A fluid biomarker reveals loss of TDP-43 splicing repression in presymptomatic ALS-FTD.

Although loss of TAR DNA-binding protein 43 kDa (TDP-43) splicing repression is well documented in postmortem tissues of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), whether this abnormality occurs during early-stage disease remains unresolved. Cryptic exon inclusion reflects loss of function of TDP-43, and thus detection of proteins containing cryptic exon-encoded neoepitopes in cerebrospinal fluid (CSF) or blood could reveal the earliest stages of TDP-43 dysregulation in patients. Here we use a newly characterized monoclonal antibody specific to a TDP-43-dependent cryptic epitope (encoded by the cryptic exon found in HDGFL2) to show that loss of TDP-43 splicing repression occurs in ALS-FTD, including in presymptomatic C9orf72 mutation carriers. Cryptic hepatoma-derived growth factor-like protein 2 (HDGFL2) accumulates in CSF at significantly higher levels in familial ALS-FTD and sporadic ALS compared with controls and is elevated earlier than neurofilament light and phosphorylated neurofilament heavy chain protein levels in familial disease. Cryptic HDGFL2 can also be detected in blood of individuals with ALS-FTD, including in presymptomatic C9orf72 mutation carriers, and accumulates at levels highly correlated with those in CSF. Our findings indicate that loss of TDP-43 cryptic splicing repression occurs early in disease progression, even presymptomatically, and that detection of the HDGFL2 cryptic neoepitope serves as a potential diagnostic biomarker for ALS, which should facilitate patient recruitment and measurement of target engagement in clinical trials.

Loss of TDP-43 splicing repression occurs early in the aging population and is associated with Alzheimer's disease neuropathologic changes and cognitive decline.

LATE-NC, the neuropathologic changes of limbic-predominant age-related TAR DNA-binding protein 43 kDa (TDP-43) encephalopathy are frequently associated with Alzheimer's disease (AD) and cognitive impairment in older adults. The association of TDP-43 proteinopathy with AD neuropathologic changes (ADNC) and its impact on specific cognitive domains are not fully understood and whether loss of TDP-43 function occurs early in the aging brain remains unknown. Here, using a large set of autopsies from the Baltimore Longitudinal Study of Aging (BLSA) and another younger cohort, we were able to study brains from subjects 21-109 years of age. Examination of these brains show that loss of TDP-43 splicing repression, as judged by TDP-43 nuclear clearance and expression of a cryptic exon in HDGFL2, first occurs during the 6th decade, preceding by a decade the appearance of TDP-43+ neuronal cytoplasmic inclusions (NCIs). We corroborated this observation using a monoclonal antibody to demonstrate a cryptic exon-encoded neoepitope within HDGFL2 in neurons exhibiting nuclear clearance of TDP-43. TDP-43 nuclear clearance is associated with increased burden of tau pathology. Age at death, female sex, high CERAD neuritic plaque score, and high Braak neurofibrillary stage significantly increase the odds of LATE-NC. Faster rates of cognitive decline on verbal memory (California Verbal Learning Test immediate recall), visuospatial ability (Card Rotations Test), mental status (MMSE) and semantic fluency (Category Fluency Test) were associated with LATE-NC. Notably, the effects of LATE-NC on verbal memory and visuospatial ability are independent of ADNC. However, the effects of TDP-43 nuclear clearance in absence of NCI on the longitudinal trajectories and levels of cognitive measures are not significant. These results establish that loss of TDP-43 splicing repression is an early event occurring in the aging population during the development of TDP-43 proteinopathy and is associated with increased tau pathology. Furthermore, LATE-NC correlates with high levels of ADNC but also has an impact on specific memory and visuospatial functions in aging that is independent of AD.

LATE-NC staging in routine neuropathologic diagnosis: an update.

An international consensus report in 2019 recommended a classification system for limbic-predominant age-related TDP-43 encephalopathy neuropathologic changes (LATE-NC). The suggested neuropathologic staging system and nomenclature have proven useful for autopsy practice and dementia research. However, some issues remain unresolved, such as cases with unusual features that do not fit with current diagnostic categories. The goal of this report is to update the neuropathologic criteria for the diagnosis and staging of LATE-NC, based primarily on published data. We provide practical suggestions about how to integrate available genetic information and comorbid pathologies [e.g., Alzheimer's disease neuropathologic changes (ADNC) and Lewy body disease]. We also describe recent research findings that have enabled more precise guidance on how to differentiate LATE-NC from other subtypes of TDP-43 pathology [e.g., frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS)], and how to render diagnoses in unusual situations in which TDP-43 pathology does not follow the staging scheme proposed in 2019. Specific recommendations are also made on when not to apply this diagnostic term based on current knowledge. Neuroanatomical regions of interest in LATE-NC are described in detail and the implications for TDP-43 immunohistochemical results are specified more precisely. We also highlight questions that remain unresolved and areas needing additional study. In summary, the current work lays out a number of recommendations to improve the precision of LATE-NC staging based on published reports and diagnostic experience.

Ketamine Mitigates Neurobehavioral Deficits in a Canine Model of Hypothermic Circulatory Arrest.

Hypothermic circulatory arrest is a protective technique used when complete cessation of circulation is required during cardiac surgery. Prior efforts to decrease neurologic injury with the NMDA receptor antagonist MK801 were limited by unacceptable side effects. We hypothesized that ketamine would provide neuroprotection without dose-limiting side effects. Canines were peripherally cannulated for cardiopulmonary bypass, cooled to 18°C, and underwent 90 minutes of circulatory arrest. Ketamine-treated canines (n = 5; total dose 2.85 mg/kg) were compared to untreated controls (n = 10). A validated neurobehavioral deficit score was obtained at 24, 48, and 72 hours (0 = no deficits/normal exam; higher score represents increasing deficits). Biomarkers of neuronal injury in the cerebrospinal fluid were examined at baseline and at 8, 24, 48, and 72 hours. Brain histopathologic injury was scored at 72 hours (higher score indicates more necrosis and apoptosis). Ketamine-treated canines had significantly improved, lower neurobehavioral deficit scores compared to controls (overall P = 0.003; 24 hours: median 72 vs 112, P = 0.030; 48 hours: 47 vs 90, P = 0.021; 72 hours: 30 vs 89, P = 0.069). Although the histopathologic injury scores of ketamine-treated canines (median 12) were lower than controls (16), there was no statistical difference (P = 0.10). Levels of phosphorylated neurofilament-H and neuron specific enolase, markers of neuronal injury, were significantly lower in ketamine-treated animals (P = 0.010 and = 0.039, respectively). Ketamine significantly reduced neurologic deficits and biomarkers of injury in canines after hypothermic circulatory arrest. Ketamine represents a safe and approved medication that may be useful as a pharmacologic neuroprotectant during cardiac surgery with circulatory arrest.

Radiologic-pathologic autopsy correlation of an internal watershed infarct, a case report

ABSTRACT Internal watershed infarcts (IWIs) occur at the junction of the deep and superficial perforating arterial branches of the cerebrum. Despite documentation in the radiology literature, IWIs are rarely encountered at the time of autopsy. Here, we report the case of a 59-year-old incarcerated male who was brought to the emergency department after being found unresponsive on the floor of his jail cell. Initial examination and imaging demonstrated right-sided hemiplegia, aphasia, right facial droop, and severe stenosis of the left middle cerebral artery, respectively. Repeat imaging 4 days after admission and 26 days before death demonstrated advanced stenosis of the intracranial, communicating segment of the right internal carotid artery, a large acute infarct in the right posterior cerebral artery territory, and bilateral deep white matter ischemic changes with a right-sided "rosary-like" pattern of injury that is typical of IWIs. Postmortem gross examination showed that the right deep white matter lesion had progressed to a confluent, "cigar-shaped" subacute IWI involving the right corona radiata. This is the first well-documented case of an IWI with radiologic imaging and photographic gross pathology correlation. This case uniquely highlights a rarely encountered lesion at the time of autopsy and provides an excellent visual representation of internal watershed neuroanatomy.

Deubiquitinase CYLD acts as a negative regulator of dopamine neuron survival in Parkinson's disease.

Mutations in PINK1 and parkin highlight the mitochondrial axis of Parkinson's disease (PD) pathogenesis. PINK1/parkin regulation of the transcriptional repressor PARIS bears direct relevance to dopamine neuron survival through augmentation of PGC-1α-dependent mitochondrial biogenesis. Notably, knockout of PARIS attenuates dopaminergic neurodegeneration in mouse models, indicating that interventions that prevent dopaminergic accumulation of PARIS could have therapeutic potential in PD. To this end, we have identified the deubiquitinase cylindromatosis (CYLD) to be a regulator of PARIS protein stability and proteasomal degradation via the PINK1/parkin pathway. Knockdown of CYLD in multiple models of PINK1 or parkin inactivation attenuates PARIS accumulation by modulating its ubiquitination levels and relieving its repressive effect on PGC-1α to promote mitochondrial biogenesis. Together, our studies identify CYLD as a negative regulator of dopamine neuron survival, and inhibition of CYLD may potentially be beneficial in PD by lowering PARIS levels and promoting mitochondrial biogenesis.

Interleukin-6 triggers toxic neuronal iron sequestration in response to pathological α-synuclein.

α-synuclein (α-syn) aggregation and accumulation drive neurodegeneration in Parkinson's disease (PD). The substantia nigra of patients with PD contains excess iron, yet the underlying mechanism accounting for this iron accumulation is unclear. Here, we show that misfolded α-syn activates microglia, which release interleukin 6 (IL-6). IL-6, via its trans-signaling pathway, induces changes in the neuronal iron transcriptome that promote ferrous iron uptake and decrease cellular iron export via a pathway we term the cellular iron sequestration response, or CISR. The brains of patients with PD exhibit molecular signatures of the IL-6-mediated CISR. Genetic deletion of IL-6, or treatment with the iron chelator deferiprone, reduces pathological α-syn toxicity in a mouse model of sporadic PD. These data suggest that IL-6-induced CISR leads to toxic neuronal iron accumulation, contributing to synuclein-induced neurodegeneration.

Genome-wide association study and functional validation implicates JADE1 in tauopathy.

Primary age-related tauopathy (PART) is a neurodegenerative pathology with features distinct from but also overlapping with Alzheimer disease (AD). While both exhibit Alzheimer-type temporal lobe neurofibrillary degeneration alongside amnestic cognitive impairment, PART develops independently of amyloid-ß (Aß) plaques. The pathogenesis of PART is not known, but evidence suggests an association with genes that promote tau pathology and others that protect from Aß toxicity. Here, we performed a genetic association study in an autopsy cohort of individuals with PART (n = 647) using Braak neurofibrillary tangle stage as a quantitative trait. We found some significant associations with candidate loci associated with AD (SLC24A4, MS4A6A, HS3ST1) and progressive supranuclear palsy (MAPT and EIF2AK3). Genome-wide association analysis revealed a novel significant association with a single nucleotide polymorphism on chromosome 4 (rs56405341) in a locus containing three genes, including JADE1 which was significantly upregulated in tangle-bearing neurons by single-soma RNA-seq. Immunohistochemical studies using antisera targeting JADE1 protein revealed localization within tau aggregates in autopsy brains with four microtubule-binding domain repeats (4R) isoforms and mixed 3R/4R, but not with 3R exclusively. Co-immunoprecipitation in post-mortem human PART brain tissue revealed a specific binding of JADE1 protein to four repeat tau lacking N-terminal inserts (0N4R). Finally, knockdown of the Drosophila JADE1 homolog rhinoceros (rno) enhanced tau-induced toxicity and apoptosis in vivo in a humanized 0N4R mutant tau knock-in model, as quantified by rough eye phenotype and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) in the fly brain. Together, these findings indicate that PART has a genetic architecture that partially overlaps with AD and other tauopathies and suggests a novel role for JADE1 as a modifier of neurofibrillary degeneration.

Amyloid-beta is present in human lymph nodes and greatly enriched in those of the cervical region.

Degradation and clearance of amyloid beta (Aß) peptide are likely critical for brain health. Animal studies have demonstrated the role of the glial-lymphatic (glymphatic) system in the clearance of Aß and other brain metabolites, but no such information has been available in humans. Here we ask whether this system contributes to the clearance of Aß from the human brain. In the absence of an applicable imaging method, we examined cervical and inguinal lymph nodes resected for cancer therapy or staging using immunohistochemistry. Aß-labeled cells were present in lymph nodes, and cervical lymph nodes showed labeled cells in far greater abundance than did inguinal nodes. This observation supports the hypothesis that the glymphatic system contributes to the clearance of Aß from the human brain.

Persistently Elevated mTOR Complex 1-S6 Kinase 1 Disrupts DARPP-32-Dependent D1 Dopamine Receptor Signaling and Behaviors.

BACKGROUND: The serine-threonine kinase mTORC1 (mechanistic target of rapamycin complex 1) is essential for normal cell function but is aberrantly activated in the brain in both genetic-developmental and sporadic diseases and is associated with a spectrum of neuropsychiatric symptoms. The underlying molecular mechanisms of cognitive and neuropsychiatric symptoms remain controversial. METHODS: The present study examines behaviors in transgenic models that express Rheb, the most proximal known activator of mTORC1, and profiles striatal phosphoproteomics in a model with persistently elevated mTORC1 signaling. Biochemistry, immunohistochemistry, electrophysiology, and behavior approaches are used to examine the impact of persistently elevated mTORC1 on D1 dopamine receptor (D1R) signaling. The effect of persistently elevated mTORC1 was confirmed using D1-Cre to elevate mTORC1 activity in D1R neurons. RESULTS: We report that persistently elevated mTORC1 signaling blocks canonical D1R signaling that is dependent on DARPP-32 (dopamine- and cAMP-regulated neuronal phosphoprotein). The immediate downstream effector of mTORC1, ribosomal S6 kinase 1 (S6K1), phosphorylates and activates DARPP-32. Persistent elevation of mTORC1-S6K1 occludes dynamic D1R signaling downstream of DARPP-32 and blocks multiple D1R responses, including dynamic gene expression, D1R-dependent corticostriatal plasticity, and D1R behavioral responses including sociability. Candidate biomarkers of mTORC1-DARPP-32 occlusion are increased in the brain of human disease subjects in association with elevated mTORC1-S6K1, supporting a role for this mechanism in cognitive disease. CONCLUSIONS: The mTORC1-S6K1 intersection with D1R signaling provides a molecular framework to understand the effects of pathological mTORC1 activation on behavioral symptoms in neuropsychiatric disease.

α-Synucleinopathy associated c-Abl activation causes p53-dependent autophagy impairment.

BACKGROUND: Studies link c-Abl activation with the accumulation of pathogenic α-synuclein (αS) and neurodegeneration in Parkinson's disease (PD). Currently, c-Abl, a tyrosine kinase activated by cellular stress, is thought to promote αS pathology by either directly phosphorylating αS or by causing autophagy deficits. METHODS: αS overexpressing transgenic (Tg) mice were used in this study. A53T Tg mice that express high levels of human mutant A53TαS under the control of prion protein promoter. Two different approaches were used in this study. Natural aging and seeding model of synucleinopathy. In seeding model, intracortical/intrastriatal (IC/IS) stereotaxic injection of toxic lysates was done using tissue lysates from end-stage symptomatic mice. In this study, nilotinib and pifithrin-α was used as a c-Abl and p53 inhibitor, respectively. Both Tg and non-transgenic (nTg) mice from each group were subjected to nilotinib (10 mg/kg) or vehicle (DMSO) treatment. Frozen brain tissues from PD and control human cases were analyzed. In vitro cells study was implied for c-Abl/p53 genetic manipulation to uncover signal transduction. RESULTS: Herein, we show that the pathologic effects of c-Abl in PD also involve activation of p53, as c-Abl activation in a transgenic mouse model of α-synucleinopathy (TgA53T) and human PD cases are associated with the increased p53 activation. Significantly, active p53 in TgA53T neurons accumulates in the cytosol, which may lead to inhibition of autophagy. Thus, we hypothesized that c-Abl-dependent p53 activation contributes to autophagy impairment in α-synucleinopathy. In support of the hypothesis, we show that c-Abl activation is sufficient to inhibit autophagy in p53-dependent manner. Moreover, inhibition of either c-Abl, using nilotinib, or p53, using pifithrin-α, was sufficient to increase autophagic flux in neuronal cells by inducing phosphorylation of AMP-activated kinase (AMPK), ULK1 activation, and down-regulation of mTORC1 signaling. Finally, we show that pharmacological attenuation of c-Abl activity by nilotinib treatment in the TgA53T mouse model reduces activation of p53, stimulates autophagy, decreases accumulation αS pathology, and delays disease onset. CONCLUSION: Collectively, our data show that c-Abl activation by α-synucleinopathy causes p53 dependent autophagy deficits and both c-Abl and p53 represent therapeutic target for PD.

Nemo-like kinase reduces mutant huntingtin levels and mitigates Huntington's disease.

Nemo-like kinase (NLK), an evolutionarily conserved serine/threonine kinase, is highly expressed in the brain, but its function in the adult brain remains not well understood. In this study, we identify NLK as an interactor of huntingtin protein (HTT). We report that NLK levels are significantly decreased in HD human brain and HD models. Importantly, overexpression of NLK in the striatum attenuates brain atrophy, preserves striatal DARPP32 levels and reduces mutant HTT (mHTT) aggregation in HD mice. In contrast, genetic reduction of NLK exacerbates brain atrophy and loss of DARPP32 in HD mice. Moreover, we demonstrate that NLK lowers mHTT levels in a kinase activity-dependent manner, while having no significant effect on normal HTT protein levels in mouse striatal cells, human cells and HD mouse models. The NLK-mediated lowering of mHTT is associated with enhanced phosphorylation of mHTT. Phosphorylation defective mutation of serine at amino acid 120 (S120) abolishes the mHTT-lowering effect of NLK, suggesting that S120 phosphorylation is an important step in the NLK-mediated lowering of mHTT. A further mechanistic study suggests that NLK promotes mHTT ubiquitination and degradation via the proteasome pathway. Taken together, our results indicate a protective role of NLK in HD and reveal a new molecular target to reduce mHTT levels.

Dysregulation of multiple metabolic networks related to brain transmethylation and polyamine pathways in Alzheimer disease: A targeted metabolomic and transcriptomic study.

BACKGROUND: There is growing evidence that Alzheimer disease (AD) is a pervasive metabolic disorder with dysregulation in multiple biochemical pathways underlying its pathogenesis. Understanding how perturbations in metabolism are related to AD is critical to identifying novel targets for disease-modifying therapies. In this study, we test whether AD pathogenesis is associated with dysregulation in brain transmethylation and polyamine pathways. METHODS AND FINDINGS: We first performed targeted and quantitative metabolomics assays using capillary electrophoresis-mass spectrometry (CE-MS) on brain samples from three groups in the Baltimore Longitudinal Study of Aging (BLSA) (AD: n = 17; Asymptomatic AD [ASY]: n = 13; Control [CN]: n = 13) (overall 37.2% female; mean age at death 86.118 ± 9.842 years) in regions both vulnerable and resistant to AD pathology. Using linear mixed-effects models within two primary brain regions (inferior temporal gyrus [ITG] and middle frontal gyrus [MFG]), we tested associations between brain tissue concentrations of 26 metabolites and the following primary outcomes: group differences, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) (neuritic plaque burden), and Braak (neurofibrillary pathology) scores. We found significant alterations in concentrations of metabolites in AD relative to CN samples, as well as associations with severity of both CERAD and Braak, mainly in the ITG. These metabolites represented biochemical reactions in the (1) methionine cycle (choline: lower in AD, p = 0.003; S-adenosyl methionine: higher in AD, p = 0.005); (2) transsulfuration and glutathione synthesis (cysteine: higher in AD, p < 0.001; reduced glutathione [GSH]: higher in AD, p < 0.001); (3) polyamine synthesis/catabolism (spermidine: higher in AD, p = 0.004); (4) urea cycle (N-acetyl glutamate: lower in AD, p < 0.001); (5) glutamate-aspartate metabolism (N-acetyl aspartate: lower in AD, p = 0.002); and (6) neurotransmitter metabolism (gamma-amino-butyric acid: lower in AD, p < 0.001). Utilizing three Gene Expression Omnibus (GEO) datasets, we then examined mRNA expression levels of 71 genes encoding enzymes regulating key reactions within these pathways in the entorhinal cortex (ERC; AD: n = 25; CN: n = 52) and hippocampus (AD: n = 29; CN: n = 56). Complementing our metabolomics results, our transcriptomics analyses also revealed significant alterations in gene expression levels of key enzymatic regulators of biochemical reactions linked to transmethylation and polyamine metabolism. Our study has limitations: our metabolomics assays measured only a small proportion of all metabolites participating in the pathways we examined. Our study is also cross-sectional, limiting our ability to directly test how AD progression may impact changes in metabolite concentrations or differential-gene expression. Additionally, the relatively small number of brain tissue samples may have limited our power to detect alterations in all pathway-specific metabolites and their genetic regulators. CONCLUSIONS: In this study, we observed broad dysregulation of transmethylation and polyamine synthesis/catabolism, including abnormalities in neurotransmitter signaling, urea cycle, aspartate-glutamate metabolism, and glutathione synthesis. Our results implicate alterations in cellular methylation potential and increased flux in the transmethylation pathways, increased demand on antioxidant defense mechanisms, perturbations in intermediate metabolism in the urea cycle and aspartate-glutamate pathways disrupting mitochondrial bioenergetics, increased polyamine biosynthesis and breakdown, as well as abnormalities in neurotransmitter metabolism that are related to AD.

A comprehensive screening of copy number variability in dementia with Lewy bodies.

The role of genetic variability in dementia with Lewy bodies (DLB) is now indisputable; however, data regarding copy number variation (CNV) in this disease has been lacking. Here, we used whole-genome genotyping of 1454 DLB cases and 1525 controls to assess copy number variability. We used 2 algorithms to confidently detect CNVs, performed a case-control association analysis, screened for candidate CNVs previously associated with DLB-related diseases, and performed a candidate gene approach to fully explore the data. We identified 5 CNV regions with a significant genome-wide association to DLB; 2 of these were only present in cases and absent from publicly available databases: one of the regions overlapped LAPTM4B, a known lysosomal protein, whereas the other overlapped the NME1 locus and SPAG9. We also identified DLB cases presenting rare CNVs in genes previously associated with DLB or related neurodegenerative diseases, such as SNCA, APP, and MAPT. To our knowledge, this is the first study reporting genome-wide CNVs in a large DLB cohort. These results provide preliminary evidence for the contribution of CNVs in DLB risk.

Poly(ADP-ribose) drives pathologic α-synuclein neurodegeneration in Parkinson's disease.

The pathologic accumulation and aggregation of α-synuclein (α-syn) underlies Parkinson's disease (PD). The molecular mechanisms by which pathologic α-syn causes neurodegeneration in PD are not known. Here, we found that pathologic α-syn activates poly(adenosine 5'-diphosphate-ribose) (PAR) polymerase-1 (PARP-1), and PAR generation accelerates the formation of pathologic α-syn, resulting in cell death via parthanatos. PARP inhibitors or genetic deletion of PARP-1 prevented pathologic α-syn toxicity. In a feed-forward loop, PAR converted pathologic α-syn to a more toxic strain. PAR levels were increased in the cerebrospinal fluid and brains of patients with PD, suggesting that PARP activation plays a role in PD pathogenesis. Thus, strategies aimed at inhibiting PARP-1 activation could hold promise as a disease-modifying therapy to prevent the loss of dopamine neurons in PD.

Discrete Pools of Oligomeric Amyloid-ß Track with Spatial Learning Deficits in a Mouse Model of Alzheimer Amyloidosis.

Despite increasing appreciation that oligomeric amyloid-ß (Aß) may contribute to cognitive decline of Alzheimer disease, defining the most critical forms has been thwarted by the changeable nature of these aggregates and the varying methods used for detection. Herein, using a broad approach, we quantified Aß oligomers during the evolution of cognitive deficits in an aggressive model of Aß amyloidosis. Amyloid precursor protein/tetracycline transactivator mice underwent behavioral testing at 3, 6, 9, and 12 months of age to evaluate spatial learning and memory, followed by histologic assessment of amyloid burden and biochemical characterization of oligomeric Aß species. Transgenic mice displayed progressive impairments in acquisition and immediate recall of the trained platform location. Biochemical analysis of cortical extracts from behaviorally tested mice revealed distinct age-dependent patterns of accumulation in multiple oligomeric species. Dot blot analysis demonstrated that nonfibrillar Aß oligomers were highly soluble and extracted into a fraction enriched for extracellular proteins, whereas prefibrillar species required high-detergent conditions to retrieve, consistent with membrane localization. Low-detergent extracts tested by 82E1 enzyme-linked immunosorbent assay confirmed the presence of bona fide Aß oligomers, whereas immunoprecipitation-Western blotting using high-detergent extracts revealed a variety of SDS-stable low-n species. These findings show that different Aß oligomers vary in solubility, consistent with distinct localization, and identify nonfibrillar Aß oligomer-positive aggregates as tracking most closely with cognitive decline in this model.

NPTX2 and cognitive dysfunction in Alzheimer's Disease.

Memory loss in Alzheimer's disease (AD) is attributed to pervasive weakening and loss of synapses. Here, we present findings supporting a special role for excitatory synapses connecting pyramidal neurons of the hippocampus and cortex with fast-spiking parvalbumin (PV) interneurons that control network excitability and rhythmicity. Excitatory synapses on PV interneurons are dependent on the AMPA receptor subunit GluA4, which is regulated by presynaptic expression of the synaptogenic immediate early gene NPTX2 by pyramidal neurons. In a mouse model of AD amyloidosis, Nptx2-/- results in reduced GluA4 expression, disrupted rhythmicity, and increased pyramidal neuron excitability. Postmortem human AD cortex shows profound reductions of NPTX2 and coordinate reductions of GluA4. NPTX2 in human CSF is reduced in subjects with AD and shows robust correlations with cognitive performance and hippocampal volume. These findings implicate failure of adaptive control of pyramidal neuron-PV circuits as a pathophysiological mechanism contributing to cognitive failure in AD.

Estrogen receptor activation contributes to RNF146 expression and neuroprotection in Parkinson's disease models.

RNF146 is an E3 ubiquitin ligase that specifically recognizes and polyubiquitinates poly (ADP-ribose) (PAR)-conjugated substrates for proteasomal degradation. RNF146 has been shown to be neuroprotective against PAR polymerase-1 (PARP1)-induced cell death during stroke. Here we report that RNF146 expression and RNF146 inducers can prevent cell death elicited by Parkinson's disease (PD)-associated and PARP1-activating stimuli. In SH-SY5Y cells, RNF146 expression conferred resistance to toxic stimuli that lead to PARP1 activation. High-throughput screen using a luciferase construct harboring the RNF146 promoter identified liquiritigenin as an RNF146 inducer. We found that RNF146 expression by liquiritigenin was mediated by estrogen receptor activation and contributed to cytoprotective effect of liquiritigenin. Finally, RNF146 expression by liquiritigenin in mouse brains provided dopaminergic neuroprotection in a 6-hydroxydopamine PD mouse model. Given the presence of PARP1 activity and RNF146 deficits in PD, it could be a potential therapeutic strategy to restore RNF146 expression by natural compounds or estrogen receptor activation.

Reduction of Nuak1 Decreases Tau and Reverses Phenotypes in a Tauopathy Mouse Model.

Many neurodegenerative proteinopathies share a common pathogenic mechanism: the abnormal accumulation of disease-related proteins. As growing evidence indicates that reducing the steady-state levels of disease-causing proteins mitigates neurodegeneration in animal models, we developed a strategy to screen for genes that decrease the levels of tau, whose accumulation contributes to the pathology of both Alzheimer disease (AD) and progressive supranuclear palsy (PSP). Integrating parallel cell-based and Drosophila genetic screens, we discovered that tau levels are regulated by Nuak1, an AMPK-related kinase. Nuak1 stabilizes tau by phosphorylation specifically at Ser356. Inhibition of Nuak1 in fruit flies suppressed neurodegeneration in tau-expressing Drosophila, and Nuak1 haploinsufficiency rescued the phenotypes of a tauopathy mouse model. These results demonstrate that decreasing total tau levels is a valid strategy for mitigating tau-related neurodegeneration and reveal Nuak1 to be a novel therapeutic entry point for tauopathies.