In vivo single branch axotomy induces GAP-43-dependent sprouting and synaptic remodeling in cerebellar cortex

Year: 2013

Authors: Allegra Mascaro A.L., Cesare P., Sacconi L., Grasselli G., Mandolesi G., Maco B., Knott G.W., Huang L., De Paola V., Strata P., Pavone FS.

Autors Affiliation: European Laboratory for Non-Linear Spectroscopy, University of Florence, 50019 Sesto Fiorentino, Italy; Fondazione Santa Lucia, Istituto di ricovero e cura a carattere scientifico (IRCCS), 00179 Rome, Italy; National Institute of Neuroscience, University of Turin, 10125 Turin, Italy; National Institute of Optics, National Research Council, 50125 Florence, Italy; Department of Neurobiology, University of Chicago, Chicago, IL 60637; Centre Interdisciplinaire de Microscopie Electronique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland; Medical Research Council Clinical Science Centre, Faculty of Medicine, Imperial College London, W12 0NN London, United Kingdom; Department of Physics, University of Florence, 50019 Sesto Fiorentino, Italy; and iInternational Center of Computational Neurophotonics, 50019 Sesto Fiorentino, Italy

Abstract: Plasticity in the central nervous system in response to injury is a complex process involving axonal remodeling regulated by specific molecular pathways. Here, we dissected the role of growth-associated protein 43 (GAP-43; also known as neuromodulin and B-50) in axonal structural plasticity by using, as a model, climbing fibers. Single axonal branches were dissected by laser axotomy, avoiding collateral damage to the adjacent dendrite and the formation of a persistent glial scar. Despite the very small denervated area, the injured axons consistently reshape the connectivity with surrounding neurons. At the same time, adult climbing fibers react by sprouting new branches through the intact surroundings. Newly formed branches presented varicosities, suggesting that new axons were more than just exploratory sprouts. Correlative light and electron microscopy reveals that the sprouted branch contains large numbers of vesicles, with varicosities in the close vicinity of Purkinje dendrites. By using an RNA interference approach, we found that downregulating GAP-43 causes a significant increase in the turnover of presynaptic boutons. In addition, silencing hampers the generation of reactive sprouts. Our findings show the requirement of GAP-43 in sustaining synaptic stability and promoting the initiation of axonal regrowth.


Volume: 110 (26)      Pages from: 10824  to: 10829

More Information: We thank Dr. Francesco Vanzi and Ferdinando Rossi for helpful discussions on the manuscript; Ludovico Silvestri for discussions on image analysis; Vladimiro Batocchi for technical assistance; Prof. Luigi Naldini for the lentiviral vector; and Graham Little, Luca Mazzoni, and Raffaele Coppini for assistance with immunohistochemical analysis. The research leading to these results has received funding from LASERLAB-EUROPE (Grant 284464, European Commission\’s Seventh Framework Programme). This research project has also been supported by the Italian Ministry for Education, University and Research in the framework of the Flagship Project NANOMAX and by Italian Ministry of Health in the framework of the \”Stem Cells Call for Proposals.\” This work is part of the research activities of the European Flasghip Human Brain Project and has been carried out in the framework of the International Center of Computational Neurophotonics foundation supported by \”Ente Cassa di Risparmio di Firenze.\”
KeyWords: brain injury; two-photon imaging; neural plasticity; laser nanosurgery; long-term potentiation
DOI: 10.1073/pnas.1219256110

Citations: 89
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