Search

Neurofibrillary tangles are a pathological phenotype in Alzheimer's disease (AD) and are caused by the hyperphosphorylation of the microtubule associated protein tau. In mouse models of AD, decreasing tau protein expression limits the severity of symptoms and inhibits progression of AD. We now report that the 5' leader in the human tau mRNA contains an internal ribosomal entry site (IRES) and that IRES-dependent translation plays a role in the synthesis of tau protein. Consequently, targeting the tau IRES provides a novel target for regulating tau expression in AD and other tauopathies.

Transgenic mice expressing human tau containing the P301L tau mutation (JNPL3; tau mice) develop motor neuron loss, paralysis and death between 7 and 12 months. Surprisingly, at 5 and 7 months of age, tau transgenic mice were superior to other genotypes in the rotarod task, and had near perfect scores on the balance beam and coat hanger tests. One tau transgenic mouse was performing at a superior level in the rotarod one day prior to developing paralysis. Cognitive function was also normal in the tau mice evaluated in the radial arm water maze and the Y-maze tasks. We also crossed the tau transgenic mice with Tg2576 amyloid-beta protein precursor (AbetaPP) transgenic mice. Although AbetaPP mice were deficient in the radial arm maze task, AbetaPP + tau mice were not impaired, implying a benefit of the tau transgene. Some mice were homozygous for the retinal degeneration mutation (rd/rd) and excluded from the genotype analysis. Only the water maze task discriminated the rd/rd mice from nontransgenic mice. In conclusion, it seems that the modest tau overexpression or the presence of mutant tau in the JNPL3 tau mice may provide some benefit with respect to motor and cognitive performance before the onset of paralysis.

Purpose of Review: Great progress has been made in understanding the pathogenesis of neurofibrillary degeneration in Alzheimer's disease brains in the last two decades. In this review we summarize how neurons are degenerated in Alzheimer's disease brains and highlight the evidence of using kinases such as glycogen synthase kinase 3 and p70 S6 kinase and phosphatases such as protein phosphatase 2A as drug targets to prohibit the formation of neurofibrillary degeneration of Alzheimer's disease., Recent Findings: In general there are two types of neuronal degeneration in Alzheimer's disease brains: neurofibrillary formation and apoptosis. The microtubule-associated protein tau that stabilizes neuronal microtubules under normal physiological conditions is abnormally hyperphosphorylated in Alzheimer's disease brains, resulting in the generation of aberrant aggregates that are toxic to neurons. The processes of tau hyperphosphorylation and the formation of neurofibrillary tangles are caused by the imbalance of the activities of protein kinases and protein phosphatases in Alzheimer's disease brains. Recent findings from our and other groups have suggested glycogen synthase kinase 3 and p70 S6 kinase as main tau kinases and protein phosphatase 2A as the main tau phosphatase involved in the formation of these processes. Activities of these targets are implicated by Abeta peptide, the major component of another hallmark in Alzheimer's disease brains, senile plaques., Summary: To prevent the clinical progression of neurodegeneration, a combination strategy is suggested to target both senile plaques with immunization and neurofibrillary tangles with drugs to prevent the synthesis and phosphorylation of tau.

We recently provided evidence for a mitochondrial dysfunction in P301L tau transgenic mice, a strain modeling the tau pathology of Alzheimer's disease (AD) and frontotemporal dementia (FTD). In addition to tau aggregates, the AD brain is further characterized by A beta peptide-containing plaques. When we addressed the role of A beta, this indicated a synergistic action of tau and A beta pathology on the mitochondria. In the present study, we compared the toxicity of different A beta 42 conformations in light of recent studies suggesting that oligomeric rather than fibrillar A beta might be the actual toxic species. Interestingly, both oligomeric and fibrillar, but not disaggregated (mainly monomeric) A beta 42 caused a decreased mitochondrial membrane potential in cortical brain cells obtained from FTD P301L tau transgenic mice. This was not observed with cerebellar preparations indicating selective vulnerability of cortical neurons. Furthermore, we found reductions in state 3 respiration, the respiratory control ratio, and uncoupled respiration when incubating P301L tau mitochondria either with oligomeric or fibrillar preparations of A beta 42. Finally, we found that aging specifically increased the sensitivity of mitochondria to oligomeric A beta 42 damage indicating that oligomeric and fibrillar A beta 42 are both toxic, but exert different degrees of toxicity.

Early onset increases in oxidative stress and tau pathology are present in the brain of senescence-accelerated mice prone (SAMP8). Astrocytes play an essential role, both in determining the brain's susceptibility to oxidative damage and in protecting neurons. In this study, we examine changes in tau phosphorylation, oxidative stress and glutamate uptake in primary cultures of cortical astrocytes from neonatal SAMP8 mice and senescence-accelerated-resistant mice (SAMR1). We demonstrated an enhancement of abnormally phosphorylated tau in Ser(199) and Ser(396) in SAMP8 astrocytes compared with that of SAMR1 control mice. Gsk3beta and Cdk5 kinase activity, which regulate tau phosphorylation, was also increased in SAMP8 astrocytes. Inhibition of Gsk3beta by lithium or Cdk5 by roscovitine reduced tau phosphorylation at Ser(396). Moreover, we detected an increase in radical superoxide generation, which may be responsible for the corresponding increase in lipoperoxidation and protein oxidation. We also observed a reduced mitochondrial membrane potential in SAMP8 mouse astrocytes. Glutamate uptake in astrocytes is a critical neuroprotective mechanism. SAMP8 astrocytes showed a decreased glutamate uptake compared with those of SAMR1 controls. Interestingly, survival of SAMP8 or SAMR1 neurons cocultured with SAMP8 astrocytes was significantly reduced. Our results indicate that alterations in astrocyte cultures from SAMP8 mice are similar to those detected in whole brains of SAMP8 mice at 1-5 months. Moreover, our findings suggest that this in vitro preparation is suitable for studying the molecular and cellular processes underlying early aging in this murine model. In addition, our study supports the contention that astrocytes play a key role in neurodegeneration during the aging process.

Alternative splicing has emerged as a promising therapeutic target in a number of human disorders. However, the discovery of compounds that target the splicing reaction has been hindered by the lack of suitable high-throughput screening assays. Conversely, the effects of known drugs on the splicing reaction are mostly unclear and not routinely assessed. We have developed a two-color fluorescent reporter for cellular assays of exon inclusion that can accommodate nearly any cassette exon and minimizes interfering effects from changes in transcription and translation. We used microtubule-associated protein tau (MAPT) exon 10, whose missplicing causes frontotemporal dementia, to test the reporter in screening libraries of known bioactive compounds. These screens yielded several compounds that alter the splicing of the exon, both in the reporter and in the endogenous MAPT mRNA. One compound, digoxin, has long been used in the treatment of heart failure, but was not known to modulate splicing. The positive compounds target different signal transduction pathways, and microarray analysis shows that each compound affects the splicing of a different set of exons in addition to MAPT exon 10. Our results identify currently prescribed cardiotonic steroids as modulators of alternative splicing and demonstrate the feasibility of screening for drugs that alter exon inclusion.

The heat-shock proteins (HSPs) Hsp27 and alphaB-crystallin are up-regulated in Alzheimer's disease (AD), but the extent of this and the consequences are still largely unknown. The HSPs are involved in protein degradation and protection against protein aggregation, and they interact with several cytoskeletal components such as microtubules (MT) and neurofilaments (NF). AD pathology includes aggregated proteins (tau, NF), decreased protein degradation, and cytoskeletal disruption. It is thus of interest to investigate more closely the possible roles of the HSPs in AD pathology. The expressions of Hsp27 and alphaB-crystallin in AD brain samples were significantly increased (by approximately 20% and approximately 30%, respectively) and correlated significantly with phosphorylated tau and NF proteins. To investigate the consequences of increased HSP levels on tau and NF regulation, N2a cells were transfected with Hsp27 or alphaB-crystallin constructs, and overexpression of the HSPs was confirmed in the cells. Increased tau phosphorylation at the Ser262 site in the N2a cells was regulated by Hsp27 overexpression (possibly through p70S6k), whereas the overexpression of alphaB-crystallin resulted in decreased levels of phosphorylated tau, NF, and GSK-3beta. It was also shown that overexpression of HSPs causes an increase in the percentage of cells present in the G(1) phase. The results presented suggest that a cellular defense against dysregulated proteins, in the form of Hsp27 and alphaB-crystallin, might contribute to the cell cycle reentry seen in AD cells. Furthermore, Hsp27 might also be involved in AD pathology by aggravating MT disruption by tau phosphorylation., (2007 Wiley-Liss, Inc.)

Background & Aims: The isolation and culture of primary enteric neurons is a difficult process and yields a small number of neurons. We developed fetal and postnatal enteric neuronal cell lines using H-2K(b)-tsA58 transgenic mice (immortomice) that have a temperature-sensitive mutation of the SV40 large tumor antigen gene under the control of an interferon gamma-inducible H-2K(b) promoter element., Methods: Enteric neuronal precursors were isolated from the intestines of E13-mouse fetuses and second day postnatal mice using magnetic immunoselection with a p75NTR antibody. The cells were maintained at the permissive temperature, 33 degrees C, and interferon-gamma for 24 or 48 hours, and then transferred to 39 degrees C in the presence of glial cell line-derived neurotrophic factor for 7 days for further differentiation. Neuronal markers were assessed by reverse-transcription polymerase chain reaction, Western blot, and immunocytochemistry. Neuronal function was assessed by transplanting these cells into the colons of Piebald or nNOS(-/-) mice., Results: Expression analysis of cells showed the presence of neuronal markers peripherin, PGP9.5, HuD, tau, synaptic marker synaptophysin, characteristic receptors of enteric neurons, Ret, and 5-hydroxytryptamine-receptor subtypes at 33 degrees C and 39 degrees C. Nestin, S-100beta, and alpha-smooth muscle actin were expressed minimally at 39 degrees C. Glial cell line-derived neurotrophic factor resulted in increased phosphorylation of Akt in these cells, similar to primary enteric neurons. Transplantation of cells into the piebald or nNOS(-/-) mice colon improved colonic motility., Conclusions: We have developed novel enteric neuronal cell lines that have neuronal characteristics similar to primary enteric neurons. These cells can help us in understanding newer therapeutic options for Hirschsprung's disease.

Neurodegenerative diseases involving neurofibrillary tangle pathology are pernicious. By expressing the microtubule-associated protein tau, a major component of tangles, with a viral vector, we induce neuropathological sequelae in rats that are similar to those seen in human tauopathies. We tested several variants of the adeno-associated virus (AAV) vector for tau expression in the nigrostriatal system in order to develop models with graded onset and completeness. Whereas previous studies with AAV2 tau vectors produced partial lesions of the nigrostriatal system, AAV9 or AAV10 tau vectors were more robust. These vectors had formidable efficacy relative to 6-hydroxydopamine for dopamine loss in the striatum. Time-courses for tau transgene expression, dopamine loss and rotational behavior tracked the disease progression with the AAV9 tau vector. There was a nearly complete lesion over a delayed time-course relative to 6-hydroxydopamine, with a sequence of tau expression by 1 week, dopamine loss by 2 weeks and then behavior effect by 3-4 weeks. Relative to AAV2 or AAV8, tau expression from AAV9 or AAV10 peaked earlier and caused more dopamine loss. Varying vector efficiencies produced graded states of disease up to nearly complete. The disease models stemming from the AAV variants AAV9 or AAV10 may be useful for rapid drug screening, particularly for tau diseases that affect the nigrostriatal system, such as progressive supranuclear palsy.

The intracellular assembly of tau aggregates is a pathological hallmark shared by Alzheimer's disease and other neurodegenerative disorders known collectively as tauopathies. To model how tau fibrillogenesis evolves in tauopathies, we previously established transfectant M1C cultures from human neuroblastoma BE(2)-M17D cells that inducibly express human tau. In the present study, these cells were used to determine the role of the autophagic-lysosomal system in the degradation and aggregation of wild-type tau. Tau induction for 5 days led to the accumulation of tau with nominal assembly of tau aggregates within cells. When the lysosomotropic agent, chloroquine (CQ), was added following the termination of tau induction, tau clearance was delayed. Decreased tau truncation and increased levels of intact tau were observed. When present during tau induction, CQ led to tau accumulation and promoted the formation of sarkosyl-insoluble aggregates containing both truncated and full-length tau. CQ treatment significantly decreased the activities of cathepsins D, B and L, and the inhibition of cathepsins B and L mimicked the effect of CQ and increased tau levels in cells. Additionally, exposure of cells to the autophagy inhibitor, 3-methyladenine, led to tau accumulation and aggregation. These results suggest that the autophagic-lysosomal system plays a role in the clearance of tau, and that dysfunction of this system results in the formation of tau oligomers and insoluble aggregates.

Increasing evidence suggests that neuroimmune networks play key roles in the thymic histophysiology and pathology. Prompted by this, we analyzed by immunohistochemistry the distribution of human thymic cells expressing major neural and neuroendocrine markers and neural growth factor (NGF) receptors in combination with the expression patterns of various cytokeratins. Additionally, since some beta-tubulin isotypes are preferentially expressed in neuronal cells, the immunotopographical distribution of thymic cells expressing beta-tubulin II, III and IV was analyzed. Thymic epithelial cells (TECs) expressed protein gene product 9.5 (PGP 9.5), chromogranin A (CHRA), synaptophysin (SYN), neuron-specific enolase (NSE), tyrosine hydroxylase (TH), CD56, CD57, neurofilaments (NF) (140-160 kDa), NGF receptors (TrKA and p75), beta-tubulin II and IV isotypes and cytokeratin 7, 8, 10, 13, 14, 18 and 19. PGP 9.5 was preferentially expressed in cortical TEC whereas SYN, CHRA, NSE, TH and NF 140-160 kDa were preferentially expressed in medullary TECs and Hassal corpuscles. Variable levels of expression of beta-tubulin II and IV were observed in all TEC subtypes whereas beta-tubulin III was undetectable in TECs. Subcapsular and cortical TECs display higher expression of beta-tubulin IV and lower expression of beta-tubulin II in comparison to those observed in medullary TEC and Hassal corpuscles. The diversity of the immunotopographical distibution and the expression of neural and neuroendocrine markers, the NGF receptors TrKA and p75, and the beta-tubulin II and IV isotypes in the distinct subtypes of TEC may reflect the diversity of their biological functions and/or their different stages of differentiation. The present results provide further immunohistological evidence that numerous neural and neuroendocrine factors may be required for the development and function of the human thymic microenvironment.

In many cases of sporadic frontotemporal dementia (FTD) and in FTD caused by tau mutations (FTDP-17) there is disruption of the normal splicing of tau leading to the aberrant expression of tau isoforms and neurodegeneration. This suggests a central role for tau in the pathogenesis of FTD. However, more than half the cases of sporadic FTD show no tau deposition. We question whether altered expression is also involved in the pathogenesis of tau-negative FTD. Real-time polymerase chain reaction was used to investigate tau isoform expression in tau-negative FTD and age-matched controls. There were no differences in total tau mRNA or 4R versus 3R isoform expression. Our study suggests that perturbed tau mRNA expression is unlikely to be involved in the pathogenesis of tau-negative FTD.

Alzheimer's disease and related dementias are devastating disorders that lead to the progressive decline of cognitive functions. Characteristic features are severe brain atrophy, paralleled by accumulation of beta amyloid and neurofibrillary tangles. With the discovery of neurogenesis in the adult brain, the hopes have risen that these neurodegenerative conditions could be overcome, or at least ameliorated, by the generation of new neurons. The location of the adult neurogenic zones in the hippocampus and the lateral ventricle wall, close to corpus callosum and neocortex, indicates strategic positions for potential repair processes. However, we also need to consider that the generation of new neurons is possibly involved in cognitive functions and could, therefore, be influenced by disease pathology. Moreover, aberrant neurogenic mechanisms could even be a part of the pathological events of neurodegenerative diseases. It is the scope of this review to summarize and analyze the recent data from neurogenesis research with respect to Alzheimer's disease and its animal models.

Microarrays enable the observation of gene expression in experimental models of Alzheimer's disease (AD), with implications for the human pathology. Histopathologically, AD is characterized by Abeta-containing plaques and tau-containing neurofibrillary tangles. Here, we used a human SH-SY5Y neuroblastoma cell system to assess the role of P301L mutant human tau expression, and treatment with or without Abeta on gene regulation. We found that Abeta and P301L tau expression independently affect the regulation of genes controlling cell proliferation and synaptic elements. Moreover, Abeta and P301L tau act synergistically on cell cycle and DNA damage genes, yet influence specific genes within these categories. By using neuronally differentiated P301L tau cells, we can show that Abeta treatment induces an early upregulation of cell cycle control and synaptic genes. At the protein level, by using Kinetworks multi-immunoblotting and BrdU labelling, we found that although P301L tau and Abeta both affected levels of cell cycle proteins, their effects were distinct, in particular concerning DNA damage proteins. Moreover, DNA synthesis was observed only when SH-SY5Y cells overexpressed human wild-type or P301L tau and were incubated with Abeta. Thus, our study shows that Abeta treatment and human tau overexpression in an AD cell culture model act synergistically to promote aberrant cell cycle re-entry, supporting the mitosis failure hypothesis in AD.

Tau-tubulin kinase 2 (TTBK2) is a Ser/Thr kinase that putatively phosphorylates residues Ser208 and Ser210 (numbered according to a 441-residue human tau isoform) in tau protein. Functional analyses revealed that a recombinant kinase domain (residues 1-331) of human TTBK2 expressed in insect cells with a baculovirus overexpression system retains kinase activity for tau protein. The kinase domain of TTBK2 was crystallized using the hanging-drop vapour-diffusion method. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 55.6, b = 113.7, c = 117.3 A, alpha = beta = gamma = 90.0 degrees. Diffraction data were collected to 2.9 A resolution using synchrotron radiation at BL24XU of SPring-8.

The microtubule-binding protein tau has been investigated for its contribution to various neurodegenerative disorders. However, the findings from transgenic studies, using the same tau transgene, vary widely among different laboratories. Here, we have investigated the potential mechanisms underlying tauopathies by comparing Drosophila (d-tau) and human (h-tau) tau in a Drosophila model. Overexpression of a single copy of either tau isoform in the retina results in a similar rough eye phenotype. However, co-expression of Par-1 with d-tau leads to lethality, whereas co-expression of Par-1 with h-tau has little effect on the rough eye phenotype. We have found analogous results by comparing larval proteomes. Through genetic screening and proteomic analysis, we have identified some important potential modifiers and tau-associated proteins. These results suggest that the two tau genes differ significantly. This comparison between species-specific isoforms may help to clarify whether the homologous tau genes are conserved.

The role of tau phosphorylation and tau aggregation in the pathology of a transgenic mouse model that overexpresses GSK-3beta and FTDP-17 tau has been analyzed. In that model we have suggested a possible role for tau phosphorylation, but not for tau aggregation, in the cognitive impairment found in the transgenic mouse.

Growing evidence suggests that one of the earliest events in the neuronal degeneration of Alzheimer's disease (AD) is aberrant cell-cycle activation in postmitotic neurons, which may, in fact, be sufficient to initiate the neurodegenerative cascade. In the present study we examined whether cyclins and cyclin-dependent kinases, molecules normally associated with cell-cycle control, may be involved in delayed expression of altered Alzheimer's proteins in two interconnected areas, the entorhinal cortex (EC) and the dentate gyrus (DG), after a hippocampal excitotoxic lesion. Several cell-cycle proteins of the G1 and S phases and even of the G2 phase were found to be up-regulated in the EC after kainic acid evoked neuronal death in the hippocampus. In addition, we describe the progressive expression of two Alzheimer's-related proteins, PHF-1 and APP, which reached higher levels immediately after the increase in G1/S-phase markers. Hence, the results of the present study support the participation of cell-cycle dysregulation as a key component of the process that may ultimately lead to expression of AD proteins and neuronal death in a brain area when the target site for synaptic inputs in that area is damaged by an excitotoxic insult., (Copyright (c) 2007 Wiley-Liss, Inc.)

Unlike the mechanisms involved in the death of neuronal cell bodies, those causing the elimination of processes are not well understood owing to the lack of suitable experimental systems. As the neurotrophin receptor p75(NTR) is known to restrict the growth of neuronal processes, we engineered mouse embryonic stem (ES) cells to express an Ngfr (p75(NTR)) cDNA under the control of the Mapt locus (the gene encoding tau), which begins to be active when ES cell-derived progenitors start elongating processes. This caused a progressive, synchronous degeneration of all processes, and a prospective proteomic analysis showed increased levels of the sugar-binding protein galectin-1 in the p75(NTR)-engineered cells. Function-blocking galectin-1 antibodies prevented the degeneration of processes, and recombinant galectin-1 caused the processes of wild-type neurons to degenerate first, followed by the cell bodies. In vivo, the application of a glutamate receptor agonist, a maneuver known to upregulate p75(NTR), led to an increase in the amount of galectin-1 and to the degeneration of neurons and their processes in a galectin-1-dependent fashion. Section of the sciatic nerve also rapidly upregulated levels of p75(NTR) and galectin-1 in terminal Schwann cells, and the elimination of nerve endings was delayed at the neuromuscular junction of mice lacking Lgals1 (the gene encoding galectin-1). These results indicate that galectin-1 actively participates in the elimination of neuronal processes after lesion, and that engineered ES cells are a useful tool for studying relevant aspects of neuronal degeneration that have been hitherto difficult to analyze.

Abnormal accumulation of tau as filamentous structures is a neuropathological hallmark of neurodegenerative diseases referred to as tauopathies. Little is known about the role of native cysteine residues in tau assembly because their substitution with other amino acids has no effect on tau filament morphology. To understand the process involved in tau oligomerization, we analysed both heparin-induced assembly of different forms of recombinant human tau and assembly of tau from COS-7 cells transiently expressing different human tau constructs. Here, we demonstrated that tau assembly involves two distinct dimers (cysteine-dependent and cysteine-independent) that differ in resistance to reduction. During assembly, an increase of cysteine-dependent tau oligomer was observed prior to detection of increased thioflavin T fluorescence signals. The latter event was accompanied by an increase of cysteine-independent dimer. Fewer higher-order oligomers and aggregates were assembled from four-repeat tau containing two amino-terminus inserts that have either the C291A/C322A mutation (cysless-4R2N) or a hexapeptide deletion at residues 306-311 (DeltaPHF6-4R2N) compared with those assembled from wild-type tau. Assembly of distinct types of dimers was also observed in lysates from COS-7 cells expressing wild-type 4R2N and brain extracts from mice expressing P301L mutant tau. In contrast, COS-7 cells expressing cysless- or DeltaPHF6-4R2N tau contained very little cysteine-dependent dimer. Together, the results indicate that intermolecular disulfide crosslinking along with PHF6 hexapeptide facilitates tau oligomerization and that this event is accompanied by cysteine-independent intermolecular bridging of microtubule-binding domain, leading to assembly of higher-order oligomers. The levels of these dimers may be used to gauge the potential for tau assembly.

The underlying cause of sporadic Alzheimer disease (AD) is unknown, but a number of environmental and genetic factors are likely to be involved. One environmental factor that is increasingly being recognized as contributing to brain aging is diet, which has evolved markedly over modern history. Here we show that dietary supplementation with docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, in the 3xTg-AD mouse model of AD reduced the intraneuronal accumulation of both amyloid-beta (Abeta) and tau. In contrast, combining DHA with n-6 fatty acids, either arachidonic acid or docosapentaenoic acid (DPAn-6), diminished the efficacy of DHA over a 12 month period. Here we report the novel finding that the mechanism accounting for the reduction in soluble Abeta was attributable to a decrease in steady-state levels of presenilin 1, and not to altered processing of the amyloid precursor protein by either the alpha- or beta-secretase. Furthermore, the presence of DPAn-6 in the diet reduced levels of early-stage phospho-tau epitopes, which correlated with a reduction in phosphorylated c-Jun N-terminal kinase, a putative tau kinase. Collectively, these results suggest that DHA and DPAn-6 supplementations could be a beneficial natural therapy for AD.

Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease and other tauopathies, but recent studies in a conditional mouse model of tauopathy (rTg4510) have suggested that NFT formation can be dissociated from memory loss and neurodegeneration. This suggests that NFTs are not the major neurotoxic tau species, at least during the early stages of pathogenesis. To identify other neurotoxic tau protein species, we performed biochemical analyses on brain tissues from the rTg4510 mouse model and then correlated the levels of these tau proteins with memory loss. We describe the identification and characterization of two forms of tau multimers (140 and 170 kDa), whose molecular weight suggests an oligomeric aggregate, that accumulate early in the pathogenic cascade in this mouse model. Similar tau multimers were detected in a second mouse model of tauopathy (JNPL3) and in tissue from patients with Alzheimer's disease and FTDP-17 (frontotemporal dementia and parkinsonism linked to chromosome 17). Moreover, levels of the tau multimers correlated consistently with memory loss at various ages in the rTg4510 mouse model. Our findings suggest that accumulation of early-stage aggregated tau species, before the formation of NFT, is associated with the development of functional deficits during the pathogenic progression of tauopathy.

The present study quantified the cleaved form of the microtubule-associated protein tau (cleaved MAP-tau, C-tau), a previously demonstrated marker of CNS toxicity, following the administration of monoamine-depleting regimens of the psychostimulant drugs amphetamine (AMPH), methamphetamine (METH), +/-3,4-methylenedioxymethamphetamine (MDMA), or para-methoxyamphetamine (PMA) in an attempt to further characterize psychostimulant-induced toxicity. A dopamine (DA)-depleting regimen of AMPH produced an increase in C-tau immunoreactivity in the striatum, while a DA- and serotonin (5-HT)-depleting regimen of METH produced an increase in the number of C-tau immunoreactive cells in the striatum and CA2/CA3 and dentate gyrus regions of the hippocampus. MDMA and PMA, two psychostimulant drugs that produce selective 5-HT depletion in the striatum, had no effect on C-tau immunoreactivity in the striatum or hippocampus. Furthermore, 5,7-dihydroxytryptamine (5,7-DHT), an established 5-HT selective neurotoxin, did not produce an increase in C-tau immunoreactivity. Dual fluorescent immunocytochemistry with antibodies to glial fibrillary acidic protein (GFAP) and C-tau indicated that C-tau immunoreactivity was present in astrocytes, not neurons, suggesting that increased C-tau may be an alternative indicator of reactive gliosis. The present results are consistent with previous findings that the DA-depleting psychostimulants AMPH and METH produce reactive gliosis whereas the 5-HT-depleting drugs MDMA and PMA, as well as the known 5-HT selective neurotoxin 5,7-DHT, do not produce an appreciable glial response.

Tau is a microtubule-associated protein with a developmentally regulated expression of multiple isoforms. The neonatal isoform is devoid of two amino terminal inserts and contains only three instead of four microtubule-binding repeats (0N/3R-tau). We investigated the temporal expression pattern of 0N-tau and 3R-tau in the rat hippocampus. After the decline of 0N- and 3R-tau immunoreactivity during the postnatal development both isoforms remain highly expressed in a few cells residing beneath the granule cell layer. Coexpression of the polysialylated neuronal cell adhesion molecule, doublecortin, and incorporated bromodeoxyuridine showed that these cells are proliferating progenitor cells. In contrast mature granule cells express the adult tau protein isoform containing one aminoterminal insert domain (1N-tau). Therefore a shift in tau isoform expression takes place during adult neurogenesis, which might be related to migration, differentiation, and integration in the granule cell layer. A model for studying shifts in tau isoform expression in a defined subset of neurons might help to understand the etiology of tauopathies, when isoform composition is crucial for neurodegeneration, as in Pick's disease or FTDP-17.

Alterations in tau mRNA splicing and association with H1/H1 tau genotype have been described in some sporadic tauopathies. We evaluated the 4R/3R tau mRNA ratio in 18 patients with frontotemporal lobar degeneration (FTLD), and the effect of the H1/H1 genotype on this ratio. The 4R/3R mRNA ratio in frontal cortex was similar in FTLD patients and controls. The H1/H1 genotype carriers showed a significant increase in 4R/3R mRNA ratio, suggesting that this genotype could modulate the tau mRNA splicing.

The microtubule-associated protein tau is important to normal neuronal function in the mammalian nervous system. Aggregated tau is the major component of neurofibrillary tangles (NFTs), present in several neurodegenerative diseases, including Alzheimer's and frontotemporal dementia with Parkinsonism (FTDP). Splicing misregulation of adult-specific exon 10 results in expression of abnormal ratios of tau isoforms, leading to FTDP. Positions +3 to +16 of the intron downstream of exon 10 define a clustering region for point mutations that are found in FTDP. The serine/arginine-rich (SR) factor 9G8 strongly inhibits inclusion of tau exon 10. In this study, we established that 9G8 binds directly to this clustering region, requires a wild-type residue at position +14 to inhibit exon inclusion, and RNAi constructs against 9G8 increase exon 10 inclusion. These results indicate that 9G8 plays a key role in regulation of exon 10 splicing and imply a pathogenic role in neurodegenerative diseases.

During aging basal forebrain cholinergic neurons (BFCNs) degenerate, and we hypothesize this to be the result of a degeneration of the cytoskeleton. As a corollary, retrograde transport of the complex of nerve growth factor (NGF) and its activated receptor phospho-TrkA (P-TrkA) is impaired. Using immunocytochemistry, we here compare young and aged rat brains in their subcellular localization of NGF and P-TrkA in relation to the compartmentalization of phosphorylation-dependent tau protein isoforms. Despite lower P-TrkA immunoreactivity in cortex and hippocampus of aged rats, NGF immunoreactivity was not altered in these areas, but was significantly lower in aged basal forebrain. In young animals, expression of tau isoforms and glycogen synthase kinase-3beta (GSK-3beta) was restricted to neuritic structures in cortex, hippocampus, and basal forebrain. In contrast, tau and GSK-3beta labeling was confined to cell bodies in aged rats. Since a somatic localization of phospho-tau is indicative of cytoskeletal breakdown, we suggest this to be the mechanism the breakdown of trophic support in aging BFCNs.

A recent study disclosed that breast cancer cases with low 'tau' expression can predict susceptibility to Paclitaxel administration. In the current study, the clinical significance of tau expression in gastric cancer cases was established by identifying candidates with Paclitaxel administration. Tissue specimens from 20 cases of in-operable or noncuratively resected gastric cancer were examined. Subsequent to the administration of 80 mg m(-2) of Paclitaxel in six 3-h intravenous infusions, the clinical effectiveness of Paclitaxel was evaluated by the size of metastatic lesions with computed tomography. The status of the tau expression was determined by immunohistochemistry. Based on a previously reported classification scheme, six were classified as tau-negative expression (0, 1+) cases and 14 were classified as tau-positive expression (2+, 3+) cases. All six (100%) cases of tau-negative expression showed a favourable response (partial response or minor response) to Paclitaxel administration. However, 12 (86%) of the 14 cases of tau-positive expression showed progressive disease (n = 11) or no change (n = 1) after Paclitaxel administration. The serum carcinoembryonic antigen values of the six cases of tau-negative expression were markedly decreased in comparison to the 14 tau-positive cases. These data indicate that tau-negative expression can be used to select gastric cancer patients, which will favourably respond to Paclitaxel treatment.

Adeno-associated virus (AAV) serotype 8 appears to be the strongest of the natural serotypes reported to date for gene transfer in liver and muscle. In this study, we evaluated AAV8 in the brain by several methods, including biophotonic imaging of green fluorescent protein (GFP). In the adult rat hippocampus, levels of GFP expressed were clearly greater with AAV8 than with AAV2 or AAV5 by Western blot and biophotonic imaging and slightly but significantly greater than AAV1 by Western blot. In the substantia nigra, the GFP expression conferred by AAV8 was toxic to dopamine neurons, although toxicity could be avoided with dose titration. At the low dose at which there was no GFP toxicity from the GFP vector, another AAV8 vector for a disease-related (P301L) form of the microtubule-associated protein tau caused a 78% loss of dopamine neurons and significant amphetamine-stimulated rotational behavior. The AAV8 tau vector-induced cell loss was greater than that from AAV2 or AAV5 tau vectors, demonstrating that the increased gene transfer was functional. While the toxicity observed with GFP expression warrants great caution, the efficient AAV8 is promising for animal models of neurodegenerative diseases and potentially as well for gene therapy of brain diseases.

Abundant filamentous tau inclusions in oligodendrocytes (OLGs) are hallmarks of neurodegenerative tauopathies, including sporadic corticobasal degeneration and hereditary frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). However, mechanisms of neurodegeneration in these tauopathies are unclear in part because of the lack of animal models for experimental analysis. We address this by generating transgenic (Tg) mice expressing human tau exclusively in OLGs using the 2',3'-cyclic nucleotide 3'-phosphodiesterase promoter. Filamentous OLG tau inclusions developed in these Tg mice as a result of human tau expression in OLGs, especially those expressing the FTDP-17 human P301L mutant tau. Notably, structural disruption of myelin and axons preceded the emergence of thioflavin-S positive tau inclusions in OLGs, but impairments in axonal transport occurred even earlier, whereas motor deficits developed subsequently, especially in Tg mice with the highest tau expression levels. These data suggest that the accumulation of tau in OLG cause neurodegeneration, and we infer they do so by disrupting axonal transport. We suggest that similar defects may also occur in sporadic and hereditary human tauopathies with OLG tau pathologies.

Objective: To explore the effect of different culture media on viability and expression of tau protein in organotypic hippocampal slice., Methods: Brain slices (400 microm) from 1, 2, 4, and 8 week-old Wistar rats were prepared and cultured in minimum essential medium (MEM) or Dulbecco's modified eagle medium: nutrient mixture (DMEM/F12) medium respectively for 21 days. Viability of the slices was measured by lactate dehydrogenase (LDH) assay and expression of tau protein was detected by Western blot., Results: The viability of the slices was not influenced significantly by the two different culture media, while the expression level of tau protein was significantly higher in DMEM/F12 than in MEM (P < 0.05), especially in the slices from 2 and 4 week-old rats., Conclusion: The slices from 2 or 4 week-old rat hippocampi and DMEM/F12 medium may be the preferred choice for tau associated researches. An ideal Alzheimer's disease model may be established based on the results of these researches.

Alzheimer's disease-like neurofibrillary pathology is neither seen in rodents nor in transgenic animals expressing the disease causing mutant human APP or mutant human presenilins. Whether the absence of this pathology is due to inability of the murine tau to self assemble into filaments or due to some other factors is not understood. In this study, we compared recombinant murine and human taus in their ability to form filaments by AD-like hyperphosphorylation in vitro. Human and murine taus, 0N4R, were generated as recombinant proteins and phosphorylated with rat brain extract as a source of protein kinases. We found that murine tau could be hyperphosphorylated to similar stoichiometry and manner as human tau. Upon hyperphosphorylation, murine tau was able to self polymerize into bundles of paired helical filament- and straight filament-like morphology. The filaments obtained from self assembly of murine tau closely resembled those formed from identically treated human tau. Moreover, like human tau, 60-70% of murine tau aggregated on hyperphosphorylation.

Mutations in the microtubule-associated protein tau gene have been linked to neurofibrillary tangle (NFT) formation in several neurodegenerative diseases known as tauopathies; however, no tau mutations occur in Alzheimer's disease, although this disease is also characterized by NFT formation and cell death. Importantly, the mechanism of tau-mediated neuronal death remains elusive. Aged mice expressing nonmutant human tau in the absence of mouse tau (htau mice) developed NFTs and extensive cell death. The mechanism of neuron death was investigated in htau mice, and surprisingly, the presence of tau filaments did not correlate directly with death within individual cells, suggesting that cell death can occur independently of NFT formation. Our observations show that the mechanism of neurodegeneration involved reexpression of cell-cycle proteins and DNA synthesis, indicating that nonmutant tau pathology and neurodegeneration may be linked via abnormal, incomplete cell-cycle reentry.

In mammals, olfactory signals received by odorant receptors (ORs) in the olfactory epithelium (OE) are converted to a topographical map of activated glomeruli in the olfactory bulb (OB). It has been reported that the OE can be divided into four topographically distinct zones and that olfactory sensory neurons (OSNs) expressing a particular OR gene are randomly distributed within one zone. Here, we analyzed 80 different class II OR genes for their expression patterns in the OE by in situ hybridization. It was found that the expression area in the OE does not always fit into one of the four conventional zones. Expression areas are specific to each OR gene and are arranged in an overlapping and continuous manner in the OE. We also analyzed a spatial relationship between the OE and the OB for OSN projection. Our transgenic as well as DiI retrograde staining experiments demonstrated that the dorsal/ventral arrangement of glomeruli in the OB is correlated with the expression areas of corresponding ORs along the dorsomedial/ventrolateral axis in the OE. The present study indicates that the OR gene choice may be more restricted by the OSN location in the OE than what has been thought.

Objective: To investigate the effects of intracerebroventricular (ICV) administration of streptozotocin (STZ) on the expressions of Abeta and hyperphosphorylation of tau protein in rat brain., Methods: Twenty-four adult SD rats were randomized into 2 groups to receive ICV of STZ bilaterally at the dose of 3 mg/kg (with the injection repeated on day 3) or normal saline injection in an identical manner. Twenty-one days later, the expressions of Abeta(1-40), Abeta(1-42), tau(202), tau(396) and tau(404) were investigated immunohistochemically., Results: After STZ administration, the expressions of Abeta(1-40), Abeta(1-42), tau(202), tau(396) and tau(404) increased in both the cortex and hippocampus in the rat brain., Conclusion: ICV injection of STZ increases the expression of Abeta and promotes hyerphosphorylation of tau protein.

The aim of this study was to explore the regulatory effects of cytokines, such as EGF and bFGF, on expression of the neural-specific molecules tau and MAP2 mRNA in mononuclear cells (MNCs) derived from human umbilical cord blood (UCB). Phenotypic changes were monitored by inverse phase-contrast microscopy. Tau and MAP2 mRNA were determined by reverse-transcriptase polymerase chain reaction (RT-PCR). Tau and MAP2-positive cells were determined by immunocytochemistry. The expression of tau mRNA was negative in uncultured cells, but MAP2 mRNA was positive; in cultured cells, tau protein mRNA expression was positive, MAP2 mRNA expression was upregulated by EGF+bFGF, EGF and bFGF compared to the control group (no cytokines). EGF+bFGF had a greater effect on MAP2 mRNA expression than EGF or bFGF alone. The same upregulatory tendency was noted for tau mRNA expression. It is concluded that MNCs derived from human UCB cells may express some neural specific molecules that can be upregulated by cytokines, especially EGF and bFGF together.

Missense mutations of the tau gene cause autosomal dominant frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), an illness characterized by progressive personality changes, dementia, and parkinsonism. There is prominent frontotemporal lobe atrophy of the brain accompanied by abundant tau accumulation with neurofibrillary tangles and neuronal cell loss. Using a hamster prion protein gene expression vector, we generated several independent lines of transgenic (Tg) mice expressing the longest form of the human four-repeat tau with the R406W mutation associated with FTDP-17. The TgTauR406W 21807 line showed tau accumulation beginning in the hippocampus and amygdala at 6 months of age, which subsequently spread to the cortices and subcortical areas. The accumulated tau was phosphorylated, ubiquitinated, conformationally changed, argyrophilic, and sarcosyl-insoluble. Activation of GSK-3beta and astrocytic induction of mouse tau were observed. Astrogliosis and microgliosis correlated with prominent tau accumulation. Electron microscopic examination revealed the presence of straight filaments. Behavioral tests showed motor disturbances and progressive acquired memory loss between 10 to 12 months of age. These findings suggested that TgTauR406W mice would be a useful model in the study of frontotemporal dementia and other tauopathies such as Alzheimer's disease (AD).

Background: Increased attention has been given to alpha-synuclein aggregation in nonsynucleinopathies because alpha-synuclein-containing Lewy bodies (LBs) influence symptoms. However, the spectrum of disorders in which secondary inclusions are likely to occur has not been defined. Amygdala neurons commonly develop large numbers of secondary LBs, making it a practical region for studying this phenomenon., Objective: To characterize the spectrum of diseases associated with LB formation in the amygdala of neurodegenerative disease and control cases., Design: An autopsy series of 101 neurodegenerative disease and 34 aged control cases. Using immunohistochemistry studies, we examined the amygdala for alpha-synuclein aggregates., Results: Lewy bodies were often abundant in classic Pick disease, argyrophilic grain disease, Alzheimer disease, and dementia with LBs but not in cases with amygdala degeneration lacking tau-based inclusions, control cases, preclinical disease carriers, or degenerative diseases lacking pathologic involvement of the amygdala. The exposed alpha-synuclein epitopes were similar in all cases containing LBs., Conclusions: Abnormal alpha-synuclein aggregation in the amygdala is disease selective, but not restricted to disorders of alpha-synuclein and beta-amyloid. Our data are compatible with the notion that tau aggregates predispose neurons to develop secondary LBs.

APPsw transgenic mice bearing the "Swedish" amyloid precursor protein (APP) mutation and JNPL3 transgenic mice bearing the P301L (Tau) mutation were compared to control non-transgenic (NT) mice in an extensive behavioral test battery administered between 5 and 8.5 months of age. APP mice were impaired in a variety of cognitive-based tasks prior to overt Abeta plaque development, making involvement of mutant APP overexpression and/or oligomeric Abeta assemblies most likely. Although Tau mice, as a group, were not impaired in any single behavioral measure, a collective assessment of behavioral measures through discriminant function analysis showed that Tau mice were impaired in overall behavioral (cognitive) performance. Moreover, correlation analyses involving Tau mice alone revealed linkage between poorer cognitive performance in all three water maze tasks and the number of neurofibrillary tangle (NFT)-containing neurons in neocortex and hippocampus. These findings indicate that: (1) APP mice show early and extensive cognitive impairment before evident Abeta deposition, and (2) the process or product of NFT formation in Tau mice is sufficient to deleteriously impact cognitive performance., (Copyright 2004 Elsevier B.V.)

Neurofibrillary tangles, insoluble protein deposits composed of filamentous tau aggregates, are neuropathological hallmarks of Alzheimer's disease and familial frontotemporal dementia (FTDP-17). Transgenic mice expressing the FTDP-17 mutation P301L of tau recapitulate key features of the human pathology, that is, tau proteins aggregate and neurofibrillary tangles begin to appear in the amygdala at 6 months of age. To detect early signs of tau aggregate-associated changes, we investigated behavioral alterations and cognitive deficits in such mice using an amygdala-specific test battery for anxiety-related and cognitive behavior. P301L mice had anxiety levels not different from wild-types, but their exploratory behavior was significantly increased. Acquisition of a fear response to tone and context as well as taste aversion was comparable to wild-types. However, extinction of a conditioned taste aversion was significantly accelerated. We conclude that already aggregation of tau proteins not yet accompanied by massive formation of neurofibrillary tangles causes selective behavioral deficits.

Disorders of olfaction are among the first clinical signs of neurodegenerative diseases such as Alzheimer's disease (AD) and idiopathic Parkinson's disease (PD). In this study, we employed an odor habituation paradigm to evaluate the olfactory function of T alpha 1-3RT transgenic mice that overexpress tau, a key pathogenic protein in AD, and compared such function to that of wild-type controls who do not overexpress this protein. The T alpha 1-3RT mice, but not the controls, exhibited responses indicative of decreased olfactory function. These data lend support to the notion that tau may be involved in the pathogenesis of the olfactory dysfunction of some neurodegenerative diseases. Future studies need to similarly assess other pathogenic markers, as well as their distribution within various sectors of the brain, to determine the specificity of this phenomenon.

It has previously been reported that amyloid-beta (Abeta) peptide is neurotrophic to undifferentiated but neurotoxic to differentiated primary neurons. The underlying reasons for this differential effect is not understood. Recently, the toxicity of Abeta to neurons was shown to be dependent upon the activation of cyclin-dependent kinase 5 (Cdk5), thought to promote tau phosphorylation that leads to cytoskeletal disruption, morphological degeneration and apoptosis. Here we report that Cdk5, tau, and phosphorylated-tau (P-tau) are expressed at very low levels in undifferentiated primary neurons, but that the expression of Cdk5 and tau and the phosphorylation of tau increase markedly between 4 and 8 days of differentiation in vitro. Tau expression decreased after this time, as did the level of P-tau, to low levels by 17 days. Abeta induced tau phosphorylation of neurons only after >or= 4 days of differentiation, a time that coincides with the onset of Abeta toxicity. Blocking tau expression (and therefore tau phosphorylation) with an antisense oligonucleotide completely blocked Abeta toxicity of differentiated primary neurons, thereby confirming that tau was essential for mediating Abeta toxicity. Our results demonstrate that differentiation-associated changes in tau and Cdk-5 modulate the toxicity of Abeta and explain the opposite responses of differentiated and undifferentiated neurons to Abeta. Our results predict that only cells containing appreciable levels of tau are susceptible to Abeta-induced toxicity and may explain why Abeta is more toxic to neurons compared with other cell types.

Tauopathies, including Alzheimer's disease, are neurodegenerative disorders in which tau protein accumulates as a consequence of alterations in its metabolism. At least three different types of alterations have been described; in some cases, an aberrant mRNA splicing of tau exon 10 occurs; in other cases, the disorder is a consequence of missense mutations and, in most cases, aberrant tau hyperphosphorylation takes place. Glycogen synthase kinase-3 (GSK-3) has emerged as a key kinase that is able to interact with several proteins involved in the etiology of Alzheimer's disease and other tauopathies. Here, we have evaluated whether GSK-3 is also able to modulate tau-mRNA splicing. Our data demonstrate that GSK-3 inhibition in cultured neurons affects tau splicing resulting in an increase in tau mRNA containing exon 10. Pre-mRNA splicing is catalyzed by a multimolecular complex including members of the serine/arginine-rich (SR) family of splicing factors. Immunofluorescence studies showed that after GSK-3 inhibition, SC35, a member of the SR family, is redistributed and enriched in nuclear speckles and colocalizes with the kinase. Furthermore, immunoprecipitated SC35 is phosphorylated by recombinant GSK-3beta. Phosphorylation of a peptide from the SR domain by GSK-3 revealed that the peptide needs to be prephosphorylated, suggesting the involvement of a priming kinase. Our results demonstrate that GSK-3 plays a crucial role in tau exon 10 splicing, raising the possibility that GSK3 could contribute to tauopathies via aberrant tau splicing.

NMR spectroscopy of the full-length neuronal Tau protein has proved to be difficult due to the length of the protein and the unfavorable amino acid composition. We show that the random-coil chemical shift values and their dependence on the presence of a proline residue in the (i+1) position can successfully be exploited to assign all proline-directed phosphorylation sites. This is a first step toward the study of the phosphorylation of Tau by NMR spectroscopy.

The possible link between tau phosphorylation and tau assembly in these neurodegenerative diseases known as tauopathies is described. Additionally, this link is supported by an in vitro experiment showing the higher capacity of phosphotau to assemble in some specific conditions; and, by a recently reported experiment using a tau transgenic mouse model.

Several human neurodegenerative diseases are associated with abnormal accumulations of aggregated tau proteins and glial degeneration in astrocytes, but the mechanism whereby tau proteins cause astrocytic degeneration is unclear. Here, we analyzed the biological consequences of overexpressing the longest human tau isoform in primary cultures of rat astrocytes using adenoviral-mediated gene transfer. Significantly, we found specific decreases in stable detyrosinated [glutamate (Glu)] microtubules (MTs) with concomitant increases in tubulin biosynthesis and the accumulation of acetylated, tyrosinated, alpha- and beta-tubulin. The consequences of this selective reduction in stable Glu-MTs included contemporaneous decreases in kinesin levels, collapse of the intermediate filament network, progressive disruption of kinesin-dependent trafficking of organelles, fragmentation of the Golgi apparatus that culminated in atrophy, and non-apoptotic death of astrocytes. These results suggest that reduced stable Glu-MTs is a primary consequence of tau accumulation that initiates mechanisms underlying astrocyte dysfunction and death in human neurodegenerative glial tauopathies.

Transgenic mice expressing mutant (P301L) human tau develop neurofibrillary tangles, amyotrophy and progressive motor disturbance. We present ultrastructural features of neuronal degeneration in this model that suggests involvement of both neurofibrillary and autophagic processes in neurodegeneration. Neurons undergoing neurofibrillary degeneration contain tau-immunoreactive, 15-20 nm-wide straight or wavy filaments with no periodic twists. Tau filaments were found in two types of affected neurons. One type resembled neurons with neurofibrillary tangles (NFT) that were filled with numerous filaments that displaced sparse cytoplasmic organelles to the periphery. Microtubules were almost completely absent. The nucleus remained centrally located, but showed lobulations due to deep infoldings. The other type resembled ballooned neurons seen in some human tauopathies. The nucleus was peripherally placed, but normal appearing. The cytoplasmic organelles were dispersed throughout the swollen perikarya, the Golgi complex was fragmented and duplicated, while mitochondria and other organelles appeared normal. Tau filaments similar to those in NFT were sparse and not tightly packed. Microtubules were also sparse. Many autophagic vacuoles were present in these cells. Heterogeneous appearing axonal swellings resembling spheroids in human tauopathies were present in gray and white matter. Unlike normal appearing axons, axonal spheroids were filled with tau-immunoreactive filaments and autophagic vacuoles, in addition to normal appearing neurofilaments and microtubules. These P301L transgenic mice exhibit many features common to human tauopathies, making them a valuable model to study the pathogenesis of these uncommon disorders.

Paired helical filaments (PHF) are the principal pathologic components of neurofibrillary tangles in Alzheimer's disease (AD). To reproduce the formation of PHF in tissue culture, we stably expressed human tau with and without pathogenic mutations in human SH-SY5Y cells and exposed them for 5 days to aggregated synthetic beta-amyloid peptide (A beta 42). This caused a decreased solubility of tau along with the generation of PHF-like tau-containing filaments. These were 20 nm wide and had periodicities of 130-140 nm in the presence of P301L mutant tau or 150-160 nm in the presence of wild-type tau. Mutagenesis of the phosphoepitope serine 422 of tau prevented both the A beta 42-mediated decrease in solubility and the generation of PHF-like filaments, suggesting a role of serine 422 or its phosphorylation in tau filament formation. Together, our data underscore a role of A beta 42 in the formation of PHF-like filaments. Our culture system will be useful to map phosphoepitopes of tau involved in PHF formation and to identify and characterize modifiers of the tau pathology. Further adaptation of the system may allow the screening and validation of compounds designed to prevent PHF formation.

The authors describe a case of clinically diagnosed young onset progressive supranuclear palsy (PSP) with symptom onset at 40 years of age and no family history of neurodegenerative disease. There was no history of falls during the first year of symptoms. Genetic analysis identified this patient as having a tau exon 10 +16 mutation (MAPT, IVS10, C-U, +16). Neuropathologic examination confirmed the genetic diagnosis of frontotemporal dementia. An age at onset younger than 50 years combined with the absence of early falls may indicate the possibility of a tau mutation in clinically diagnosed PSP.