title: Extracellular signal-regulated kinase 1/2 mediates survival, but not axon regeneration, of adult injured central nervous system neurons in vivo.
abstract: Neurotrophins play important roles in the response of adult neurons to injury. The intracellular signaling mechanisms used by neurotrophins to regulate survival and axon growth in the mature CNS in vivo are not well understood. The goal of this study was to define the role of the extracellular signal-regulated kinases 1/2 (Erk1/2) pathway in the survival and axon regeneration of adult rat retinal ganglion cells (RGCs), a prototypical central neuron population. We used recombinant adeno-associated virus (AAV) to selectively transduce RGCs with genes encoding constitutively active or wild-type mitogen-activated protein kinase kinase 1 (MEK1), the upstream activator of Erk1/2. In combination with anterograde and retrograde tracing techniques, we monitored neuronal survival and axon regeneration in vivo. MEK1 gene delivery led to robust and selective transgene expression in multiple RGC compartments including cell bodies, dendrites, axons and targets in the brain. Furthermore, MEK1 activation induced in vivo phosphorylation of Erk1/2 in RGC bodies and axons. Quantitative analysis of cell survival demonstrated that Erk1/2 activation promoted robust RGC neuroprotection after optic nerve injury. In contrast, stimulation of the Erk1/2 pathway was not sufficient to induce RGC axon growth beyond the lesion site. We conclude that the Erk1/2 pathway plays a key role in the survival of axotomized mammalian RGCs in vivo, and that activation of other signaling components is required for axon regeneration in the growth inhibitory CNS environment.
authors.affiliation: Department of Pathology and Cell Biology, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Pernet
authors.forename: William W
authors.initials: WW
authors.lastname: Hauswirth
authors.forename: Adriana
authors.initials: A
authors.lastname: Di Polo
mesh_terms: D000818:Animals; D019771:Axotomy / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000378:metabolism / Q000821:virology; D002452:Cell Count / Q000379:methods; D002470:Cell Survival / Q000502:physiology; D002490:Central Nervous System / Q000166:cytology*; D002772:Cholera Toxin / Q000378:metabolism; D000229:Dependovirus / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000008:administration & dosage; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006388:Hemagglutinins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology*; D009474:Neurons / Q000502:physiology* / Q000821:virology; D009900:Optic Nerve / Q000378:metabolism / Q000821:virology; D020221:Optic Nerve Injuries / Q000378:metabolism / Q000503:physiopathology* / Q000821:virology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism / Q000821:virology; D012165:Retinal Ganglion Cells / Q000502:physiology / Q000821:virology; D013266:Stilbamidines / Q000378:metabolism; D013997:Time Factors
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D006388:Hemagglutinins; D013266:Stilbamidines; D049452:Green Fluorescent Proteins; D002772:Cholera Toxin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3