title: In vivo single branch axotomy induces GAP-43-dependent sprouting and synaptic remodeling in cerebellar cortex.
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.
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, University of Florence, 50019 Sesto Fiorentino, Italy. allegra@lens.unifi.it
authors.forename: Anna Letizia
authors.initials: AL
authors.lastname: Allegra Mascaro
authors.forename: Paolo
authors.initials: P
authors.lastname: Cesare
authors.forename: Leonardo
authors.initials: L
authors.lastname: Sacconi
authors.forename: Giorgio
authors.initials: G
authors.lastname: Grasselli
authors.forename: Georgia
authors.initials: G
authors.lastname: Mandolesi
authors.forename: Bohumil
authors.initials: B
authors.lastname: Maco
authors.forename: Graham W
authors.initials: GW
authors.lastname: Knott
authors.forename: Lieven
authors.initials: L
authors.lastname: Huang
authors.forename: Vincenzo
authors.initials: V
authors.lastname: De Paola
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Strata
authors.forename: Francesco S
authors.initials: FS
authors.lastname: Pavone
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D019771:Axotomy; D002525:Cerebellar Cortex / Q000293:injuries* / Q000503:physiopathology* / Q000648:ultrastructure; D019922:GAP-43 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D021621:Imaging, Three-Dimensional; D051379:Mice; D008822:Mice, Transgenic; D008959:Models, Neurological; D009410:Nerve Degeneration / Q000473:pathology / Q000503:physiopathology; D009412:Nerve Fibers / Q000502:physiology / Q000648:ultrastructure; D009416:Nerve Regeneration / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D017729:Presynaptic Terminals / Q000502:physiology / Q000648:ultrastructure; D034622:RNA Interference
chemical_list: D019922:GAP-43 Protein
keywords: brain injury; laser nanosurgery; neural plasticity; two-photon imaging