Saitohin, Which Is Nested in the tau Locus and Confers Allele-specific Susceptibility to Several Neurodegenerative Diseases, Interacts with Peroxiredoxin 6

The Roles of Peroxiredoxin 6 in Brain Diseases

Peroxiredoxin 6 (PRDX6), the only mammalian 1-Cys member of the peroxiredoxins (PRDXs) family, has multiple functions of glutathione peroxidase (Gpx) activity, acidic calcium-independent phospholipase (aiPLA2) activity, and lysophosphatidylcholine acyl transferase (LPCAT) activity. It has been documented to be involved in redox homeostasis, phospholipid turnover, glycolipid metabolism, and cellular signaling. Here, we reviewed the characteristics of the available Prdx6 genetic mouse models and the research progresses made with regard to PRDX6 in neuropsychiatric disorders, including neurodegenerative diseases, brain aging, stroke, neurotrauma, gliomas, major depressive disorder, drug addiction, post-traumatic stress disorder, and schizophrenia. The present review highlights the important roles of PRDX6 in neuropsychiatric disorders and may provide novel insights for the development of effective pharmacological treatments and genetic therapies.

The physiological roles of tau and Aβ: implications for Alzheimer's disease pathology and therapeutics

Tau and amyloid beta (Aβ) are the prime suspects for driving pathology in Alzheimer's disease (AD) and, as such, have become the focus of therapeutic development. Recent research, however, shows that these proteins have been highly conserved throughout evolution and may have crucial, physiological roles. Such functions may be lost during AD progression or be unintentionally disrupted by tau- or Aβ-targeting therapies. Tau has been revealed to be more than a simple stabiliser of microtubules, reported to play a role in a range of biological processes including myelination, glucose metabolism, axonal transport, microtubule dynamics, iron homeostasis, neurogenesis, motor function, learning and memory, neuronal excitability, and DNA protection. Aβ is similarly multifunctional, and is proposed to regulate learning and memory, angiogenesis, neurogenesis, repair leaks in the blood-brain barrier, promote recovery from injury, and act as an antimicrobial peptide and tumour suppressor. This review will discuss potential physiological roles of tau and Aβ, highlighting how changes to these functions may contribute to pathology, as well as the implications for therapeutic development. We propose that a balanced consideration of both the physiological and pathological roles of tau and Aβ will be essential for the design of safe and effective therapeutics.

Salidroside influences the cellular cross-talk of human fetal lung diploid fibroblasts: A proteomic approach

Senescence is a complex multiple factor proces, which is still poorly understood. The purpose of this study was to find the proteome of cultured human fetal lung diploid fibroblasts (2BS) of different population doubling (PD), as well as the altered proteome induced by salidroside (SAL) in 2BS cells. Proteins were identified by two-dimensional electrophoresis (2-DE) combining matrix-assisted laser desorption/ionization-time and flight mass spectrometry (MAL DI-TOF/MS). As a result, we found 16 proteins with two-fold variations in senescent cells or after SAL treatment, some being reduced such as reticulocalbin-1, heat shock protein beta-6, elongation factor 1-delta, F-actin-capping protein subunit alpha-1, and chloride intracellular channel 1. In contrast, 40S ribosomal protein SA, proteasome subunit alpha type-5, and zinc finger BED domain-containing protein 5 increased with cell age. Furthermore, heat shock protein beta-6, Zinc finger BED domain-containing protein 5 was increased in PD30 cells after 10 μM SAL treatment, whereas, elongation factor 1-delta, 6-phosphogluconolactonase, Nucleoside diphosphate kinase A, F-actin-capping protein subunit alpha-1, Probable ATP-dependent RNA helicase DDX41, Chloride intracellular channel 1, and Peroxiredoxin-6 were increased in PD50 cells after 10 μM SAL treatment. Some of these proteins were involved in the protein synthetic and degradative pathways, which emphasizes the metabolic disorder or functional impairment of cell senescence. Moreover, these proteins could be candidate biomarkers for evaluating the SAL anti-senescence effect.

Saitohin Q7R polymorphism is associated with late-onset Alzheimer's disease susceptibility among caucasian populations: a meta-analysis

Saitohin (STH) Q7R polymorphism has been reported to influence the individual's susceptibility to Alzheimer's disease (AD); however, conclusions remain controversial. Therefore, we performed this meta-analysis to explore the association between STH Q7R polymorphism and AD risk. Systematic literature searches were performed in the PubMed, Embase, Cochrane Library and Web of Science for studies published before 31 August 2016. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association using a fixed- or random-effects model. Subgroup analyses, Galbraith plot and sensitivity analyses were also performed. All statistical analyses were performed with STATA Version 12.0. A total of 19 case-control studies from 17 publications with 4387 cases and 3972 controls were included in our meta-analysis. The results showed that the Q7R polymorphism was significantly associated with an increased risk of AD in a recessive model (RR versus QQ+QR, OR = 1.27, 95% CI = 1.01-1.60, P = 0.040). After excluding the four studies not carried out in caucasians, the overall association was unchanged in all comparison models. Further subgroup analyses stratified by the time of AD onset, and the quality of included studies provided statistical evidence of significant increased risk of AD in RR versus QQ+QR model only in late-onset subjects (OR = 1.56, 95% CI = 1.07-2.26, P = 0.021) and in studies with high quality (OR = 1.37, 95% CI = 1.01-1.86, P = 0.043). This meta-analysis suggests that the RR genotype in saitohin Q7R polymorphism may be a human-specific risk factor for AD, especially among late-onset AD subjects and caucasian populations.

New Features about Tau Function and Dysfunction

Tau is a brain microtubule-associated protein that directly binds to a microtubule and dynamically regulates its structure and function. Under pathological conditions, tau self-assembles into filamentous structures that end up forming neurofibrillary tangles. Prominent tau neurofibrillary pathology is a common feature in a number of neurodegenerative disorders, collectively referred to as tauopathies, the most common of which is Alzheimer’s disease (AD). Beyond its classical role as a microtubule-associated protein, recent advances in our understanding of tau cellular functions have revealed novel insights into their important role during pathogenesis and provided potential novel therapeutic targets. Regulation of tau behavior and function under physiological and pathological conditions is mainly achieved through post-translational modifications, including phosphorylation, glycosylation, acetylation, and truncation, among others, indicating the complexity and variability of factors influencing regulation of tau toxicity, all of which have significant implications for the development of novel therapeutic approaches in various neurodegenerative disorders. A more comprehensive understanding of the molecular mechanisms regulating tau function and dysfunction will provide us with a better outline of tau cellular networking and, hopefully, offer new clues for designing more efficient approaches to tackle tauopathies in the near future.

The use of matrix coating assisted by an electric field (MCAEF) to enhance mass spectrometric imaging of human prostate cancer biomarkers

In this work, we combined a newly developed matrix coating technique - matrix coating assisted by an electric field (MCAEF) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to enhance the imaging of peptides and proteins in tissue specimens of human prostate cancer. MCAEF increased the signal-to-noise ratios of the detected proteins by a factor of 2 to 5, and 232 signals were detected within the m/z 3500-37500 mass range on a time-of-flight mass spectrometer and with the sinapinic acid MALDI matrix. Among these species, three proteins (S100-A9, S100-A10, and S100-A12) were only observed in the cancerous cell region and 14 proteins, including a fragment of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 2, a fragment of cAMP-regulated phosphoprotein 19, 3 apolipoproteins (C-I, A-I, and A-II), 2 S100 proteins (A6 and A8), β-microseminoprotein, tumor protein D52, α-1-acid glycoprotein 1, heat shock protein β-1, prostate-specific antigen, and 2 unidentified large peptides at m/z 5002.2 and 6704.2, showed significantly differential distributions at the p < 0.05 (t-test) level between the cancerous and the noncancerous regions of the tissue. Among these 17 species, the distributions of apolipoprotein C-I, S100-A6, and S100-A8 were verified by immunohistological staining. In summary, this study resulted in the imaging of the largest group of proteins in prostate cancer tissues by MALDI-MS reported thus far, and is the first to show a correlation between S100 proteins and prostate cancer in a MS imaging study. The successful imaging of the three proteins only found in the cancerous tissues, as well as those showing differential expressions demonstrated the potential of MCAEF-MALDI/MS for the in situ detection of potential cancer biomarkers. Copyright © 2015 John Wiley & Sons, Ltd.

Aberrant sumoylation signaling evoked by reactive oxygen species impairs protective function of Prdx6 by destabilization and repression of its transcription

Loss of the cytoprotective protein peroxiredoxin 6 (Prdx6) in cells that are aging or under oxidative stress is known to be linked to the pathobiology of many age-related diseases. However, the mechanism by which Prdx6 activity goes awry is largely unknown. Using Prdx6-deficient (Prdx6(-/-) ) cells as a model for aging or redox active cells, human/mouse lens epithelial cells (LECs) facing oxidative stress and aging lenses, we found a significant increase in the levels of small ubiquitin-like modifier (Sumo)1 conjugates. These cells displayed increased levels of Sumo1 and reduced the expression of Prdx6. Specifically, we observed that Prdx6 is a target for aberrant sumoylation signaling, and that Sumo1 modification reduces its cellular abundance. LECs overexpressing Sumo1 showed reduced expression and activity of Prdx6 and its transactivator specificity protein 1 (Sp1), mRNA and protein with increased levels of reactive oxygen species; those cells were vulnerable to oxidative stress-induced cell death. A significant reduction in Prdx6, Sp1 protein and mRNA expression was observed in redox active Prdx6(-/-) cells and in aging lenses/LECs. The reduction was correlated with increased expression of Sumo1 and enrichment of the inactive form (dimeric) of Sumo-specific protease (Senp)1. Experiments with Sumo1-fused Prdx6 and Prdx6 promoter-linked to chloramphenicol acetyltransferase reporter gene constructs indicated that Sumo1 dysregulated Prdx6 activity by reducing its abundance and attenuating its transcription; in contrast, the delivery of Senp1 or Prdx6 reversed the process. The data show that reactive oxygen species-evoked aberrant sumoylation signaling affects Prdx6 activity by reducing Prdx6 abundance, as well as transcription. The findings of the present study may provide a foundation for a strategy to repair deleterious oxidative signaling generated by a reduced activity of Prdx6.

Copy number variations involving the microtubule-associated protein tau in human diseases

Mutations of the MAPT (microtubule-associated protein tau) gene are associated with FTLD (frontotemporal lobar degeneration) with tau pathology. These mutations result in a decreased ability of tau to bind MTs (microtubules), an increased production of tau with four MT-binding repeats or enhanced tau aggregation. In two FTLD patients, we recently described CNVs (copy number variations) affecting the MAPT gene, consisting of a partial deletion and a complete duplication of the gene. The partial deletion resulted in a truncated protein lacking the first MT-binding domain, which had a dramatic decrease in the binding to MTs but acquired the ability to bind MAP (microtubule-associated protein) 1-B. In this case, tauopathy probably resulted from both a loss of normal function and a gain of function by which truncated tau would sequester another MAP. In the other FTLD patient, the complete duplication might result in the overexpression of tau, which in the mouse model induces axonopathy and tau aggregates reminiscent of FTLD-tau pathology. Interestingly, the same rearrangement was also described in several children with mental retardation, autism spectrum disorders and dysmorphic features, as well as in a schizophrenic patient. Finally, complete deletions of the MAPT gene have been associated with mental retardation, hypotonia and facial dysmorphism.

Tau splicing and the intricacies of dementia

Tau is a microtubule-associated protein that fulfills several functions critical for neuronal formation and health. Tau discharges its functions by producing multiple isoforms via regulated alternative splicing. These isoforms modulate tau function in normal brain by altering the domains of the protein, thereby influencing its localization, conformation, and post-translational modifications and hence its availability and affinity for microtubules and other ligands. Disturbances in tau expression result in disruption of the neuronal cytoskeleton and formation of tau structures (neurofibrillary tangles) found in brains of dementia sufferers. More specifically, aberrations in tau splicing regulation directly cause several neurodegenerative diseases, which lead to dementia. In this review, I present our cumulative knowledge of tau splicing regulation in connection with neurodegeneration and also briefly go over the still-extensive list of questions that are connected to tau (dys)function.

Saitohin, which is nested within the tau gene, interacts with tau and Abl and its human-specific allele influences Abl phosphorylation

Saitohin (STH) is a gene unique to humans and their closest relatives whose function is not yet known. STH contains a single polymorphism (Q7R); the Q allele is human-specific and confers susceptibility to several neurodegenerative diseases. In previous work, we discovered that STH interacts with Peroxiredoxin 6 (Prdx6), a unique member of that family which is bifunctional and whose levels increase in Pick's disease. In this study, we report that STH also interacts with tau and the non-receptor tyrosine kinase c-Abl (Abl). Furthermore, Abl phosphorylates STH on its single tyrosine residue and STH increases tyrosine phosphorylation by Abl. The effect of Saitohin on Abl-mediated phosphorylation appears to be allele-specific, providing evidence for a new cellular function for STH.

The antioxidant enzyme peroxiredoxin and its protective role in neurological disorders

Peroxiredoxin (Prx) represents a family of sulfhydryl-dependent peroxidases that reduce hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. There are six known mammalian isozymes (Prx1-6), classified as typical 2-Cys, atypical 2-Cys, or 1-Cys Prxs. In addition to their well-established peroxide-scavenging activity, Prxs also participate in the regulation of various cell signaling pathways. Experimental studies provide substantial evidence for a protective role of Prxs in various neurological disorders involving oxidative and inflammatory stress. There is also evidence suggesting a potential benefit of Prxs in certain neurological diseases in human subjects. This review first describes the biochemical properties and molecular regulation of Prxs, then summarizes the major findings on the neuroprotective functions of Prxs and finally discusses the feasibility of using natural compounds, including those from herbal remedies to augment Prx expression to counteract oxidative neurological disorders.

Saitohin polymorphism and executive dysfunction in schizophrenia

Saitohin (STH) is an intronless gene nested within the human tau gene, which contains a single nucleotide polymorphism (A/G), suggested to be involved in the physiopathology and clinical course of several neurodegenerative and neuropsychiatric diseases. Recently, an association between this polymorphism and frontal hypoperfusion and clinical prognosis in frontotemporal dementia was reported. The present study sought to evaluate the possible role of the STH polymorphism as a concurring factor of cognitive decline in schizophrenia, a disease sharing both early psychotic manifestations, a core deficit of executive functions and hypofrontality with frontotemporal lobe dementia. 220 clinically stabilized patients with schizophrenia were assessed with the Wisconsin Card Sorting Test (WCST) for evaluation of executive functions and compared for STH allele frequency with 48 patients affected by frontotemporal dementia and 47 healthy subjects. There was no significant difference in allelic distribution between the healthy controls and all other groups, while we observed a significantly greater frequency of G allele among both patients with frontotemporal dementia (p = 0.037) and schizophrenia patients with poor performances of WCST (p = 0.044), compared to schizophrenia patients with best WCST performances. Among the patients with schizophrenia, stratified for age and gender, the STH polymorphism resulted in a significant predictor of WCST performance (p = 0.007). These results suggest a possible contribution of STH gene products on the heterogeneity of core frontal executive functions deterioration, probably through complex interactions with mechanism involved in neurodevelopment and neurodegeneration.

Peroxiredoxin 6: a bifunctional enzyme with glutathione peroxidase and phospholipase A₂ activities

Peroxiredoxin 6 (Prdx6) is the prototype and the only mammalian 1-Cys member of the Prdx family. Major differences from 2-Cys Prdxs include the use of glutathione (GSH) instead of thioredoxin as the physiological reductant, heterodimerization with πGSH S-transferase as part of the catalytic cycle, and the ability either to reduce the oxidized sn-2 fatty acyl group of phospholipids (peroxidase activity) or to hydrolyze the sn-2 ester (alkyl) bond of phospholipids (phospholipase A(2) [PLA(2)] activity). The bifunctional protein has separate active sites for peroxidase (C47, R132, H39) and PLA(2) (S32, D140, H26) activities. These activities are dependent on binding of the protein to phospholipids at acidic pH and to oxidized phospholipids at cytosolic pH. Prdx6 can be phosphorylated by MAP kinases at T177, which markedly increases its PLA(2) activity and broadens its pH-activity spectrum. Prdx6 is primarily cytosolic but also is targeted to acidic organelles (lysosomes, lamellar bodies) by a specific targeting sequence (amino acids 31-40). Oxidant stress and keratinocyte growth factor are potent regulators of Prdx6 gene expression. Prdx6 has important roles in both antioxidant defense based on its ability to reduce peroxidized membrane phospholipids and in phospholipid homeostasis based on its ability to generate lysophospholipid substrate for the remodeling pathway of phospholipid synthesis.

Peroxiredoxin 6 interferes with TRAIL-induced death-inducing signaling complex formation by binding to death effector domain caspase

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent with cancer-selective apoptogenic activity. It evokes the canonical caspase-mediated cell death pathway through death-inducing signaling complex (DISC) formation. We identified that Peroxiredoxin 6 (Prx6) interacts with caspase-10 and caspase-8 via the death effector domain (DED). Prx6 suppresses TRAIL-mediated cell death in human cancer cells, but not that induced by intrinsic apoptosis inducers such as etoposide, staurosporine, or A23187. Among Prx1-6 members, only Prx6 binds to DED caspases and is most effective in suppressing TRAIL or DED caspase-induced cell death. The antiapoptotic activity of Prx6 against TRAIL is not likely associated with its peroxidase activity but is associated with its ability to bind to DED caspases. Increased expression of Prx6 enhances the binding of Prx6 to caspase-10 but reduces TRAIL-induced DISC formation and subsequently caspase activation. Interestingly, Prx6 is highly upregulated in metastatic gastric cancer cells, which are relatively resistant to TRAIL as compared with primary cancer cells. Downregulation of Prx6 sensitizes the metastatic cancer cells to TRAIL-induced cell death. Taken together, these results suggest that Prx6 modulates TRAIL signaling as a negative regulator of caspase-8 and caspase-10 in DISC formation of TRAIL-resistant metastatic cancer cells.

Non-apolipoprotein E and apolipoprotein E genetics of sporadic Alzheimer's disease

The genetic epidemiology of sporadic Alzheimer's disease (SAD) remains a very active area of research,making it one of the most prolifically published areas in medicine and biology. Numerous putative candidate genes have been proposed. However, with the exception of apolipoprotein E (APOE), the only confirmed genetic risk factor for SAD, all the other data appear to be not consistent. Nevertheless, the genetic risk for SAD attributable to the APOE gene in the general population is 20-0%, providing a strong evidence for the existence of additional genetic risk factors. The first part of the present article was dedicated to non-APOE genetics of SAD, reviewing chromosomes-by-chromosomes the available data concerning the major candidate genes. The second part of this article focused on some recently discovered aspects of the APOE polymorphism and their implications for SAD. An attempt to identify the future directions for non-APOE genetic research in SAD was also discussed.

The dual functions of thiol-based peroxidases in H2O2 scavenging and signaling

Thiol-based peroxidases consist of the peroxiredoxins (Prx) and the related glutathione peroxidase (GPx)-like enzymes. Their catalytic function is to reduce peroxides by using the reactivity of the cysteine residue, and their presumed primary physiologic role is to protect living organisms from peroxide toxicity. However, as peroxide-metabolizing enzymes, they also regulate hydrogen peroxide (H2O2) signaling. We review here enzymatic and biochemical attributes of thiol peroxidases that specify both distinctive peroxide-scavenging functions and the property of regulating H2O2 signaling. We then discuss possible thiol peroxidase physiologic functions, based on selected observations made in microorganisms and mammals.

Haplotypes and gene expression implicate the MAPT region for Parkinson disease: the GenePD Study

BACKGROUND

Microtubule-associated protein tau (MAPT) has been associated with several neurodegenerative disorders including forms of parkinsonism and Parkinson disease (PD). We evaluated the association of the MAPT region with PD in a large cohort of familial PD cases recruited by the GenePD Study. In addition, postmortem brain samples from patients with PD and neurologically normal controls were used to evaluate whether the expression of the 3-repeat and 4-repeat isoforms of MAPT, and neighboring genes Saitohin (STH) and KIAA1267, are altered in PD cerebellum.

METHODS

Twenty-one single-nucleotide polymorphisms (SNPs) in the region of MAPT on chromosome 17q21 were genotyped in the GenePD Study. Single SNPs and haplotypes, including the H1 haplotype, were evaluated for association to PD. Relative quantification of gene expression was performed using real-time RT-PCR.

RESULTS

After adjusting for multiple comparisons, SNP rs1800547 was significantly associated with PD affection. While the H1 haplotype was associated with a significantly increased risk for PD, a novel H1 subhaplotype was identified that predicted a greater increased risk for PD. The expression of 4-repeat MAPT, STH, and KIAA1267 was significantly increased in PD brains relative to controls. No difference in expression was observed for 3-repeat MAPT.

CONCLUSIONS

This study supports a role for MAPT in the pathogenesis of familial and idiopathic Parkinson disease (PD). Interestingly, the results of the gene expression studies suggest that other genes in the vicinity of MAPT, specifically STH and KIAA1267, may also have a role in PD and suggest complex effects for the genes in this region on PD risk.

HD phenocopies--possible role of Saitohin gene

Saitohin (STH) is located in the intron of the human gene for microtubule-associated protein tau. Q7R polymorphism has been identified in the STH gene. Some neurodegenerative disorders were found to be associated with the presence of certain STH allele. This study genotyped 37 subjects with diagnosis of Huntington's disease, but lacking mutations in HD, PRNP, JPH-3, and FTL genes for STH polymorphism. It was determined that Q allele of STH gene was over-represented in a tested group of patients (P > Pt). Over-representation of Q allele in a group of patients might be considered as genetic risk factor for HD like diseases.

Genetic analysis of tumor necrosis factor-alpha (TNF-alpha) G-308A and Saitohin Q7R polymorphisms with Alzheimer's disease

Neuroinflammation and abnormal phosphorylation of TAU proteins have been implicated in the etiology of Alzheimer's disease (AD). Several studies have suggested the G-308A promoter polymorphism in one of the proinflammatory cytokine genes tumor necrosis factor-alpha (TNF-alpha) encoding TNF-alpha may be associated with AD pathogenesis. Association between the Q7R polymorphism in saitohin (STH), a gene nested within the intron of the Tau gene, has also been reported. To determine whether these two polymorphisms contribute to the risk for late-onset AD (LOAD) in Chinese, we have investigated 207 sporadic LOAD patients and 222 healthy controls. The associations of the AA genotype and A-allele with LOAD (chi(2) = 8.74, df = 1, P = 0.0031, and chi(2) = 4.47, df = 1, P = 0.035) were found. After stratifying by apolipoprotein E allele 4 (APOE epsilon4) status, increased LOAD risks associated with the AA genotype and A-allele only in the APOE epsilon4 non-carriers (chi(2) = 9.21, df = 1, P = 0.002; chi(2) = 10.02, df = 1, P = 0.0015) were seen. These results suggested that the TNF-alpha gene G-308A polymorphism might be a risk factor for LOAD and dependent on APOE epsilon4 status in Chinese. Homozygous Q/Q of STH Q7R polymorphism was the only one genotype found in either LOAD group or controls. No R allele was detected in LOAD and control groups. The extremely rare frequency of the ancestral R allele differs sharply from that observed in studies in the Caucasian population, suggesting obvious ethnic differences.

Tau and saitohin gene expression pattern in progressive supranuclear palsy

Deregulation of tau mRNA splicing may contribute to causing progressive supranuclear palsy (PSP). The inclusion of exon 10 produces tau protein isoforms containing all four microtubule-binding repeats (4R). Its exclusion gives rise to isoforms with three microtubule-binding repeats (3R). Alternative splicing of exons 2 and 3 produces the 0N, 1N or 2N protein isoforms. Saitohin (STH) is a nested gene included in intron 9 of tau. It has an unknown function, but could also be involved in the pathological process associated with PSP. We used real-time PCR to investigate the level of expression of tau mRNA isoforms and STH mRNA in the frontal cortex and globus pallidus of PSP patients' brains. mRNA levels were compared with those in the brains of two controls groups: healthy controls and Alzheimer's disease patients (AD). The 4R/3R mRNA ratio was significantly higher in the globus pallidus of PSP patients than in controls. The 0N mRNA isoform levels were statistically higher in the frontal cortex and globus pallidus of AD patients and were borderline higher in the globus pallidus of PSP patients than controls. In addition, when all samples were taken into account (PSP+AD+controls), a significant correlation was found between the 4R/3R mRNA tau ratio and STH expression. This correlation was stronger in the globus pallidus than in the frontal cortex. Our results suggest that abnormalities in the alternative splicing of the tau gene are involved in the molecular mechanism related to PSP pathogenesis. Such abnormalities cause an increase in the 4R/3R ratio and may lead to an overexpression of 0N tau isoforms.

SR protein 9G8 modulates splicing of tau exon 10 via its proximal downstream intron, a clustering region for frontotemporal dementia mutations

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.