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Functional characterization of FTDP-17 tau gene mutations through their effects on Xenopus oocyte maturation
Patrice Delobel1, Stéphane Flament, Malika Hamdane
1INSERM U422, Institut de Médecine Prédictive et Recherche Thérapeutique, 59045 Lille, France.
Abstract:
tau gene mutations cause frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Here we have used Xenopus oocyte maturation as an indicator of microtubule function. We show that wild-type four-repeat Tau protein inhibits maturation in a concentration-dependent manner, whereas three-repeat Tau has no effect. Of the seven four-repeat Tau proteins with FTDP-17 mutations tested, five (G272V, DeltaK280, P301L, P301S, and V337M) failed to interfere significantly with oocyte maturation, demonstrating a greatly reduced ability to interact with microtubules. One mutant protein (R406W) almost behaved like wild-type Tau, and one (S305N) inhibited maturation more strongly than wild-type Tau. With the exception of R406W, wild-type Tau and all the mutants studied were similarly phosphorylated during the Xenopus oocyte maturation, and this was independent of their effects on this process. Data obtained with R406W and S305N may be related to charge changes (phosphorylation and basic amino acids). Our results demonstrate variable effects of FTDP-17 mutations on microtubules in an intact cell situation. Those findings establish Xenopus oocyte maturation as a system allowing the study of the functional effects of tau gene mutations in a quantitative manner.
Insights
Frontotemporal dementia mutations in the tau gene affect microtubule interactions. Xenopus oocyte maturation reveals variable impacts of these tau gene mutations on microtubule function.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) are neurodegenerative diseases.
- Tau gene mutations are implicated in the pathogenesis of FTDP-17.
- Microtubule dysfunction is a key feature in tauopathies.
Purpose of the Study:
- To investigate the functional effects of FTDP-17 tau gene mutations on microtubule function.
- To establish Xenopus oocyte maturation as a model system for studying tauopathies.
Main Methods:
- Utilized Xenopus oocyte maturation as an indicator of microtubule function.
- Compared the effects of wild-type tau protein and seven FTDP-17 mutant tau proteins on oocyte maturation.
- Assessed protein phosphorylation levels in Xenopus oocytes.
Main Results:
- Wild-type four-repeat tau inhibited oocyte maturation concentration-dependently; three-repeat tau had no effect.
- Five of seven FTDP-17 tau mutants showed significantly reduced interaction with microtubules.
- One mutant (R406W) behaved similarly to wild-type tau, while another (S305N) showed enhanced inhibition.
- Phosphorylation patterns were similar across most tau variants and independent of their effect on maturation.
Conclusions:
- FTDP-17 tau mutations exhibit variable effects on microtubule function within an intact cellular system.
- Xenopus oocyte maturation provides a quantitative system for assessing the functional consequences of tau gene mutations.
- Understanding these functional differences is crucial for elucidating the mechanisms of FTDP-17 and developing therapeutic strategies.