title: Early axonal loss accompanied by impaired endocytosis, abnormal axonal transport, and decreased microtubule stability occur in the model of Krabbe's disease.
abstract: In Krabbe's disease (KD), a leukodystrophy caused by β-galactosylceramidase deficiency, demyelination and a myelin-independent axonopathy contributes to the severe neuropathology. Beyond axonopathy, we show that in Twitcher mice, a model of KD, a decreased number of axons both in the PNS and in the CNS, and of neurons in dorsal root ganglia (DRG), occurred before the onset of demyelination. Despite the early axonal loss, and although in vitro Twitcher neurites degenerated over time, Twitcher DRG neurons displayed an initial neurite overgrowth and, following sciatic nerve injury, Twitcher axons were regeneration-competent, at a time point where axonopathy was already ongoing. Psychosine, the toxic substrate that accumulates in KD, induced lipid raft clustering. At the mechanistic level, TrkA recruitment to lipid rafts was dysregulated in Twitcher neurons, and defective activation of the ERK1/2 and AKT pathways was identified. Besides defective recruitment of signaling molecules to lipid rafts, the early steps of endocytosis and the transport of endocytic and synaptic vesicles were impaired in Twitcher DRG neurons. Defects in axonal transport, specifically in the retrograde component, correlated with decreased levels of dynein, abnormal levels of post-translational tubulin modifications and decreased microtubule stability. The identification of the axonal defects that precede demyelination in KD, together with the finding that Twitcher axons are regeneration-competent when axonopathy is already installed, opens new windows of action to effectively correct the neuropathology that characterizes this disorder.
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Carla Andreia
authors.initials: CA
authors.lastname: Teixeira
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal; ICBAS - Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Largo Prof. Abel Salazar, 2, 4099-003 Porto, Portugal.
authors.forename: Catarina Oliveira
authors.initials: CO
authors.lastname: Miranda
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal; ICBAS - Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Largo Prof. Abel Salazar, 2, 4099-003 Porto, Portugal.
authors.forename: Vera Filipe
authors.initials: VF
authors.lastname: Sousa
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Telma Emanuela
authors.initials: TE
authors.lastname: Santos
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Ana Rita
authors.initials: AR
authors.lastname: Malheiro
authors.affiliation: McKusick-Nathans Institute of Genetic Medicine and Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Melani
authors.initials: M
authors.lastname: Solomon
authors.affiliation: McKusick-Nathans Institute of Genetic Medicine and Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Gustavo H
authors.initials: GH
authors.lastname: Maegawa
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Brites
authors.affiliation: Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 823, 4150-180 Porto, Portugal. Electronic address: msousa@ibmc.up.pt.
authors.forename: Mónica Mendes
authors.initials: MM
authors.lastname: Sousa
mesh_terms: D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D001369:Axons / Q000473:pathology / Q000502:physiology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004398:Dyneins / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D005260:Female; D005727:Ganglia, Spinal / Q000473:pathology / Q000503:physiopathology; D007965:Leukodystrophy, Globoid Cell / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D021962:Membrane Microdomains / Q000473:pathology / Q000502:physiology; D051379:Mice; D008818:Mice, Neurologic Mutants; D008870:Microtubules / Q000378:metabolism*; D009046:Motor Neurons / Q000473:pathology / Q000502:physiology; D016501:Neurites / Q000473:pathology / Q000502:physiology; D009474:Neurons / Q000473:pathology / Q000502:physiology; D012584:Sciatic Nerve / Q000293:injuries / Q000473:pathology / Q000503:physiopathology; D013572:Synaptic Vesicles / Q000473:pathology / Q000502:physiology; D022161:Transport Vesicles / Q000473:pathology / Q000502:physiology; D014404:Tubulin / Q000378:metabolism
chemical_list: D014404:Tubulin; D004398:Dyneins
keywords: Axonal transport; Endocytosis; Krabbe's disease; Leukodystrophy; Myelin; Twitcher