Microtubule-associated Protein Tau mRNA Research Articles

WVE‐005, a stereopure antisense oligonucleotide for MAPT silencing in tauopathies

Abstract Background: Tau is a neuronal scaffolding protein which aggregates intracellularly upon hyperphosphorylation to form neurofibrillary tangles (NFT). NFTs are a hallmark of various microtubule associated protein tau (MAPT)‐associated neurodegenerative diseases, including Alzheimer’s disease, frontotemporal dementia, and progressive supranuclear palsy. Currently, there is no approved treatment targeting Tau pathology, nor any other disease‐modifying therapy for these diseases. Wave Life Sciences has developed a stereopure antisense oligonucleotide to reduce MAPT expression in patients with MAPT‐associated neurodegenerative diseases. Method: Using Wave’s proprietary PRISM platform, we designed and screened stereopure oligonucleotides targeting MAPT in vitro and identified a lead sequence. PN chemistry was applied to the lead sequence in subsequent studies to further improve pharmacological properties. In vitro target engagement was measured in human iCell neurons after treatment with Wave’s oligonucleotide, WVE‐005, or a published reference stereorandom oligonucleotide under gymnotic conditions. For in vivo analysis, transgenic mice received a single dose of 12.5, 25, 50, or 100µg oligonucleotide, and target engagement was measured after 4 weeks. To measure duration, transgenic mice received a single 100µg ICV dose and target engagement was tracked over 6 months. Finally, oligonucleotides were tested in non‐human primates (NHP) in a 12mg single‐dose intrathecal (IT) study. MAPT mRNA levels were quantified by qPCR, and intracellular distribution was evaluated by ViewRNA. Result: WVE‐005 showed dose‐dependent silencing of MAPT mRNA in iPSC‐derived neurons with an IC50 of 84nM. In a dose‐response study, 12.5µg and 25µg WVE‐005 led to 50% knockdown after 4 weeks in hippocampus and cortex, respectively, in transgenic mice. WVE‐005 led to >77% MAPT mRNA knockdown at 12 weeks post 100µg dosing, with knockdown of approximately 50% persisting 6 months post‐injection. In NHPs, WVE‐005 showed improved distribution and potency compared to non‐PN oligonucleotide with the same sequence. WVE‐005 decreased MAPT expression across NHP brain regions 28 days post‐single dose much greater than the non‐PN oligonucleotide and was detected in neuronal and glial cells. Conclusion: WVE‐005 potently and durably decreased MAPT mRNA expression in vitro and in multiple animal models, including throughout CNS upon IT administration in NHPs. These data support continued evaluation of WVE‐005 as a potential therapeutic for MAPT‐associated neurodegenerative diseases.

Blood MAPT expression and methylation status in Alzheimer's disease.

This study aimed to investigate the expression levels and methylation status of microtubule-associated protein tau (MAPT) in the blood of Alzheimer's disease (AD) patients and age- and sex-matched healthy controls. Fifty AD outpatients and 50 healthy contorls were enrolled. Blood samples were collected for processing of complementary DNA and genomic DNA. MAPT messenger ribonucleic acid (mRNA) expression was analyzed by real-time quantitative polymerase chain reaction. The methylation rates of four cytosine-phosphate-guanine (CpG) sites in the upstream region of MAPT exon1 were evaluated by the pyrosequencing method. No significant differences in MAPT mRNA expression levels were found between AD and control subjects (AD 0.97 ± 0.49 vs. control 1.0 ± 0.64, p = 0.62). MAPT mRNA expression levels were not correlated with any other clinical characteristics or results of psychological tests. MAPT mRNA expression levels were significantly higher in AD subjects treated with acetylcholinesterase inhibitors (AchEIs) (n = 25) than in subjects not treated with AChEIs (n = 25) (unmedicated 0.83 ± 0.33 vs. medicated 1.12 ± 0.59, p = 0.049). The AD subjects did not differ from the control subjects in methylation rates at selected CpG sites. MAPT methylation status were not correlated with clinical characteristics, the results of psychological tests, or MAPT mRNA expression. MAPT mRNA expression levels and methylation status in blood do not appear useful as biomarkers for AD or the examined CpG sites were not genetically significant for MAPT gene expression or AD pathology. However, AChEIs may alter MAPT mRNA expression. Further studies are needed to explore blood biomarkers that can discriminate AD patients from controls.

Regulation of microtubule-associated protein tau (MAPT) by miR-34c-5p determines the chemosensitivity of gastric cancer to paclitaxel

Human miR-34c has been reported to be associated with various human malignancies; however, it remains unknown whether miR-34c is involved in chemoresistance in gastric cancer. The aim of this study was to investigate the role of miR-34c in gastric cancer. The adenosine triphosphate-based tumor chemosensitivity assay was used to measure drug sensitivity in gastric cancer samples. The expression levels of miRNA were determined by reverse transcriptase polymerase chain reaction (PCR) and those of protein were by Western blot analysis. Luciferase activity assay was used to verify the target genes of miRNAs. MTT assay was used to test the drug-resistant phenotype changes in cancer cells via overregulation of miRNAs. The methylation status of neighboring CpG islands of miR-34c-5p was analyzed by Bisulfite Sequencing PCR and methylation-specific PCR. Quantitative real-time polymerase chain reaction demonstrated that expression of miR-34c-5p was downregulated in paclitaxel-resistant gastric cancer samples (p < 0.01). Cells derived from gastric cancer tissues with low miR-34c-5p expression and high microtubule-associated protein tau (MAPT) protein expression tended to have increased chemoresistance to paclitaxel in vitro. Luciferase activity assay confirmed that the 3'-UTR of MAPT mRNA contains a functional miR-34c-5p binding site. Overexpression of miR-34c-5p significantly downregulated MAPT protein expression and increased the chemosensitivity of paclitaxel-resistant gastric cancer cells. Further investigation demonstrated that differential methylation of CpG islands neighboring the miR-34c promoter regulated the expression of miR-34c-5p in gastric cancer cell lines. DNA methylation, dysregulation of miR-34c-5p, and MAPT expression are critical factors in the chemoresistance of gastric cancer to paclitaxel.

Tau alternative splicing in familial and sporadic tauopathies

Six tau isoforms differing in their affinity for microtubules are produced by alternative splicing from the MAPT (microtubule-associated protein tau) gene in adult human brain. Several MAPT mutations causing the familial tauopathy, FTDP-17 (frontotemporal dementia with parkinsonism linked to chromosome 17), affect alternative splicing of exon 10, encoding a microtubule-binding motif. Advanced RNA analysis methods have suggested that levels of exon 10-containing MAPT mRNA are elevated in Alzheimer's disease. Furthermore, the MAPT H1 haplotype, associated with Alzheimer's disease, promotes exon 10 inclusion in MAPT mRNA. Thus an accurate regulation of tau alternative splicing is critical for the maintenance of neuronal viability, and its alteration might be a contributing factor to Alzheimer's disease. Tau alternative splicing could represent a target for therapeutic intervention to delay the progression of pathology in familial as well as sporadic tauopathies.

Microtubule Associated Protein-Tau (MAPT) Is Influenced by ER: ICI182,780, a Selective ER Inhibitor, Down-Regulates MAPT Expression and Reverses Resistance to Taxanes in MAPT- and ER-Positive Breast Cancer Cells.

Abstract Background: Taxanes are important drugs in treatment of breast cancer. These drugs bind to tubulin and suppress spindle microtubule dynamics, which leads to cell cycle arrest in the G2/M phase followed by apoptosis. However, resistance to taxane therapy prevents some patients from benefiting from these drugs. Several mechanisms of taxane resistance have been described, including the involvement of microtubule-associated protein-tau (MAPT). MAPT binds to the same pocket as taxanes in microtubules and obstructs the function of the drug. Estrogen receptors (ER) are transcriptional factors that play an important role in the development and progression of breast cancer. However, the relationship between ER and MAPT in breast cancer is not entirely clear. In this study we examined the correlation between MAPT expression and the sensitivity of human breast cancer cells to taxanes, and the relationship between ER and MAPT at the protein level in these cells. We also examined combination therapy with hormone drugs and taxanes.Methods: The correlation between MAPT expression and sensitivity to taxanes was examined in 12 human breast cancer cell lines using real time PCR, western blotting analysis and an MTS assay. Following small interfering RNA (siRNA) knockdown of MAPT expression, the alteration of cellular sensitivity to taxanes was examined by MTS assay, flow cytometry and immunofluorescence. To examine the relationship between ER and MAPT, ER expression was knocked down with siRNA or stimulated with 17-β-estradiol in MAPT- and ER-positive cell lines (MCF-7 and ZR75.1, respectively). The cells were also treated with hormone drugs (tamoxifen and ICI182,780) and changes in MAPT protein expression were examined.Results: Six cell lines showed high MAPT mRNA expression and four showed high MAPT protein expression; that is, expression at the mRNA level did not always correlate with that at the protein level. MAPT mRNA expression did not correlate with taxane resistance, but expression of MAPT protein isoforms under 70 kDa correlated with taxane resistance. Downregulation of MAPT increased sensitivity to taxanes. MAPT protein expression was decreased by ER knockdown and increased by 17-β-estradiol stimulation. The MAPT protein level was also increased by tamoxifen, but decreased by ICI182,780. Combination treatment of taxanes with ICI182,780 showed a strong synergistic effect, but similar treatment with tamoxifen had an antagonistic effect in both cell lines.Conclusions: Expression of MAPT protein isoforms under 70 kDa correlates with taxane resistance in breast cancer cells. MAPT expression is influenced by ER in breast cancer and ICI182,780, a selective ER inhibitor, can reverse the resistance to taxanes in both MAPT- and ER-positive breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2118.

A high-throughput screening strategy identifies cardiotonic steroids as alternative splicing modulators

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.

Gene expression of estrogen receptor, progesterone receptor and microtubule-associated protein Tau in high-risk early breast cancer: a quest for molecular predictors of treatment benefit in the context of a Hellenic Cooperative Oncology Group trial

Estrogen receptor (ER) and progesterone receptor (PgR) protein expression carry weak prognostic and moderate predictive utility for the outcome of early breast cancer patients on adjuvant chemohormonotherapy. We sought to study the predictive significance and correlations of transcriptional profiling of the ER, PgR and microtubule-associated protein Tau (MAP-Tau) genes in early breast cancer. Messenger RNA (mRNA) was extracted from 279 formalin-fixed paraffin-embedded breast carcinomas (T1-3N0-1M0) of patients enrolled in the Hellenic Cooperative Oncology Group (HeCOG) trial HE 10/97, evaluating epirubicin-alkylator based adjuvant chemotherapy with or without paclitaxel (E-T-CMF versus E-CMF). Kinetic reverse transcription polymerase chain reaction (kRT-PCR) was applied for assessment of the expression of estrogen receptor, progesterone receptor and MAP-Tau genes in 274 evaluable patients. Cohort-based cut-offs were defined at the 25th percentile mRNA value for ER and PgR and the median for MAP-Tau. Two hundred and ten patients (77%) were ER and/or PgR-positive by immunohistochemistry (IHC). Positive ER and MAP-Tau mRNA status was significantly associated with administration of hormonal therapy and low grade, while MAP-Tau mRNA status correlated with premenopausal patient status. MAP-Tau strongly correlated with ER and PgR mRNA status (Spearmann r = 0.52 and 0.64, P < 0.001). The observed chance corrected agreement between determination of hormonal receptor status by kRT-PCR and IHC was moderate (Kappa = 0.41) for ER and fair (Kappa = 0.33) for PgR. At a median follow-up of 8 years, univariate analysis adjusted for treatment showed positive ER mRNA status to be of borderline significance for reduced risk of relapse (HR = 0.65, 95% CI 0.41-1.01, P = 0.055) and death (HR = 0.62, 95% CI 0.36-1.05, P = 0.077), while positive MAP-Tau mRNA status was significantly associated with reduced risk of relapse (HR = 0.50, 95% CI 0.32-0.78, P = 0.002) and death (HR = 0.49, 95% CI 0.29-0.83, P = 0.008). In multivariate analysis, only axillary nodal metastases (HR = 2.33, 95% CI 1.05-5.16, P = 0.04) and MAP-Tau mRNA status (HR = 0.46, 95% CI 0.25-0.85, P = 0.01) independently predicted patient outcome. However, MAP-Tau mRNA levels did not predict enhanced benefit from inclusion of paclitaxel in the adjuvant chemotherapy regimen (test for interaction P = 0.99). No correlation was evident between increasing ER and PgR mRNA transcription and increasing benefit from endocrine therapy in 203 ER and/or PgR IHC-positive patients receiving adjuvant hormone therapy (Wald P = 0.54 for ER, 0.51 for PR). ER gene transcription carries weak predictive significance for benefit from endocrine therapy or for outcome, with no apparent dose-response association. The predictive significance is possibly exerted via MAP-Tau gene expression, an ER-inducible tubulin modulator with strong predictive significance for patient outcome. However, MAP-Tau mRNA did not predict benefit from the addition of a taxane to adjuvant chemotherapy. Further study of the biologic function and utility of MAP-Tau for individualising adjuvant therapy is warranted.

Microtubule-associated protein tau is a marker of pathological complete response in Her-2/neu positive neoadjuvant treated breast cancer patients

Gene expression analysis in breast cancer patients undergoing neoadjuvant chemotherapy is an interesting tool for identification of gene signatures and new markers to predict tumor response. However, the detection of predictive markers strongly depends on the drugs used in the specific therapeutic setting. There is growing evidence that topoisomerase II-alpha (TOPO IIα) is a marker for anthracycline-, and microtubule-associated protein tau (MAPT) for taxane sensitivity. HER-2 has been described as a marker of both anthracycline and taxane sensitivity. We performed gene expression profiling of 50 patients within the GEPARTRIO study, an anthracycline and taxane neoadjuvant chemotherapy trial. Here we investigate the predictive value of TOPO IIα, MAPT and HER-2 mRNA expression for pathological complete response (pCR) in this setting. Interestingly, HER-2 gene expression was strongly predictive of pCR (P=0.017) as well as overall response (P=0.037) and clinical complete response (cCR, P=0.050). In contrast, for both TOPO IIα and MAPT no correlation with pCR was observed in our sample group.

Development of two novel benzoylphenylurea sulfur analogues and evidence that the microtubule-associated protein tau is predictive of their activity in pancreatic cancer

In this work, we evaluated two lead compounds, referred to as SG410 and SG430, obtained from a screen of sulfur benzoylphenylurea analogues, against in vitro and in vivo models of pancreas cancer. Both drugs showed a similar mechanism of action profile, with SG410 being more potent as an inhibitor of tubulin assembly. We determined the best in vivo administration schedule and tested SG410 and SG430 in nine cases of a novel platform of direct pancreas cancer xenografts. Both compounds had antiproliferative activity in vitro in the low nanomolar range, but only SG410 showed significant activity in vivo. Administration of SG410 resulted in significant tumor growth delay in five of nine groups tested. In a direct comparison in three of the cases, SG410 was at least as efficacious as docetaxel. We also sought markers that would be predictive of the efficacy of these agents, and we found such a marker in microtubule-associated protein tau (MAPT). This protein enhances the assembly and stability of microtubules. In both the cell lines and the direct human xenografts, MAPT mRNA and protein levels correlated well. There was also a statistically significant inverse correlation between MAPT expression and sensitivity to the tested agents. In summary, the novel sulfur benzoylphenylurea SG410 showed activity inversely related to MAPT expression in a preclinical model of pancreatic cancer comparable with that observed with docetaxel, another microtubule-targeting agent.

Haplotype-specific expression of exon 10 at the human MAPT locus

Neurofibrillary tangles composed of exon 10+ microtubule associated protein tau (MAPT) deposits are the characteristic feature of the neurodegenerative diseases progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). PSP, CBD and more recently Alzheimer's disease and Parkinson's disease, are associated with the MAPT H1 haplotype, but the relationship between genotype and disease remains unclear. Here, we investigate the hypothesis that H1 expresses more exon 10+ MAPT mRNA compared to the other haplotype, H2, leading to a greater susceptibility to neurodegeneration in H1 carriers. We performed allele-specific gene expression on two H1/H2 heterozygous human neuronal cell lines, and 14 H1/H2 heterozygous control individual post-mortem brain tissue from two brain regions. In both tissue culture and post-mortem brain tissue, we show that the MAPT H1 haplotype expresses significantly more exon 10+ MAPT mRNA than H2. In post-mortem brain tissue, we show that the total level of MAPT expression from H1 and H2 is not significantly different, but that the H1 chromosome expresses up to 1.43-fold more exon 10+ MAPT mRNA than H2 in the globus pallidus, a brain region highly affected by tauopathy (maximum exon 10+ MAPT H1:H2 transcript ratio=1.425, SD=0.205, P<0.0001), and up to 1.29-fold more exon 10+ MAPT mRNA than H2 in the frontal cortex (maximum exon 10+ MAPT H1:H2 transcript ratio=1.291, SD=0.315, P=0.006). These data may explain the increased susceptibility of H1 carriers to neurodegeneration and suggest a potential mechanism between MAPT genetic variability and the pathogenesis of neurodegenerative disease.

Pharmacologic reductions of total tau levels; implications for the role of microtubule dynamics in regulating tau expression

The microtubule-associated protein tau (MAPT) is a pathological component of several neurodegenerative diseases and clinical dementias. Here, we have investigated the effects of a series of commercially available FDA-approved compounds and natural products on total tau protein levels using a cell-based approach that allows for the rapid and efficient measurement of changes in protein expression.ResultsThe compounds that reduced tau largely fell within 3 functional categories with the largest percentage being microtubule regulators. Several of these candidates were validated in both a human neuroglioma and a human neuroblastoma cell line. While these drugs lead to a rapid reduction in tau protein levels, a selective decrease in MAPT mRNA expression was also observed.ConclusionThese findings suggest that the identified compounds that reduce tau levels may act either through direct effects on the MAPT promoter itself or by altering a feedback transcriptional mechanism regulating MAPT transcription. This is particularly interesting in light of recent evidence suggesting that MAPT 5' UTR mutations in late-onset PD and PSP cases alter the expression of tau mRNA. In fact, one of the compounds we identified, rotenone, has been used extensively to model PD in rodents. These observations may provide key insights into the mechanism of tau turnover within the neuron while also providing the first evidence that selectively reducing tau protein levels may be possible using compounds that are FDA-approved for other uses.