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A152T tau allele causes neurodegeneration that can be ameliorated in a zebrafish model by autophagy induction

View Article: PubMed Central - PubMed

ABSTRACT

Mutations in MAPT cause a variety of neurodegenerative disorders. Lopez et al. confirm that A152T-variant tau is associated with increased risk for frontotemporal dementia and progressive supranuclear palsy syndrome. Upregulation of autophagy increases tau clearance and ameliorates pathology in zebrafish expressing A152T-tau, suggesting potential for the treatment of tauopathies.

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Tau aggregation and cell death in Dendra-tau transgenic zebrafish. (A) Levels of sarkosyl-soluble and insoluble tau reflect accumulation of the insoluble form only in A152T-tau fish at 6 dpf. The level of total tau was analysed by immunoblotting using Tau5 antibody (four independent clutches for WT-tau and A152T-tau). (B) Antibody staining for the conformational marker MC1 in cryosections across the eye of WT-tau and A152T-tau fish. No staining was observed in either WT-tau or A152T-tau fish at 3 dpf (left), whereas only A152T-tau presented positive staining for conformational changes at 6 dpf (right). Scale bar = 100 μm. (C) Western blot for active Caspase 3 (Casp3) (quantified below), indicative of increased cell death in fish expressing the A152T variant (mean ± SEM of nine independent clutches; Student-Newman-Keuls one-way ANOVA, *P < 0.01 versus negative, ##P < 0.01 versus WT-tau). (D) The increased cell death in A152T-tau fish was confirmed by quantification of TUNEL labelling on transverse sections (mean ± SD; n = 5 fish, from a minimum of five sections; Student-Newman-Keuls one-way ANOVA, ***P < 0.001 versus negative; ###P < 0.001 versus WT-tau). See also Supplementary Fig. 4. (E) Morphologically abnormal A152T-tau fish showed increased cell death (quantification of TUNEL-positive nuclei) compared to morphologically normal A152T- or WT-tau fish (mean ± SD; Student-Newman-Keuls one-way ANOVA, **P < 0.01 and ***P < 0.001 versus WT-tau). Representative images in Supplementary Fig. 7.
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awx005-F4: Tau aggregation and cell death in Dendra-tau transgenic zebrafish. (A) Levels of sarkosyl-soluble and insoluble tau reflect accumulation of the insoluble form only in A152T-tau fish at 6 dpf. The level of total tau was analysed by immunoblotting using Tau5 antibody (four independent clutches for WT-tau and A152T-tau). (B) Antibody staining for the conformational marker MC1 in cryosections across the eye of WT-tau and A152T-tau fish. No staining was observed in either WT-tau or A152T-tau fish at 3 dpf (left), whereas only A152T-tau presented positive staining for conformational changes at 6 dpf (right). Scale bar = 100 μm. (C) Western blot for active Caspase 3 (Casp3) (quantified below), indicative of increased cell death in fish expressing the A152T variant (mean ± SEM of nine independent clutches; Student-Newman-Keuls one-way ANOVA, *P < 0.01 versus negative, ##P < 0.01 versus WT-tau). (D) The increased cell death in A152T-tau fish was confirmed by quantification of TUNEL labelling on transverse sections (mean ± SD; n = 5 fish, from a minimum of five sections; Student-Newman-Keuls one-way ANOVA, ***P < 0.001 versus negative; ###P < 0.001 versus WT-tau). See also Supplementary Fig. 4. (E) Morphologically abnormal A152T-tau fish showed increased cell death (quantification of TUNEL-positive nuclei) compared to morphologically normal A152T- or WT-tau fish (mean ± SD; Student-Newman-Keuls one-way ANOVA, **P < 0.01 and ***P < 0.001 versus WT-tau). Representative images in Supplementary Fig. 7.

Mentions: We next investigated the two transgenic lines for evidence of tau-associated pathology. Pathological hyperphosphorylation of tau is a hallmark of tauopathies (Iqbal et al., 2010). Both transgenic WT-tau and A152T-tau fish showed positive staining for the hyperphosphorylation markers AT270 (residue Thr181), AT8 (residues Ser202/Thr205) and PHF1 (residues Ser396/Ser404) by whole-mount immunostaining (Fig. 3A and Supplementary Fig. 5). By western blotting, we observed that phosphorylation at multiple sites was increased in the A152T-tau fish relative to total protein (actin) levels and total tau (Dendra) levels (Fig. 3B and C). To determine whether transgene expression resulted in the formation of tau aggregates, we performed analysis of soluble and sarkosyl-insoluble tau. An abundance of sarkosyl insoluble tau was observed only in samples from A152T-tau fish (Fig. 4A). In addition, positive MC1 antibody staining, a marker of tau conformational change, was detected only in A152T-tau samples at 6 dpf and not in WT-tau transgenic fish (Fig. 4B). We also observed thioflavin-S staining, a well-established staining technique for neurofibrillary tangles (Guntern et al., 1992), which are a characteristic of tau pathology, to be more abundant in the A152T-tau fish (Supplementary Fig. 6). Likewise, the levels of activated caspase 3, a marker for apoptosis (Fig. 4C), and number of apoptotic cells were increased in the A152T-tau zebrafish, and correlated with the morphological abnormalities (Fig. 4D and E and Supplementary Fig. 7). Together, these results demonstrate that A152T-tau expression is associated with greater tau-associated pathology and neurodegeneration.Figure 3


A152T tau allele causes neurodegeneration that can be ameliorated in a zebrafish model by autophagy induction
Tau aggregation and cell death in Dendra-tau transgenic zebrafish. (A) Levels of sarkosyl-soluble and insoluble tau reflect accumulation of the insoluble form only in A152T-tau fish at 6 dpf. The level of total tau was analysed by immunoblotting using Tau5 antibody (four independent clutches for WT-tau and A152T-tau). (B) Antibody staining for the conformational marker MC1 in cryosections across the eye of WT-tau and A152T-tau fish. No staining was observed in either WT-tau or A152T-tau fish at 3 dpf (left), whereas only A152T-tau presented positive staining for conformational changes at 6 dpf (right). Scale bar = 100 μm. (C) Western blot for active Caspase 3 (Casp3) (quantified below), indicative of increased cell death in fish expressing the A152T variant (mean ± SEM of nine independent clutches; Student-Newman-Keuls one-way ANOVA, *P < 0.01 versus negative, ##P < 0.01 versus WT-tau). (D) The increased cell death in A152T-tau fish was confirmed by quantification of TUNEL labelling on transverse sections (mean ± SD; n = 5 fish, from a minimum of five sections; Student-Newman-Keuls one-way ANOVA, ***P < 0.001 versus negative; ###P < 0.001 versus WT-tau). See also Supplementary Fig. 4. (E) Morphologically abnormal A152T-tau fish showed increased cell death (quantification of TUNEL-positive nuclei) compared to morphologically normal A152T- or WT-tau fish (mean ± SD; Student-Newman-Keuls one-way ANOVA, **P < 0.01 and ***P < 0.001 versus WT-tau). Representative images in Supplementary Fig. 7.
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awx005-F4: Tau aggregation and cell death in Dendra-tau transgenic zebrafish. (A) Levels of sarkosyl-soluble and insoluble tau reflect accumulation of the insoluble form only in A152T-tau fish at 6 dpf. The level of total tau was analysed by immunoblotting using Tau5 antibody (four independent clutches for WT-tau and A152T-tau). (B) Antibody staining for the conformational marker MC1 in cryosections across the eye of WT-tau and A152T-tau fish. No staining was observed in either WT-tau or A152T-tau fish at 3 dpf (left), whereas only A152T-tau presented positive staining for conformational changes at 6 dpf (right). Scale bar = 100 μm. (C) Western blot for active Caspase 3 (Casp3) (quantified below), indicative of increased cell death in fish expressing the A152T variant (mean ± SEM of nine independent clutches; Student-Newman-Keuls one-way ANOVA, *P < 0.01 versus negative, ##P < 0.01 versus WT-tau). (D) The increased cell death in A152T-tau fish was confirmed by quantification of TUNEL labelling on transverse sections (mean ± SD; n = 5 fish, from a minimum of five sections; Student-Newman-Keuls one-way ANOVA, ***P < 0.001 versus negative; ###P < 0.001 versus WT-tau). See also Supplementary Fig. 4. (E) Morphologically abnormal A152T-tau fish showed increased cell death (quantification of TUNEL-positive nuclei) compared to morphologically normal A152T- or WT-tau fish (mean ± SD; Student-Newman-Keuls one-way ANOVA, **P < 0.01 and ***P < 0.001 versus WT-tau). Representative images in Supplementary Fig. 7.
Mentions: We next investigated the two transgenic lines for evidence of tau-associated pathology. Pathological hyperphosphorylation of tau is a hallmark of tauopathies (Iqbal et al., 2010). Both transgenic WT-tau and A152T-tau fish showed positive staining for the hyperphosphorylation markers AT270 (residue Thr181), AT8 (residues Ser202/Thr205) and PHF1 (residues Ser396/Ser404) by whole-mount immunostaining (Fig. 3A and Supplementary Fig. 5). By western blotting, we observed that phosphorylation at multiple sites was increased in the A152T-tau fish relative to total protein (actin) levels and total tau (Dendra) levels (Fig. 3B and C). To determine whether transgene expression resulted in the formation of tau aggregates, we performed analysis of soluble and sarkosyl-insoluble tau. An abundance of sarkosyl insoluble tau was observed only in samples from A152T-tau fish (Fig. 4A). In addition, positive MC1 antibody staining, a marker of tau conformational change, was detected only in A152T-tau samples at 6 dpf and not in WT-tau transgenic fish (Fig. 4B). We also observed thioflavin-S staining, a well-established staining technique for neurofibrillary tangles (Guntern et al., 1992), which are a characteristic of tau pathology, to be more abundant in the A152T-tau fish (Supplementary Fig. 6). Likewise, the levels of activated caspase 3, a marker for apoptosis (Fig. 4C), and number of apoptotic cells were increased in the A152T-tau zebrafish, and correlated with the morphological abnormalities (Fig. 4D and E and Supplementary Fig. 7). Together, these results demonstrate that A152T-tau expression is associated with greater tau-associated pathology and neurodegeneration.Figure 3

View Article: PubMed Central - PubMed

ABSTRACT

Mutations in MAPT cause a variety of neurodegenerative disorders. Lopez et al. confirm that A152T-variant tau is associated with increased risk for frontotemporal dementia and progressive supranuclear palsy syndrome. Upregulation of autophagy increases tau clearance and ameliorates pathology in zebrafish expressing A152T-tau, suggesting potential for the treatment of tauopathies.

No MeSH data available.


Related in: MedlinePlus