Age-dependent neuroinflammation and cognitive decline in a novel Ala152Thr-Tau transgenic mouse model of PSP and AD
- Astrid Sydow†1, 2Email author,
- Katja Hochgräfe†2,
- Stefanie Könen1,
- Daniela Cadinu2,
- Dorthe Matenia1,
- Olga Petrova1,
- Maria Joseph1, 2,
- Frank Johannes Dennissen1 and
- Eva-Maria Mandelkow1, 2, 3Email author
© Sydow et al. 2016
Received: 23 January 2016
Accepted: 23 January 2016
Published: 25 February 2016
Mutations of Tau are associated with several neurodegenerative disorders. Recently, the Tau mutation A152T was described as a novel risk factor for frontotemporal dementia spectrum disorders and Alzheimer disease. In vitro Tau-A152T shows a decreased binding to microtubules and a reduced tendency to form abnormal fibers.
To study the effects of this mutation we generated a mouse model expressing human full-length Tau with this mutation (hTau40AT). At young age (2–3 months) immunohistological analysis reveals pathological Tau conformation and Tau-hyperphosphorylation combined with Tau missorting into the somatodendritic compartment of neurons. With increasing age there is Tau aggregation including co-aggregates of endogenous mouse Tau and exogenous human Tau, accompanied by loss of synapses (especially presynaptic failure) and neurons. From ~10 months onwards the mice show a prominent neuroinflammatory response as judged by activation of microglia and astrocytes. This progressive neuroinflammation becomes visible by in vivo bioluminescence imaging after crossbreeding of hTau40AT mice and Gfap-luciferase reporter mice. In contrast to other Tau-transgenic models and Alzheimer disease patients with reduced protein clearance, hTau40AT mice show a strong induction of autophagy. Although Tau-hyperphosphorylation and aggregation is also present in spinal cord and motor cortex (due to the Thy1.2 promoter), neuromotor performance is not affected. Deficits in spatial reference memory are manifest at ~16 months and are accompanied by neuronal death.
The hTau40AT mice mimic pathological hallmarks of tauopathies including a cognitive phenotype combined with pronounced neuroinflammation visible by bioluminescence. Thus the mice are suitable for mechanistic studies of Tau induced toxicity and in vivo validation of neuroprotective compounds.
KeywordsProgressive supranuclear palsy Tau mutation Mouse model Inflammation Autophagy Behavior
Tauopathies define a class of neurodegenerative diseases associated with the pathological deposition of Tau protein in different substructures of the human brain. The neuropathological profiles and clinical symptoms are rather heterogeneous and dependent on the affected brain areas . The most prominent tauopathy is Alzheimer disease (AD), where insoluble aggregated Tau fibers ("PHFs") are the major component of neurofibrillary lesions. The pathology propagates from transentorhinal regions to the limbic system and neocortical areas as described by the Braak stages for AD-patients and transgenic mice [15, 22, 41, 63]. As a consequence of synapse loss and neuronal death in the affected brain areas, AD is clinically characterized by short- and long-term memory loss . Other tauopathies include the group of frontotemporal dementias (FTD) with the major pathological subtypes of progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), Pick disease (PiD), argyrophilic grain disease (AgD), multiple system tauopathy with dementia (MSTD) and frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) . Major risk factors for FTDs are mutations within the microtubule associated protein Tau (MAPT) gene located on chromosome 17 (17q21) . Most MAPT mutations are clustered in exons 9–13, encoding for the Tau repeat domain and flanking regions responsible for microtubule (MT) binding. Consequently, these Tau mutations destabilize microtubules and enhance Tau-aggregation since the β-sheet rich repeat domain plays a major role in Tau filament assembly .
Recently, a rare MAPT p.A152T mutation was identified as a novel risk factor among patients diagnosed with PSP, AD, PD, CBD and unclassifiable tauopathy presenting with atypical clinical and neuropathological features [20, 38, 55, 57, 60]. Besides p.A152T, several other MAPT mutations cause clinical and neuropathological phenotypes resembling PSP, i.e. R5L, N279K, L284R, homozygous ΔN296, G303V, S305S, S352L and R406W, and an extended H1 haplotype [8, 90, 113].
The MAPT p.A152T mutation is located in exon 7 encoding the N-terminal part or “projection domain” of Tau, which is far from MT binding domain . In comparison to wild-type Tau, hTau40AT is less efficient in stabilizing MT, it reduces the aggregation into filaments and enhances oligomeric structures in vitro . Expression of hTau40AT in human induced pluripotent stem cells (hIPSC) shows an increased Tau- fragmentation and phosphorylation leading to axonal degeneration . However, it is still not known how the mutant hTau40AT contributes to neurotoxicity.
To this end we generated a new mouse model expressing human full-length Tau (hTau40, 2N4R) with the point mutation A152T (hTau40AT for short) and characterized the pathological and functional effects under physiological conditions. The transgenic hTau40AT mice develop a progressive Tau pathology including Tau conformational changes, Tau-hyperphosphorylation and Tau-aggregation. This is accompanied by loss of synapses (especially presynaptic failure), neuronal death and upregulation of protein clearance mechanisms such as autophagy. In addition the expression of hTau40AT causes a marked increase of astrocytic and microglia activity, indicating a strong neuroinflammatory response. In spite of pan-neuronal expression in the brain and spinal cord, hTau40AT mice exhibit intact motor functions but develop cognitive decline at advanced age (~16 mo). The study shows that hTau40AT -expression at low near-physiological levels (1-2-fold over endogenous Tau) is sufficient to induce a severe neuropathology leading to functional deficits and neurodegeneration in vivo, consistent with a neurotoxic gain of function. Thus the new tauopathy mouse model expressing hTau40AT is suitable for mechanistic studies of Tau induced toxicity and for in vivo validation of neuroprotective compounds.
Materials and methods
Generation of hTau40AT mice
To achieve expression at moderate levels the transgene (human full-length Tau carrying the mutation A152T) was inserted into the ROSA26-locus  of C57BL/6 N embryonic stem (ES) cells and injected into BALB/c blastocysts (Taconic). Injected blastocysts were transferred into the uterine horn of pseudopregnant NMR1 females. Highly chimeric mice were bred to C57BL/6 N females. Germline transmission was identified by the presence of black offspring. The transgene expression is controlled by the neuron specific murine Thy1.2 promoter and occurs pan-neuronally in brain and spinal cord. The present study shows data of heterozygous hTau40AT mice with identical C57BL/6 N background. Non-transgenic littermates were used as negative controls. All animals were housed and tested according to standards of the German Animal Welfare Act. hTau40AT mice were identified by PCR using primers 5’-AGCACCCTTAGTGGATGAGG-3’ and 5’-TTGTCATCGCTTCCAGTCC-3’, amplifying the human Tau target fragment.
Sarcosyl extraction, total protein preparation and western blots analysis were performed as described . Briefly, 3–40 μg of total protein or 3 μl of sarcosyl extraction lysates from tissues (cortex, hippocampus, cerebellum, spinal cord) were separated on 10 % SDS-gels or gradient gels (4 %–20 %, Biorad) and transferred to PVDF-membranes for detection with the following antibodies: K9JA (1:20000, Dako), 12E8 (pS262/pS356, 1:1000, a gift from Dr. P. Seubert, Elan Pharma, South San Francisco, CA), AT8 (pSer202/pThr205, 1:500, Thermo Scientific), PHF-1 (pS396/pS404, 1:50, a gift from Dr. P. Davies, Albert Einstein College of Medicine, NY), synaptophysin (1:20000, Sigma), PSD95 (1:2000, Dianova), NeuN (1:1000, Millipore), PSMD13 (1:1000, Abcam), Prot 20S C2 (1:1000, Abcam), LC3 (1:1000, Novus Biologicals), p62 (1:2500, Abnova), Iba1 (1:1000, WAKO), iNOS (1:1000, Abcam), CD11b (1:500, Novus) and GFAP (1:2000, Sigma). Blots were normalized by the concentration of ß-actin (1:20000, Sigma) or GAPDH (1:10000, Sigma), visualized with ECL Plus detection system (GE Healthcare) and analyzed by densitometry (LAS 3000/ChemiBis, AIDA software). Bars represent mean ± SEM; n = 3–17.
Immunohistochemistry was performed with 5 μm paraffin sections as described . Tissue (brain and spinal cord) was fixed in histofix (Roth; 4 % PFA, pH 7.4 for 24 h) and dehydrated by a series of ethanol and chloroform. Sagittal brain and coronal spinal cord sections were incubated with primary antibodies prepared in 1 % horse serum overnight at 4 °C. The following antibodies were used: TauY9 (1:2000, Enzo), 12E8 (pS262/pS356, 1:2000) (a gift from Dr. P. Seubert, Elan Pharma, South San Francisco, CA), AT180 (pThr231/pSer235, 1:500, Pierce), AT8 (pSer202/pThr205, 1:500, Thermo Scientific), Alz-50 (1:50) and PHF-1 (pS396/pS404, 1:50) (Alz-50 and PHF-1 are gifts from Dr. P. Davies, Albert Einstein College of Medicine, NY), Iba1 (1:1000, Wako), GFAP (1:2000, Sigma), S100b (1:100000, Novus), IL1ß (1:25, SantaCruz), TLR2 (1:150, Millipore). Inflammatory markers like CD11b (1:5000, Serotec) and CD45 (1:500, Serotec) were analyzed using 20 μm sagittal cryo sections. Counterstaining with hematoxylin (Roth) was performed according to the company´s instructions. To visualize co-pathologies (neuroinflammation vs. Tau phosphorylation), sections were first incubated with antibodies against inflammatory markers and developed with Vectastain Universal Elite ABC kit + DAB (Vector Laboratories). Afterwards sections were re-incubated with primary antibodies against Tau-phospho epitopes and developed with Alkaline Phosphatase Universal kit + Alkaline Phosphatase substrate kit III (Vector Laboratories). Stainings were performed on paraffin sections of 4–6 mice, respectively, for genotype, age and antibody used.
Fluoro Jade C staining
To label neurodegeneration, 30 μm floating sections of 3 WT and 3 hTau40AT mice were mounted on gelatin coated slides and rehydrated in a series of ethanol. Tissue autofluorescence was reduced by 0.06 % potassium permanganate treatment for 15 min. Washed slices were stored for 30 min in 0.001 % Fluoro Jade C staining solution (Merck) in the dark. Rinsed and dried slides were immersed in xylene and coverslipped with Histokitt (Roth). Fluoro Jade C staining was analyzed using FITC filter settings.
Gallyas silver staining
5 μm paraffin sections were stained as published . To visualize co-pathologies (neuroinflammation vs. Tau-aggregation), Gallyas silver stained sections were incubated with antibodies against inflammatory markers and developed with Vectastain Universal Elite ABC kit + DAB (Vector Laboratories). Stainings were performed on paraffin sections of 4 mice, respectively for genotype and age.
Thioflavin S staining
Autofluorescence of 5 μm paraffin brain sections was quenched , sections were incubated in 0.05 % Thioflavin S (Sigma) for 8 min, and excess Thioflavin S was removed by brief washing with 80%EtOH and three washing steps in large volumes of tap water. Stained sections were stored in cold 3xPBS for 30 min to avoid photobleaching. After rinsing in 1xPBS, the tissue was counterstained with TOPRO-3 (nuclear marker; Invitrogen Molecular Probes) and mounted in Aqua Poly/Mount (Polysciences Inc.). Analysis was performed on paraffin sections of 4 mice, respectively, for genotype and age.
Golgi-staining and quantification of spines
For Golgi-Cox impregnation of neurons , the FD rapid GolgiStain TM kit (FD NeuroTechnologies) was used according to the manufacturer’s protocol. 80 μm floating sections of transgenic and WT mice at 10 and 20 months of age were Golgi-impregnated and hippocampal pyramidal CA1- or CA3-neurons were used for quantification of dendritic spines as described . For each mouse (n = 2–3 per group), ~10 neurons and 1–2 secondary dendrites per neuron of 20–30 μm lengths were quantified using ImageJ software (NIH). Bars represent mean ± SEM.
In vivo bioluminescence imaging (BLI) of astrocyte activation
hTau40AT/C57BL/6N mice were crossbred to Tg(Gfap-lucFVB/N) reporter mice, expressing firefly luciferase under control of the murine Gfap-promoter . Heterozygous, bigenic Tg(Gfap-luc: hTau40AT/mixed bkg) offspring (n = 18) were used to monitor luciferase activity as surrogate marker for astrocyte activation and Tau pathology. Heterozygous Tg(Gfap-lucmixed bkg) (n = 9) were used as controls. Mice of both genders were imaged monthly starting at 3 months of age and continued until 18 months of age.
In vivo BLI was performed using an Ivis Lumina II system (Caliper Life Science) according to a standardized protocol. Ten minutes prior to each imaging session, mice received an intraperitoneal (i.p.) injection of 150 mg/kg D-luciferin (Caliper Life Science) dissolved in sterile PBS and the heads of the animals were shaved. Mice were anesthetized using 2 % isoflurane (Abbott) vaporized in a constant O2 flow. Anesthesia was maintained during the whole imaging session. Mice were placed into the heated, light-tight imaging chamber of the Ivis Lumina II and the ears were covered using black paper to shield unspecific luminescence signals. A sequence of 6 images taken in 2 min intervals starting at 10 min post i.p. injection was recorded using a highly sensitive charged coupled device camera. Images were analyzed using Living Image 4.0 software (Caliper Life Science). The bioluminescence emission was normalized and the surface radiance was displayed in photons per second per centimeter squared per steradian (photons/s/cm2/sr). For quantification of bioluminescence signals, a region of interest (ROI) was defined to convert surface radiance (photons/s/cm2/sr) into total flux of the bioluminescent source (photons/s). To compare bioluminescence signals of Tg(Gfap-luc: hTau40AT/mixed bkg) and controls, total flux values of each experimental cohort were converted to percentage. Data represent mean values ± standard error of the mean (SEM). Statistical comparisons were accomplished by two-way repeated ANOVA followed by a post hoc Bonferroni´s multiple comparison test using Prism 5.0 (GraphPad Software). The accepted level of significance was p < 0.05. Asterisks indicate significant differences between Tg(Gfap-luc: hTau40AT/mixed bkg) and controls for each time point (*:p < 0.05, **:p < 0.01, ***:p < 0.001, ****:p < 0.0001).
Mice were housed in groups of 2–5 animals under standard conditions (23 °C, 40 %–50 % humidity, food and water ad libitum) with a 12 h light/dark cycle (with light on from 7 a.m. to 7 p.m.). After 2 weeks of acclimatization and handling, behavior tests were carried out between 9 a.m. and 4 p.m. Transgenic hTau40AT mice (mixed genders) were tested at 10 months (n = 18) and 16 months of age (n = 20) and compared to age-matched wild-type control littermates (mixed genders, n = 14 and n = 11 respectively).
Morris water maze (MWM)
A 2 day pretraining protocol was conducted to habituate the mice to swimming and climbing onto a hidden platform (water temperature: 22 °C, 4 trials/day, maximum duration/trial 60s, 60 min inter-trial interval). To avoid any interference with the MWM learning, the pretraining was performed in a different apparatus (Makrolon cage type III, 42 × 26.5 × 15.5 cm) than used for the MWM (circular pool, diameter of 150 cm). The position of the pretraining platform (diameter of 10 cm, 1 cm below the water surface) was randomized and could not be located by orientation via landmarks, thus mice had to swim at random to escape from the water.
MWM acquisition and probe trials
Spatial memory abilities were examined in the standard hidden-platform acquisition and retention version of the Morris water maze . A 150 cm circular pool was filled with water opacified with non-toxic white paint (Biofa Primasol 3011), and kept at 22 °C. Four positions around the edge of the tank were arbitrarily designated 1, 2, 3 and 4 thus dividing the tank into four quadrants: target (T), right adjacent (R), opposite (O), and left adjacent (L). A 15 cm round platform was hidden 1 cm beneath the surface of the water at a fixed position in the center of target quadrant. The water maze was equipped with inner maze cues arranged in an asymmetrical manner to facilitate orientation. Each mouse performed 4 swimming trials per day (maximum duration 60s, 10 min inter-trial interval) for five consecutive days. Mice were started from 4 symmetrical positions in a pseudo-randomized order across trials. Mice that failed to find the submerged platform within 60s were guided to the platform, where they remained for 15 s before being returned to their home cage. The time required to locate the hidden escape platform (escape latency), the distance travelled (path length), and swimming speed (velocity) were determined. On acquisition day 3, 4, 5, as well as 2 days after the acquisition phase ended (day 8), a probe trial was conducted with the platform removed and the search pattern of the mice was recorded for 60s. On day 3, 4 and 5 the probe trial was performed between learning trial 2 and 3. The following learning trials 3–4 were carried out with the platform returned to former position inside the target quadrant to avoid extinction. During acquisition and probe trials the Viewer II video tracking system was used to record and analyze behavior (Noldus).
Statistical comparisons between groups were accomplished by two-way repeated ANOVA followed by a post hoc Fisher LSD multiple comparison test. Stars presented in graphs indicate differences between hTau40AT mice and wild-type littermates (MWM acquisition). For analysis of probe trials a two-tailed one sample t-test against chance level (25 %) or a one-way ANOVA with post hoc Newman-Keuls multiple comparison test was done. All data are presented as group mean values with standard error of mean (SEM), the accepted level of significance was p < 0.05. Statistical comparisons were performed using STATISTICA 10.0 software (StatSoft Germany), graphs were designed using Prism 5.0 (GraphPad Software). *:p < 0.05, **:p < 0.01, ***:p < 0.001.
Generation of hTau40AT mice
Co-aggregation of exogenous hTau40AT and endogenous mouse Tau
Gallyas-silver positive Tau inclusions detected in cortical, hippocampal, cerebellar and spinal neurons of hTau40AT mice were considered as fully developed NFTs, exhibiting the typical flame-shaped structure (Fig. 2e9-13). In comparison non-transgenic littermates were silver-negative (Fig. 2e4-8). The formation of NFTs started as early as 3 months of age in cortical brain regions of hTau40AT mice (data not shown) and the number of neurons containing NFTs increased in an age-dependent manner (Fig. 2e1-3). The presence of NFTs in hippocampal and cortical neurons of young and old hTau40AT mice was confirmed by Thioflavin S stainings (Fig. 2f2, f4). One major neuropathological hallmark of PSP patients is the abnormal deposition of NFTs inside glial cells, the so called "tuft-shaped astrocytes" or "oligodendral coiled bodies" . However, no Tau inclusions inside astrocytes or oligodendrocytes were detected in hTau40AT mice from 5 to 20 months of age; similar to the lack of tufted astrocytes in a patient with A152T-mutated Tau .
hTau40AT induces pathological hyperphosphorylation and conformational changes of Tau at young age
The A152T mutation correlates with pronounced neuroinflammation
By contrast, the majority of microglia in age-matched WT mice exhibited a ramified morphology with small somata and fine cellular processes (Fig. 5a7), characteristic of resting microglia. In addition, WT mice were immune-negative for microglia antigens (CD45, CD11b), pro-inflammatory cytokines (IL1ß) and TLR2 (Fig. 5a9,11,13,15). At 12 months of age, hTau40AT mice demonstrated an overall increase of neuroinflammatory protein levels relative to age-matched WT mice in cortical brain extracts (Fig. 5c, GFAP: +40 %, Iba1: +20 %, iNOS: +150 %, CD11b: +40 %).
The upregulation of Gfap expression is a widely accepted marker of astrogliosis  and reporter strains optimized for non-invasive in vivo bioluminescence imaging (BLI) of neuroinflammation are available [reviewed in ]. In Tg(Gfap-luc) mice  luciferase is expressed upon induction of the murine Gfap promoter. Consequently, crossbreeding of Tg(GFAP-luc) mice with hTau40AT mice allows longitudinal monitoring and quantification of astrocyte activation by in vivo BLI during the disease progression, similar to the monitoring of prion infectivity in prion-inoculated GFAP-luc mice .
At 3 months of age, hTau40AT transgenic mice exhibited no overt signs of neuroinflammation as judged by histology (data not shown). Thus bioluminescence emission at 3 months of age was considered as background luciferase activity indicating the basal expression level of the Gfap promoter, which was defined as 100 %. At 5 months of age, bigenic Tg(Gfap-luc: hTau40AT/mixed bkg) demonstrated a significant rise in luciferase activity to 150 % as compared to the baseline Gfap promoter activity. After this initial upregulation, a further increase of Gfap-driven luciferase activity was observed in Tg(Gfap-luc: hTau40AT/mixed bkg) mice reaching a plateau of ~180 % at the age of 14 months. In contrast, luciferase activity in the brains of Tg(Gfap-lucmixed bkg) control animals remained stable over time (~100–120 %; Fig. 6a-b). The results demonstrate a strong upregulation of astrocyte activation in response to expression and accumulation of toxic hTau40AT.
Protein degradation systems are altered in hTau40AT mice
Impaired protein quality control and impaired clearance via ubiquitin-proteasome and autophagosome-lysosome pathways are known to cause abnormal accumulation of disease-related proteins, which are deposited in intracellular or extracellular aggregates [21, 47, 71].
Synaptic and neuronal loss in hippocampus and cortex of aged hTau40AT mice
In conclusion, hTau40AT mice show a strong defect of pre-synapses already at 12 months, whereas the post-synapse is only weakly affected at this stage, and damage becomes pronounced only at a later time point.
Accumulation of hTau40AT correlates with cognitive but not motoric deficits at advanced age
Transgenic hTau40AT mice did not show abnormal motoric deficits up to 20 months of age. To show this, a detailed analysis was carried out at 10 and 16 months of age to characterize potential behavioral alterations caused by the expression and accumulation of hTau40AT. In the spinal cord, despite a ~3-fold overexpression of hTau40AT and overt Tau-related pathological changes, we did not detect any motor deficiencies in a Rotarod test (Additional file 1: Figure S4) up to 16 months of age. In addition hTau40AT mice did not exhibit any gait abnormalities in comparison to controls as determined by a Catwalk digital foot print analysis for single paw and inter-limb coordination (Additional file 1: Figure S5).
In recent years several Tau mutations have been identified as genetic risk factors for FTDP-17 [36, 48]. Most of the mutations are located in the repeat domain (microtubule binding region; e.g. P301L, P301S and ΔK280) and reduce the Tau-MT-interaction and MT-assembly and/or increase Tau-aggregation by enhancing the ß-propensity of Tau. This results in Tau-hyperphosphorylation, missorting and aggregation [42, 109]. By contrast, mutations in the N-terminal Tau projection domain (i.e. R5L, G55R), which are partly related to PSP [R5L, ], and their underlying mechanisms are not well understood at present. However, N-terminal mutations may impact on the 3D-structure of Tau (e.g. the "paperclip conformation", ) or influence intra- and intermolecular interactions that might affect MT and neuronal cell functions . The MAPT p.A152T variant was recently recognized as a risk factor for several FTD spectrum disorders including AD, highlighting the clinical and pathological variability associated with MAPT p.A152T [20, 38, 55, 57, 60]. To address the question of how p.A152T Tau induces neuropathological features including cognitive decline, we generated a novel transgenic mouse model expressing human full-length Tau with mutation A152T (hTau40AT).
Neuropathology of hTau40AT mice in comparison to AD- and PSP-cases and Tau transgenic mouse models
In spite of the low, near-physiological transgene expression, hTau40AT causes Tau-hyperphosphorylation at several diagnostic sites (e.g. AT8, PHF1) and Tau-missorting of transgenic and endogenous Tau into the somatodendritic compartment of neurons starting at early age (Figs. 3, 4, Additional file 1: Figure S1). The results are comparable to tauopathy mouse models with FTDP-17-related Tau-mutations [30, 62, 75, 87, 92] and to pathological reports of AD- and PSP-cases [16, 76].
Furthermore MAPT p.A152T increases the hydrophilic character of Tau and generates an additional phosphorylation site just upstream of the TP-motif 153–154 , which is one of numerous targets in Tau by proline-directed kinases (i.e. MAPK, cdk5 and GSK3). This type of phosphorylation is characteristically increased in most tauopathies, and indeed, the phosphorylation of T153 is observed both in cell models and AD brain [5, 49]. Thus the mutation Ala→Thr in the preceding residue 152 could impact the phosphorylation pattern and function of this region of Tau.
In vitro, hTau40AT shows a somewhat reduced tendency to form Tau-fibers and an increase in oligomers . However, in mice the exogenous hTau40AT is able to interact with endogenous mouse Tau to form stable co-aggregates and flame-shape NFTs (Fig. 2), comparable to transgenic mice expressing human Tau variants with mutations in the repeat domain or C-terminus, such as G272V, ΔK280, P301S, P301L and R406W [3, 75, 91, 104, 116].
Neuropathologically, Tau-co-aggregates detected in hTau40AT mice resemble neuronal NFTs of AD-patients rather than the spherical tangles of PSP-patients [13, 17, 105]. Furthermore "tufted astrocytes" containing abnormal Tau deposits, a classical marker of PSP , are lacking in mice and in patients with mutated hTau40AT .
Although hTau40AT mice develop remarkable Tau phosphorylation and aggregation in spinal and motor cortical neurons (Figs. 2 and 3), motor functions were preserved (Additional file 1: Figures S4, S5). This is in contrast to earlier generations of Tau-transgenic mice with high overexpression of mutant Tau in the CNS including spinal cord, which show strong motor deficits and thus interfere with cognitive assays such as MWM and others [61, 62, 96, 107, 116]. However, the hTau40AT-expression (due to a single copy in the ROSA26-locus) seems to be low enough to avoid motor deficits in hTau40AT mice and thus to allow cognitive testing, similar to other mouse models with rather near-physiological levels of Tau transgene expression in the spinal cord [82, 92].
From our results we conclude that the expression of A152T-Tau (a Tau-variant mutated in the N-terminal half, near the proline-rich region) leads to hyperphosphorylation, missorting and aggregation of Tau, similar to pathological features of FTDP-mouse models expressing human Tau-variants with mutations in the C-terminal half that are known to affect Tau-microtubule interactions and Tau-aggregation [91, 92, 116]. How this A152T-Tau promotes tauopathy (e.g. by impacting the 3D-structure of Tau, alterations in MT dynamics, phosphorylation pattern, sensitivity to proteases etc.) will require further investigation. But the proximity to the central proline-rich domain which harbors interaction sites with proteins with SH3 domains  is suggestive of a role in altered signaling pathways. In this context it is interesting to note that the trans-cellular spreading of Tau-pathology appears to be mediated by high MW non-fibrillar oligomers of Tau with pronounced hyperphosphorylation by proline-directed kinases .
Inflammatory response versus hTau40AT -pathology
Neuroinflammation plays a crucial role in the development and progression of neurodegenerative diseases, but it is still a matter of debate whether inflammatory processes trigger the pathology (e.g. Tau-aggregation) or whether activated glial cells react to the aggregation of toxic proteins in their surrounding . The hTau40AT mice develop a remarkable neuroinflammatory response as judged by the activation of astrocytes and microglia and the upregulation of inflammation-related proteins, starting from 5 months onwards (Figs. 5 and 6), similar to reports of patients with chronic neurodegenerative diseases including AD, PSP, PD, ALS and prion disease [1, 31, 43, 83].
Microglia cells are locally activated by misfolded proteins (e.g. Aß and alpha-synuclein) , in particular by structural changes which activate toll-like receptors (TLR) and by expression of pro-inflammatory cytokines (e.g. IL-1ß) or inflammation-induced enzymes like iNOS [28, 45]. Apart from glial cells, neurons can serve as source of cytokines (i.e. IL-1ß), and express inducible nitric oxide synthase (iNOS) in pathological conditions [43, 44], as shown here for CA1-neurons of hTau40AT mice (Fig. 5).
Similar to the accumulation of activated glial cells in the surrounding of NFT-bearing neurons in hTau40AT mice (Fig. 7), activated microglia are also associated with Aß-plaques in AD patients and transgenic APP-23 mice [93, 97]. Furthermore, misfolded α-synuclein activates directly microglia with a classical cytokine upregulation, morphological changes and alterations in TLR gene expression . Reports on transgenic mice (expressing aggregation-prone Tau variants) strengthen the linkage between the accumulation of intracellular aggregated Tau species and an inflammatory response [10, 75, 116]; whilst the expression of an anti-aggregant Tau variant “protects” mice against a pronounced gliosis .
Experiments with implanted IL-1-releasing pellets into rat brains, leading to Tau-hyperphosphorylation, have suggested a function of IL-1 as trigger for the progression of neurofibrillary pathology in AD [39, 94]. Furthermore, the proinflammatory cytokine TNF initiates the accumulation of Tau preferentially in neurites via reactive oxygen species . Conversely, neuroinflammation and Tau pathology were diminished in PS19 mice by treatment with the anti-inflammatory compound FK506 . Gene expression profiles of rTg4510 mice suggest a correlation of Tau-pathology, cognitive decline and upregulation of inflammatory genes similar to AD cases . All of these observations point to a tight relationship between Tau toxicity and pro-inflammatory cytokines.
In patients with AD or PSP, ongoing gliosis is visualized and quantified by positron emission tomography (PET) and usually increases with the disease stage in affected regions [85, 118]. In comparison, in aging bigenic mice (Gfap-luc:hTau40AT/m.bkg) the rise of GFAP-dependent luciferase activity reflects the kinetics of astrocyte activation in vivo as monitored by bioluminescence imaging (Fig. 6), confirmed by staining for inflammation markers (Figs. 5 and 6). This underscores the potential of BLI to characterize progressive neurodegenerative diseases (e.g. AD and ALS) . In hTau40AT mice the neuroinflammation precedes cognitive decline (Figs. 5, 6, 7, and 10). Based on the probable link between neuroinflammation, Tau-pathology and cognitive failure, BLI of bigenic (Gfap-luc: hTau40AT/mixed bkg) mice may be used to validate and improve treatment strategies and define time points of early therapeutic intervention before onset of behavioral deficits.
From our results, we conclude that neuroinflammation in hTau40AT mice occurs in response to early Tau-phosphorylation and Tau-aggregation at young age (Figs. 2 and 3). At later stages, neuroinflammatory changes might further boost Tau pathology and neurotoxic processes, which finally lead to synaptic damage and neuronal death (Figs. 9 and 10).
Accumulation of hTau40AT, neuroinflammation and protein degradation: a reciprocal relationship
Aberrations in protein clearance systems contribute to the pathogenesis of neurodegeneration, causing the accumulation and aggregation of disease-relevant proteins [47, 59, 74, 80]. In the present study, 20 months old hTau40AT mice show a reduced proteasome activity and an upregulation of the autophagosome-lysosome pathway (Fig. 8), pointing towards a cross-talk between both protein degradation pathways, as suggested by others . In this regard, provoked proteasome impairments (by drugs or gene silencing) induce autophagy as a compensatory protein degradation pathway in various cell models [26, 65, 81]. Similar changes occur after lipopolysaccharide (LPS)-induced neuroinflammation, which decreases proteasome activity and causes hippocampal neurodegeneration . Moreover, autophagy can be upregulated by immune signaling molecules (e.g. TLRs) or the IL1R pathway [95, 98]. Therefore, the observed changes in the protein degradation systems in the aged hTau40AT mice are likely explained by the progressive neuroinflammation (Figs. 5, 6, 7 and 8).
Conversely, the activation of autophagy would appear as a promising strategy against neurodegeneration, since aggregated proteins (e.g. Tau) are preferentially degraded by chaperone-mediated autophagy . Furthermore, application of autophagy inducers (e.g. rapamycin, trehalose) lowers Tau-hyperphosphorylation and neuroinflammation and improves cognition in transgenic mouse models [29, 68, 89]. Beyond that, trehalose suppresses Tau-aggregation in an inducible N2a cell model of Tau pathology and diminishes cytotoxicity . However, the activation of autophagy in hTau40AT mice occurs only after NFT formation and onset of neuronal loss, obviously too late to rescue Tau induced toxicity and cognitive phenotype (Figs. 2, 8, 9 and 10), similar to old 3xTg-AD mice with NFTs showing no cognitive recovery after autophagy-activation .
Synaptic decay and neuronal loss parallel cognitive impairments in hTau40AT mice
Synapse loss is a fundamental correlate of cognitive decline in AD . Our data indicate an age-dependent failure of learning and memory capacities in hTau40AT mice. At 10 months, when dendritic spine densities are still unaffected, hTau40AT mice are still cognitively normal (Additional file 1: Figure S2; Fig. 10). However, 12 months old hTau40AT mice show already incipient “synaptotoxicity” observed by reduced levels of synaptic proteins (especially presynaptic markers). Decreased level of synaptophysin (Fig. 9a-b), presumably caused by the accumulation of toxic hTau40AT inside presynaptic termini, might serve as a first indicator for pathological changes in the synaptic connectivity, as described for other Tau transgenic mice [75, 108, 116]. From 12 months onwards progressive neurodegeneration (Fig. 9e) destroys cognitive pathways, resulting in severe learning and memory deficits of 16 months old hTau40AT mice (Fig. 10c-d). Consistent with this, cognitively impaired ~20 months old hTau40AT mice show a profound loss of CA1- and CA3-synaptic spines (Fig. 9c-d), similar to other tauopathy mouse models, where synapse loss was correlated to cognitive decline [87, 92, 100, 108].
Toxic gain and loss of function in hTau40AT mice affects cognition
The mechanisms leading to Tau-dependent neurotoxicity in AD- or FTDP-17-patients remain unclear in detail, but there is evidence that a combination of toxic gain of function and the loss of normal Tau function serves as a trigger for neurodegenerative processes . Under physiological conditions non-mutated Tau stabilizes MTs in axons, but post-translational modifications (e.g. phosphorylation) could alter its interaction with MTs and other cell components and thus might result in impairment of axonal transport, Tau-missorting and formation of PHFs . By contrast, hTau40AT shows a reduced MT affinity and slower aggregation in vitro, but exhibits an enhanced tendency to form Tau oligomers . Whether the MAPT p.A152T mutation alters the function of the Tau projection domain as MT-spacer  or its interaction with the dynactin complex , histone deacetylase 6 , tyrosine kinases such as Fyn  or other proteins is still unknown. Further intramolecular changes of hTau40AT impacting the 3D-structure cannot be excluded. Since transgenic mice, expressing aggregation-prone Tau proteins, develop early cognitive decline [87, 92, 100], the co-aggregates of hTau40AT mice (Fig. 2) might have less beta structure and might be less neurotoxic, postponing memory loss in hTau40AT mice to older age (Fig. 10).
A proper function of the ubiquitin-proteasome system (UPS) is essential for correct synaptic transmission, since the UPS operates in the pre- and postsynaptic compartment by regulating neurotransmitter release, synaptic vesicle recycling and the dynamic behavior of the PSD and dendritic spines . Proteasome inhibition causes impairment of neuronal protein synthesis , loss of synaptic proteins  and LTP impairments . Furthermore bilateral hippocampal injection of lactacystin (proteasome inhibitor) produces retrograde amnesia in rats . In this context, reduced proteasome activity in old hTau40AT mice (Fig. 8) might impact on synaptic function and trigger synapse loss (Fig. 9) and cognitive decline (Fig. 10).
Neuroinflammatory processes interfere with learning and memory and are related to synaptic decay and neuronal loss in neurodegenerative disorders [66, 115]. Although physiological levels of IL-1ß are beneficial for synaptic plasticity , IL-1ß-treatments of cultured neurons induced a marked loss of synaptic connections . In astrocytes, elevated levels of IL-1 trigger the overexpression of the neurotrophic cytokine S100b, a calcium binding protein. S100b increases the free calcium concentration in neurons; whereas mice overexpressing S100b show enhanced excitotoxicity, altered synaptic plasticity and cognitive impairment [9, 34, 78]. Since neuroinflammation is a major hallmark of hTau40AT mice (Figs. 5, 6 and 7), the presence of activated glial cells and inflammatory proteins might serve as major trigger for cognitive decline.
In summary, the present study shows that expression of hTau40AT at low near-physiological levels is sufficient to induce a severe neuropathology leading to functional deficits and neuronal death in vivo (Fig. 11). Our results support the hypothesis that the rare MAPT p.A152T mutation promotes a neurotoxic gain of function, most likely triggered by the enhanced neuroinflammation and excitotoxic events. Thus the new hTau40AT mouse model is suitable for further mechanistic studies of Tau induced neurotoxicity and for in vivo validation of compounds covering Tau-pathology and neuroinflammation.
Amyotrophic lateral sclerosis
behavioral variant of frontotemporal dementia
central nervous system
Tau mutant with deletion of lysine 280
embryonic stem cells
frontotemporal dementia and parkinsonism linked to chromosome 17
frontotemporal dementia spectrum disorders
Glyceraldehyde 3-phosphate dehydrogenase
glial fibrillary acidic protein
heat shock cognate protein 70
human full-length Tau (2N4R, 441 residues)
- hTau40AT :
hTau40 with mutation A152T
inducible nitric oxide synthase
microtubule-associated protein 1 light chain 3
Morris water maze
neuronal nuclear antigen
N-methyl D-aspartate receptor
positron emission tomography, PHF, paired helical filament
- Prot 20S C2:
C2 subunit of the 20S proteasome
postsynaptic density protein 95
a regulatory subunit of the 26S proteasome
Progressive Supranuclear Palsy SSCtx, somatosensory cortex
- TauΔK :
full-length human Tau (2N4R, residues 1–441) with ΔK280 deletion mutation
- TauRDΔK :
Tau 4-repeat domain (construct K18, residues 244–372) with ΔK280 mutation
- hTau40AT :
full-length human Tau (2N4R, residues 1–441) with A152T mutation
We thank the following lab members for their expert help and advice: Dr. Jacek Biernat (DZNE, Bonn) and S. Hübschmann (DZNE, Bonn) for providing cDNA to generate hTau40AT mice; Dr. Yipeng Wang (DZNE, Bonn) for fruitful discussions; Stina Hahn (MPI, Hamburg) and Daniel Küver (MPI, Hamburg) for their excellent technical assistance. We owe special thanks to the team of the animal facility of CAESAR (headed by Dr. Dagmar Wachten) and of DZNE Bonn (headed by Dr. Christina Ginkel & Dr. Michaela Möhring) for their continuous help in mouse breeding. We gratefully acknowledge reagents from Dr. P. Seubert (Elan Pharma, South San Francisco, CA; 12E8 antibody) and Dr. P. Davies, Albert Einstein College of Medicine, NY (PHF1 and Alz-50 antibodies). This research was supported by MPG, DZNE, Tau Consortium, and Katharina-Hardt-Foundation.
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- Akiyama H, Barger S, Barnum S, Bradt B, Bauer J, Cole GM, et al. Inflammation and Alzheimer's disease. Neurobiol Aging. 2000;21:383–421.PubMed CentralPubMedView ArticleGoogle Scholar
- Amor S, Peferoen LA, Vogel DY, Breur M, van der Valk P, Baker D, et al. Inflammation in neurodegenerative diseases--an update. Immunology. 2014;142:151–66. doi:10.1111/imm.12233.PubMed CentralPubMedView ArticleGoogle Scholar
- Ando K, Leroy K, Heraud C, Yilmaz Z, Authelet M, Suain V, et al. Accelerated human mutant tau aggregation by knocking out murine tau in a transgenic mouse model. Am J Pathol. 2011;178:803–16. doi:10.1016/j.ajpath.2010.10.034.PubMed CentralPubMedView ArticleGoogle Scholar
- Andreadis A, Brown WM, Kosik KS. Structure and novel exons of the human tau gene. Biochemistry. 1992;31:10626–33.PubMedView ArticleGoogle Scholar
- Augustinack JC, Schneider A, Mandelkow EM, Hyman BT. Specific tau phosphorylation sites correlate with severity of neuronal cytopathology in Alzheimer's disease. Acta Neuropathol. 2002;103:26–35.PubMedView ArticleGoogle Scholar
- Avital A, Goshen I, Kamsler A, Segal M, Iverfeldt K, Richter-Levin G, et al. Impaired interleukin-1 signaling is associated with deficits in hippocampal memory processes and neural plasticity. Hippocampus. 2003;13:826–34. doi:10.1002/hipo.10135.PubMedView ArticleGoogle Scholar
- Bajic N, Jenner P, Ballard CG, Francis PT. Proteasome inhibition leads to early loss of synaptic proteins in neuronal culture. J Neural Transm. 2012;119:1467–76. doi:10.1007/s00702-012-0816-9.PubMedView ArticleGoogle Scholar
- Baker M, Litvan I, Houlden H, Adamson J, Dickson D, Perez-Tur J, et al. Association of an extended haplotype in the tau gene with progressive supranuclear palsy. Hum Mol Genet. 1999;8:711–5.PubMedView ArticleGoogle Scholar
- Barger SW, Van Eldik LJ. S100 beta stimulates calcium fluxes in glial and neuronal cells. J Biol Chem. 1992;267:9689–94.PubMedGoogle Scholar
- Bellucci A, Westwood AJ, Ingram E, Casamenti F, Goedert M, Spillantini MG. Induction of inflammatory mediators and microglial activation in mice transgenic for mutant human P301S tau protein. Am J Pathol. 2004;165:1643–52. doi:10.1016/S0002-9440(10)63421-9.PubMed CentralPubMedView ArticleGoogle Scholar
- Beraud D, Maguire-Zeiss KA. Misfolded alpha-synuclein and Toll-like receptors: therapeutic targets for Parkinson's disease. Parkinsonism Relat Disord. 2012;18 Suppl 1:S17–20. doi:10.1016/S1353-8020(11)70008-6.PubMed CentralPubMedView ArticleGoogle Scholar
- Bergeron C, Pollanen MS, Weyer L, Lang AE. Cortical degeneration in progressive supranuclear palsy. A comparison with cortical-basal ganglionic degeneration. J Neuropathol Exp Neurol. 1997;56:726–34.PubMedView ArticleGoogle Scholar
- Binder LI, Guillozet-Bongaarts AL, Garcia-Sierra F, Berry RW. Tau, tangles, and Alzheimer's disease. Biochim Biophys Acta. 1739;2005:216–23. doi:10.1016/j.bbadis.2004.08.014.Google Scholar
- Bouabe H, Okkenhaug K. Gene targeting in mice: a review. Methods Mol Biol. 2013;1064:315–36. doi:10.1007/978-1-62703-601-6_23.PubMed CentralPubMedView ArticleGoogle Scholar
- Braak H, Braak E. Neuropathological stageing of Alzheimer-related changes. Acta Neuropathol. 1991;82:239–59.PubMedView ArticleGoogle Scholar
- Buee L, Bussiere T, Buee-Scherrer V, Delacourte A, Hof PR. Tau protein isoforms, phosphorylation and role in neurodegenerative disorders. Brain Res Brain Res Rev. 2000;33:95–130.PubMedView ArticleGoogle Scholar
- Bugiani O, Mancardi GL, Brusa A, Ederli A. The fine structure of subcortical neurofibrillary tangles in progressive supranuclear palsy. Acta Neuropathol. 1979;45:147–52.PubMedView ArticleGoogle Scholar
- Caroni P. Overexpression of growth-associated proteins in the neurons of adult transgenic mice. J Neurosci Methods. 1997;71:3–9.PubMedView ArticleGoogle Scholar
- Chen J, Kanai Y, Cowan NJ, Hirokawa N. Projection domains of MAP2 and tau determine spacings between microtubules in dendrites and axons. Nature. 1992;360:674–7. doi:10.1038/360674a0.PubMedView ArticleGoogle Scholar
- Coppola G, Chinnathambi S, Lee JJ, Dombroski BA, Baker MC, Soto-Ortolaza AI, et al. Evidence for a role of the rare p.A152T variant in MAPT in increasing the risk for FTD-spectrum and Alzheimer's diseases. Hum Mol Genet. 2012;21:3500–12. doi:10.1093/hmg/dds161.PubMed CentralPubMedView ArticleGoogle Scholar
- Cuervo AM, Wong E. Chaperone-mediated autophagy: roles in disease and aging. Cell Res. 2014;24:92–104. doi:10.1038/cr.2013.153.PubMed CentralPubMedView ArticleGoogle Scholar
- de Calignon A, Polydoro M, Suarez-Calvet M, William C, Adamowicz DH, Kopeikina KJ, et al. Propagation of tau pathology in a model of early Alzheimer's disease. Neuron. 2012;73:685–97. doi:10.1016/j.neuron.2011.11.033.PubMed CentralPubMedView ArticleGoogle Scholar
- Dickson DW, Kouri N, Murray ME, Josephs KA. Neuropathology of frontotemporal lobar degeneration-tau (FTLD-tau). J Mol Neurosci. 2011;45:384–9. doi:10.1007/s12031-011-9589-0.PubMed CentralPubMedView ArticleGoogle Scholar
- Ding H, Dolan PJ, Johnson GV. Histone deacetylase 6 interacts with the microtubule-associated protein tau. J Neurochem. 2008;106:2119–30. doi:10.1111/j.1471-4159.2008.05564.x.PubMed CentralPubMedView ArticleGoogle Scholar
- Ding Q, Dimayuga E, Markesbery WR, Keller JN. Proteasome inhibition induces reversible impairments in protein synthesis. FASEB J. 2006;20:1055–63. doi:10.1096/fj.05-5495com.PubMedView ArticleGoogle Scholar
- Ding WX, Ni HM, Gao W, Yoshimori T, Stolz DB, Ron D, et al. Linking of autophagy to ubiquitin-proteasome system is important for the regulation of endoplasmic reticulum stress and cell viability. Am J Pathol. 2007;171:513–24. doi:10.2353/ajpath.2007.070188.PubMed CentralPubMedView ArticleGoogle Scholar
- Dong C, Upadhya SC, Ding L, Smith TK, Hegde AN. Proteasome inhibition enhances the induction and impairs the maintenance of late-phase long-term potentiation. Learn Mem. 2008;15:335–47. doi:10.1101/lm.984508.PubMed CentralPubMedView ArticleGoogle Scholar
- Doorn KJ, Moors T, Drukarch B, van de Berg W, Lucassen PJ, van Dam AM. Microglial phenotypes and toll-like receptor 2 in the substantia nigra and hippocampus of incidental Lewy body disease cases and Parkinson's disease patients. Acta Neuropathol Commun. 2014;2:90. doi:10.1186/s40478-014-0090-1.PubMed CentralPubMedGoogle Scholar
- Du J, Liang Y, Xu F, Sun B, Wang Z. Trehalose rescues Alzheimer's disease phenotypes in APP/PS1 transgenic mice. J Pharm Pharmacol. 2013;65:1753–6. doi:10.1111/jphp.12108.PubMedView ArticleGoogle Scholar
- Eckermann K, Mocanu MM, Khlistunova I, Biernat J, Nissen A, Hofmann A, et al. The beta-propensity of Tau determines aggregation and synaptic loss in inducible mouse models of tauopathy. J Biol Chem. 2007;282:31755–65. doi:10.1074/jbc.M705282200.PubMedView ArticleGoogle Scholar
- Fernandez-Botran R, Ahmed Z, Crespo FA, Gatenbee C, Gonzalez J, Dickson DW, et al. Cytokine expression and microglial activation in progressive supranuclear palsy. Parkinsonism Relat Disord. 2011;17:683–8. doi:10.1016/j.parkreldis.2011.06.007.PubMed CentralPubMedView ArticleGoogle Scholar
- Fong H, Wang C, Knoferle J, Walker D, Balestra ME, Tong LM, et al. Genetic correction of tauopathy phenotypes in neurons derived from human induced pluripotent stem cells. Stem Cell Rep. 2013;1:226–34. doi:10.1016/j.stemcr.2013.08.001.View ArticleGoogle Scholar
- Friedrich G, Soriano P. Promoter traps in embryonic stem cells: a genetic screen to identify and mutate developmental genes in mice. Genes Dev. 1991;5:1513–23.PubMedView ArticleGoogle Scholar
- Gerlai R, Wojtowicz JM, Marks A, Roder J. Overexpression of a calcium-binding protein, S100 beta, in astrocytes alters synaptic plasticity and impairs spatial learning in transgenic mice. Learn Mem. 1995;2:26–39.PubMedView ArticleGoogle Scholar
- Glaser EM, Van der Loos H. Analysis of thick brain sections by obverse-reverse computer microscopy: application of a new, high clarity Golgi-Nissl stain. J Neurosci Methods. 1981;4:117–25.PubMedView ArticleGoogle Scholar
- Goedert M, Jakes R. Mutations causing neurodegenerative tauopathies. Biochim Biophys Acta. 1739;2005:240–50. doi:10.1016/j.bbadis.2004.08.007.Google Scholar
- Gorlovoy P, Larionov S, Pham TT, Neumann H. Accumulation of tau induced in neurites by microglial proinflammatory mediators. FASEB J. 2009;23:2502–13. doi:10.1096/fj.08-123877.PubMedView ArticleGoogle Scholar
- Graff-Radford J, Whitwell JL, Dickson DW, Josephs KA. Pallidonigroluysian atrophy associated with p.A152T variant in MAPT. Parkinsonism Relat Disord. 2013;19:838–41. doi:10.1016/j.parkreldis.2013.04.023.PubMedView ArticleGoogle Scholar
- Griffin WS, Sheng JG, Royston MC, Gentleman SM, McKenzie JE, Graham DI, et al. Glial-neuronal interactions in Alzheimer's disease: the potential role of a 'cytokine cycle' in disease progression. Brain Pathol. 1998;8:65–72.PubMedView ArticleGoogle Scholar
- Hanger DP, Anderton BH, Noble W. Tau phosphorylation: the therapeutic challenge for neurodegenerative disease. Trends Mol Med. 2009;15:112–9. doi:10.1016/j.molmed.2009.01.003.PubMedView ArticleGoogle Scholar
- Harris JA, Koyama A, Maeda S, Ho K, Devidze N, Dubal DB, et al. Human P301L-mutant tau expression in mouse entorhinal-hippocampal network causes tau aggregation and presynaptic pathology but no cognitive deficits. PLoS One. 2012;7, e45881. doi:10.1371/journal.pone.0045881.PubMed CentralPubMedView ArticleGoogle Scholar
- Hasegawa M, Smith MJ, Goedert M. Tau proteins with FTDP-17 mutations have a reduced ability to promote microtubule assembly. FEBS Lett. 1998;437:207–10.PubMedView ArticleGoogle Scholar
- Heneka MT, O'Banion MK. Inflammatory processes in Alzheimer's disease. J Neuroimmunol. 2007;184:69–91. doi:10.1016/j.jneuroim.2006.11.017.PubMedView ArticleGoogle Scholar
- Heneka MT, Wiesinger H, Dumitrescu-Ozimek L, Riederer P, Feinstein DL, Klockgether T. Neuronal and glial coexpression of argininosuccinate synthetase and inducible nitric oxide synthase in Alzheimer disease. J Neuropathol Exp Neurol. 2001;60:906–16.PubMedView ArticleGoogle Scholar
- Hirsch EC, Hunot S. Neuroinflammation in Parkinson's disease: a target for neuroprotection? Lancet Neurol. 2009;8:382–97. doi:10.1016/S1474-4422(09)70062-6.PubMedView ArticleGoogle Scholar
- Hochgräfe K, Mandelkow EM. Making the brain glow: in vivo bioluminescence imaging to study neurodegeneration. Mol Neurobiol. 2013;47:868–82. doi:10.1007/s12035-012-8379-1.PubMedView ArticleGoogle Scholar
- Huang Q, Figueiredo-Pereira ME. Ubiquitin/proteasome pathway impairment in neurodegeneration: therapeutic implications. Apoptosis. 2010;15:1292–311. doi:10.1007/s10495-010-0466-z.PubMed CentralPubMedView ArticleGoogle Scholar
- Hutton M, Lendon CL, Rizzu P, Baker M, Froelich S, Houlden H, et al. Association of missense and 5'-splice-site mutations in tau with the inherited dementia FTDP-17. Nature. 1998;393:702–5. doi:10.1038/31508.PubMedView ArticleGoogle Scholar
- Illenberger S, Zheng-Fischhofer Q, Preuss U, Stamer K, Baumann K, Trinczek B, et al. The endogenous and cell cycle-dependent phosphorylation of tau protein in living cells: implications for Alzheimer's disease. Mol Biol Cell. 1998;9:1495–512.PubMed CentralPubMedView ArticleGoogle Scholar
- Ittner LM, Ke YD, Delerue F, Bi M, Gladbach A, van Eersel J, et al. Dendritic function of tau mediates amyloid-beta toxicity in Alzheimer's disease mouse models. Cell. 2010;142:387–97. doi:10.1016/j.cell.2010.06.036.PubMedView ArticleGoogle Scholar
- Iyer A, Lapointe NE, Zielke K, Berdynski M, Guzman E, Barczak A, et al. A novel MAPT mutation, G55R, in a frontotemporal dementia patient leads to altered Tau function. PLoS One. 2013;8, e76409. doi:10.1371/journal.pone.0076409.PubMed CentralPubMedView ArticleGoogle Scholar
- Jeganathan S, von Bergen M, Brutlach H, Steinhoff HJ, Mandelkow E. Global hairpin folding of tau in solution. Biochemistry. 2006;45:2283–93. doi:10.1021/bi0521543.PubMedView ArticleGoogle Scholar
- Jicha GA, Berenfeld B, Davies P. Sequence requirements for formation of conformational variants of tau similar to those found in Alzheimer's disease. J Neurosci Res. 1999;55:713–23.PubMedView ArticleGoogle Scholar
- Josephs KA, Hodges JR, Snowden JS, Mackenzie IR, Neumann M, Mann DM, et al. Neuropathological background of phenotypical variability in frontotemporal dementia. Acta Neuropathol. 2011;122:137–53. doi:10.1007/s00401-011-0839-6.PubMed CentralPubMedView ArticleGoogle Scholar
- Kara E, Ling H, Pittman AM, Shaw K, de Silva R, Simone R, et al. The MAPT p.A152T variant is a risk factor associated with tauopathies with atypical clinical and neuropathological features. Neurobiol Aging. 2012;33:2231 e2237–14. doi:10.1016/j.neurobiolaging.2012.04.006.Google Scholar
- Korolchuk VI, Menzies FM, Rubinsztein DC. Mechanisms of cross-talk between the ubiquitin-proteasome and autophagy-lysosome systems. FEBS Lett. 2010;584:1393–8. doi:10.1016/j.febslet.2009.12.047.PubMedView ArticleGoogle Scholar
- Kovacs GG, Wohrer A, Strobel T, Botond G, Attems J, Budka H. Unclassifiable tauopathy associated with an A152T variation in MAPT exon 7. Clin Neuropathol. 2011;30:3–10.PubMedView ArticleGoogle Scholar
- Krüger U, Wang Y, Kumar S, Mandelkow EM. Autophagic degradation of tau in primary neurons and its enhancement by trehalose. Neurobiol Aging. 2012;33:2291–305. doi:10.1016/j.neurobiolaging.2011.11.009.PubMedView ArticleGoogle Scholar
- Lee MJ, Lee JH, Rubinsztein DC. Tau degradation: the ubiquitin-proteasome system versus the autophagy-lysosome system. Prog Neurobiol. 2013;105:49–59. doi:10.1016/j.pneurobio.2013.03.001.PubMedView ArticleGoogle Scholar
- Lee SE, Tartaglia MC, Yener G, Genc S, Seeley WW, Sanchez-Juan P, et al. Neurodegenerative disease phenotypes in carriers of MAPT p.A152T, a risk factor for frontotemporal dementia spectrum disorders and Alzheimer disease. Alzheimer Dis Assoc Disord. 2013;27:302–9. doi:10.1097/WAD.0b013e31828cc357.PubMedView ArticleGoogle Scholar
- Leroy K, Bretteville A, Schindowski K, Gilissen E, Authelet M, De Decker R, et al. Early axonopathy preceding neurofibrillary tangles in mutant tau transgenic mice. Am J Pathol. 2007;171:976–92. doi:10.2353/ajpath.2007.070345.PubMed CentralPubMedView ArticleGoogle Scholar
- Lewis J, McGowan E, Rockwood J, Melrose H, Nacharaju P, Van Slegtenhorst M, et al. Neurofibrillary tangles, amyotrophy and progressive motor disturbance in mice expressing mutant (P301L) tau protein. Nat Genet. 2000;25:402–5. doi:10.1038/78078.PubMedView ArticleGoogle Scholar
- Liu L, Drouet V, Wu JW, Witter MP, Small SA, Clelland C, et al. Trans-synaptic spread of tau pathology in vivo. PLoS One. 2012;7, e31302. doi:10.1371/journal.pone.0031302.PubMed CentralPubMedView ArticleGoogle Scholar
- Lopez-Salon M, Alonso M, Vianna MR, Viola H, Mello e Souza T, Izquierdo I, et al. The ubiquitin-proteasome cascade is required for mammalian long-term memory formation. Eur J Neurosci. 2001;14:1820–6.PubMedView ArticleGoogle Scholar
- Low P, Varga A, Pircs K, Nagy P, Szatmari Z, Sass M, et al. Impaired proteasomal degradation enhances autophagy via hypoxia signaling in Drosophila. BMC Cell Biol. 2013;14:29. doi:10.1186/1471-2121-14-29.PubMed CentralPubMedView ArticleGoogle Scholar
- Lyman M, Lloyd DG, Ji X, Vizcaychipi MP, Ma D. Neuroinflammation: the role and consequences. Neurosci Res. 2014;79:1–12. doi:10.1016/j.neures.2013.10.004.PubMedView ArticleGoogle Scholar
- Magnani E, Fan J, Gasparini L, Golding M, Williams M, Schiavo G, et al. Interaction of tau protein with the dynactin complex. EMBO J. 2007;26:4546–54. doi:10.1038/sj.emboj.7601878.PubMed CentralPubMedView ArticleGoogle Scholar
- Majumder S, Caccamo A, Medina DX, Benavides AD, Javors MA, Kraig E, et al. Lifelong rapamycin administration ameliorates age-dependent cognitive deficits by reducing IL-1beta and enhancing NMDA signaling. Aging Cell. 2012;11:326–35. doi:10.1111/j.1474-9726.2011.00791.x.PubMed CentralPubMedView ArticleGoogle Scholar
- Majumder S, Richardson A, Strong R, Oddo S. Inducing autophagy by rapamycin before, but not after, the formation of plaques and tangles ameliorates cognitive deficits. PLoS One. 2011;6, e25416. doi:10.1371/journal.pone.0025416.PubMed CentralPubMedView ArticleGoogle Scholar
- Mandelkow EM, Mandelkow E. Biochemistry and cell biology of tau protein in neurofibrillary degeneration. Cold Spring Harb Perspect Med. 2012;2:a006247. doi:10.1101/cshperspect.a006247.PubMed CentralPubMedView ArticleGoogle Scholar
- Metcalf DJ, Garcia-Arencibia M, Hochfeld WE, Rubinsztein DC. Autophagy and misfolded proteins in neurodegeneration. Exp Neurol. 2012;238:22–8. doi:10.1016/j.expneurol.2010.11.003.PubMed CentralPubMedView ArticleGoogle Scholar
- Middeldorp J, Hol EM. GFAP in health and disease. Prog Neurobiol. 2011;93:421–43. doi:10.1016/j.pneurobio.2011.01.005.PubMedView ArticleGoogle Scholar
- Mishra A, Kim HJ, Shin AH, Thayer SA. Synapse loss induced by interleukin-1beta requires pre- and post-synaptic mechanisms. J Neuroimmune Pharmacol. 2012;7:571–8. doi:10.1007/s11481-012-9342-7.PubMed CentralPubMedView ArticleGoogle Scholar
- Mittal S, Ganesh S. Protein quality control mechanisms and neurodegenerative disorders: Checks, balances and deadlocks. Neurosci Res. 2010;68:159–66. doi:10.1016/j.neures.2010.08.002.PubMedView ArticleGoogle Scholar
- Mocanu MM, Nissen A, Eckermann K, Khlistunova I, Biernat J, Drexler D, et al. The potential for beta-structure in the repeat domain of tau protein determines aggregation, synaptic decay, neuronal loss, and coassembly with endogenous Tau in inducible mouse models of tauopathy. J Neurosci. 2008;28:737–48. doi:10.1523/JNEUROSCI.2824-07.2008.PubMedView ArticleGoogle Scholar
- Morishima-Kawashima M, Hasegawa M, Takio K, Suzuki M, Yoshida H, Titani K, et al. Proline-directed and non-proline-directed phosphorylation of PHF-tau. J Biol Chem. 1995;270:823–9.PubMedView ArticleGoogle Scholar
- Morris R. Developments of a water-maze procedure for studying spatial learning in the rat. J Neurosci Methods. 1984;11:47–60.PubMedView ArticleGoogle Scholar
- Mrak RE, Griffin WS. Interleukin-1, neuroinflammation, and Alzheimer's disease. Neurobiol Aging. 2001;22:903–8.PubMedView ArticleGoogle Scholar
- Neumann M, Tolnay M, Mackenzie IR. The molecular basis of frontotemporal dementia. Expert Rev Mol Med. 2009;11, e23. doi:10.1017/S1462399409001136.PubMedView ArticleGoogle Scholar
- Pan T, Kondo S, Le W, Jankovic J. The role of autophagy-lysosome pathway in neurodegeneration associated with Parkinson's disease. Brain. 2008;131:1969–78. doi:10.1093/brain/awm318.PubMedView ArticleGoogle Scholar
- Pandey UB, Nie Z, Batlevi Y, McCray BA, Ritson GP, Nedelsky NB, et al. HDAC6 rescues neurodegeneration and provides an essential link between autophagy and the UPS. Nature. 2007;447:859–63. doi:10.1038/nature05853.PubMedView ArticleGoogle Scholar
- Pennanen L, Wolfer DP, Nitsch RM, Gotz J. Impaired spatial reference memory and increased exploratory behavior in P301L tau transgenic mice. Genes Brain Behav. 2006;5:369–79. doi:10.1111/j.1601-183X.2005.00165.x.PubMedView ArticleGoogle Scholar
- Perry VH, Nicoll JA, Holmes C. Microglia in neurodegenerative disease. Nat Rev Neurol. 2010;6:193–201. doi:10.1038/nrneurol.2010.17.PubMedView ArticleGoogle Scholar
- Pintado C, Gavilan MP, Gavilan E, Garcia-Cuervo L, Gutierrez A, Vitorica J, et al. Lipopolysaccharide-induced neuroinflammation leads to the accumulation of ubiquitinated proteins and increases susceptibility to neurodegeneration induced by proteasome inhibition in rat hippocampus. J Neuroinflammation. 2012;9:87. doi:10.1186/1742-2094-9-87.PubMed CentralPubMedView ArticleGoogle Scholar
- Politis M, Su P, Piccini P. Imaging of microglia in patients with neurodegenerative disorders. Front Pharmacol. 2012;3:96. doi:10.3389/fphar.2012.00096.PubMed CentralPubMedView ArticleGoogle Scholar
- Poorkaj P, Muma NA, Zhukareva V, Cochran EJ, Shannon KM, Hurtig H, et al. An R5L tau mutation in a subject with a progressive supranuclear palsy phenotype. Ann Neurol. 2002;52:511–6. doi:10.1002/ana.10340.PubMedView ArticleGoogle Scholar
- Ramsden M, Kotilinek L, Forster C, Paulson J, McGowan E, SantaCruz K, et al. Age-dependent neurofibrillary tangle formation, neuron loss, and memory impairment in a mouse model of human tauopathy (P301L). J Neurosci. 2005;25:10637–47. doi:10.1523/JNEUROSCI.3279-05.2005.PubMedView ArticleGoogle Scholar
- Ricobaraza A, Cuadrado-Tejedor M, Marco S, Perez-Otano I, Garcia-Osta A. Phenylbutyrate rescues dendritic spine loss associated with memory deficits in a mouse model of Alzheimer disease. Hippocampus. 2010. doi:10.1002/hipo.20883
- Rodriguez-Navarro JA, Rodriguez L, Casarejos MJ, Solano RM, Gomez A, Perucho J, et al. Trehalose ameliorates dopaminergic and tau pathology in parkin deleted/tau overexpressing mice through autophagy activation. Neurobiol Dis. 2010;39:423–38. doi:10.1016/j.nbd.2010.05.014.PubMedView ArticleGoogle Scholar
- Rohrer JD, Paviour D, Vandrovcova J, Hodges J, de Silva R, Rossor MN. Novel L284R MAPT mutation in a family with an autosomal dominant progressive supranuclear palsy syndrome. Neurodegener Dis. 2011;8:149–52. doi:10.1159/000319454.PubMed CentralPubMedView ArticleGoogle Scholar
- Santacruz K, Lewis J, Spires T, Paulson J, Kotilinek L, Ingelsson M, et al. Tau suppression in a neurodegenerative mouse model improves memory function. Science. 2005;309:476–81. doi:10.1126/science.1113694.PubMed CentralPubMedView ArticleGoogle Scholar
- Schindowski K, Bretteville A, Leroy K, Begard S, Brion JP, Hamdane M, et al. Alzheimer's disease-like tau neuropathology leads to memory deficits and loss of functional synapses in a novel mutated tau transgenic mouse without any motor deficits. Am J Pathol. 2006;169:599–616. doi:10.2353/ajpath.2006.060002.PubMed CentralPubMedView ArticleGoogle Scholar
- Sheng JG, Ito K, Skinner RD, Mrak RE, Rovnaghi CR, Van Eldik LJ, et al. In vivo and in vitro evidence supporting a role for the inflammatory cytokine interleukin-1 as a driving force in Alzheimer pathogenesis. Neurobiol Aging. 1996;17:761–6.PubMed CentralPubMedView ArticleGoogle Scholar
- Sheng JG, Zhu SG, Jones RA, Griffin WS, Mrak RE. Interleukin-1 promotes expression and phosphorylation of neurofilament and tau proteins in vivo. Exp Neurol. 2000;163:388–91. doi:10.1006/exnr.2000.7393.PubMedView ArticleGoogle Scholar
- Shi CS, Kehrl JH. TRAF6 and A20 regulate lysine 63-linked ubiquitination of Beclin-1 to control TLR4-induced autophagy. Sci Signal. 2010;3:ra42. doi:10.1126/scisignal.2000751.PubMedGoogle Scholar
- Spittaels K, Van den Haute C, Van Dorpe J, Bruynseels K, Vandezande K, Laenen I, et al. Prominent axonopathy in the brain and spinal cord of transgenic mice overexpressing four-repeat human tau protein. Am J Pathol. 1999;155:2153–65. doi:10.1016/S0002-9440(10)65533-2.PubMed CentralPubMedView ArticleGoogle Scholar
- Stalder M, Phinney A, Probst A, Sommer B, Staufenbiel M, Jucker M. Association of microglia with amyloid plaques in brains of APP23 transgenic mice. Am J Pathol. 1999;154:1673–84. doi:10.1016/S0002-9440(10)65423-5.PubMed CentralPubMedView ArticleGoogle Scholar
- Sumpter Jr R, Levine B. Autophagy and innate immunity: triggering, targeting and tuning. Semin Cell Dev Biol. 2010;21:699–711. doi:10.1016/j.semcdb.2010.04.003.PubMed CentralPubMedView ArticleGoogle Scholar
- Sun A, Nguyen XV, Bing G. Comparative analysis of an improved thioflavin-s stain, Gallyas silver stain, and immunohistochemistry for neurofibrillary tangle demonstration on the same sections. J Histochem Cytochem. 2002;50:463–72.PubMedView ArticleGoogle Scholar
- Sydow A, Van der Jeugd A, Zheng F, Ahmed T, Balschun D, Petrova O, et al. Tau-induced defects in synaptic plasticity, learning, and memory are reversible in transgenic mice after switching off the toxic Tau mutant. J Neurosci. 2011;31:2511–25. doi:10.1523/JNEUROSCI.5245-10.2011.PubMedView ArticleGoogle Scholar
- Takeda S, Wegmann S, Cho H, DeVos SL, Commins C, Roe AD, et al. Neuronal uptake and propagation of a rare phosphorylated high-molecular-weight tau derived from Alzheimer's disease brain. Nat Commun. 2015;6:8490. doi:10.1038/ncomms9490.PubMed CentralPubMedView ArticleGoogle Scholar
- Tamguney G, Francis KP, Giles K, Lemus A, DeArmond SJ, Prusiner SB. Measuring prions by bioluminescence imaging. Proc Natl Acad Sci U S A. 2009;106:15002–6. doi:10.1073/pnas.0907339106.PubMed CentralPubMedView ArticleGoogle Scholar
- Tarawneh R, Holtzman DM. The clinical problem of symptomatic Alzheimer disease and mild cognitive impairment. Cold Spring Harb Perspect Med. 2012;2:a006148. doi:10.1101/cshperspect.a006148.PubMed CentralPubMedView ArticleGoogle Scholar
- Tatebayashi Y, Miyasaka T, Chui DH, Akagi T, Mishima K, Iwasaki K, et al. Tau filament formation and associative memory deficit in aged mice expressing mutant (R406W) human tau. Proc Natl Acad Sci U S A. 2002;99:13896–901. doi:10.1073/pnas.202205599202205599.PubMed CentralPubMedView ArticleGoogle Scholar
- Tellez-Nagel I, Wisniewski HM. Ultrastructure of neurofibrillary tangles in Steele-Richardson-Olszewski syndrome. Arch Neurol. 1973;29:324–7.PubMedView ArticleGoogle Scholar
- Terry RD, Masliah E, Salmon DP, Butters N, DeTeresa R, Hill R, et al. Physical basis of cognitive alterations in Alzheimer's disease: synapse loss is the major correlate of cognitive impairment. Ann Neurol. 1991;30:572–80. doi:10.1002/ana.410300410.PubMedView ArticleGoogle Scholar
- Terwel D, Lasrado R, Snauwaert J, Vandeweert E, Van Haesendonck C, Borghgraef P, et al. Changed conformation of mutant Tau-P301L underlies the moribund tauopathy, absent in progressive, nonlethal axonopathy of Tau-4R/2N transgenic mice. J Biol Chem. 2005;280:3963–73. doi:10.1074/jbc.M409876200.PubMedView ArticleGoogle Scholar
- Van der Jeugd A, Hochgräfe K, Ahmed T, Decker JM, Sydow A, Hofmann A, et al. Cognitive defects are reversible in inducible mice expressing pro-aggregant full-length human Tau. Acta Neuropathol. 2012;123:787–805. doi:10.1007/s00401-012-0987-3.PubMedView ArticleGoogle Scholar
- von Bergen M, Barghorn S, Li L, Marx A, Biernat J, Mandelkow EM, et al. Mutations of tau protein in frontotemporal dementia promote aggregation of paired helical filaments by enhancing local beta-structure. J Biol Chem. 2001;276:48165–74. doi:10.1074/jbc.M105196200.Google Scholar
- Wang M-VM, Kruger U, Kaushik S, Wong E, Mandelkow EM, Cuervo AM, et al. Tau fragmentation, aggregation and clearance: the dual role of lysosomal processing. Hum Mol Genet. 2009;18:4153–70. doi:10.1093/hmg/ddp367.PubMed CentralPubMedView ArticleGoogle Scholar
- Wes PD, Easton A, Corradi J, Barten DM, Devidze N, DeCarr LB, et al. Tau overexpression impacts a neuroinflammation gene expression network perturbed in Alzheimer's disease. PLoS One. 2014;9, e106050. doi:10.1371/journal.pone.0106050.PubMed CentralPubMedView ArticleGoogle Scholar
- Wolfe MS. The role of tau in neurodegenerative diseases and its potential as a therapeutic target. Scientifica (Cairo). 2012;2012:796024. doi:10.6064/2012/796024.Google Scholar
- Wszolek ZK, Slowinski J, Golan M, Dickson DW. Frontotemporal dementia and parkinsonism linked to chromosome 17. Folia Neuropathol. 2005;43:258–70.PubMedGoogle Scholar
- Yi JJ, Ehlers MD. Ubiquitin and protein turnover in synapse function. Neuron. 2005;47:629–32. doi:10.1016/j.neuron.2005.07.008.PubMedView ArticleGoogle Scholar
- Yirmiya R, Goshen I. Immune modulation of learning, memory, neural plasticity and neurogenesis. Brain Behav Immun. 2011;25:181–213. doi:10.1016/j.bbi.2010.10.015.PubMedView ArticleGoogle Scholar
- Yoshiyama Y, Higuchi M, Zhang B, Huang SM, Iwata N, Saido TC, et al. Synapse loss and microglial activation precede tangles in a P301S tauopathy mouse model. Neuron. 2007;53:337–51. doi:10.1016/j.neuron.2007.01.010.PubMedView ArticleGoogle Scholar
- Zhu L, Ramboz S, Hewitt D, Boring L, Grass DS, Purchio AF. Non-invasive imaging of GFAP expression after neuronal damage in mice. Neurosci Lett. 2004;367:210–2. doi:10.1016/j.neulet.2004.06.020.PubMedView ArticleGoogle Scholar
- Zimmer ER, Leuzy A, Benedet AL, Breitner J, Gauthier S, Rosa-Neto P. Tracking neuroinflammation in Alzheimer's disease: the role of positron emission tomography imaging. J Neuroinflammation. 2014;11:120. doi:10.1186/1742-2094-11-120.PubMed CentralPubMedView ArticleGoogle Scholar