Functional Characterization of FTDP-17 tau Gene Mutations through Their Effects on Xenopus Oocyte Maturation

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 wildtype 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, ⌬K280, 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 wildtype 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.

Modelling Alzheimer‐specific abnormal Tau phosphorylation independently of GSK3β and PKA kinase activities

“…As previously described [5], oocyte injection of 50 ng htau412 did not interfere with maturation (Fig. 1A).…”

“…Recombinant Tau proteins or bu¡er alone were microinjected in oocytes at a constant volume of 50 nl per stage VI oocyte by the use of a positive displacement digital micropipette (Nichiryo) as previously described [5].…”

Retarded Axonal Transport of R406W Mutant Tau in Transgenic Mice with a Neurodegenerative Tauopathy

“…Western blot analyses using a panel of phosphorylation-dependent anti-tau antibodies demonstrate a selective and dramatic reduction in the phosphorylation of Ser396 and Ser404, consistent with previously published studies (data not shown) Perez et al, 2000;Sahara et al, 2000;VogelsbergRagaglia et al, 2000, Delobel et al, 2002. Finally, human tau serially extracted from the spinal cord of RW and hWT mice also showed a similar age-related increase in insoluble tau and reduction in Ser396 -Ser404 phosphorylation (data not shown).…”

“…Some of these mutations (e.g., P301L) also facilitate the pathological fibrillogenesis of tau (Hasegawa et al, 1998;Hong et al, 1998;Bugiani et al, 1999;D'Souza et al, 1999;Murrell et al, 1999;Rizzu et al, 1999;Barghorn et al, 2000;Pickering-Brown et al, 2000;Rizzini et al, 2000). Finally, several tau gene mutations, most notably R406W, alter the phosphorylation state and solubility of tau, thereby contributing to the formation of fibrillary tau aggregates (Lee et al, 1991;Crowther and Goedert, 2000;Perez et al, 2000;Sahara et al, 2000;Vogelsberg-Ragaglia et al, 2000;Connell et al, 2001;Delobel et al, 2002).…”

La maladie d’Alzheimer : une tauopathie parmi d’autres ?

“…L'étude in vitro de l'effet des mutations non-sens du premier groupe montre que les protéines tau mutées se lient moins aux microtubules et ne permettent pas une bonne polymérisation de la tubuline en microtubules. Cela a été récem-ment vérifié in situ, montrant que la plupart des mutations non-sens, à l'exception de la mutation R406W, ne modifient pas la phosphorylation des protéines tau mais bien leur liaison aux microtubules [23]. Lorsque la mutation est située dans la région exonique commune aux six isoformes, et en dehors de l'exon 10 (G272V, V337M), les six isoformes perdent leur fonctionnalité.…”