title: Tar DNA-binding protein-43 (TDP-43) regulates axon growth in vitro and in vivo.
abstract: Intracellular inclusions of the TAR-DNA binding protein 43 (TDP-43) have been reported in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD-TDP). Rare mutations in TARDBP have been linked to both ALS and FTD-TDP suggesting that TDP-43 dysfunction is mechanistic in causing disease. TDP-43 is a predominantly nuclear protein with roles in regulating RNA transcription, splicing, stability and transport. In ALS, TDP-43 aberrantly accumulates in the cytoplasm of motor neurons where it forms aggregates. However it has until recently been unclear whether the toxic effects of TDP-43 involve recruitment to motor axons, and what effects this might have on axonal growth and integrity. Here we use chick embryonic motor neurons, in vivo and in vitro, to model the acute effects of TDP-43. We show that wild-type and two TDP-43 mutant proteins cause toxicity in chick embryonic motor neurons in vivo. Moreover, TDP-43 is increasingly mislocalised to axons over time in vivo, axon growth to peripheral targets is truncated, and expression of neurofilament-associated antigen is reduced relative to control motor neurons. In primary spinal motor neurons in vitro, a progressive translocation of TDP-43 to the cytoplasm occurs over time, similar to that observed in vivo. This coincides with the appearance of cytoplasmic aggregates, a reduction in the axonal length, and cellular toxicity, which was most striking for neurons expressing TDP-43 mutant forms. These observations suggest that the capacity of spinal motor neurons to produce and maintain an axon is compromised by dysregulation of TDP-43 and that the disruption of cytoskeletal integrity may play a role in the pathogenesis of ALS and FTD-TDP.
authors.affiliation: MRC Centre for Developmental Neurobiology, King's College, 4th Floor New Hunt's House, Guy's Campus, London SE1 1UL, UK; Kings College Centre for Neurodegeneration Research, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK. Electronic address: V.Tripathi@ucl.ac.uk.
authors.forename: Vineeta Bhasker
authors.initials: VB
authors.lastname: Tripathi
authors.affiliation: MRC Centre for Developmental Neurobiology, King's College, 4th Floor New Hunt's House, Guy's Campus, London SE1 1UL, UK.
authors.forename: Pranetha
authors.initials: P
authors.lastname: Baskaran
authors.affiliation: Kings College Centre for Neurodegeneration Research, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Shaw
authors.affiliation: MRC Centre for Developmental Neurobiology, King's College, 4th Floor New Hunt's House, Guy's Campus, London SE1 1UL, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Guthrie
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001369:Axons / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D002642:Chick Embryo; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018274:Electroporation; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D009154:Mutation / Q000235:genetics*; D009474:Neurons / Q000166:cytology*; D051381:Rats; D013116:Spinal Cord / Q000166:cytology*
chemical_list: D004268:DNA-Binding Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins
keywords: ALS; Axon growth cytoskeleton; Chick embryo; Cytoplasmic mislocalisation; FTD-TDP; Motor neuron; Neurotoxicity; TDP-43