression following injury may contribute to the ineffective regenerative response of these long‐tract CNS neurons. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neuroscience Research Wiley

Corticospinal neurons exhibit a novel pattern of cytoskeletal gene expression after injury

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Publisher
Wiley
Copyright
Copyright © 1991 Wiley‐Liss, Inc.
ISSN
0360-4012
eISSN
1097-4547
D.O.I.
10.1002/jnr.490300122
Publisher site
See Article on Publisher Site

Abstract

We examined changes in the expression of major cytoskeletal protein mRNAs in adult hamster corticospinal neurons after axotomy. While a number of studies had determined that peripheral neurons exhibit major alterations in cytoskeletal gene expression after axotomy, no previous studies had addressed the question of whether or not intrinsic mammalian CNS neurons, which do not have the ability to successfully regenerate axons after injury, alter their expression of tubulin and neurofilament genes after injury. In the present study we used in situ hybridization methods to examine this issue. 35S‐labeled cDNA probe for the low molecular weight neurofilament protein (NF‐L) mRNA and an α‐tubulin mRNA species (Mα1) were used for in situ hybridizations of sections of the sensorimotor cortex obtained 2, 7, and 14 days after unilateral axotomy of the corticospinal tract in the caudal medulla. Film as well as emulsion autoradiography showed dramatic decreases in both α‐tubulin and NF‐L mRNA levels within axotomized neurons in layer Vb of the sensorimotor cortex. Tubulin mRNA levels were decreased as early as 2 days after injury whereas NF‐L mRNA levels were not decreased until later times. Ribosomal RNA (rRNA) levels in axotomized corticospinal neurons were also examined using in situ hybridization with a 35S‐labeled rDNA probe. These studies showed only a slight decrease in rRNA levels in corticospinal neurons at 14 days after axotomy. Immunoblotting experiments of total protein from corticospinal axons in the medulla were performed to assess whether the axonal composition immediately proximal to the injury site reflected changes in cell body gene expression. Both α‐tubulin and NF‐L levels were found to decrease in corticospinal axons by 28 days after injury. These findings, to our knowledge, are the first to demonstrate that a class of mammalian CNS neurons have an intrinsically different cytoskeletal response to axonal injury than do PNS neurons. The failure to up‐regulate tubulin gene expression following injury may contribute to the ineffective regenerative response of these long‐tract CNS neurons.

Journal

Journal of Neuroscience ResearchWiley

Published: Sep 1, 1991

References

  • Slow components of axonal transport: Two cytoskeletal networks
    Black, Black; Lasek, Lasek
  • The multitubulin hypothesis revisited: What have we learned?
    Cleveland, Cleveland
  • Changes in glial fibrillary acidic protein mRNA expression after corticospinal axotomy in the adult hamster
    Kost‐Mikucki, Kost‐Mikucki; Oblinger, Oblinger
  • Five mouse tubulin isotypes and their regulated expression during development
    Lewis, Lewis; Lee, Lee; Cowan, Cowan
  • Microtubule‐associated proteins: Their potential role in determining neuronal morphology
    Matus, Matus
  • Differential regulation of peripherin and neurofilament gene expression in regenerating rat DRG neurons
    Wong, Wong; Oblinger, Oblinger

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