Search

Most of the mutations in the presenilin-1 gene (PS-1) are associated with familial Alzheimer's disease (AD). However, certain examples can be associated with frontotemporal dementia (FTD). We performed a clinical evaluation of individuals belonging to a family with the FTD phenotype, and additional molecular studies and neuropathological assessment of the proband. The PS-1 M146V mutation was found in the 50-year-old subject (the proband) with family history of early-onset FTD. Neuropathological examination showed abundant amyloid plaques, widespread neurofibrillary pathology, Pick bodies in the hippocampus and cortex, cortical globose tangles and ubiquitin-positive nuclear inclusions in white matter oligodendrocytes. We report a kindred with clinical features of FTD, whose proband bore the PS-1 M146V mutation and showed diffuse Alzheimer's type pathology and Pick bodies on post-mortem neuropathological examination. As with other mutations within the same codon, this substitution may predispose to both diseases by affecting APP and/or tau processing.

Summary Multiple loss‐of‐function mutations in TRIAD3 (a.k.a. RNF216) have recently been identified in patients suffering from Gordon Holmes syndrome (GHS), characterized by cognitive decline, dementia, and movement disorders. TRIAD3A is an E3 ubiquitin ligase that recognizes and facilitates the ubiquitination of its target for degradation by the ubiquitin‐proteasome system (UPS). Here, we demonstrate that two of these missense substitutions in TRIAD3 (R660C and R694C) could not regulate the degradation of their neuronal target, activity‐regulated cytoskeletal‐associated protein (Arc/Arg 3.1), whose expression is critical for synaptic plasticity and memory. The synaptic deficits due to the loss of endogenous TRIAD3A could not be rescued by TRIAD3A harboring GHS‐associated missense mutations. Moreover, we demonstrate that the loss of endogenous TRIAD3A in the mouse hippocampal CA1 region led to deficits in spatial learning and memory. Finally, we show that these missense mutations abolished the interaction of TRIAD3A with Arc, disrupting Arc ubiquitination, and consequently Arc degradation. Our current findings of Arc misregulation by TRIAD3A variants suggest that loss‐of‐function mutations in TRIAD3A may contribute to dementia observed in patients with GHS driven by dysfunctional UPS components, leading to cognitive impairments through the synaptic protein Arc.

Visual Abstract, Parkinson’s disease (PD) is a chronic progressive neurodegenerative disorder. Recent studies have implicated a role for peroxisome proliferator-activated receptor γ coactivator protein-1α (PGC-1α) in PD and in animal or cellular models of PD. The role of PGC-1α in the function and survival of substantia nigra pars compacta (SNpc) dopamine neurons is not clear. Here we find that there are four different PGC-1α isoforms expressed in SH-SY5Y cells, and these four isoforms are expressed across subregions of mouse brain. Adult conditional PGC-1α knock-out mice show a significant loss of dopaminergic neurons that is accompanied by a reduction of dopamine in the striatum. In human PD postmortem tissue from the SNpc, there is a reduction of PGC-1α isoforms and mitochondria markers. Our findings suggest that all four isoforms of PGC-1α are required for the proper expression of mitochondrial proteins in SNpc DA neurons and that PGC-1α is essential for SNpc DA neuronal survival, possibly through the maintenance of mitochondrial function.

The pathogenesis of HD and HDL2, similar progressive neurodegenerative disorders caused by expansion mutations, remains incompletely understood. No systematic quantitative proteomics studies, assessing global changes in HD or HDL2 human brain, were reported. To address this deficit, we used a stable isotope labeling-based approach to quantify the changes in protein abundances in the cortex of 12 HD and 12 control cases and, separately, of 6 HDL2 and 6 control cases. The quality of the tissues was assessed to minimize variability due to post mortem autolysis. We applied a robust median sweep algorithm to quantify protein abundance and performed statistical inference using moderated test statistics. 1211 proteins showed statistically significant fold changes between HD and control tissues; the differences in selected proteins were verified by Western blotting. Differentially abundant proteins were enriched in cellular pathways previously implicated in HD, including Rho-mediated, actin cytoskeleton and integrin signaling, mitochondrial dysfunction, endocytosis, axonal guidance, DNA/RNA processing, and protein transport. The abundance of 717 proteins significantly differed between control and HDL2 brain. Comparative analysis of the disease-associated changes in the HD and HDL2 proteomes revealed that similar pathways were altered, suggesting the commonality of pathogenesis between the two disorders.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a CAG expansion in the gene-encoding Huntingtin (HTT). Transcriptome dysregulation is a major feature of HD pathogenesis, as revealed by a large body of work on gene expression profiling of tissues from human HD patients and mouse models. These studies were primarily focused on transcriptional changes affecting steady-state overall gene expression levels using microarray based approaches. A major missing component, however, has been the study of transcriptome changes at the post-transcriptional level, such as alternative splicing. Alternative splicing is a critical mechanism for expanding regulatory and functional diversity from a limited number of genes, and is particularly complex in the mammalian brain. Here we carried out a deep RNA-seq analysis of the BA4 (Brodmann area 4) motor cortex from seven human HD brains and seven controls to systematically discover aberrant alternative splicing events and characterize potential associated splicing factors in HD. We identified 593 differential alternative splicing events between HD and control brains. Using two expanded panels with a total of 108 BA4 tissues from patients and controls, we identified four splicing factors exhibiting significantly altered expression levels in HD patient brains. Moreover, follow-up molecular analyses of one splicing factor PTBP1 revealed its impact on disease-associated splicing patterns in HD. Collectively, our data provide genomic evidence for widespread splicing dysregulation in HD brains, and suggest the role of aberrant alternative splicing in the pathogenesis of HD.

Preclinical changes that precede the onset of symptoms and eventual diagnosis of Alzheimer’s disease (AD) are a target for potential preventive interventions. A large body of evidence suggests that inflammation is closely associated with AD pathogenesis and may be a promising target pathway for such interventions. However, little is known about the association between systemic inflammation and preclinical AD pathophysiology. We first examined whether the acute-phase protein, alpha-2 macroglobulin (A2M), a major component of the innate immune system, was associated with cerebrospinal fluid (CSF) markers of neuronal injury in preclinical AD and risk of incident AD in the predictors of cognitive decline among normal individuals (BIOCARD) cohort. We find that A2M concentration in blood is significantly associated with CSF concentrations of the neuronal injury markers, tau and phosphorylated tau, and that higher baseline serum A2M concentration is associated with an almost threefold greater risk of progression to clinical symptoms of AD in men. These findings were replicated in the Alzheimer’s Disease Neuroimaging (ADNI) study. Then, utilizing a systems level approach combining large multi-tissue gene expression datasets with mass spectrometry-based proteomic analyses of brain tissue, we identified an A2M gene network that includes regulator of calcineurin (RCAN1), an inhibitor of calcineurin, a well-characterized tau phosphatase. A2M gene and protein expression in the brain were significantly associated with gene and protein expression levels of calcineurin. Collectively these novel findings suggest that A2M is associated with preclinical AD, reflects early neuronal injury in the disease course and may be responsive to tau phosphorylation in the brain through the RCAN1-calcineurin pathway.

Gait impairment in Parkinson's Disease (PD) is often severely disabling, yet frequently remains refractory to treatment. The locus coeruleus (LC) has diffuse noradrenergic projections that are thought to play a role in gait function. Enhancement of norepinephrine transmission may improve gait in some PD patients. We hypothesized that the severity of PD pathology, and more specifically, Lewy bodies and neuronal loss in the LC, would correlate with the severity of gait dysfunction in PD.Autopsy data from 51 patients, collected through the Morris K. Udall Parkinson's Disease Research Center, were correlated with clinical gait-related measures, including individual Unified Parkinson's Disease Rating Scale (UPDRS) Part II and III questions, total UPDRS Part III scores, and timed up-and-go speed (TUG).Neither the presence nor degree of Lewy body pathology in the LC on autopsy was associated with a higher UPDRS part III gait score. LC tau deposition and frontal Lewy body deposition were not correlated with any of the assessed gait measures. The degree of Lewy body pathology, independent of Braak stage, was positively associated with the severity of motor symptoms overall (UPDRS Part III total score).Neither the degree of Lewy body nor tau pathology in the LC is associated with severity of gait disorders in PD. This finding may have implications for targeted noradrenergic therapies in patients with refractory gait disorders.

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative dementia affecting the elderly. The GGGGCC hexanucleotide expansion mutation at the C9orf72 locus has been identified as a major cause of amyotrophic lateral sclerosis and frontotemporal dementia, raising the question of whether this mutation is a factor in DLB. Furthermore, a small number of clinically diagnosed DLB patients have previously been reported to carry the pathologic C9orf72 hexanucleotide repeat expansion.To explore whether the C9orf72 mutation is present in pathologically confirmed DLB patients.We screened a cohort of 111 definite DLB cases with extensive Lewy body pathology for the C9orf72 hexanucleotide repeat expansion using the repeat-primed polymerase chain reaction assay.No pathogenic expansions of the C9orf72 hexanucleotide repeat were found, suggesting that there is no causal relationship between C9orf72 and DLB.Our data illustrate that C9orf72 screening of clinically diagnosed DLB patients should only be considered in cases with a family history of motor neuron disease or frontotemporal dementia to distinguish between mimic diseases.

Background Huntington disease is characterized clinically by chorea, motor impairment, psychiatric manifestations and dementia. Atrophy of the striatum is the neuropathological hallmark of Huntington disease and previous studies have suggested that striatal atrophy correlates more closely with motor impairment than with chorea. Motor impairment, as measured by motor impairment score, correlates with functional disability in Huntington patients, but chorea does not. In this study, we investigate the relation between neuronal loss and these motor features.

Asymptomatic Alzheimer disease (ASYMAD) is characterized by normal cognition despite substantial AD pathology. To identify factors contributing to cognitive resilience, we compared early changes in regional cerebral blood flow (rCBF) in individuals subsequently diagnosed as ASYMAD with changes in cognitively impaired (CI) and normal older participants from the Baltimore Longitudinal Study of Aging. Participants underwent annual positron emission tomography (PET) rCBF measurements beginning 10.0 (SD 3.6) years before death and while cognitively intact. Based on clinical and autopsy information, subjects were grouped as cognitively normal (CN = 7), ASYMAD (n= 6), and CI (=6). Autopsy material was analyzed using CERAD and Braak scores and quantitative stereologic measures of tau and amyloid. ASYMAD and CI groups had similar CERAD and Braak scores, similar amounts of β-amyloid and tau in middle frontal (MFG), middle temporal (MTG), and inferior parietal (IP) regions, and more β-amyloid than CN in precuneus, MFG, and IP areas. Voxel-based PET analysis identified similarities and differences in longitudinal rCBF change among groups across a 7.2-year interval. Both ASYMAD and CI groups showed similar longitudinal rCBF declines in precuneus, lingual, and MTG regions relative to CN. The CI also showed greater rCBF decreases in anterior and posterior cingulate, cuneus, and brainstem regions relative to ASYMAD and CN, whereas ASYMAD showed greater relative rCBF increases over time in medial temporal and thalamic regions relative to CI and CN. Our findings provide evidence of early functional alterations that may contribute to cognitive resilience in those who accumulate AD pathology but maintain normal cognition.

Aggregation of α-synuclein contributes to the formation of Lewy bodies and neurites, the pathologic hallmarks of Parkinson disease (PD) and α-synucleinopathies. Although a number of human mutations have been identified in familial PD, the mechanisms that promote α-synuclein accumulation and toxicity are poorly understood. Here, we report that hyperactivity of the nonreceptor tyrosine kinase c-Abl critically regulates α-synuclein-induced neuropathology. In mice expressing a human α-synucleinopathy-associated mutation (hA53Tα-syn mice), deletion of the gene encoding c-Abl reduced α-synuclein aggregation, neuropathology, and neurobehavioral deficits. Conversely, overexpression of constitutively active c-Abl in hA53Tα-syn mice accelerated α-synuclein aggregation, neuropathology, and neurobehavioral deficits. Moreover, c-Abl activation led to an age-dependent increase in phosphotyrosine 39 α-synuclein. In human postmortem samples, there was an accumulation of phosphotyrosine 39 α-synuclein in brain tissues and Lewy bodies of PD patients compared with age-matched controls. Furthermore, in vitro studies show that c-Abl phosphorylation of α-synuclein at tyrosine 39 enhances α-synuclein aggregation. Taken together, this work establishes a critical role for c-Abl in α-synuclein-induced neurodegeneration and demonstrates that selective inhibition of c-Abl may be neuroprotective. This study further indicates that phosphotyrosine 39 α-synuclein is a potential disease indicator for PD and related α-synucleinopathies.

Summary Huntington disease (HD) is caused by a CAG⋅CTG expansion in the huntingtin ( HTT ) gene. While most research has focused on the HTT polyGln-expansion protein, we demonstrate that four additional, novel, homopolymeric expansion proteins (polyAla, polySer, polyLeu, and polyCys) accumulate in HD human brains. These sense and antisense repeat-associated non-ATG (RAN) translation proteins accumulate most abundantly in brain regions with neuronal loss, microglial activation and apoptosis, including caudate/putamen, white matter, and, in juvenile-onset cases, also the cerebellum. RAN protein accumulation and aggregation are length dependent, and individual RAN proteins are toxic to neural cells independent of RNA effects. These data suggest RAN proteins contribute to HD and that therapeutic strategies targeting both sense and antisense genes may be required for efficacy in HD patients. This is the first demonstration that RAN proteins are expressed across an expansion located in an open reading frame and suggests RAN translation may also contribute to other polyglutamine diseases.

We tested the independent utility of β-amyloid precursor protein (β-APP) immunohistochemical staining as evidence of brain trauma in the deaths of young children. Blinded reviewers retrospectively reviewed immunostained brain tissues from homicidal deaths, age-matched control cases without evidence of trauma, as well as cases of sudden infant death syndrome (SIDS). The reviewers correctly identified five of the seven cases with documented inflicted head trauma. However, one of seven age-matched control cases and one of 10 SIDS/sudden unexplained death in infancy (SUDI) cases demonstrated staining patterns similar to those seen in cases of inflicted trauma. We discuss these cases and the circumstances surrounding them with the intent to explain the difficulties associated with immunohistological interpretation of axonal injury. Although the utility of β-APP is quite powerful if not confounded by global hypoxic-ischemic injury, ultimately, β-APP studies should be only one piece of information in the determination of cause and manner of death.

Mutations in PARK2/Parkin , which encodes a ubiquitin E3 ligase, cause autosomal recessive Parkinson disease (PD). Here we show that the nonreceptor tyrosine kinase c-Abl phosphorylates tyrosine 143 of parkin, inhibiting parkin's ubiquitin E3 ligase activity and protective function. c-Abl is activated by dopaminergic stress and by dopaminergic neurotoxins, 1-methyl-4-phenylpyridinium (MPP + ) in vitro and in vivo by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), leading to parkin inactivation, accumulation of the parkin substrates aminoacyl-tRNA synthetase-interacting multifunctional protein type 2 (AIMP2) (p38/JTV-1) and fuse-binding protein 1 (FBP1), and cell death. STI-571, a c-Abl-family kinase inhibitor, prevents the phosphorylation of parkin, maintaining parkin in a catalytically active and protective state. STI-571’s protective effects require parkin, as shRNA knockdown of parkin prevents STI-571 protection. Conditional knockout of c-Abl in the nervous system also prevents the phosphorylation of parkin, the accumulation of its substrates, and subsequent neurotoxicity in response to MPTP intoxication. In human postmortem PD brain, c-Abl is active, parkin is tyrosine-phosphorylated, and AIMP2 and FBP1 accumulate in the substantia nigra and striatum. Thus, tyrosine phosphorylation of parkin by c-Abl is a major posttranslational modification that inhibits parkin function, possibly contributing to pathogenesis of sporadic PD. Moreover, inhibition of c-Abl may be a neuroprotective approach in the treatment of PD.

Inhibitors of apoptosis (IAPs) are a family of highly-conserved proteins that regulate cell survival through binding to caspases, the final executioners of apoptosis. X-linked IAP (XIAP) is the most widely expressed IAP and plays an important function in regulating cell survival. XIAP contains 3 baculoviral IAP repeats (BIRs) followed by a RING finger domain at the C terminal. The BIR domains of XIAP possess anticaspase activities, whereas the RING finger domain enables XIAP to function as an E3 ubiquitin ligase in the ubiquitin and proteasomal system. Our previous study showed that parkin, a protein that is important for the survival of dopaminergic neurons in Parkinson's disease (PD), is S-nitrosylated both in vitro and in vivo in PD patients. S-nitrosylation of parkin compromises its ubiquitin E3 ligase activity and its protective function, which suggests that nitrosative stress is an important factor in regulating neuronal survival during the pathogenesis of PD. In this study we show that XIAP is S-nitrosylated in vitro and in vivo in an animal model of PD and in PD patients. Nitric oxide modifies mainly cysteine residues within the BIR domains. In contrast to parkin, S-nitrosylation of XIAP does not affect its E3 ligase activity, but instead directly compromises its anticaspase-3 and antiapoptotic function. Our results confirm that nitrosative stress contributes to PD pathogenesis through the impairment of prosurvival proteins such as parkin and XIAP through different mechanisms, indicating that abnormal S-nitrosylation plays an important role in the process of neurodegeneration.

To define the magnitude and mechanism of the effect of brain infarcts on the odds of dementia in a prospective study.We examined the effects of brain infarcts and Alzheimer's disease (AD) pathology on the risk for dementia in 179 subjects from the Baltimore Longitudinal Study of Aging Autopsy Program. All subjects had longitudinal clinical and cognitive evaluations, and underwent postmortem examination of the brain.Brain infarcts were common in our cohort, and both symptomatic and asymptomatic infarcts conferred a significant increase in the odds of dementia. Risk factors for stroke in the absence of an infarct did not increase the odds of dementia, which was quantitatively related to the number but not the size of hemispheral infarcts; deep subcortical infarcts conferred no increased risk for dementia. The contribution of microscopic infarcts to dementia was significant and equivalent to that of macroscopic infarcts. In subjects with intermediate AD pathology scores, a single macroscopic hemispheral infarct was sufficient to cause dementia. A logistic regression model of the effect of infarcts and AD pathology on dementia indicated that AD pathology alone accounts for 50% of the dementia seen in this cohort, and that hemispheral infarcts alone or in conjunction with AD pathology account for 35%.Cerebrovascular disease is a significant and potentially preventable cause of dementia in the Baltimore Longitudinal Study of Aging. Burden and location of infarcts are significantly associated with cognitive decline.

The pathologic changes of Alzheimer disease (AD) evolve very gradually over decades before the disease becomes clinically manifest. Thus, it is not uncommon to find substantial numbers of Abeta plaques and neurofibrillary tangles in autopsy brains of older subjects with documented normal cognition, a state that we define as asymptomatic AD (ASYMAD). The goal of this study is to understand the morphometric substrate of ASYMAD subjects compared with mild cognitive impairment and definite AD cases. We used designed-based stereology to measure the volumes of neuronal cell bodies, nuclei, and nucleoli in 4 cerebral regions: anterior cingulate gyrus, posterior cingulate gyrus, primary visual cortex, and CA1 of hippocampus. We examined and compared autopsy brains from 4 groups (n = 15 each) of participants in the Baltimore Longitudinal Study of Aging: ASYMAD, mild cognitive impairment, AD, and age-matched controls. We found significant hypertrophy of the neuronal cell bodies, nuclei, and nucleoli of CA1 of hippocampus and anterior cingulate gyrus neurons in ASYMAD subjects compared with control and mild cognitive impairment cases. In the posterior cingulate gyrus and primary visual cortex, the hypertrophy was limited to the nuclei and nucleoli. The hypertrophy of cortical neurons and their nuclei and nucleoli in ASYMAD may represent an early reaction to the presence of neurotoxic Abeta or tau, or a compensatory mechanism that prevents the progression of the disease into dementia.

Udgivelsesdato: 2008-Apr To investigate the relation between the loss of substantia nigra (SN) neurons in normal ageing and Parkinson's disease (PD), we measured the total number and the cell body volume of pigmented (neuromelanin) neurons in the SN. We examined young (n = 7, mean age: 19.9), middle-aged (n = 9, mean age: 50.1), and older controls from the Baltimore Longitudinal Study of Aging (n = 7, mean age: 87.6), as well as PD cases (n = 8, mean age: 74.8). On random-systematically selected paraffin Nissl-stained sections, we used the Optical Fractionator to estimate the total number of neurons on one side of the SN. Using the Nucleator probe, we measured the volume of these neurons. In young and older controls, we also estimated the total number and volume of tyrosine hydroxylase (TH) positive (+) nigral neurons. We observed a significant loss of pigmented (-28.3%, P < 0.01) and TH (+) (-36.2%, P < 0.001) neurons in older controls compared with younger subjects. Analysis of the size distribution of pigmented and TH (+) neurons showed a significant hypertrophy in older controls compared to young controls (P < 0.01). In contrast, in PD we observed a significant atrophy of pigmented neurons compared to all control groups (P < 0.01). These data suggest that neuronal hypertrophy represents a compensatory mechanism within individual SN neurons that allows for normal motor function despite the loss of neurons in normal ageing. Presumably, this compensatory mechanism breaks down or is overwhelmed by the pathological events of PD leading to the onset of the characteristic motor disturbances.

Although ubiquitin-enriched protein inclusions represent an almost invariant feature of neurodegenerative diseases, the mechanism underlying their biogenesis remains unclear. In particular, whether the topology of ubiquitin linkages influences the dynamics of inclusions is not well explored. Here, we report that lysine 48 (K48)- and lysine 63 (K63)-linked polyubiquitination, as well as monoubiquitin modification contribute to the biogenesis of inclusions. K63-linked polyubiquitin is the most consistent enhancer of inclusions formation. Under basal conditions, ectopic expression of K63 mutant ubiquitin in cultured cells promotes the accumulation of proteins and the formation of intracellular inclusions in the apparent absence of proteasome impairment. When co-expressed with disease-associated tau and SOD1 mutants, K63 ubiquitin mutant facilitates the formation of tau- and SOD-1-positive inclusions. Moreover, K63-linked ubiquitination was found to selectively facilitate the clearance of inclusions via autophagy. These data indicate that K63-linked ubiquitin chains may represent a common denominator underlying inclusions biogenesis, as well as a general cellular strategy for defining cargo destined for the autophagic system. Collectively, our results provide a novel mechanistic route that underlies the life cycle of an inclusion body. Harnessing this pathway may offer innovative approaches in the treatment of neurodegenerative disorders.

This study focuses on the morphometric changes of neurons in asymptomatic Alzheimer's disease (AD), a state characterized by the presence of AD lesions in subjects without cognitive impairment. In autopsy brains, we used stereological methods to compare the cell body and nuclear volumes of anterior cingulate gyrus (ACG) and CA1 hippocampal neurons in asymptomatic AD subjects (n=9), subjects with AD dementia (AD, n=8), mild cognitive impairment (MCI, n=9), and age-matched controls (controls, n=9). In ACG, we observed a significant decrease in the neuronal volume of MCI and AD compared to controls; by contrast, no atrophy was present in asymptomatic AD. Moreover, we found a significant increase in nuclear volume in asymptomatic AD compared to controls (P0.001), MCI (P0.01) and AD (P0.001) brains. Similar results were found in the CA1 region of the hippocampus. This nuclear hypertrophy may represent an early neuronal reaction to Abeta or Tau, or a compensatory mechanism which forestalls the progression of AD and allows the brain to resist the development of dementia.

Objective To test the hypothesis that asymptomatic Alzheimer disease lesions may appear before 50 years of age. Background Alzheimer disease has an asymptomatic stage during which people are cognitively intact despite having substantial pathologic changes in the brain. While this asymptomatic stage is common in older people, how early in life it may develop has been unknown. Methods We microscopically examined the postmortem brains of 154 people aged 30 to 39 years (n=59) and 40 to 50 years (n=95) for specific Alzheimer lesions: beta-amyloid plaques, neurofibrillary tangles, and tau-positive neurites. We genotyped DNA samples for the apolipoprotein E gene (APOE). Results We found beta-amyloid lesions in 13 brains, all of them from people aged 40 to 49 with no history of dementia. These plaques were of the diffuse type only and appeared throughout the neocortex. Among these 13 brains, five had very subtle tau lesions in the entorhinal cortex and/or hippocampus. All individuals with beta-amyloid deposits carried one or two APOE4 alleles. Among the individuals aged 40 to 50 with genotype APOE3/4, 10 (36%) had beta-amyloid deposits but 18 (64%) had none. Conclusions Our study demonstrates that beta-amyloid deposits in the cerebral cortex appear as early as 40 years of age in APOE4 carriers, suggesting that these lesions may constitute a very early stage of Alzheimer disease. Future preventive and therapeutic measures for this disease may have to be stratified by risk factors like APOE genotype and may need to target people in their 40s or even earlier.

In Alzheimer’s disease (AD), one of the early responses to Aβ amyloidosis is recruitment of microglia to areas of new plaque. Microglial receptors such as cannabinoid receptor 2 (CB2) might be a suitable target for development of PET radiotracers that could serve as imaging biomarkers of Aβ-induced neuroinflammation. Mouse models of amyloidosis (J20APPswe/ind and APPswe/PS1ΔE9) were used to investigate the cellular distribution of CB2 receptors. Specificity of CB2 antibody (H60) was confirmed using J20APPswe/ind mice lacking CB2 receptors. APPswe/PS1ΔE9 mice were used in small animal PET with a CB2-targeting radiotracer, [11C]A836339. These studies revealed increased binding of [11C]A836339 in amyloid-bearing mice. Specificity of the PET signal was confirmed in a blockade study with a specific CB2 antagonist, AM630. Confocal microscopy revealed that CB2-receptor immunoreactivity was associated with astroglial (GFAP) and, predominantly, microglial (CD68) markers. CB2 receptors were observed, in particular, in microglial processes forming engulfment synapses with Aβ plaques. In contrast to glial cells, neuron (NeuN)-derived CB2 signal was equal between amyloid-bearing and control mice. The pattern of neuronal CB2 staining in amyloid-bearing mice was similar to that in human cases of AD. The data collected in this study indicate that Aβ amyloidosis without concomitant tau pathology is sufficient to activate CB2 receptors that are suitable as an imaging biomarker of neuroinflammation. The main source of enhanced CB2 PET binding in amyloid-bearing mice is increased CB2 immunoreactivity in activated microglia. The presence of CB2 immunoreactivity in neurons does not likely contribute to the enhanced CB2 PET signal in amyloid-bearing mice due to a lack of significant neuronal loss in this model. However, significant loss of neurons as seen at late stages of AD might decrease the CB2 PET signal due to loss of neuronally-derived CB2. Thus this study in mouse models of AD indicates that a CB2-specific radiotracer can be used as a biomarker of neuroinflammation in the early preclinical stages of AD, when no significant neuronal loss has yet developed.

Mutations in parkin are currently recognized as the most common cause of familial Parkinsonism. Emerging evidence also suggests that parkin expression variability may confer a risk for the development of the more common, sporadic form of Parkinson's disease (PD). Supporting this, we have recently demonstrated that parkin solubility in the human brain becomes altered with age. As parkin apparently functions as a broad-spectrum neuroprotectant, the resulting decrease in the availability of soluble parkin with age may underlie the progressive susceptibility of the brain to stress. Interestingly, we also observed that many familial-PD mutations of parkin alter its solubility in a manner that is highly reminiscent of our observations with the aged brain. The converging effects on parkin brought about by aging and PD-causing mutations are probably not trivial and suggest that environmental modulators affecting parkin solubility would increase an individual's risk of developing PD. Using both cell culture and in vivo models, we demonstrate here that several PD-linked stressors, including neurotoxins (MPP+, rotenone, 6-hydroxydopamine), paraquat, NO, dopamine and iron, induce alterations in parkin solubility and result in its intracellular aggregation. Furthermore, the depletion of soluble, functional forms of parkin is associated with reduced proteasomal activities and increased cell death. Our results suggest that exogenously introduced stress as well as endogenous dopamine could affect the native structure of parkin, promote its misfolding, and concomitantly compromise its protective functions. Mechanistically, our results provide a link between the influence of environmental and intrinsic factors and genetic susceptibilities in PD pathogenesis.

In order to understand better the neuropathological substrate of dementia in Parkinson's disease (PD) and to examine its interactions with Alzheimer's disease (AD), we examined autopsy brains from 21 cases of PD and Lewy body disease (LBD) with dementia. We separated brains in two groups according to the presence of Abeta deposits. In brains without Abeta, we found few or no Lewy bodies (LB) in the cerebral cortex. By contrast, in brains with Abeta, we observed significant increases in LB in the cerebral cortex (p < 0.01) and alpha-synuclein immunoreactive lesions in the cingulate cortex (p < 0.01). Immunoblots of alpha-synuclein from cingulate cortex in brains with Abeta showed significantly higher levels of insoluble alpha-synuclein compared to brains without Abeta. Our observations indicate that in cases of PD with dementia, the neocortex is not necessarily involved by LB. Furthermore, the presence of Abeta deposits in the cerebral cortex was associated with extensive alpha-synuclein lesions and higher levels of insoluble alpha-synuclein. This suggests that Abeta enhances the development of cortical alpha-synuclein lesions in cases of PD.

Alpha-synuclein (α-synuclein) lesions are characteristic of idiopathic Parkinson disease (PD) and other α-synucleinopathies. To study the frequency of α-synuclein lesions in normal aging and how frequently they coexist with lesions of Alzheimer disease (AD), we examined the autopsy brains from normal and demented subjects in the Baltimore Longitudinal Study of Aging (BLSA) (n = 117). We found that the overall frequency of α-synuclein lesions was 25%, with 100% in 7 cases of PD, 31.5% in 56 cases with AD lesions, and 8.3% among 36 older control brains. Among brains with AD lesions, the frequency of α-synuclein pathology was higher in those with higher scores for neuritic plaques, but not in those with higher scores for neurofibrillary tangles. Our observations indicate that α-synuclein lesions are uncommon in aged control subjects. Finally, the coexistence of Aβ amyloid and α-synuclein pathology in AD brains suggests that the pathogenic mechanism/s leading to the accumulation of Aβ and α-synuclein may be similar. Copyright © 2005 by the American Association of Neuropathologists, Inc.

Hippocampal sclerosis dementia (HSD) is a disease of unknown etiology and pathogenesis. To determine whether HSD cases could be reclassified as variants of frontotemporal dementia (FTD), a heterogeneous group of disorders, 18 brain autopsy cases previously diagnosed as HSD were re-evaluated. In 11 cases, ubiquitinated neuronal inclusions, similar to those of motor neuron disease inclusion dementia (MNDID), were found. Brain levels of soluble and insoluble tau were normal. Most patients with pathologic findings of HSD may actually have the MNDID variant of FTD.

Parkin is an E3 ubiquitin ligase involved in the ubiquitination of proteins that are important in the survival of dopamine neurons in Parkinson's disease (PD). We show that parkin is S- nitrosylated in vitro, as well as in vivo in a mouse model of PD and in brains of patients with PD and diffuse Lewy body disease. Moreover, S- nitrosylation inhibits parkin's ubiquitin E3 ligase activity and its protective function. The inhibition of parkin's ubiquitin E3 ligase activity by S- nitrosylation could contribute to the degenerative process in these disorders by impairing the ubiquitination of parkin substrates.

Huntington's disease (HD) is caused by an expanded CAG repeat in the Huntingtin (HTT) gene. The mechanism(s) by which mutant HTT (mHTT) causes disease is unclear. Nucleocytoplasmic transport, the trafficking of macromolecules between the nucleus and cytoplasm, is tightly regulated by nuclear porecomplexes (NPCs) made up of nucleoporins (NUPs). Previous studies offered clues that mHTT may disrupt nucleocytoplasmic transport and a mutation of an NUP can cause HD-like pathology. Therefore, we evaluated the NPC and nucleocytoplasmic transport in multiple models of HD, including mouse and fly models, neurons transfected with mHTT, HD iPSC-derived neurons, and human HD brain regions. These studies revealed severe mislocalization and aggregation of NUPs and defective nucleocytoplasmic transport. HD repeat-associated non-ATG (RAN) translation proteins also disrupted nucleocytoplasmic transport. Additionally, overexpression of NUPs and treatment with drugs that prevent aberrant NUP biology also mitigated this transport defect and neurotoxicity, providing future novel therapy targets.

Introduction Blast injury to brain, a hundred-year old problem with poorly characterized neuropathology, has resurfaced as health concern in recent deployments in Iraq and Afghanistan. To characterize the neuropathology of blast injury, we examined the brains of veterans for the presence of amyloid precursor protein (APP)-positive axonal swellings typical of diffuse axonal injury (DAI) and compared them to healthy controls as well as controls with opiate overdose, anoxic-ischemic encephalopathy, and non-blast TBI (falls and motor vehicle crashes). Results In cases with blast history, we found APP (+) axonal abnormalities in several brain sites, especially the medial dorsal frontal white matter. In white matter, these abnormalities were featured primarily by clusters of axonal spheroids or varicosities in a honeycomb pattern with perivascular distribution. Axonal abnormalities colocalized with IBA1 (+) reactive microglia and had an appearance that was distinct from classical DAI encountered in TBI due to motor vehicle crashes. Opiate overdose cases also showed APP (+) axonal abnormalities, but the intensity of these lesions was lower compared to cases with blast histories and there was no clear association of such lesions with microglial activation. Conclusions Our findings demonstrate that many cases with history of blast exposure are featured by APP (+) axonopathy that may be related to blast exposure, but an important role for opiate overdose, antemortem anoxia, and concurrent blunt TBI events in war theater or elsewhere cannot be discounted. Electronic supplementary material The online version of this article (doi:10.1186/s40478-014-0153-3) contains supplementary material, which is available to authorized users.

Mutations in the ATP13A2 (PARK9) gene cause early-onset, autosomal recessive Parkinson's disease (PD) and Kufor-Rakeb syndrome. ATP13A2 mRNA is spliced into three distinct isoforms encoding a P5-type ATPase involved in regulating heavy metal transport across vesicular membranes. Here, we demonstrate that three ATP13A2 mRNA isoforms are expressed in the normal human brain and are modestly increased in the cingulate cortex of PD cases. ATP13A2 can mediate protection toward a number of stressors in mammalian cells and can protect against α-synuclein-induced toxicity in cellular and invertebrate models of PD. Using a primary cortical neuronal model combined with lentiviral-mediated gene transfer, we demonstrate that human ATP13A2 isoforms 1 and 2 display selective neuroprotective effects toward toxicity induced by manganese and hydrogen peroxide exposure through an ATPase-independent mechanism. The familial PD mutations, F182L and G504R, abolish the neuroprotective effects of ATP13A2 consistent with a loss-of-function mechanism. We further demonstrate that the AAV-mediated overexpression of human ATP13A2 is not sufficient to attenuate dopaminergic neurodegeneration, neuropathology, and striatal dopamine and motoric deficits induced by human α-synuclein expression in a rat model of PD. Intriguingly, the delivery of an ATPase-deficient form of ATP13A2 (D513N) to the substantia nigra is sufficient to induce dopaminergic neuronal degeneration and motor deficits in rats, potentially suggesting a dominant-negative mechanism of action. Collectively, our data demonstrate a distinct lack of ATP13A2-mediated protection against α-synuclein-induced neurotoxicity in the rat nigrostriatal dopaminergic pathway, and limited neuroprotective capacity overall, and raise doubts about the potential of ATP13A2 as a therapeutic target for PD.

Greater than 160 missense mutations in copper-zinc superoxide dismutase-1 (SOD1) can cause amyotrophic lateral sclerosis (ALS). These mutations produce conformational changes that reveal novel antibody binding epitopes. A monoclonal antibody, clone C4F6 - raised against the ALS variant G93A of SOD1, has been identified as specifically recognizing a conformation shared by many ALS mutants of SOD1. Attempts to determine whether non-mutant SOD1 adopts a C4F6-reactive conformation in spinal tissues of sporadic ALS (sALS) patients has produced inconsistent results. To define the epitope recognized by C4F6, we tested its binding to a panel of recombinant ALS-SOD1 proteins expressed in cultured cells, producing data to suggest that the C4F6 epitope minimally contains amino acids 90–93, which are normally folded into a tight hairpin loop. Multiple van der Waals interactions between the 90–93 loop and a loop formed by amino acids 37–42, particularly a leucine at position 38, form a stable structure termed the β-plug. Based on published modeling predictions, we suggest that the binding of C4F6 to multiple ALS mutants of SOD1 occurs when the local structure within the β-plug, including the loop at 90–93, is destabilized. In using the antibody to stain tissues from transgenic mice or humans, the specificity of the antibody for ALS mutant SOD1 was influenced by antigen retrieval protocols. Using conditions that showed the best discrimination between normal and misfolded mutant SOD1 in cell and mouse models, we could find no obvious difference in C4F6 reactivity to spinal motor neurons between sALS and controls tissues. Electronic supplementary material The online version of this article (doi: 10.1186/2051-5960-2-55) contains supplementary material, which is available to authorized users.

Older adults with intact cognition before death and substantial Alzheimer disease (AD) lesions at autopsy have been termed "asymptomatic AD subjects" (ASYMAD). We previously reported hypertrophy of neuronal cell bodies, nuclei, and nucleoli in the CA1 of the hippocampus (CA1), anterior cingulate gyrus, posterior cingulate gyrus, and primary visual cortex of ASYMAD versus age-matched Control and mild cognitive impairment (MCI) subjects. However, it was unclear whether the neuronal hypertrophy could be attributed to differences in the severity of AD pathology. Here, we performed quantitative analyses of the severity of β-amyloid (Aβ) and phosphorylated tau (tau) loads in the brains of ASYMAD, Control, MCI, and AD subjects (n = 15 per group) from the Baltimore Longitudinal Study of Aging. Tissue sections from CA1, anterior cingulate gyrus, posterior cingulate gyrus, and primary visual cortex were immunostained for Aβ and tau; the respective loads were assessed using unbiased stereology by measuring the fractional areas of immunoreactivity for each protein in each region. The ASYMAD and MCI groups did not differ in Aβ and tau loads. These data confirm that ASYMAD and MCI subjects have comparable loads of insoluble Aβ and tau in regions vulnerable to AD pathology despite divergent cognitive outcomes. These findings imply that cognitive impairment in AD may be caused or modulated by factors other than insoluble forms of Aβ and tau.

The finding that a GGGGCC (G4C2) hexanucleotide repeat expansion in the chromosome 9 ORF 72 (C9ORF72) gene is a common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) links ALS/FTD to a large group of unstable microsatellite diseases. Previously, we showed that microsatellite expansion mutations can be bidirectionally transcribed and that these mutations express unexpected proteins by a unique mechanism, repeat-associated non-ATG (RAN) translation. In this study, we show that C9ORF72 antisense transcripts are elevated in the brains of C9ORF72 expansion-positive [C9(+)] patients, and antisense GGCCCC (G2C4) repeat-expansion RNAs accumulate in nuclear foci in brain. Additionally, sense and antisense foci accumulate in blood and are potential biomarkers of the disease. Furthermore, we show that RAN translation occurs from both sense and antisense expansion transcripts, resulting in the expression of six RAN proteins (antisense: Pro-Arg, Pro-Ala, Gly-Pro; and sense: Gly-Ala, Gly-Arg, Gly-Pro). These proteins accumulate in cytoplasmic aggregates in affected brain regions, including the frontal and motor cortex, hippocampus, and spinal cord neurons, with some brain regions showing dramatic RAN protein accumulation and clustering. The finding that unique antisense G2C4 RNA foci and three unique antisense RAN proteins accumulate in patient tissues indicates that bidirectional transcription of expanded alleles is a fundamental pathologic feature of C9ORF72 ALS/FTD. Additionally, these findings suggest the need to test therapeutic strategies that target both sense and antisense RNAs and RAN proteins in C9ORF72 ALS/FTD, and to more broadly consider the role of antisense expression and RAN translation across microsatellite expansion diseases.

The primarily neuronal RNA-binding protein HuD is implicated in learning and memory. Here, we report the identification of several HuD target transcripts linked to Alzheimer’s disease (AD) pathogenesis. HuD interacted with the 3’-untranslated regions (UTRs) of APP mRNA (encoding amyloid precursor protein) and BACE1 mRNA (encoding β-site APP-cleaving enzyme) and increased the half-lives of these mRNAs. HuD also associated with and stabilized the long noncoding (lnc)RNA BACE1AS, which partly complements BACE1 mRNA and enhances BACE1 expression. Consistent with HuD promoting production of APP and APP-cleaving enzyme, the levels of APP, BACE1, BACE1AS, and Aβ were higher in the brain of HuD-overexpressing mice. Importantly, cortex (superior temporal gyrus) from AD patients displayed significantly higher levels of HuD, and accordingly elevated APP, BACE1, BACE1AS, and Aβ than did cortical tissue from healthy age-matched individuals. We propose that HuD jointly promotes the production of APP and the cleavage of its amyloidogenic fragment, Aβ.

A three-dimensional stereotaxic atlas of the human brainstem based on high resolution ex vivo diffusion tensor imaging (DTI) is introduced. The atlas consists of high resolution (125-255 μm isotropic) three-dimensional DT images of the formalin-fixed brainstem acquired at 11.7 T. The DTI data revealed microscopic neuroanatomical details, allowing three-dimensional visualization and reconstruction of fiber pathways including the decussation of the pyramidal tract fibers, and interdigitating fascicles of the corticospinal and transverse pontine fibers. Additionally, strong gray-white matter contrasts in the apparent diffusion coefficient (ADC) maps enabled precise delineation of gray matter nuclei in the brainstem, including the cranial nerve and the inferior olivary nuclei. Comparison with myelin-stained histology shows that at the level of resolution achieved in this study, the structural details resolved with DTI contrasts in the brainstem were comparable to anatomical delineation obtained with histological sectioning. Major neural structures delineated from DTI contrasts in the brainstem are segmented and three-dimensionally reconstructed. Further, the ex vivo DTI data are nonlinearly mapped to a widely-used in vivo human brain atlas, to construct a high-resolution atlas of the brainstem in the Montreal Neurological Institute (MNI) stereotaxic coordinate space. The results demonstrate the feasibility of developing a 3D DTI based atlas for detailed characterization of brainstem neuroanatomy with high resolution and contrasts, which will be a useful resource for research and clinical applications.

Most of the mutations in the presenilin-1 gene (PS-1) are associated with familial Alzheimer’s disease (AD). However, certain examples can be associated with frontotemporal dementia (FTD). We performed a clinical evaluation of individuals belonging to a family with the FTD phenotype, and additional molecular studies and neuropathological assessment of the proband. The PS-1 M146V mutation was found in the 50-year-old subject (the proband) with family history of early-onset FTD. Neuropathological examination showed abundant amyloid plaques, widespread neurofibrillary pathology, Pick bodies in the hippocampus and cortex, cortical globose tangles and ubiquitin-positive nuclear inclusions in white matter oligodendrocytes. We report a kindred with clinical features of FTD, whose proband bore the PS-1 M146V mutation and showed diffuse Alzheimer’s type pathology and Pick bodies on post-mortem neuropathological examination. As with other mutations within the same codon, this substitution may predispose to both diseases by affecting APP and/or tau processing.

Huntington’s disease (HD) is caused by a CAG CTG expansion in the huntingtin (HTT) gene. While most research has focused on the HTT polyGln-expansion protein, we recently reported that four additional, novel, homopolymeric expansion proteins (polyAla, polySer, polyLeu, polyCys) accumulate in HD human brains. These sense and antisense repeat-associated non-ATG (RAN) translation proteins accumulate most abundantly in brain regions with neuronal loss, microglial activation and apoptosis, including caudate/putamen, white matter, and in juvenile-onset cases, also the cerebellum. RAN protein accumulation and aggregation patterns are length-dependent. Codon substitution experiments show HD-RAN proteins are toxic to neural cells independent of RNA effects. These data support an important role for RAN proteins in HD, and suggest that therapeutic strategies targeting both sense and antisense transcripts, RAN proteins or RAN translation may be important for treating HD patients. We are currently using mouse models of HD to understand the time-course and impact that HD-RAN proteins play in disease and also to examine which models best mimic the findings we have seen in human autopsy patients. The discovery of HD RAN proteins was the first demonstration that RAN translation can occur across an expansion located in an open reading frame and suggests RAN translation may also contribute to other polyglutamine diseases. Recent efforts to understand the mechanisms of RAN translation and insights into the roles that RNA gain of function and RAN mechanisms play in HD as well as ALS/FTD, ataxia and myotonic dystrophy will be discussed.

In Parkinson's disease (PD) and other α-synucleinopathies, prefibrillar α-synuclein (αS) oligomer is implicated in the pathogenesis. However, toxic αS oligomers observed usingin vitrosystems are not generally seen to be associated with α-synucleinopathyin vivo. Thus, the pathologic significance of αS oligomers to αS neurotoxicity is unknown. Herein, we show that, αS that accumulate within endoplasmic reticulum (ER)/microsome forms toxic oligomers in mouse and human brain with the α-synucleinopathy. In the mouse model of α-synucleinopathy, αS oligomers initially form before the onset of disease and continue to accumulate with the disease progression. Significantly, treatment of αS transgenic mice with Salubrinal, an anti-ER stress compound that delays the onset of disease, reduces ER accumulation of αS oligomers. These results indicate that αS oligomers with toxic conformation accumulate in ER, and αS oligomer-dependent ER stress is pathologically relevant for PD.

Accumulation of misfolded α-synuclein (αS) is mechanistically linked to neurodegeneration in Parkinson's disease (PD) and other α-synucleinopathies. However, how αS causes neurodegeneration is unresolved. Because cellular accumulation of misfolded proteins can lead to endoplasmic reticulum stress/unfolded protein response (ERS/UPR), chronic ERS could contribute to neurodegeneration in α-synucleinopathy. Using the A53T mutant human αS transgenic (A53TαSTg) mouse model of α-synucleinopathy, we show that disease onset in the αS Tg model is coincident with induction of ER chaperones in neurons exhibiting αS pathology. However, the neuronal ER chaperone induction was not accompanied by the activation of phospho-eIF2α, indicating that α-synucleinopathy is associated with abnormal UPR that could promote cell death. Induction of ERS/UPR was associated with increased levels of ER/microsomal (ER/M) associated αS monomers and aggregates. Significantly, human PD cases also exhibit higher relative levels of ER/M αS than the control cases. Moreover, αS interacts with ER chaperones and overexpression of αS sensitizes neuronal cells to ERS-induced toxicity, suggesting that αS may have direct impact on ER function. This view is supported by the presence of ERS-activated caspase-12 and the accumulation of ER-associated polyubiquitin. More important, treatment with Salubrinal, an anti-ERS compound, significantly attenuates disease manifestations in both theA53TαSTg mouse model and the adeno-associated virus-transduced rat model ofA53TαS-dependent dopaminergic neurodegeneration. Our data indicate that the accumulation αS within ER leads to chronic ER stress conditions that contribute to neurodegeneration in α-synucleinopathies. Attenuating chronic ERS could be an effective therapy for PD and other α-synucleinopathies.

Mutations in the genes encoding LRRK2 and α-synuclein cause autosomal dominant forms of familial Parkinson's disease (PD). Fibrillar forms of α-synuclein are a major component of Lewy bodies, the intracytoplasmic proteinaceous inclusions that are a pathological hallmark of idiopathic and certain familial forms of PD. LRRK2 mutations cause late-onset familial PD with a clinical, neurochemical and, for the most part, neuropathological phenotype that is indistinguishable from idiopathic PD. Importantly, α-synuclein-positive Lewy bodies are the most common pathology identified in the brains of PD subjects harboring LRRK2 mutations. These observations may suggest that LRRK2 functions in a common pathway with α-synuclein to regulate its aggregation. To explore the potential pathophysiological interaction between LRRK2 and α-synuclein in vivo, we modulated LRRK2 expression in a well-established human A53T α-synuclein transgenic mouse model with transgene expression driven by the hindbrain-selective prion protein promoter. Deletion of LRRK2 or overexpression of human G2019S-LRRK2 has minimal impact on the lethal neurodegenerative phenotype that develops in A53T α-synuclein transgenic mice, including premature lethality, pre-symptomatic behavioral deficits and human α-synuclein or glial neuropathology. We also find that endogenous or human LRRK2 and A53T α-synuclein do not interact together to influence the number of nigrostriatal dopaminergic neurons. Taken together, our data suggest that α-synuclein-related pathology, which occurs predominantly in the hindbrain of this A53T α-synuclein mouse model, occurs largely independently from LRRK2 expression. These observations fail to provide support for a pathophysiological interaction of LRRK2 and α-synuclein in vivo, at least within neurons of the mouse hindbrain.

The definitive Alzheimer's disease (AD) diagnosis requires postmortem confirmation of neuropathological hallmarks-amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs). The advent of radiotracers for amyloid imaging presents an opportunity to investigate amyloid deposition in vivo. The (11)C-Pittsburgh compound-B (PiB)-PET ligand remains the most widely studied to date; however, regional variations in (11)C-PiB binding and the extent of agreement with neuropathological assessment have not been thoroughly investigated. Sojkova and colleagues [35] reported variable agreement between CERAD-based neuropathologic diagnosis of AD lesions and mean cortical PiB, suggesting the need for a more direct quantification of regional Aβ in relation to in vivo imaging. In the present study, we extend these findings by examining the correspondence among regional (11)C-PiB load, region-matched quantitative immunohistological assessments of Aβ and NFTs, and brain atrophy (MRI) in six older Baltimore Longitudinal Study of Aging participants who came to autopsy (imaging-autopsy interval range 0.2-2.4 years). The total number of Aβ plaques (6E10) and NFTs (PHF1) in paraffin sections from hippocampus, orbito-frontal cortex, anterior and posterior cingulate gyrus, precuneus and cerebellum was quantified using a technique guided by unbiased stereological principles. We report a general agreement between the regional measures of amyloid obtained via stereological assessment and imaging, with significant relationships evident for the anterior (r = 0.83; p = 0.04) and posterior (r = 0.94; p = 0.005) cingulate gyri, and the precuneus (r = 0.94; p = 0.005). No associations were observed between (11)C-PiB load and NFT count for any of the regions examined (p 0.2 in all regions), or between regional Aβ or NFT counts and corresponding brain volumes. The strong associations of PiB retention with region-matched, quantitative analyses of Aβ in postmortem tissue offer support for the validity of (11)C-PiB-PET imaging as a method for evaluation of plaque burden in vivo.

A hexanucleotide repeat expansion in the gene C9ORF72 has been implicated in the development of amyotrophic lateral sclerosis and frontotemporal dementia. The variant has also been found in a small percentage of patients with probable late-onset Alzheimer's disease.

Glucocerebrosidase (GCase) functions as a lysosomal enzyme and its mutations are known to be related to many neurodegenerative diseases, including Gaucher's disease (GD), Parkinson's disease (PD), and Dementia with Lewy Bodies (DLB). However, there is little information about the role of GCase in the pathogenesis of Alzheimer's disease (AD). Here we demonstrate that GCase protein levels and enzyme activity are significantly decreased in sporadic AD. Moreover, Aβ1-42 oligomer treatment results in neuronal cell death that is concomitant with decreased GCase protein levels and enzyme activity, as well as impairment in lysosomal biogenesis and acidification. Importantly, overexpression of GCase promotes the lysosomal degradation of Aβ1-42 oligomers, restores the lysosomal impairment, and protects against the toxicity in neurons treated with Aβ1-42 oligomers. Our findings indicate that a deficiency of GCase could be involved in progression of AD pathology and suggest that augmentation of GCase activity may be a potential therapeutic option for the treatment of AD.

Mutations in the ATP13A2 gene (PARK9, OMIM 610513) cause autosomal recessive, juvenile-onset Kufor-Rakeb syndrome and early-onset parkinsonism. ATP13A2 is an uncharacterized protein belonging to the P(5)-type ATPase subfamily that is predicted to regulate the membrane transport of cations. The physiological function of ATP13A2 in the mammalian brain is poorly understood. Here, we demonstrate that ATP13A2 is localized to intracellular acidic vesicular compartments in cultured neurons. In the human brain, ATP13A2 is localized to pyramidal neurons within the cerebral cortex and dopaminergic neurons of the substantia nigra. ATP13A2 protein levels are increased in nigral dopaminergic and cortical pyramidal neurons of Parkinson's disease brains compared with normal control brains. ATP13A2 levels are increased in cortical neurons bearing Lewy bodies (LBs) compared with neurons without LBs. Using short hairpin RNA-mediated silencing or overexpression to explore the function of ATP13A2, we find that modulating the expression of ATP13A2 reduces the neurite outgrowth of cultured midbrain dopaminergic neurons. We also find that silencing of ATP13A2 expression in cortical neurons alters the kinetics of intracellular pH in response to cadmium exposure. Furthermore, modulation of ATP13A2 expression leads to reduced intracellular calcium levels in cortical neurons. Finally, we demonstrate that silencing of ATP13A2 expression induces mitochondrial fragmentation in neurons. Oppositely, overexpression of ATP13A2 delays cadmium-induced mitochondrial fragmentation in neurons consistent with a neuroprotective effect. Collectively, this study reveals a number of intriguing neuronal phenotypes due to the loss- or gain-of-function of ATP13A2 that support a role for this protein in regulating intracellular cation homeostasis and neuronal integrity.

Primate-specific genes and isoforms could provide insight into human brain diseases. Our bioinformatic analysis revealed that there are possibly five isoforms of human GDNF gene with different pre- and pro-regions by inter- and intra-exon splicing. By using TaqMan primer probe sets, designed between exons, we verified the expression of all isoforms. Furthermore, a novel GDNFOS gene was found to be transcribed from the opposite strand of GDNF gene. GDNFOS gene has four exons that are spliced into different isoforms. GDNFOS1 and GDNFOS2 are long noncoding RNAs, and GDNFOS3 encodes a protein of 105 amino acids. To study human GDNF and GDNFOS regulation in neurodegenerative diseases, the protein and mRNA levels were measured by Western blot and RT-quantitative PCR, respectively, in postmortem middle temporal gyrus (MTG) of Alzheimer disease (AD) and Huntington disease (HD) patients in comparison with those of normal controls. In the MTG of AD patients, the mature GDNF peptide was down-regulated; however, the transcript of GDNF isoform from human exon 2 was up-regulated, whereas that of the conserved isoform from exon 1 remained unchanged in comparison with those of normal controls. In contrast, the mature GDNF peptide and the isoform mRNA levels were not changed in the MTG of HD. The findings of novel GDNF and GDNFOS isoforms and differences in tissue expression patterns dysregulated in AD brains may further reveal the role of endogenous GDNF in human brain diseases.

Positron emission tomography (PET) amyloid imaging agents, such as carbon 11–labeled Pittsburgh Compound B ([11C]PiB), have facilitated in vivo evaluation of cerebral amyloidosis,1 including detection of fibrillar β-amyloid (Aβ) in diffuse, cored, and neuritic (NP) plaques1,2 and in blood vessels in cerebral amyloid angiopathy (CAA).1–3 Brain biopsies of patients with symptomatic normal-pressure hydrocephalus4 and postmortem evaluation of 2 demented patients2,5 demonstrated good overall agreement between [11C]PiB imaging and Aβ load detected by means of immunohistochemical analysis or the age-based, semiquantitative Consortium to Establish a Registry for AD (CERAD) scale.6 However, recent articles have also described a case of sparse NPs in a demented older adult with negligible [11C]PiB retention7 and an example of an elevated Aβ level by means of immunohistochemical analysis in an individual with a [11C]PiB distribution volume ratio (DVR) of 1.2.4 Thus, the extent of agreement between in vivo [11C]PiB imaging and neuropathologic assessment remains unclear, especially in nondemented older adults who have lower Aβ loads and greater variability in Aβ levels.8 To investigate the relation between [11C]PiB imaging and CERAD-based neuropathologic diagnosis of Alzheimer disease (AD) lesions, we evaluated 5 nondemented and 1 demented participant from the Neuroimaging Substudy of the Baltimore Longitudinal Study of Aging (NI-BLSA)9 who underwent in vivo [11C]PiB imaging and postmortem evaluation. We also investigated the [11C]PiB-positive threshold that maximizes agreement between in vivo Aβ imaging and CERAD NP scores and related it to the level at which Aβ is detectable by [11C]PiB imaging. We then examined cases with limited agreement to identify factors that affect interpretation of in vivo Aβ imaging relative to neuropathologic assessment.