Showing papers by "John Q. Trojanowski published in 2009"

Cerebrospinal fluid biomarker signature in Alzheimer's disease neuroimaging initiative subjects.

Abstract: If the clinical diagnosis of probable AD is imprecise with accuracy rates of approximately 90% or lower using established consensus criteria for probable AD, but definite AD requires autopsy confirmation, it is not surprising that diagnostic accuracy is lower at early and presymptomatic stages of AD.1–4 It is believed that the development of full-blown AD takes place over an approximately 20-year prodromal period, but this is difficult to determine in the absence of biomarkers that reliably signal the onset of nascent disease before the emergence of measurable cognitive impairments. Because intervention with disease-modifying therapies for AD is likely to be most efficacious before significant neurodegeneration has occurred, there is an urgent need for biomarker-based tests that enable a more accurate and early diagnosis of AD.5–7 Moreover, such tests could also improve monitoring AD progression, evaluation of new AD therapies, and enrichment of AD cohorts with specific subsets of AD subjects in clinical trials. The defining lesions of AD are neurofibrillary tangles and senile plaques formed, respectively, by neuronal accumulations of abnormal hyperphosphorylated tau filaments and extracellular deposits of amyloid β (Aβ) fibrils, mostly the 1 to 42 peptide (Aβ1-42), the least soluble of the known Aβ peptides produced from Aβ precursor protein by the action of various peptidases.1–3 Hence, for these and other reasons summarized in consensus reports on AD biomarkers, cerebrospinal fluid (CSF), total tau (t-tau), and Aβ were identified as being among the most promising and informative AD biomarkers.5,6 Increased levels of tau in CSF are thought to occur after its release from damaged and dying neurons that harbor dystrophic tau neurites and tangles, whereas reduced CSF levels of Aβ1-42 are believed to result from large-scale accumulation of this least soluble of Aβ peptides into insoluble plaques in the AD brain. The combination of increased CSF concentrations of t-tau and phosphotau (p-tau) species and decreased concentrations of Aβ1-42 are considered to be a pathological CSF biomarker signature that is diagnostic for AD.5,6,8,9 Notably, recent studies have provided compelling preliminary data to suggest that this combination of CSF tau and Aβ biomarker changes may predict the conversion to AD in mild cognitive impairment (MCI) subjects.10 Thus, an increase in levels of CSF tau associated with a decline in levels of CSF Aβ1-42 may herald the onset of AD before it becomes clinically manifest. However, before the utility of CSF Aβ1-42 and tau concentrations for diagnosis of AD can be established, it is critical to standardize the methodology for their measurement.5–8,10 For example, among the published studies of CSF tau and Aβ, there is considerable variability in the observed levels of these analytes, as well as their diagnostic sensitivity and specificity. This is attributable to variability in analytical methodology standardization and other factors that differ between studies of the same CSF analytes in similar but not identical cohorts.5–7 The Alzheimer’s Disease Neuroimaging Initiative (ADNI) was launched in 2004 to address these and other limitations in AD biomarkers (see reviews in Shaw and colleagues7 and Mueller and coauthors,11 and the ADNI Web site [http://www.adni-info.org/index] where the ADNI grant and all ADNI data are posted for public access). To this end, the Biomarker Core of ADNI conducts studies on ADNI-derived CSF samples to measure CSF Aβ1-42, t-tau, and p-tau (tau phosphorylated at threonine181 [p-tau181p]) in standardized assays. Evaluation of CSF obtained at baseline evaluation of 416 of the 819 ADNI subjects is now complete, and we report here our findings on the performance of these tests using a standardized multiplex immunoassay system that measures the biomarkers simultaneously in the same sample aliquot in ADNI subjects and in an independent cohort of autopsy-confirmed AD cases.

Exogenous α-synuclein fibrils seed the formation of Lewy body-like intracellular inclusions in cultured cells

Abstract: Cytoplasmic inclusions containing α-synuclein (α-Syn) fibrils, referred to as Lewy bodies (LBs), are the signature neuropathological hallmarks of Parkinson's disease (PD). Although α-Syn fibrils can be generated from recombinant α-Syn protein in vitro, the production of fibrillar α-Syn inclusions similar to authentic LBs in cultured cells has not been achieved. We show here that intracellular α-Syn aggregation can be triggered by the introduction of exogenously produced recombinant α-Syn fibrils into cultured cells engineered to overexpress α-Syn. Unlike unassembled α-Syn, these α-Syn fibrils “seeded” recruitment of endogenous soluble α-Syn protein and their conversion into insoluble, hyperphosphorylated, and ubiquitinated pathological species. Thus, this cell model recapitulates key features of LBs in human PD brains. Also, these findings support the concept that intracellular α-Syn aggregation is normally limited by the number of active nucleation sites present in the cytoplasm and that small quantities of α-Syn fibrils can alter this balance by acting as seeds for aggregation.

Phosphorylation of S409/410 of TDP-43 is a consistent feature in all sporadic and familial forms of TDP-43 proteinopathies

Abstract: Accumulation of hyperphosphorylated, ubiquitinated and N-terminally truncated TAR DNA-binding protein (TDP-43) is the pathological hallmark lesion in most familial and sporadic forms of FTLD-U and ALS, which can be subsumed as TDP-43 proteinopathies. In order to get more insight into the role of abnormal phosphorylation in the disease process, the identification of specific phosphorylation sites and the generation of phosphorylation-specific antibodies are mandatory. Here, we developed and characterized novel rat monoclonal antibodies (1D3 and 7A9) raised against phosphorylated S409/410 of TDP-43. These antibodies were used to study the presence of S409/410 phosphorylation by immunohistochemistry and biochemical analysis in a large series of 64 FTLD-U cases with or without motor neuron disease including familial cases with mutations in progranulin (n = 5), valosin-containing protein (n = 4) and linkage to chromosome 9p (n = 4), 18 ALS cases as well as other neurodegenerative diseases with concomitant TDP-43 pathology (n = 5). Our data demonstrate that phosphorylation of S409/410 of TDP-43 is a highly consistent feature in pathologic inclusions in the whole spectrum of sporadic and familial forms of TDP-43 proteinopathies. Physiological nuclear TDP-43 was not detectable with these mAbs by immunohistochemistry and by immunoblot analyses. While the accumulation of phosphorylated C-terminal fragments was a robust finding in the cortical brain regions of FTLD-U and ALS, usually being much more abundant than the phosphorylated full-length TDP-43 band, spinal cord samples revealed a predominance of full-length TDP-43 over C-terminal fragments. This argues for a distinct TDP-43 species composition in inclusions in cortical versus spinal cord cells. Overall, these mAbs are powerful tools for the highly specific detection of disease-associated abnormal TDP-43 species and will be extremely useful for the neuropathological routine diagnostics of TDP-43 proteinopathies and for the investigation of emerging cellular and animal models for TDP-43 proteinopathies.

Relationships between biomarkers in aging and dementia.

Abstract: Background: PET imaging using [ 18 F]fluorodeoxyglucose (FDG) and [ 11 C]Pittsburgh compound B (PIB) have been proposed as biomarkers of Alzheimer disease (AD), as have CSF measures of the 42 amino acid β-amyloid protein (Aβ 1-42 ) and total and phosphorylated tau (t-tau and p-tau). Relationships between biomarkers and with disease severity are incompletely understood. Methods: Ten subjects with AD, 11 control subjects, and 34 subjects with mild cognitive impairment from the Alzheimer’s Disease Neuroimaging Initiative underwent clinical evaluation; CSF measurement of Aβ 1-42 , t-tau, and p-tau; and PIB-PET and FDG-PET scanning. Data were analyzed using continuous regression and dichotomous outcomes with subjects classified as “positive” or “negative” for AD based on cutoffs established in patients with AD and controls from other cohorts. Results: Dichotomous categorization showed substantial agreement between PIB-PET and CSF Aβ 1-42 measures (91% agreement, κ = 0.74), modest agreement between PIB-PET and p-tau (76% agreement, κ = 0.50), and minimal agreement for other comparisons (κ 1-42 . Regression models adjusted for diagnosis showed that PIB-PET was significantly correlated with Aβ 1-42 , t-tau, and p-tau 181p , whereas FDG-PET was correlated only with Aβ 1-42 . Conclusions: PET and CSF biomarkers of Aβ agree with one another but are not related to cognitive impairment. [ 18 F]fluorodeoxyglucose-PET is modestly related to other biomarkers but is better related to cognition. Different biomarkers for Alzheimer disease provide different information from one another that is likely to be complementary.

Advances in tau-focused drug discovery for Alzheimer's disease and related tauopathies

Abstract: Neuronal inclusions comprised of the microtubule-associated protein tau are found in numerous neurodegenerative diseases, commonly known as tauopathies. In Alzheimer's disease - the most prevalent tauopathy - misfolded tau is probably a key pathological agent. The recent failure of amyloid-beta-targeted therapeutics in Phase III clinical trials suggests that it is timely and prudent to consider alternative drug discovery strategies for Alzheimer's disease. Here, we focus on strategies directed at reducing misfolded tau and compensating for the loss of normal tau function.

Nomenclature for neuropathologic subtypes of frontotemporal lobar degeneration : consensus recommendations

Abstract: Nomenclature for neuropathologic subtypes of frontotemporal lobar degeneration : consensus recommendations

MRI and CSF biomarkers in normal, MCI, and AD subjects: predicting future clinical change.

Abstract: Objective: To investigate the relationship between baseline MRI and CSF biomarkers and subsequent change in continuous measures of cognitive and functional abilities in cognitively normal (CN) subjects and patients with amnestic mild cognitive impairment (aMCI) and Alzheimer disease (AD) and to examine the ability of these biomarkers to predict time to conversion from aMCI to AD. Methods: Data from the Alzheimer9s Disease Neuroimaging Initiative, which consists of CN, aMCI, and AD cohorts with both CSF and MRI, were used. Baseline CSF (t-tau, Aβ 1–42 , and p-tau 181P ) and MRI scans were obtained in 399 subjects (109 CN, 192 aMCI, 98 AD). Structural Abnormality Index (STAND) scores, which reflect the degree of AD-like features in MRI, were computed for each subject. Results: Change on continuous measures of cognitive and functional performance was modeled as average Clinical Dementia Rating–sum of boxes and Mini-Mental State Examination scores over a 2-year period. STAND was a better predictor of subsequent cognitive/functional change than CSF biomarkers. Single-predictor Cox proportional hazard models for time to conversion from aMCI to AD showed that STAND and log (t-tau/Aβ 1–42 ) were both predictive of future conversion. The age-adjusted hazard ratio for an interquartile change (95% confidence interval) of STAND was 2.6 (1.7, 4.2) and log (t-tau/Aβ 1–42 ) was 2.0 (1.1, 3.4). Both MRI and CSF provided information about future cognitive change even after adjusting for baseline cognitive performance. Conclusions: MRI and CSF provide complimentary predictive information about time to conversion from amnestic mild cognitive impairment to Alzheimer disease and combination of the 2 provides better prediction than either source alone. However, we found that MRI was a slightly better predictor of future clinical/functional decline than the CSF biomarkers tested.

Mutations in TDP-43 link glycine-rich domain functions to amyotrophic lateral sclerosis

Abstract: Amyotrophic lateral sclerosis (ALS) is the most common adult motor neuron disease that affects approximately 2/100,000 individuals each year worldwide. Patients with ALS suffer from rapidly progressive degeneration of motor neurons ultimately leading to death. The major pathological features observed in post-mortem tissue from patients with ALS are motor neuron loss, cortical spinal tract degeneration, gliosis and cytoplasmic neuronal inclusions formed by TDP-43 or TAR DNA binding Protein with a molecular mass of 43 kDa, which are now recognized as the signature lesions of sporadic ALS. TDP-43 possesses two RNA binding domains (RBD) and a glycine-rich C terminus classifying it with other heterogeneous nuclear ribonucleoproteins known as 2XRBD-Gly proteins. A number of reports showed that a subset of patients with ALS possess mutations in the TDP-43 (TARDBP) gene. This further strengthens the hypotheses that gain of toxic function or loss of function in TDP-43 causes ALS. Currently, 29 different TARDBP missense mutations have been reported in 51 unrelated sporadic or familial ALS cases and two cases of ALS plus concomitant frontotemporal lobar degeneration with a remarkable concentration of mutations in the C-terminal glycine-rich domain of TDP-43. As these mutations will most certainly be an invaluable tool for the design and implementation of ALS animal and cell models, as well as serve as a platform for exploring the pathobiology of TDP-43, here we summarize the identified pathogenic TARDBP mutations and their potential impact on our understanding of the role of TDP-43 in disease.

MRI and CSF biomarkers in normal, MCI, and AD subjects: Diagnostic discrimination and cognitive correlations

Abstract: Objective: To assess the correlations of both MRI and CSF biomarkers with clinical diagnosis and with cognitive performance in cognitively normal (CN) subjects and patients with amnestic mild cognitive impairment (aMCI) and Alzheimer disease (AD). Methods: This is a cross-sectional study with data from the Alzheimer9s Disease Neuroimaging Initiative, which consists of CN subjects, subjects with aMCI, and subjects with AD with both CSF and MRI. Baseline CSF (t-tau, Aβ 1-42 , and p-tau 181P ) and MRI scans were obtained in 399 subjects (109 CN, 192 aMCI, 98 AD). Structural Abnormality Index (STAND) scores, which reflect the degree of AD-like anatomic features on MRI, were computed for each subject. Results: We found no significant correlation between CSF biomarkers and cognitive scores in any of the 3 clinical groups individually. Conversely, STAND scores correlated with both Clinical Dementia Rating–sum of boxes and Mini-Mental State Examination in aMCI and AD ( p ≤ 0.01). While STAND and all CSF biomarkers were predictors of clinical group membership (CN, aMCI, or AD) univariately ( p Conclusions: CSF and MRI biomarkers independently contribute to intergroup diagnostic discrimination and the combination of CSF and MRI provides better prediction than either source of data alone. However, MRI provides greater power to effect cross-sectional groupwise discrimination and better correlation with general cognition and functional status cross-sectionally. We therefore conclude that although MRI and CSF provide complementary information, MRI reflects clinically defined disease stage better than the CSF biomarkers tested.

Clinical and Pathological Continuum of Multisystem TDP-43 Proteinopathies

Abstract: Objective: To determine the extent of transactivation response DNA-binding protein with a molecular weight of 43 kDa (TDP-43) pathology in the central nervous system of patients with clinically and autopsyconfirmed diagnoses of frontotemporal lobar degeneration with and without motor neuron disease and amyotrophic lateral sclerosis with and without cognitive impairment. Design: Performance of immunohistochemical whole– central nervous system scans for evidence of pathological TDP-43 and retrospective clinical medical record review.

A Lack of Amyloid β Plaques Despite Persistent Accumulation of Amyloid β in Axons of Long-Term Survivors of Traumatic Brain Injury

Abstract: Traumatic brain injury (TBI) is a risk factor for developing Alzheimer's disease (AD). Additionally, TBI induces AD-like amyloid β (Aβ) plaque pathology within days of injury potentially resulting from massive accumulation of amyloid precursor protein (APP) in damaged axons. Here, progression of Aβ accumulation was examined using brain tissue from 23 cases with post-TBI survival of up to 3 years. Even years after injury, widespread axonal pathology was consistently observed and was accompanied by intra-axonal co-accumulations of APP with its cleavage enzymes, beta-site APP cleaving enzyme and presenilin-1 and their product, Aβ. However, in marked contrast to the plaque pathology noted in short-term cases post TBI, virtually no Aβ plaques were found in long-term survivors. A potential mechanism for Aβ plaque regression was suggested by the post-injury accumulation of an Aβ degrading enzyme, neprilysin. These findings fail to support the premise that progressive plaque pathology after TBI ultimately results in AD.

Amyotrophic lateral sclerosis, frontotemporal dementia and beyond: the TDP-43 diseases

Abstract: Ever since the significance of pathological 43-kDa transactivating responsive sequence DNA-binding protein (TDP-43) for human disease has been recognized in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin positive inclusions (FTLD-U), a number of publications have emerged reporting on this pathology in a variety of neurodegenerative diseases. Given the heterogeneous and, in part, conflicting nature of the recent findings, we here review pathological TDP-43 and its relationship to human disease with a special focus on ALS and FTLD-U. To this end, we propose a classification scheme in which pathological TDP-43 is the major disease defining pathology in one group, or is present in addition to other neurodegenerative hallmark pathologies in a second category. We conclude that the TDP-43 proteinopathies represent a novel class of neurodegenerative disorders akin to α-synucleinopathies and tauopathies, with the concept of ALS and FTLD-U to be widened to a broad clinico-pathological multisystem disease, i.e., TDP-43 proteinopathy.

Inhibition of tau fibrillization by oleocanthal via reaction with the amino groups of tau

Abstract: Tau is a microtubule-associated protein that promotes microtubule assembly and stability. In Alzheimer's disease and related tauopathies, tau fibrillizes and aggregates into neurofibrillary tangles. Recently, oleocanthal isolated from extra virgin olive oil was found to display non-steroidal anti-inflammatory activity similar to ibuprofen. As our unpublished data indicates an inhibitory effect of oleocanthal on amyloid beta peptide fibrillization, we reasoned that it might inhibit tau fibrillization as well. Herein, we demonstrate that oleocanthal abrogates fibrillization of tau by locking tau into the naturally unfolded state. Using PHF6 consisting of the amino acid residues VQIVYK, a hexapeptide within the third repeat of tau that is essential for fibrillization, we show that oleocanthal forms an adduct with the lysine via initial Schiff base formation. Structure and function studies demonstrate that the two aldehyde groups of oleocanthal are required for the inhibitory activity. These two aldehyde groups show certain specificity when titrated with free lysine and oleocanthal does not significantly affect the normal function of tau. These findings provide a potential scheme for the development of novel therapies for neurodegenerative tauopathies.

Effect of apolipoprotein E on biomarkers of amyloid load and neuronal pathology in Alzheimer disease.

Abstract: Apolipoprotein E (APOE) e4 is the most important known genetic risk factor for typical late onset Alzheimer disease (AD). The lifetime risk of developing AD is increased and the age of onset of the disease is lowered with increasing number of APOE e4 alleles.1–4 Aβ1–42 and tau levels measured in cerebrospinal fluid (CSF) and atrophy seen on magnetic resonance imaging (MRI) are indicators of important disease-related pathological processes in AD. Low CSF Aβ1–42 reflects deposition of Aβ in plaques.5 High CSF t-tau levels reflect active axonal and neuronal damage.6 Atrophy seen on MRI is the direct result of loss of neurons, synapses, and dendritic arborization.7 In this paper, we use Structural Abnormality Index (STAND) scores as an indicator of severity of an AD-like pattern of atrophy on structural MRI. STAND scores were developed in our lab to condense the severity and location of AD-related atrophy on the 3-dimensional MRI scan into a single number.8 The effect of APOE genotype on neuronal pathology and amyloid load has been studied in autopsy specimens.9–13 Several in vivo CSF Aβ1–42 and t-tau studies,14–17 MRI studies,18–22 and fluorodeoxyglucose-positron emission tomography (PET) imaging studies23–25 have also studied the effect of APOE independently in each of these modalities. The first Alzheimer's Disease Neuroimaging Initiative (ADNI) CSF biomarker study also investigated the effect of APOE on CSF biomarkers, and found that Aβ1–42 concentration is lowest in subjects with 2 APOE e4 alleles and rises as the number of alleles decreases.26 However, there have not been in vivo studies that have investigated the influence of e4 allele on the surrogates of Aβ amyloid deposition and neuronal pathology together as measured by CSF and MRI in a cohort of subjects that spans the cognitive spectrum. The main aim of our paper was to evaluate the effect of APOE genotype on biomarkers of Aβ amyloid load and neuronal pathology by answering these questions: (1) How does APOE genotype effect CSF Aβ1–42 and t-tau levels and atrophy on MRI within each clinical group? (2) How does APOE genotype affect biomarker discrimination between different clinical groups (cognitively normal [CN], amnestic mild cognitive impairment [aMCI], AD)? (3) How much of the variability in the biomarkers is explained by clinical diagnosis versus APOE genotype? and (4) Does the relationship between continuous measures of cognitive performance and the biomarkers differ by APOE genotype?

Identification of aminothienopyridazine inhibitors of tau assembly by quantitative high-throughput screening.

Abstract: Inclusions comprised of fibrils of the microtubule- (MT-) associated protein tau are found in the brains of those with Alzheimer's disease (AD) and other neurodegenerative tauopathies. The pathology that is observed in these diseases is believed to result from the formation of toxic tau oligomers or fibrils and/or from the loss of normal tau function due to its sequestration into insoluble deposits. Hence, small molecules that prevent tau oligomerization and/or fibrillization might have therapeutic value. Indeed, examples of such compounds have been published, but nearly all have properties that render them unsuitable as drug candidates. For these reasons, we conducted quantitative high-throughput screening (qHTS) of approximately 292000 compounds to identify drug-like inhibitors of tau assembly. The fibrillization of a truncated tau fragment that contains four MT-binding domains was monitored in an assay that employed complementary thioflavin T fluorescence and fluorescence polarization methods. Previously described classes of inhibitors as well as new scaffolds were identified, including novel aminothienopyridazines (ATPZs). A number of ATPZ analogues were synthesized, and structure-activity relationships were defined. Further characterization of representative ATPZ compounds showed they do not interfere with tau-mediated MT assembly, and they are significantly more effective at preventing the fibrillization of tau than the Abeta(1-42) peptide which forms AD senile plaques. Thus, the ATPZ molecules described here represent a novel class of tau assembly inhibitors that merit further development for testing in animal models of AD-like tau pathology.

Survival Profiles of Patients With Frontotemporal Dementia and Motor Neuron Disease

Abstract: Background Frontotemporal dementia and amyotrophic lateral sclerosis are neurodegenerative diseases associated with TAR DNA-binding protein 43– and ubiquitin-immunoreactive pathologic lesions. Objective To determine whether survival is influenced by symptom of onset in patients with frontotemporal dementia and amyotrophic lateral sclerosis. Design, Setting, and Patients Retrospective review of patients with both cognitive impairment and motor neuron disease consecutively evaluated at 4 academic medical centers in 2 countries. Main Outcome Measures Clinical phenotypes and survival patterns of patients. Results A total of 87 patients were identified, including 60 who developed cognitive symptoms first, 19 who developed motor symptoms first, and 8 who had simultaneous onset of cognitive and motor symptoms. Among the 59 deceased patients, we identified 2 distinct subgroups of patients according to survival. Long-term survivors had cognitive onset and delayed emergence of motor symptoms after a long monosymptomatic phase and had significantly longer survival than the typical survivors (mean, 67.5 months vs 28.2 months, respectively; P P = .005). Conclusions Distinct patterns of survival profiles exist in patients with frontotemporal dementia and motor neuron disease, and overall survival may depend on the relative timing of the emergence of secondary symptoms.

Transactive response DNA-binding protein 43 burden in familial Alzheimer disease and Down syndrome.

Abstract: Transactive response DNA-binding protein 43 (TDP-43) is a nuclear ribonucleo-protein that plays a role in a variety of cellular functions including protein processing, particularly, modulating transcription and exon splicing.1 It is also a major pathological hallmark of ubiquitinated inclusions in amyotrophic lateral sclerosis and forms of frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U,2,3 more recently abbreviated FTLD-TDP by Mackenzie et al4). In these conditions, both sporadic and familial cases show abnormal accumulation of hyper-phosphorylated, ubiquitinated, and truncated TDP-43 fragments.2,3 Recently, we developed phosphorylation-specific TDP-43 monoclonal antibodies that recognize only pathological TDP-43, to study the altered phosphorylation patterns of abnormal TDP-43 in amyotrophic lateral sclerosis, FTLD-TDP, and other neurode-generative diseases.5 These and other studies with previously reported anti–TDP-43 antibodies have shown that phosphorylation of S409/410 in TDP-43 is detected in neuronal and glial inclusions of a variety of central nervous system (CNS)–degenerative diseases including Alzheimer disease (AD) as well as in other older individuals with cognitive impairment.5–8 There is also an association between cognitive status and the intensity of TDP-43 pathology in subjects with age-related cognitive impairment.7 Interestingly, in the Nelson et al study,7 there was no association between cognitive status and other pathology, including AD neuropathological features such as amyloid plaque or neurofibrillary tangle burden. Together, these data raise the possibility that TDP-43 plays a significant role in the pathogenic mechanisms underlying cognitive impairment in AD and other age-related brain disorders. Alzheimer disease is the most common neurodegenerative disease affecting cognition, found in increasing numbers in our elderly population. However, only limited study has been performed to investigate TDP-43 pathology and AD.5–7,9 Caspase-cleaved TDP-43 has been variably described in Hirano bodies, neurofibrillary tangles, reactive glia, and dystrophic plaque-associated neurites,10 but further studies are needed to confirm these findings. Taken together, these studies support the notion that TDP-43 may contribute to the pathobiology of AD. However, no studies have been done to look at the presence of TDP-43 inclusions in genetic forms of AD such as familial AD (FAD) and Down syndrome (DS) to determine whether participants with genetic etiologies have similar TDP-43 pathologies. Hence, the current study was undertaken to assess the presence of TDP-43 immunopathology in a series of well-characterized participants with FAD and DS to determine whether this pathobiological feature differs from that of sporadic forms of AD or other types of CNS degeneration.

A roadmap for the prevention of dementia II. Leon Thal Symposium 2008

Abstract: This document proposes an array of recommendations for a National Plan of Action to accelerate the discovery and development of therapies to delay or prevent the onset of disabling symptoms of Alzheimer's disease. A number of key scientific and public-policy needs identified in this document will be incorporated by the Alzheimer Study Group into a broader National Alzheimer's Strategic Plan, which will be presented to the 111th Congress and the Obama administration in March 2009. The Alzheimer's Strategic Plan is expected to include additional recommendations for governance, family support, healthcare, and delivery of social services.

Early marker for Alzheimer's disease: Hippocampus T1rho (T1ρ) estimation

Abstract: Alzheimer’s disease (AD) is the most common form of neurodegenerative disorder in elderly and results in progressive memory loss and cognitive decline. The appearance of senile plaques and neurofibrillary tangles are the neuropathological hallmarks of AD (1). Autopsy studies have shown the hippocampus to be affected by AD pathology early in the disease process, with ≈20%–50% loss of neurons by the time individuals are moderately affected (2,3). As a result, imaging studies have focused on this region in order to detect the early changes during the disease progression. Currently the diagnosis of clinically probable AD can be confirmed only once the stage of dementia has been reached. Neuropsychological tests are necessary to recognize and monitor the subjects at risk. However, to date there is no accurate cognitive marker to identify AD in the early disease process. Moreover, cognitive performances depend not only on age and education but also on mood and attention at the time of testing, and thus lack wide generalizability. Quantitative analysis of tau protein and amyloid-Aβ in the cerebrospinal fluid (CSF) has shown some diagnostic value in probable AD (4,5), but the procedure is totally invasive and has thus received only little attention so far in diagnosing AD. An accurate diagnosis of AD in the early symptomatic stage is extremely challenging despite the development of useful clinical constructs like mild cognitive impairment (MCI), which enables the identification of individuals who may be in an early clinical phase of AD. MCI was previously defined as a transitional state that can precede dementia, but the condition and the rates of conversion remain controversial. Despite many consensus conferences, experts cannot agree on critical aspects of MCI, particularly with respect to its clinical utility. Based on neuropsychological studies, a hippocampal memory profile has been proposed for MCI as prodromal AD (6). In light of current drug development aimed at slowing AD progression, diagnosing AD at its prodromal stage is particularly important. Recently, research has begun to focus on developing new tools, such as neuroimaging and CSF biomarkers, that could increase the specificity of the prodromal AD diagnosis. The goal of research in this area is therefore to develop highly specific and sensitive methods capable of identifying the subjects in the early stage who progress to AD. Neuroimaging markers provide an alternative and objective assessment of progression of AD. Out of various imaging techniques MRI is the most widely accepted technique to diagnose the various pathological conditions, and to monitor the treatment response, based on the changes in T2 and T1 contrast relaxation properties. It has been shown that the T2 value was not significantly different between normal subjects and AD patients (7). In one recent study, Yuan et al (8) have shown that fluorodeoxyglucose positron emission tomography (FDG-PET) performs slightly better than single photon emission tomography (SPECT) and structural imaging in prediction of conversion to AD in patients with MCI. However, the wide clinical utility of the PET technique is hampered by its poor resolution and necessity of a cyclotron at the imaging center that can produce the radioactive tracers. Other MR techniques like diffusion tensor imaging (DTI) and proton spectroscopy (1HMRS) have also been used in detection of normal white matter changes in patients with AD (9, 10). Ukmar et al (9) have shown a significant difference in fractional anisotropy (FA) between control and AD, while the FA was not significantly different in AD compare to MCI. Similarly, in a 1HMRS study it has been shown that the hippocampal metabolite profile in MCI is similar to AD (10). An alternative contrast mechanism is T1rho (T1ρ), the spin lattice relaxation time constant in the rotating frame, which determines the decay of the transverse magnetization in the presence of a “spin-lock” radiofrequency field (11). In biological tissue, exchange between protons in different environments is expected to contribute T1ρ relaxation. The molecular process that occurs in the milliseconds range influences the T1ρ relaxation time constant. T1ρ MRI has been previously used to measure T1ρ relaxation time in normal human brain and showed the higher range of values compared to T2 (11). Earlier, T1ρ has been used to delineate brain tumors, characterize breast cancer tissue, and monitor the level of cartilage degeneration (12–14). The current study was performed with an aim to measure the baseline T1ρ in hippocampus in the brain of AD (n = 49), MCI (n = 48), and control (n = 31) cohorts and to determine whether the T1ρ value shows any significant difference between these cohorts.

Amyotrophic lateral sclerosis-plus syndrome with TAR DNA-binding protein-43 pathology.

Abstract: Background Amyotrophic lateral sclerosis (ALS)–Plus syndromes meet clinical criteria for ALS but also include 1 or more additional features such as dementia, geographic clustering, extrapyramidal signs, objective sensory loss, autonomic dysfunction, cerebellar degeneration, or ocular motility disturbance. Methods We performed a whole-brain and spinal cord pathologic analysis in a patient with an ALS-Plus syndrome that included repetitive behaviors along with extrapyramidal and supranuclear ocular motility disturbances resembling the clinical phenotype of progressive supranuclear palsy. Results There was motoneuron cell loss and degeneration of the corticospinal tracts. Bunina bodies were present. TAR DNA-binding protein-43 pathology was diffuse. Significant tau pathology was absent. Conclusions TAR DNA-binding protein-43 disorders can produce a clinical spectrum of neurodegeneration that includes ALS, frontotemporal lobar degeneration, and ALS with frontotemporal lobar degeneration. The present case illustrates that isolated TAR DNA-binding protein-43 disorders can produce an ALS-Plus syndrome with extrapyramidal features and supranuclear gaze palsy resembling progressive supranuclear palsy.

FGF20 and Parkinson's disease: No evidence of association or pathogenicity via α-synuclein expression

Abstract: Genetic variation in fibroblast growth factor 20 (FGF20) has been associated with risk of Parkinson's disease (PD). Functional evidence suggested the T allele of one SNP, rs12720208 C/T, altered PD risk by increasing FGF20 and α-synuclein protein levels. Herein we report our association study of FGF20 and PD risk in four patient-control series (total: 1,262 patients and 1,881 controls), and measurements of FGF20 and α-synuclein protein levels in brain samples (nine patients). We found no evidence of association between FGF20 variability and PD risk, and no relationship between the rs12720208 genotype, FGF20 and α-synuclein protein levels.

Use of Alzheimer disease biomarkers: potentially yes for clinical trials but not yet for clinical practice.

Abstract: Research in Alzheimer disease (AD) is rapidly moving toward the point of the earliest identification of the underlying disease processes. These include the accumulation of AB plaques, tau tangles and neuron as well as synaptic loss, and it is likely that these do not all occur contemporaneously. Many investigators contend that, by the time the clinical symptoms appear, sufficient AD pathology and neurodegeneration have occurred, which if irreversible, may reduce the efficacy of disease modifying therapy for clinically manifest AD.1 As such, efforts are underway to try to identify the onset of these pathological processes that culminate in clinically manifest AD dementia. However, to accomplish this, the underlying pathology must be detected, possibly through the use of neuroimaging and chemical biomarker measures. In this issue of JAMA, Mattsson and colleagues2 report their evaluation of the utility of cerebrospinal fluid (CSF) markers for AD in a large multicenter study. The investigators from the Swedish Brainpower CSF Initiative enrolled individuals with mild cognitive impairment (MCI) from 12 centers in Europe as well as healthy individuals as controls and those with mild AD for comparison. They identified 750 individuals as having MCI and followed them for at least two years to determine whether the CSF profile at baseline of Aβ42, total tau (T-tau), and phosphorylated tau (P-tau) predicted the ultimate clinical course. They found that CSF Aβ42, T-tau, and P-tau could be used to predict outcomes and thus suggest that these markers may be useful in identifying patients for clinical trials and possibly screening tests in memory clinics. This group of investigators has been studying these issues for several years, and their study represents a tour de force of clinical and laboratory data collections. However, their study also represents several key challenges that need to be addressed before CSF markers are ready for broad clinical applications, although these markers already are being used in clinical trials of disease-modifying therapies for AD. Mild Cognitive Impairment is a heterogeneous condition, and based on the underlying conceptual nature of the condition, this is to be expected.3–4 International consensus meetings have characterized the construct by subtypes into amnestic and non amnestic MCI5–6 in an attempt to explain some of the heterogeneity. Amnestic MCI of a presumed degenerative etiology is generally considered to be the forerunner of clinical AD, and Mattsson et al2 have diagnosed MCI with that presumption. However, the investigators combined clinical data from 12 different memory disorders centers, using different instruments and likely different implementation of the criteria and consequently may have assembled a group of individuals with significant clinical variability. As such, while they present the Mini-Mental State Examination scores and demographic data, without the presentation of the other clinical data a precise comparison of the individuals from the different centers is difficult. The investigators describe that they enrolled a consecutive series of individuals presenting to memory centers with symptoms leading to the diagnoses of MCI or AD. Despite this variability, the investigators reported an annual rate of progression to AD of 11% which is typical for referral center cohorts.7 Similarly, there was likely considerable variability with respect to the CSF collection and assays, and the authors clearly acknowledge that their CSF assays require further standardization. The coefficients of a variation from other sites were discrepant from the primary site, and a formula was used to “correct” these data. This may have made the results comparable in a statistical sense from the various sites; however, it is also likely that the significant variability in the laboratory data could have compounded the problems with the clinical variability. The investigators in this report are accomplished in AD biomarker research and aware of the hurdles that need to be surmounted to bring an AD biomarker from the initial discovery stage to a validated test for AD diagnosis.8 Despite these potential sources of variability, the study documented the utility of CSF biomarkers to predict, with good accuracy, the outcome of individuals with MCI. Moreover, with further mining of their data, Mattsson et al may improve on their CSF biomarker algorithm. Shaw et al9 recently reported that APOE genotype contributed incrementally to test accuracy when combined with measures of CSF Aβ and tau. Thus, the study by Mattsson et al is an important contribution toward the goal of developing disease-modifying therapies based on the use of biomarkers and clinical measures. Despite the considerable clinical and laboratory variability, the results appear plausible and enticing. As the authors indicate, this multicenter study replicated the results of smaller single-center studies, with the caveat that some of the prior study samples were included in this study. The data likely reflect the underlying pathological processes of AD in some individuals with MCI; however, it is premature to recommend application of these techniques in clinical practice. The inherent clinical and laboratory variability precludes the adoption of these measures at this time. Significant refinement of the assay procedures is necessary before these techniques can be recommended for general clinical use along the lines described in previous publications.8–9 An effort in this direction is now underway in North America known as Alzheimer Disease Neuroimaging Initiative (ADNI)9–10 and is complemented by similar studies in Europe, Japan and Australia. This study represents 57 centers in the United States and Canada and was designed to evaluate the utility of neuroimaging and clinical biomarkers in characterizing the course of amnestic MCI with the intention of predicting clinical AD before the full criteria for dementia are met. A major focus of this study also involves reducing variability in the clinical, neuroimaging and laboratory procedures, including refining the clinical criteria for amnestic MCI (it is noteworthy that the clinical cohort recruited in ADNI has identical clinical features and rates of progression to AD as seen in an earlier clinical trial on amnestic MCI11); standardizing neuroimaging procedures for magnetic resonance imaging, fluorodeoxyglucose positron emission tomography (PET), and PiB (Pittsburgh Compound B) PET; and centralizing the laboratory analysis of CSF biomarkers to ensure consistency and reliability. The biomarker data will be integrated with imaging and clinical data with the goal of identifying the optimal panel to use for predictive testing for AD, AD diagnosis, and clinical trial monitoring. Of critical importance, however, is what the clinician and patient will do with such results. The sensitivity and specificity of Aβ42, T-tau, and P-tau in the study by Mattsson et al were sufficient to be used for screening but not as a diagnostic test. Alzheimer disease has no treatment to prevent or alter the course of the disease, so making the diagnosis with good accuracy may aid in planning but also could be devastating news for some patients and families. Furthermore, false positives and false negatives occur as with any screening test. However, as biomarkers become more sophisticated, they are likely to take on an increasingly important role in the diagnosis and management of AD. The study by Mattsson et al2 represents a major step forward in suggesting that biomarkers may have sufficient accuracy to be used in the AD prodromal phase. The report highlights the challenges but also suggests solutions. Subsequent prospective investigations should clarify the true utility of these measures.

A case study of an emerging visual artist with frontotemporal lobar degeneration and amyotrophic lateral sclerosis.

Abstract: Patients presenting with left-sided FTLD syndromes sometimes develop a new preoccupation with art, greater attention to visual stimuli, and increased visual creativity. We describe the case of a 53-year-old, right-handed man with a history of bipolar disorder who presented with language and behavior impairments characteristic of FTLD, then developed motor symptoms consistent with a second diagnosis of amyotrophic lateral sclerosis. Though the patient had never created visual art before, he developed a compulsion for painting beginning at the earliest stages of his disease, and continued producing art daily until he could no longer lift a paintbrush because of his motor deficits. Upon autopsy, he was found to have ubiquitin and TDP43-positive inclusions with MND pathology. This case study details the patient's longitudinal neuropsychological, emotional, behavioral, and motor symptoms, along with structural imaging, neurologic, and neuropathologic findings. Multiple examples of the patient's art are depicted throughout all stages of his illness, and the possible cognitive, behavioral, and neurologic correlates of his new-onset visual artistry are discussed.

Effects of gamma-secretase inhibition on the amyloid beta isoform pattern in a mouse model of Alzheimer's disease.

Abstract: Background:Accumulation of amyloid β (Aβ) in the brain is believed to represent one of the earliest events in the Alzheimer disease process. Aβ is generated from amyloid precursor protein after sequential cleavage by β- and γ-secretase. Alternatively, α-secretase cleaves within the Aβ sequence, thus, precluding the formation of Aβ. A lot of research has focused on Aβ production, while less is known about the non-amyloidogenic pathway. We have previously shown that Aβ is present in human cerebrospinal fluid (CSF) as several shorter C-terminal truncated isoforms (e.g. Aβ1–15 and Aβ1–16), and that the levels of these shorter isoforms are elevated in media from cells that have been treated with γ-secretase inhibitors. Objective:To explore the effect of N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT), a γ-secretase-inhibitor, treatment on the Aβ isoform pattern in brain tissue and CSF from Tg2576 mice. Methods: Immunoprecipitation using the anti-Aβ antibodies 6E10 and 4G8 was combined with either matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or nanoflow liquid chromatography and tandem mass spectrometry. Results: All fragments longer than and including Aβ1–17 displayed a tendency towards decreased levels upon γ-secretase inhibition, whereas Aβ1–15 and Aβ1–16 indicated slightly elevated levels during treatment. Conclusion: These data suggest that Aβ1–15 and Aβ1–16 may be generated through a third metabolic pathway independent of γ-secretase, and that these Aβ isoforms may serve as biomarkers for secretase inhibitor treatment.

Detection of neurodegenerative disease

Abstract: Provided are methods of assessing the absence or presence of a neurodegenerative disease in a subject comprising characterizing TDP-43 in a tissue sample of the subject. Also disclosed are methods for diagnosing a neurodegenerative disease in a subject, and methods for determining the efficacy of a drug against a neurodegenerative disease. Novel antibodies that bind to TDP-43 are also provided.