Antibody Content against Epstein-Barr Virus in Blood Extracellular Vesicles Correlates with Disease Activity and Brain Volume in Patients with Relapsing-Remitting Multiple Sclerosis.

We aimed to analyze whether EVs carry antibodies against EBV antigens and the possibility that they could serve as diagnostic and disease activity blood biomarkers in RRMS. This was a prospective and observational study including patients with RRMS with active and inactive disease and healthy controls. Blood EVs were isolated by precipitation. Titers of antibodies against nuclear (anti-EBNA1) and capsid (anti-VCA) EBV antigens in EVs and in plasma, as well as content of myelin antibodies in EVs were determined by ELISA. An exploratory analysis of correlations with clinical and radiological data was performed. Patients with RRMS had higher titers of anti-VCA inside EVs and free in plasma than healthy controls. Patients with active disease showed higher levels of anti-EBNA1 in EVs, but not in plasma, than patients with inactive disease. EV anti-VCA levels correlated with disease duration and with decreased brain volume structures-total brain, white matter, gray matter, cerebellum, hippocampus, -but not with T2/FLAIR lesion volume or EDSS, SDMT, or 9HPT. In addition, EV anti-VCA correlated with EV anti-MBP. The anti-VCA and anti-EBNA1 content in EVs could represent diagnostic and disease activity blood biomarkers, respectively, in RRMS.

CSF Aß40 Levels Do Not Correlate with the Clinical Manifestations of Alzheimer's Disease.

INTRODUCTION: Cerebrospinal fluid (CSF) biomarker quantification provides physicians with a reliable diagnosis of Alzheimer's disease (AD). However, the relationship between their concentration and disease course has not been clearly elucidated. This work aimed to investigate the clinical and prognostic significance of Aß40 CSF levels. METHODS: A retrospective cohort of 76 patients diagnosed with AD using a decreased Aß42/Aß40 ratio was subclassified into hyposecretors (Aß40 <7,755 pg/mL), normosecretors (Aß40 7,755-16,715 pg/mL), and hypersecretors (Aß40 >16,715 pg/mL). Potential differences in AD phenotype, Montreal Cognitive Assessment (MoCA) scores, and Global Deterioration Scale (GDS) stages were assessed. Correlation tests for biomarker concentrations were also performed. RESULTS: Participants were classified as hyposecretors (n = 22, median Aß40 5,870.500 pg/mL, interquartile range [IQR] 1,431), normosecretors (n = 47, median Aß40 10,817 pg/mL, IQR 3,622), and hypersecretors (n = 7, 19,767 pg/mL, IQR 3,088). The distribution of positive phosphorylated Tau (p-Tau) varied significantly between subgroups and was more common in the normo- and hypersecretor categories (p = 0.003). Aß40 and p-Tau concentrations correlated positively (ρ = 0.605, p < 0.001). No significant differences were found among subgroups regarding age, initial MoCA score, initial GDS stage, progression to the dementia stage, or changes in the MoCA score. CONCLUSION: In this study, we found no significant differences in clinical symptoms or disease progression in AD patients according to their CSF Aß40 concentration. Aß40 was positively correlated with p-Tau and total Tau concentrations, supporting their potential interaction in AD pathophysiology.

The contribution of depressive symptoms to slowness of information processing in relapsing remitting multiple sclerosis.

BACKGROUND: Slowness of information processing has been suggested as a fundamental factor modulating cognitive impairment in multiple sclerosis (MS). However, the contribution of depressive symptoms (DS) to slowness remains unclear. One of the most accepted hypotheses on the impact of depression on the general population suggests that depression interferes only with tasks requiring high cognitive demands. However, no studies have investigated if the same pattern occurs in MS. OBJECTIVE: The aim of this study was to determine the profile of the contribution of DS to slowness. METHODS: Four Reaction Time (RT) tasks requiring an increasing level of cognitive demands were administered to 35 relapsing remitting MS patients with DS, 33 MS patients without DS, 17 depressed non-MS patients and 27 controls. RESULTS: MS patients without DS obtained longer RTs than controls in all the tasks. On the contrary, depressed non-MS patients were slower than controls only in the most demanding task. Finally, MS patients with DS were slower than MS patients without DS not only in the most demanding task but also in the task requiring a lower level of cognitive demands. CONCLUSION: The contribution of DS to slowness depends on the level of cognitive demands. However, its impact on MS is more deleterious than on the general population.

Cognitive decline in diabetic mice predisposed to Alzheimer's disease is greater than in wild type.

In this work, we tested the hypothesis that the development of dementia in individuals with type 2 diabetes (T2DM) requires a genetic background of predisposition to neurodegenerative disease. As a proof of concept, we induced T2DM in middle-aged hAPP NL/F mice, a preclinical model of Alzheimer's disease. We show that T2DM produces more severe behavioral, electrophysiological, and structural alterations in these mice compared with wild-type mice. Mechanistically, the deficits are not paralleled by higher levels of toxic forms of Aß or by neuroinflammation but by a reduction in γ-secretase activity, lower levels of synaptic proteins, and by increased phosphorylation of tau. RNA-seq analysis of the cerebral cortex of hAPP NL/F and wild-type mice suggests that the former could be more susceptible to T2DM because of defects in trans-membrane transport. The results of this work, on the one hand, confirm the importance of the genetic background in the severity of the cognitive disorders in individuals with T2DM and, on the other hand, suggest, among the involved mechanisms, the inhibition of γ-secretase activity.

Therapeutic plasma exchange for myasthenia gravis, Guillain-Barre syndrome, and other immune-mediated neurological diseases, over a 40-year experience.

BACKGROUND: Therapeutic plasma exchange (TPE) was first used in neurology in the 1980s for myasthenia gravis (MG) and Guillain-Barré syndrome (GBS). Indications have since grown. Fear of complications with this treatment modality limit its use. RESEARCH DESIGN & METHODS: A study of patients undergoing TPE for neurological diseases (1981-2020) in a University Hospital in Madrid, Spain. Clinical indications, complications, procedure number, apheresis technique and replacement fluids were prospectively recorded and retrospectively analyzed. Historical trends were studied. RESULTS: 159 patients (48.69 ±18.15 years, 54.3% females) underwent TPE using central-venous catheter and replacement fluid albumin. We performed 1207 procedures over 189 cycles (6.4 ±3.8 procedures/cycle). Most patients underwent TPE for category I-II indications, mainly GBS and MG (77.7%). Complication rate was low (3.9% procedures), mostly hypotensive/vasovagal reactions (55.3%) and vascular access-related complications (38.3%). Most were mild-moderate (92.9%), permitting TPE completion, and somewhat more frequent during the first procedure (38.3%) and after periods of little TPE use. GBS patients were more prone to complications than MG patients (6.5% vs. 1.2%,p<0.001) mainly hypotensive/vasovagal reactions (3.7% vs. 1.0%,p=0.008). CONCLUSIONS: TPE is well-tolerated with low complication rate (<4% procedures), mainly hypotensive/vasovagal reactions. Patients with GBS seem more prone to them than MG patients. Acquaintance with this technique seems necessary.

LAMP2 deficiency attenuates the neurodegeneration markers induced by HSV-1 infection.

Mounting evidence suggests a major role of infectious agents in the pathogenesis of sporadic Alzheimer's disease (AD). Among them, herpes simplex virus type 1 (HSV-1) infection has emerged as a major factor in the etiology of AD. HSV-1 is able to induce some of the main alterations of the disease such as hyperphosphorylation of tau protein and accumulation of amyloid-ß peptide. Functional genomic analysis of a cell model of HSV-1 infection and oxidative stress developed in our laboratory revealed lysosomal system to be the main pathway altered, and the lysosome-associated membrane protein 2 (LAMP2) gene one of the most strongly modulated genes. The aim of this work is to study LAMP2 as an AD candidate gene and to investigate its role in the neurodegeneration induced by HSV-1 using a LAMP2 knockdown cell model. LAMP2 deficiency led to a significant reduction of viral DNA replication and formation of infectious particles. In addition, tau hyperphosphorylation and inhibition of Aß secretion induced by the virus were attenuated by the absence of LAMP2. Finally, genetic association studies revealed LAMP2 genetic variants to be associated with AD risk. In summary, our data indicate that LAMP2 could be a suitable candidate to mediate the AD-like phenotype caused by HSV-1.

Common variants in Alzheimer's disease and risk stratification by polygenic risk scores.

Genetic discoveries of Alzheimer's disease are the drivers of our understanding, and together with polygenetic risk stratification can contribute towards planning of feasible and efficient preventive and curative clinical trials. We first perform a large genetic association study by merging all available case-control datasets and by-proxy study results (discovery n = 409,435 and validation size n = 58,190). Here, we add six variants associated with Alzheimer's disease risk (near APP, CHRNE, PRKD3/NDUFAF7, PLCG2 and two exonic variants in the SHARPIN gene). Assessment of the polygenic risk score and stratifying by APOE reveal a 4 to 5.5 years difference in median age at onset of Alzheimer's disease patients in APOE ɛ4 carriers. Because of this study, the underlying mechanisms of APP can be studied to refine the amyloid cascade and the polygenic risk score provides a tool to select individuals at high risk of Alzheimer's disease.

Genomic Characterization of Host Factors Related to SARS-CoV-2 Infection in People with Dementia and Control Populations: The GR@ACE/DEGESCO Study.

Emerging studies have suggested several chromosomal regions as potential host genetic factors involved in the susceptibility to SARS-CoV-2 infection and disease outcome. We nested a COVID-19 genome-wide association study using the GR@ACE/DEGESCO study, searching for susceptibility factors associated with COVID-19 disease. To this end, we compared 221 COVID-19 confirmed cases with 17,035 individuals in whom the COVID-19 disease status was unknown. Then, we performed a meta-analysis with the publicly available data from the COVID-19 Host Genetics Initiative. Because the APOE locus has been suggested as a potential modifier of COVID-19 disease, we added sensitivity analyses stratifying by dementia status or by disease severity. We confirmed the existence of the 3p21.31 region (LZTFL1, SLC6A20) implicated in the susceptibility to SARS-CoV-2 infection and TYK2 gene might be involved in COVID-19 severity. Nevertheless, no statistically significant association was observed in the COVID-19 fatal outcome or in the stratified analyses (dementia-only and non-dementia strata) for the APOE locus not supporting its involvement in SARS-CoV-2 pathobiology or COVID-19 prognosis.

Clinical progression of moderate-to-severe Alzheimer's disease and caregiver burden: a 12-month multicenter prospective observational study.

BACKGROUND: Prospective studies on the clinical progression of Alzheimer's disease (AD) and its relationship to caregiver burden are needed to improve illness management and use of resources. METHODS: This national, multicenter, observational study evaluated 1235 moderate to severe AD patients under routine care in Spain. Baseline cross-sectional sociodemographic and clinical data, and changes from baseline to month 12 of various neuropsychological tests and clinical ratings, including Blessed Dementia Scale, Mini-mental State Examination (MMSE), Hughes Clinical Dementia Rating sum-of-boxes (CDR-SB), Clinical Global Impression of Change (CGIC) and Zarit Caregiver Burden scales, were recorded and comprehensively analyzed. RESULTS: Baseline data were in accordance with characteristics consistently reported to influence AD risk regarding anthropometrics, sociocultural features and comorbidities. Significant progressive functional impairments (i.e. in routine activities and essential daily tasks) and cognitive (i.e. MMSE and CDR-SB) impairments were found at month 12. However, patients' behavior and caregivers' burden improved slightly, but significantly, corroborating the major influence of behavioral symptoms on caregivers' distress. Caregivers showed significantly lower burden with patients with higher levels of education and, to a lesser extent, when patients received AD-specific medication. Physicians accurately detected AD clinical evolution as their CGIC ratings significantly correlated with all tests. CONCLUSIONS: These findings reinforce previous AD knowledge and add data on the clinical course of advanced stages of AD. Caregiver burden depended more on patients' behavioral alterations than on their functional or cognitive declines; and it was diminished by their patients having higher levels of education and being treated with AD-specific medications. Research into unexplored factors that might reduce caregiver burden, ultimately benefiting both patients and caregivers, is encouraged.

Prodromal Alzheimer's Disease: Constitutive Upregulation of Neuroglobin Prevents the Initiation of Alzheimer's Pathology.

In humans, a considerable number of the autopsy samples of cognitively normal individuals aged between 57 and 102 years have revealed the presence of amyloid plaques, one of the typical signs of AD, indicating that many of us use mechanisms that defend ourselves from the toxic consequences of Aß. The human APP NL/F (hAPP NL/F) knockin mouse appears as the ideal mouse model to identify these mechanisms, since they have high Aß42 levels at an early age and moderate signs of disease when old. Here we show that in these mice, the brain levels of the hemoprotein Neuroglobin (Ngb) increase with age, in parallel with the increase in Aß42. In vitro, in wild type neurons, exogenous Aß increases the expression of Ngb and Ngb over-expression prevents Aß toxicity. In vivo, in old hAPP NL/F mice, Ngb knockdown leads to dendritic tree simplification, an early sign of Alzheimer's disease. These results could indicate that Alzheimer's symptoms may start developing at the time when defense mechanisms start wearing out. In agreement, analysis of plasma Ngb levels in aged individuals revealed decreased levels in those whose cognitive abilities worsened during a 5-year longitudinal follow-up period.

Identifying Perceptual, Motor, and Cognitive Components Contributing to Slowness of Information Processing in Multiple Sclerosis with and without Depressive Symptoms.

Increasing findings suggest that different components of the stimulus-response pathway (perceptual, motor or cognitive) may account for slowed performance in Multiple Sclerosis (MS). It has also been reported that depressive symptoms (DS) exacerbate slowness in MS. However, no prior studies have explored the independent and joint impact of MS and DS on each of these components in a comprehensive manner. The objective of this work was to identify perceptual, motor, and cognitive components contributing to slowness in MS patients with and without DS. The study includes 33 Relapsing-Remitting MS patients with DS, 33 without DS, and 26 healthy controls. Five information processing components were isolated by means of ANCOVA analyses applied to five Reaction Time tasks. Perceptual, motor, and visual search components were slowed down in MS, as revealed by ANCOVA comparisons between patients without DS, and controls. Moreover, the compounding effect of MS and DS exacerbated deficits in the motor component, and slowed down the decisional component, as revealed by ANCOVA comparisons between patients with and without DS. DS seem to exacerbate slowness caused by MS in specific processing components. Identifying the effects of having MS and of having both MS and DS may have relevant implications when targeting cognitive and mood interventions.

The Epistasis Project: A Multi-Cohort Study of the Effects of BDNF, DBH, and SORT1 Epistasis on Alzheimer's Disease Risk.

Pre-synaptic secretion of brain-derived neurotrophic factor (BDNF) from noradrenergic neurons may protect the Alzheimer's disease (AD) brain from amyloid pathology. While the BDNF polymorphism (rs6265) is associated with faster cognitive decline and increased hippocampal atrophy, a replicable genetic association of BDNF with AD risk has yet to be demonstrated. This could be due to masking by underlying epistatic interactions between BDNF and other loci that encode proteins involved in moderating BDNF secretion (DBH and Sortilin). We performed a multi-cohort case-control association study of the BDNF, DBH, and SORT1 loci comprising 5,682 controls and 2,454 AD patients from Northern Europe (87% of samples) and Spain (13%). The BDNF locus was associated with increased AD risk (odds ratios; OR = 1.1-1.2, p = 0.005-0.3), an effect size that was consistent in the Northern European (OR = 1.1-1.2, p = 0.002-0.8) but not the smaller Spanish (OR = 0.8-1.6, p = 0.4-1.0) subset. A synergistic interaction between BDNF and sex (synergy factor; SF = 1.3-1.5 p = 0.002-0.02) translated to a greater risk of AD associated with BDNF in women (OR = 1.2-1.3, p = 0.007-0.00008) than men (OR = 0.9-1.0, p = 0.3-0.6). While the DBH polymorphism (rs1611115) was also associated with increased AD risk (OR = 1.1, p = 0.04) the synergistic interaction (SF = 2.2, p = 0.007) between BDNF (rs6265) and DBH (rs1611115) contributed greater AD risk than either gene alone, an effect that was greater in women (SF = 2.4, p = 0.04) than men (SF = 2.0, p = 0.2). These data support a complex genetic interaction at loci encoding proteins implicated in the DBH-BDNF inflammatory pathway that modifies AD risk, particularly in women.

MAPT H1 Haplotype is Associated with Late-Onset Alzheimer's Disease Risk in APOEɛ4 Noncarriers: Results from the Dementia Genetics Spanish Consortium.

The MAPT H1 haplotype has been linked to several disorders, but its relationship with Alzheimer's disease (AD) remains controversial. A rare variant in MAPT (p.A152T) has been linked with frontotemporal dementia (FTD) and AD. We genotyped H1/H2 and p.A152T MAPT in 11,572 subjects from Spain (4,327 AD, 563 FTD, 648 Parkinson's disease (PD), 84 progressive supranuclear palsy (PSP), and 5,950 healthy controls). Additionally, we included 101 individuals from 21 families with genetic FTD. MAPT p.A152T was borderline significantly associated with FTD [odds ratio (OR) = 2.03; p = 0.063], but not with AD. MAPT H1 haplotype was associated with AD risk (OR = 1.12; p = 0.0005). Stratification analysis showed that this association was mainly driven by APOE ɛ4 noncarriers (OR = 1.14; p = 0.0025). MAPT H1 was also associated with risk for PD (OR = 1.30; p = 0.0003) and PSP (OR = 3.18; p = 8.59 × 10-8) but not FTD. Our results suggest that the MAPT H1 haplotype increases the risk of PD, PSP, and non-APOE ɛ4 AD.

A blood-based, 7-metabolite signature for the early diagnosis of Alzheimer's disease.

Accurate blood-based biomarkers of Alzheimer's disease (AD) could constitute simple, inexpensive, and non-invasive tools for the early diagnosis and treatment of this devastating neurodegenerative disease. We sought to develop a robust AD biomarker panel by identifying alterations in plasma metabolites that persist throughout the continuum of AD pathophysiology. Using a multicenter, cross-sectional study design, we based our analysis on metabolites whose levels were altered both in AD patients and in patients with amnestic mild cognitive impairment (aMCI), the earliest identifiable stage of AD. UPLC coupled to mass spectrometry was used to independently compare the levels of 495 plasma metabolites in aMCI (n = 58) and AD (n = 100) patients with those of normal cognition controls (NC, n = 93). Metabolite alterations common to both aMCI and AD patients were used to generate a logistic regression model that accurately distinguished AD from NC patients. The final panel consisted of seven metabolites: three amino acids (glutamic acid, alanine, and aspartic acid), one non-esterified fatty acid (22:6n-3, DHA), one bile acid (deoxycholic acid), one phosphatidylethanolamine [PE(36:4)], and one sphingomyelin [SM(39:1)]. Detailed analysis ruled out the influence of potential confounding variables, including comorbidities and treatments, on each of the seven biomarkers. The final model accurately distinguished AD from NC patients (AUC, 0.918). Importantly, the model also distinguished aMCI from NC patients (AUC, 0.826), indicating its potential diagnostic utility in early disease stages. These findings describe a sensitive biomarker panel that may facilitate the specific detection of early-stage AD through the analysis of plasma samples.

Assessing the role of the TREM2 p.R47H variant as a risk factor for Alzheimer's disease and frontotemporal dementia.

A non-synonymous genetic rare variant, rs75932628-T (p.R47H), in the TREM2 gene has recently been reported to be a strong genetic risk factor for Alzheimer's disease (AD). Also, rare recessive mutations have been associated with frontotemporal dementia (FTD). We aimed to investigate the role of p.R47H variant in AD and FTD through a multi-center study comprising 3172 AD and 682 FTD patients and 2169 healthy controls from Spain. We found that 0.6% of AD patients carried this variant compared to 0.1% of controls (odds ratio [OR] = 4.12, 95% confidence interval [CI] = 1.21-14.00, p = 0.014). A meta-analysis comprising 32,598 subjects from 4 previous studies demonstrated the large effect of the p.R47H variant in AD risk (OR = 4.11, 95% CI = 2.99-5.68, p = 5.27×10(-18)). We did not find an association between p.R47H and age of onset of AD or family history of dementia. Finally, none of the FTD patients harbored this genetic variant. These data strongly support the important role of p.R47H in AD risk, and suggest that this rare genetic variant is not related to FTD.

A common BACE1 polymorphism is a risk factor for sporadic Creutzfeldt-Jakob disease.

The ß site APP cleaving enzyme 1 (BACE1) is the rate-limiting ß-secretase enzyme in the amyloidogenic processing of APP and Aß formation, and therefore it has a prominent role in Alzheimer's disease (AD) pathology. Recent evidence suggests that the prion protein (PrP) interacts directly with BACE1 regulating its ß-secretase activity. Moreover, PrP has been proposed as the cellular receptor involved in the impairment of synaptic plasticity and toxicity caused by Aß oligomers. Provided that common pathophysiologic mechanisms are shared by Alzheimer's and Creutzfeldt-Jakob (CJD) diseases, we investigated for the first time to the best of our knowledge a possible association of a common synonymous BACE1 polymorphism (rs638405) with sporadic CJD (sCJD). Our results indicate that BACE1 C-allele is associated with an increased risk for developing sCJD, mainly in PRNP M129M homozygous subjects with early onset. These results extend the very short list of genes (other than PRNP) involved in the development of human prion diseases; and support the notion that similar to AD, in sCJD several loci may contribute with modest overall effects to disease risk. These findings underscore the interplay in both pathologies of APP, Aß oligomers, ApoE, PrP and BACE1, and suggest that aging and perhaps vascular risk factors may modulate disease pathologies in part through these key players.

Genetic variability of the gene cluster CALHM 1-3 in sporadic Creutzfeldt-Jakob disease.

Perturbations of calcium homeostasis have been associated with several neurodegenerative disorders. A common polymorphism (rs2986017) in the CALHM1 gene, coding for a regulator of calcium homeostasis, is a genetic risk factor for the development of Alzheimer disease (AD). Although some authors failed to confirm these results, a meta-analysis has shown that this polymorphism modulates the age at disease onset. Furthermore, a recent association study has explored the genetic variability of CALHM1 gene and two adjacent paralog genes (CALHM3 and CALHM2) in an Asian population. Since several lines of evidence suggest that AD and prion diseases share pathophysiologic mechanisms, we investigated for the first time the genetic variability of the gene cluster formed by CALHM1 and its paralogs in a series of 235 sporadic Creutzfeldt-Jakob disease (sCJD) patients, and compared the genotypic and allelic frequencies with those presented in 329 controls from the same ancestry. As such, this work also represents the first association analysis of CALHM genes in sCJD. Sequencing analysis of the complete coding regions of the genes demonstrated the presence of 10 single nucleotide polymorphisms (SNP) within the CALHM genes. We observed that rs4918016-rs2986017-rs2986018 and rs41287502-rs41287500 polymorphic sites at CALHM1 were in linkage disequilibrium. We found marginal associations for sCJD risk at CALHM1 polymorphic sites rs41287502 and rs41287500 [coding for two linked missense mutations (p.(Met323Ile); (Gly282Cys)], and rs2986017 [p.(Leu86Pro)]. Interestingly, a TGG haplotype defined by the rs4918016-rs2986017-rs2986018 block was associated with sCJD. These findings underscore the need of future multinational collaborative initiatives in order to corroborate these seminal data.

Genetic cross-interaction between APOE and PRNP in sporadic Alzheimer's and Creutzfeldt-Jakob diseases.

Alzheimer's disease (AD) and Creutzfeldt-Jakob disease (CJD) represent two distinct clinical entities belonging to a wider group, generically named as conformational disorders that share common pathophysiologic mechanisms. It is well-established that the APOE ε4 allele and homozygosity at polymorphic codon 129 in the PRNP gene are the major genetic risk factors for AD and human prion diseases, respectively. However, the roles of PRNP in AD, and APOE in CJD are controversial. In this work, we investigated for the first time, APOE and PRNP genotypes simultaneously in 474 AD and 175 sporadic CJD (sCJD) patients compared to a common control population of 335 subjects. Differences in genotype distribution between patients and control subjects were studied by logistic regression analysis using age and gender as covariates. The effect size of risk association and synergy factors were calculated using the logistic odds ratio estimates. Our data confirmed that the presence of APOE ε4 allele is associated with a higher risk of developing AD, while homozygosity at PRNP gene constitutes a risk for sCJD. Opposite, we found no association for PRNP with AD, nor for APOE with sCJD. Interestingly, when AD and sCJD patients were stratified according to their respective main risk genes (APOE for AD, and PRNP for sCJD), we found statistically significant associations for the other gene in those strata at higher previous risk. Synergy factor analysis showed a synergistic age-dependent interaction between APOE and PRNP in both AD (SF = 3.59, p = 0.027), and sCJD (SF = 7.26, p = 0.005). We propose that this statistical epistasis can partially explain divergent data from different association studies. Moreover, these results suggest that the genetic interaction between APOE and PRNP may have a biological correlate that is indicative of shared neurodegenerative pathways involved in AD and sCJD.

Genetic variation in the tau protein phosphatase-2A pathway is not associated with Alzheimer's disease risk.

BACKGROUND: Tau abnormal hyperphosphorylation and the formation of neurofibrillary tangles in AD brain is the result of upregulation of tau kinases and downregulation of tau phosphatases. METHODS: In a group of 729 Spanish late-onset Alzheimer's disease (AD) patients and 670 healthy controls, we examined variations into a set of candidate genes (PPP2CA, PPP2R2A, ANP32A, LCMT1, PPME1 and PIN1) in the tau protein phosphatase-2A (PP2A) pathway, to address hypotheses of genetic variation that might influence AD risk. RESULTS: There were no differences in the genotypic, allelic or haplotypic distributions between cases and controls in the overall analysis or after stratification by age, gender or APOE ε4 allele. CONCLUSION: Our negative findings in the Spanish population argue against the hypothesis that genetic variation in the tau protein phosphatase-2A (PP2A) pathway is causally related to AD risk.