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Neurodegeneration and defective neurotransmission in a Caenorhabditis elegans model of tauopathy.

ABSTRACT: Frontotemporal dementia with parkinsonism chromosome 17 type (FTDP-17) is caused by mutations in MAPT, the gene encoding tau. FTDP-17 begins with executive function deficits and other abnormal behaviors, which progress to dementia. Neurodegenerative changes include accumulation of aggregated tau as neuronal and glial fibrillary tangles. Aggregated tau is seen in numerous other neurodegenerative diseases, including Alzheimer's disease (AD). We expressed normal and FTDP-17 mutant human tau (mutations P301L and V337M) in Caenorhabditis elegans to model tauopathy disorders. Tau pan-neuronal expression caused progressive uncoordinated locomotion (Unc), characteristic of nervous system defects in worms. Subsequently, insoluble tau accumulates and both soluble and insoluble tau is phosphorylated at many of the sites hyperphosphorylated in FTDP-17, AD, and other tauopathies. Substantial neurodegeneration, seen as bulges and gaps in nerve cords followed by loss of neurons, occurs after insoluble tau begins to accumulate. Axons show vacuoles, membranous infoldings, and whorls with associated amorphous tau accumulations and abnormal tau-positive aggregates. FTDP-17 mutation lines had a more severe Unc phenotype, accumulated more insoluble tau at a younger age, were more resistant to cholinergic inhibitors, and had more severe axonal degeneration when compared with lines expressing normal tau. The Unc phenotype is caused by a presynaptic defect. Postsynaptic transmission is intact. This transgenic model will enable mechanistic dissection of tau-induced neurodegeneration and identification of genes and compounds that inhibit pathological tau formation.

SUBMITTER: Kraemer BC

PROVIDER: S-EPMC187908 | biostudies-literature | 2003 Aug

REPOSITORIES: biostudies-literature

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Neurodegeneration and defective neurotransmission in a Caenorhabditis elegans model of tauopathy.

Kraemer Brian C BC Zhang Bin B Leverenz James B JB Thomas James H JH Trojanowski John Q JQ Schellenberg Gerard D GD

Proceedings of the National Academy of Sciences of the United States of America 20030718 17

Frontotemporal dementia with parkinsonism chromosome 17 type (FTDP-17) is caused by mutations in MAPT, the gene encoding tau. FTDP-17 begins with executive function deficits and other abnormal behaviors, which progress to dementia. Neurodegenerative changes include accumulation of aggregated tau as neuronal and glial fibrillary tangles. Aggregated tau is seen in numerous other neurodegenerative diseases, including Alzheimer's disease (AD). We expressed normal and FTDP-17 mutant human tau (mutati ...[more]

PMID: 12872001

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Project description:BackgroundA defining pathological hallmark of the progressive neurodegenerative disorder Alzheimer's disease (AD) is the accumulation of misfolded tau with abnormal post-translational modifications (PTMs). These include phosphorylation at Threonine 231 (T231) and acetylation at Lysine 274 (K274) and at Lysine 281 (K281). Although tau is recognized to play a central role in pathogenesis of AD, the precise mechanisms by which these abnormal PTMs contribute to the neural toxicity of tau is unclear.MethodsHuman 0N4R tau (wild type) was expressed in touch receptor neurons of the genetic model organism C. elegans through single-copy gene insertion. Defined mutations were then introduced into the single-copy tau transgene through CRISPR-Cas9 genome editing. These mutations included T231E, to mimic phosphorylation of a commonly observed pathological epitope, and K274/281Q, to mimic disease-associated lysine acetylation - collectively referred as "PTM-mimetics" - as well as a T231A phosphoablation mutant. Stereotypical touch response assays were used to assess behavioral defects in the transgenic strains as a function of age. Genetically-encoded fluorescent biosensors were expressed in touch neurons and used to measure neuronal morphology, mitochondrial morphology, mitophagy, and macro autophagy.ResultsUnlike existing tau overexpression models, C. elegans single-copy expression of tau did not elicit overt pathological phenotypes at baseline. However, strains expressing disease associated PTM-mimetics (T231E and K274/281Q) exhibited reduced touch sensation and neuronal morphological abnormalities that increased with age. In addition, the PTM-mimetic mutants lacked the ability to engage neuronal mitophagy in response to mitochondrial stress.ConclusionsLimiting the expression of tau results in a genetic model where modifications that mimic pathologic tauopathy-associated PTMs contribute to cryptic, stress-inducible phenotypes that evolve with age. These findings and their relationship to mitochondrial stress provides a new perspective into the pathogenic mechanisms underlying AD.

Dataset Information

Neurodegeneration and defective neurotransmission in a Caenorhabditis elegans model of tauopathy.

Publications

Neurodegeneration and defective neurotransmission in a Caenorhabditis elegans model of tauopathy.

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