Activation of the Wnt Signaling Pathway: A Molecular Mechanism for Lithium Action

AbstractGlycogen synthase kinase-3β (GSK-3β/zeste-white-3/shaggy) is a negative regulator of the wnt signaling pathway which plays a central role in the development of invertebrates and vertebrates; loss of function and dominant negative mutations in GSK-3β lead to activation of the wnt pathway inDrosophilaandXenopus.We now provide evidence that lithium activates downstream components of the wnt signaling pathwayin vivo,leading to accumulation of β-catenin protein. Our data indicate that this activation of the wnt pathway is a consequence of inhibition of GSK-3β by lithium. Using a novel assay for GSK-3β in oocytes, we show that lithium inhibits GSK-3β from species as diverse asDictyostelium discoideumandXenopus laevis,providing a biochemical mechanism for the action of lithium on the development of these organisms. Lithium treatment also leads to activation of an AP-1–luciferase reporter inXenopusembryos, consistent with previous observations that GSK-3β inhibits c-jun activity. Activation of the wnt pathway with a dominant negative form of GSK-3β is inhibited by myo-inositol, similar to the previously described effect of coinjecting myo-inositol with lithium. The mechanism by which myo-inositol inhibits both dominant negative GSK-3β and lithium remains uncertain

Cellular Milieu Imparts Distinct Pathological α-Synuclein Strains in α-Synucleinopathies

Introduction: In Lewy body diseases-including Parkinson\u27s disease, without or with dementia, dementia with Lewy bodies, and Alzheimer\u27s disease with Lewy body co-pathology -α-synuclein (α-Syn) aggregates in neurons as Lewy bodies and Lewy neurites. By contrast, in multiple system atrophy α-Syn accumulates mainly in oligodendrocytes as glial cytoplasmic inclusions (GCIs) Objective: Our objective was to determine the conformational and biological profiles of a-Syn strains. Methods: The following methods were used to collect and analyze data: Recombinant α-Syn purification and in vitro fibrillization. Preparation of sarkosyl-insoluble fractions from disease and control brains. Sandwich ELISA. Cell cultures. Stereotaxic injection of sarkosyl-insoluble fraction of pathological α-Syn and α-Syn PFFs. Immunohistochemistry. Purification and depletion of α-Syn from the sarkosyl-insoluble fraction by immunoprecipitation. Results: GCI-α-Syn forms structures that are more compact and it is about 1,000-fold more potent than LB-α-Syn in seeding α-Syn aggregation, consistent with the highly aggressive nature of multiple system atrophy. We found that oligodendrocytes but not neurons transform misfolded α-Syn into a GCI-like strain. Moreover, GCI-α-Syn maintains its high seeding activity when propagated in neurons. Thus, α-Syn strains are determined by both misfolded seeds and intracellular environments. Discussion: Here we report that pathological α-Syn in GCIs and Lewy bodies (GCI-α-Syn and LB- α-Syn, respectively) is conformationally and biologically distinct. Furthermore, we showed that distinct α-Syn strains had no cell type preference in seeding a-Syn pathology and are generated by different intracellular milieu

TMEM106B is a genetic modifier of frontotemporal lobar degeneration with C9orf72 hexnucleotide repeat expansion

Hexanucleotide repeat expansions in chromosome 9 open reading frame 72 (C9orf72) have recently been linked to frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), and may be the most common genetic cause of both neurodegenerative diseases. Genetic variants at TMEM106B influence risk for the most common neuropathological subtype of FTLD, characterized by inclusions of TAR DNA binding protein of 43kDa (FTLD-TDP). Previous reports have shown that TMEM106B is a genetic modifier of FTLD-TDP caused by progranulin (GRN) mutations, with the major (risk) allele of rs1990622 associating with earlier age at onset of disease. Here we report that rs1990622 genotype affects age at death in a single-site discovery cohort of FTLD patients with C9orf72 expansions (n=14), with the major allele correlated with later age at death (p=0.024). We replicate this modifier effect in a 30-site international neuropathological cohort of FTLD-TDP patients with C9orf72 expansions (n=75), again finding that the major allele associates with later age at death (p=0.016), as well as later age at onset (p=0.019). In contrast, TMEM106B genotype does not affect age at onset or death in 241 FTLD-TDP cases negative for GRN mutations or C9orf72 expansions. Thus, TMEM106B is a genetic modifier of FTLD with C9orf72 expansions. Intriguingly, the genotype that confers increased risk for developing FTLD-TDP (major, or T, allele of rs1990622) is associated with later age at onset and death in C9orf72 expansion carriers, providing an example of sign epistasis in human neurodegenerative disease

Neurofibrillary tangle-like tau pathology induced by synthetic tau fibrils in primary neurons over-expressing mutant tau

AbstractIncreasing evidence demonstrates the transmissibility of fibrillar species of tau protein, but this has never been directly tested in neurons, the cell type most affected by formation of tau inclusions in neurodegenerative tauopathies. Here we show that synthetic tau fibrils made from recombinant protein not only time-dependently recruit normal tau into neurofibrillary tangle-like insoluble aggregates in primary hippocampal neurons over-expressing human tau, but also induce neuritic tau pathology in non-transgenic neurons. This study provides highly compelling support for the protein-only hypothesis of pathological tau transmission in primary neurons and describes a useful neuronal model for studying the pathogenesis of tauopathies

α-Synuclein Immunotherapy Blocks Uptake and Templated Propagation of Misfolded α-Synuclein and Neurodegeneration

Accumulation of misfolded alpha-synuclein (α-syn) into Lewy bodies (LBs) and Lewy neurites (LNs) is a major hallmark of Parkinson’s disease (PD) and dementia with LBs (DLB). Recent studies showed that synthetic preformed fibrils (pffs) recruit endogenous α-syn and induce LB/LN pathology in vitro and in vivo, thereby implicating propagation and cell-to-cell transmission of pathological α-syn as mechanisms for the progressive spread of LBs/LNs. Here, we demonstrate that α-syn monoclonal antibodies (mAbs) reduce α-syn pff-induced LB/LN formation and rescue synapse/neuron loss in primary neuronal cultures by preventing both pff uptake and subsequent cell-to-cell transmission of pathology. Moreover, intraperitoneal (i.p.) administration of mAb specific for misfolded α-syn into nontransgenic mice injected intrastriatally with α-syn pffs reduces LB/LN pathology, ameliorates substantia nigra dopaminergic neuron loss, and improves motor impairments. We conclude that α-syn antibodies could exert therapeutic effects in PD/DLB by blocking entry of pathological α-syn and/or its propagation in neurons

Neocortical β-amyloid area is associated with dementia and APOE in the oldest-old

Objective: Apolipoprotein E (APOE) ε2 carriers may be protected from dementia because of reduced levels of cortical β-amyloid. In the oldest-old, however, APOE ε2 carriers have high β-amyloid plaque scores and preserved cognition. We compared different measures of β-amyloid pathology across APOE genotypes in the oldest-old, and their relationship with dementia. Methods: The study included 96 participants from The 90+ Study. Using all information, dementia diagnoses were made. Neuropathological examination included staging for amyloid plaques and β-amyloid cortical percent area stained by NAB228 antibody. Results: Both APOE ε2 and APOE ε4 carriers had high Consortium to Establish a Registry for Alzheimer\u27s Disease plaque scores. However, APOE ε2 carriers had low cortical β-amyloid percent areas. β-amyloid percent area was associated with dementia across APOE genotypes. Conclusions: Lower levels of percent area in APOE ε2 carriers may reflect lower total β-amyloid and may contribute to APOE ε2 carriers\u27 decreased risk of dementia, despite high β-amyloid plaque scores. The relationship between β-amyloid plaques and dementia in the oldest-old may vary by APOE genotype. © 2013 The Alzheimer\u27s Association. All rights reserved

Neocortical β-amyloid area is associated with dementia and APOE in the oldest-old

Objective: Apolipoprotein E (APOE) ε2 carriers may be protected from dementia because of reduced levels of cortical β-amyloid. In the oldest-old, however, APOE ε2 carriers have high β-amyloid plaque scores and preserved cognition. We compared different measures of β-amyloid pathology across APOE genotypes in the oldest-old, and their relationship with dementia. Methods: The study included 96 participants from The 90+ Study. Using all information, dementia diagnoses were made. Neuropathological examination included staging for amyloid plaques and β-amyloid cortical percent area stained by NAB228 antibody. Results: Both APOE ε2 and APOE ε4 carriers had high Consortium to Establish a Registry for Alzheimer\u27s Disease plaque scores. However, APOE ε2 carriers had low cortical β-amyloid percent areas. β-amyloid percent area was associated with dementia across APOE genotypes. Conclusions: Lower levels of percent area in APOE ε2 carriers may reflect lower total β-amyloid and may contribute to APOE ε2 carriers\u27 decreased risk of dementia, despite high β-amyloid plaque scores. The relationship between β-amyloid plaques and dementia in the oldest-old may vary by APOE genotype. © 2013 The Alzheimer\u27s Association. All rights reserved

Data-driven neuropathological staging and subtyping of TDP-43 proteinopathies

TAR DNA-binding protein-43 (TDP-43) accumulation is the primary pathology underlying several neurodegenerative diseases. Charting the progression and heterogeneity of TDP-43 accumulation is necessary to better characterize TDP-43 proteinopathies, but current TDP-43 staging systems are heuristic and assume each syndrome is homogeneous. Here, we use data-driven disease progression modelling to derive a fine-grained empirical staging system for the classification and differentiation of frontotemporal lobar degeneration due to TDP-43 (FTLD-TDP, n = 126), amyotrophic lateral sclerosis (ALS, n = 141) and limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) with and without Alzheimer’s disease (n = 304). The data-driven staging of ALS and FTLD-TDP complement and extend previously described human-defined staging schema for ALS and behavioural variant frontotemporal dementia. In LATE-NC individuals, progression along data-driven stages was positively associated with age, but negatively associated with age in individuals with FTLD-TDP. Using only regional TDP-43 severity, our data driven model distinguished individuals diagnosed with ALS, FTLD-TDP or LATE-NC with a cross-validated accuracy of 85.9%, with misclassifications associated with mixed pathological diagnosis, age and genetic mutations. Adding age and SuStaIn stage to this model increased accuracy to 92.3%. Our model differentiates LATE-NC from FTLD-TDP, though some overlap was observed between late-stage LATE-NC and early-stage FTLD-TDP. We further tested for the presence of subtypes with distinct regional TDP-43 progression patterns within each diagnostic group, identifying two distinct cortical-predominant and brainstem-predominant subtypes within FTLD-TDP and a further two subcortical-predominant and corticolimbic-predominant subtypes within ALS. The FTLD-TDP subtypes exhibited differing proportions of TDP-43 type, while there was a trend for age differing between ALS subtypes. Interestingly, a negative relationship between age and SuStaIn stage was seen in the brainstem/subcortical-predominant subtype of each proteinopathy. No subtypes were observed for the LATE-NC group, despite aggregating individuals with and without Alzheimer’s disease and a larger sample size for this group. Overall, we provide an empirical pathological TDP-43 staging system for ALS, FTLD-TDP and LATE-NC, which yielded accurate classification. We further demonstrate that there is substantial heterogeneity amongst ALS and FTLD-TDP progression patterns that warrants further investigation in larger cross-cohort studies

Distribution patterns of tau pathology in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a 4R-tauopathy predominated by subcortical pathology in neurons, astrocytes, and oligodendroglia associated with various clinical phenotypes. In the present international study, we addressed the question of whether or not sequential distribution patterns can be recognized for PSP pathology. We evaluated heat maps and distribution patterns of neuronal, astroglial, and oligodendroglial tau pathologies and their combinations in different clinical subtypes of PSP in postmortem brains. We used conditional probability and logistic regression to model the sequential distribution of tau pathologies across different brain regions. Tau pathology uniformly predominates in the neurons of the pallido-nigro-luysian axis in different clinical subtypes. However, clinical subtypes are distinguished not only by total tau load but rather cell-type (neuronal versus glial) specific vulnerability patterns of brain regions suggesting distinct dynamics or circuit-specific segregation of propagation of tau pathologies. For Richardson syndrome (n = 81) we recognize six sequential steps of involvement of brain regions by the combination of cellular tau pathologies. This is translated to six stages for the practical neuropathological diagnosis by the evaluation of the subthalamic nucleus, globus pallidus, striatum, cerebellum with dentate nucleus, and frontal and occipital cortices. This system can be applied to further clinical subtypes by emphasizing whether they show caudal (cerebellum/dentate nucleus) or rostral (cortical) predominant, or both types of pattern. Defining cell-specific stages of tau pathology helps to identify preclinical or early-stage cases for the better understanding of early pathogenic events, has implications for understanding the clinical subtype-specific dynamics of disease-propagation, and informs tau-neuroimaging on distribution patterns