The neuropathological examination is considered to provide the gold standard for Alzheimer disease (AD). To determine the accuracy of currently employed clinical diagnostic methods, clinical and neuropathological data from the National Alzheimer's Coordinating Center (NACC), which gathers information from the network of National Institute on Aging (NIA)-sponsored Alzheimer's Disease Centers (ADCs), were collected as part of the NACC Uniform Data Set (UDS) between 2005 and 2010. A database search initially included all 1198 subjects with at least one UDS clinical assessment and who had died and been autopsied; 279 were excluded as being not demented or because critical data fields were missing. The final subject number was 919. Sensitivity and specificity were determined based on “probable” and “possible” AD levels of clinical confidence and 4 levels of neuropathological confidence based on varying neuritic plaque densities and Braak neurofibrillary stages. Sensitivity ranged from 70.9% to 87.3%; specificity ranged from 44.3% to 70.8%. Sensitivity was generally increased with more permissive clinical criteria and specificity was increased with more restrictive criteria, whereas the opposite was true for neuropathological criteria. When a clinical diagnosis was not confirmed by minimum levels of AD histopathology, the most frequent primary neuropathological diagnoses were tangle-only dementia or argyrophilic grain disease, frontotemporal lobar degeneration, cerebrovascular disease, Lewy body disease and hippocampal sclerosis. When dementia was not clinically diagnosed as AD, 39% of these cases met or exceeded minimum threshold levels of AD histopathology. Neurologists of the NIA-ADCs had higher predictive accuracy when they diagnosed AD in demented subjects than when they diagnosed dementing diseases other than AD. The misdiagnosis rate should be considered when estimating subject numbers for AD studies, including clinical trials and epidemiological studies.
Alzheimer disease; Autopsy; Clinical trials; Diagnosis; Histopathology; Neuropathology; Non-Alzheimer dementia
Alzheimer’s disease (AD) dementia impacts all facets of higher order cognitive function and is characterized by the presence of distinctive pathological lesions in the gray matter (GM). The profound alterations in GM structure and function have fostered the view that AD impacts are primarily a consequence of GM damage. However, the white matter (WM) represents about 50% of the cerebrum and this area of the brain is substantially atrophied and profoundly abnormal in both sporadic AD (SAD) and familial AD (FAD). We examined the WM biochemistry by ELISA and Western blot analyses of key proteins in 10 FAD cases harboring mutations in the presenilin genes PSEN1 and PSEN2 as well as in 4 non-demented control (NDC) individuals and 4 subjects with SAD. The molecules examined were direct substrates of PSEN1 such as Notch-1 and amyloid precursor protein (APP). In addition, apolipoproteins, axonal transport molecules, cytoskeletal and structural proteins, neurotrophic factors and synaptic proteins were examined. PSEN-FAD subjects had, on average, higher amounts of WM amyloid-beta (Aβ) peptides compared to SAD, which may play a role in the devastating dysfunction of the brain. However, the PSEN-FAD mutations we examined did not produce uniform increases in the relative proportions of Aβ42 and exhibited substantial variability in total Aβ levels. These observations suggest that neurodegeneration and dementia do not depend solely on enhanced Aβ42 levels. Our data revealed additional complexities in PSEN-FAD individuals. Some direct substrates of γ-secretase, such as Notch, N-cadherin, Erb-B4 and APP, deviated substantially from the NDC group baseline for some, but not all, mutation types. Proteins that were not direct γ-secretase substrates, but play key structural and functional roles in the WM, likewise exhibited varied concentrations in the distinct PSEN mutation backgrounds. Detailing the diverse biochemical pathology spectrum of PSEN mutations may offer valuable insights into dementia progression and the design of effective therapeutic interventions for both SAD and FAD.
Sporadic Alzheimer’s disease; familial Alzheimer’s disease; presenilin; γ-secretase; white matter; gray matter; amyloid precursor protein; amyloid-beta
Amyloid imaging may revolutionize Alzheimer’s disease (AD) research and clinical practice but is critically limited by an inadequate correlation between cerebral cortex amyloid plaques and dementia. Also, amyloid imaging does not indicate the extent of neurofibrillary tangle (NFT) spread throughout the brain. Currently, the presence of dementia as well as a minimal brain load of both plaques and NFTs is required for the diagnosis of AD. Autopsy studies suggest that striatal amyloid plaques may be mainly restricted to subjects in higher Braak NFT stages that meet clinicopathological diagnostic criteria for AD. Striatal plaques, which are readily identified by amyloid imaging, might therefore be used to predict the presence of a higher Braak NFT stage and clinicopathological AD in living subjects. This study determined the sensitivity and specificity of striatal plaques for predicting a higher Braak NFT stage and clinicopathological AD in a postmortem series of 211 elderly subjects. Subjects included 87 clinicopathologically classified as non-demented elderly controls and 124 with AD. A higher striatal plaque density score (moderate or frequent) had 95.8% sensitivity, 75.7% specificity for Braak NFT stage V or VI and 85.6% sensitivity, 86.2% specificity for the presence of dementia and clinicopathological AD (National Institute on Aging – Reagan Institute “intermediate” or “high”). Amyloid imaging of the striatum may be useful as a predictor, in living subjects, of Braak NFT stage and the presence or absence of dementia and clinicopathological AD. Validation of this hypothesis will require autopsy studies of subjects that had amyloid imaging during life.
Alzheimer’s disease; amyloid imaging; striatum; amyloid plaques; diagnosis; therapy; asymptomatic; preclinical; autopsy
Parkinson's disease (PD) afflicts approximately 1-2% of the population over 50 years of age. No cures or effective modifying treatments exist and clinical diagnosis is currently confounded by a lack of definitive biomarkers. We sought to discover potential biomarkers in the cerebrospinal fluid (CSF) of neuropathologically confirmed PD cases.
We compared postmortem ventricular CSF (V-CSF) from PD and normal control (NC) subjects using two-dimensional difference gel electrophoresis (2D-DIGE). Spots exhibiting a 1.5-fold or greater difference in volume between PD patients and controls were excised from the 2D gels, subjected to tryptic digestion and identification of peptides assigned using mass spectrometric/data bank correlation methods.
Employing this strategy six molecules: fibrinogen, transthyretin, apolipoprotein E, clusterin, apolipoprotein A-1 and glutathione-S-transferase-Pi were found to be different between PD and NC populations.
These molecules have been implicated in PD pathogenesis. Combining biomarker data from multiple laboratories may create a consensus panel of proteins that may serve as a diagnostic tool for this neurodegenerative disorder.
2D-DIGE; cerebrospinal fluid; Parkinson's disease; proteomics
Missense mutations in LRRK2 (leucine-rich repeat kinase 2) are a major cause of PD (Parkinson's disease). Several antibodies against LRRK2 have been developed, but results using these polyclonal antibodies have varied widely leading to conflicting conclusions. To address this challenge, the Michael J. Fox Foundation for Parkinson's Research generated a number of monoclonal antibodies targeting epitopes across the LRRK2 protein. In the present paper, we report optimized protocols and results for ten monoclonal antibodies for immunoblotting, immunohistochemistry, immunoprecipitation and kinase activity assays, in rat, mouse and human brain tissue. Several efficacious antibodies were identified, but results demonstrate that the mouse monoclonal N241A/34 is suitable for most applications, with the best overall rabbit monoclonal antibody being c41-2. These antibodies produced a dominant band of the expected size via immunoblotting and a lack of labelling in tissue derived from LRRK2-knockout animals under optimized conditions. A significant proportion of LRRK2 protein localizes to insoluble fractions and no evidence of truncated LRRK2 protein was detected in any fraction from rodent or human tissues. An assay was developed for the robust detection of LRRK2 kinase activity directly from frozen mouse and human brain tissue, but precipitous declines in activity were observed that corresponded to increasing post-mortem intervals and processing times. Finally, we demonstrate the highest levels of brain-localized LRRK2 in the striatum, but note differential expression patterns between rat and mouse in both striatum and cortex. Anti-LRRK2 monoclonal antibodies that are unlimited in availability together with the proposed standardized protocols should aid in the definition of LRRK2 function in both health and disease.
immunohistochemistry; kinase assay; leucine-rich repeat kinase 2 (LRRK2); Parkinson’s disease; DAB, 3,3′-diaminobenzidine; DMEM, Dulbecco’s modified Eagle’s medium; eGFP, enhanced green fluorescent protein; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HEK, human embryonic kidney; KO, knockout; LRRK2, leucine-rich repeat kinase 2; MEF, mouse embryonic fibroblast; MJFF, Michael J. Fox Foundation for Parkinson’s Research; PD, Parkinson’s disease; PEI, polyethyleneimine; PFA, paraformaldehyde; UTSW, University of Texas Southwestern; VDAC, voltage-dependent anion channel; WT, wild-type
Dysphagia (impaired swallowing) is common in Parkinson disease (PD) patients and is related to aspiration pneumonia, the primary cause of death in PD. Therapies that ameliorate the limb motor symptoms of PD are ineffective for dysphagia. This suggests that the pathophysiology of PD dysphagia may differ from that affecting limb muscles but little is known about potential neuromuscular abnormalities in the swallowing muscles in PD. This study examined the fiber histochemistry of pharyngeal constrictor (PC) and cricopharyngeal (CP) sphincter muscles in postmortem specimens from 8 PD and 4 age-matched control patients. Pharyngeal muscles in PD patients exhibited many atrophic fibers, fiber type grouping, and fast-to-slow myosin heavy chain transformation. These alterations indicate that the pharyngeal muscles experienced neural degeneration and regeneration over the course of PD. Notably, the PD patients with dysphagia had a higher percentage of atrophic myofibers vs. with those without dysphagia and controls. The fast-to-slow fiber type transition is consistent with abnormalities in swallowing, slow movement of food and increased tone in the CP sphincter in PD patients. The alterations in the pharyngeal muscles may play a pathogenic role in the development of dysphagia in PD patients.
Dysphagia; Fiber types; Immunohistochemistry; Muscle fiber atrophy; Myosin heavy chain isoforms; Parkinson disease; Pharyngeal constrictor muscles; Swallowing; Upper esophageal sphincter
To compare autonomic function of subjects with Parkinson’s disease (PD) and essential tremor (ET) relative to controls.
It has been reported that patients with PD have autonomic dysfunction while no literature exists regarding autonomic function in ET.
Subjects with PD, ET, and controls had autonomic function measured using the SCOPA-Autonomic questionnaire, with the total and domain scores transformed to a scale of 0–100 points.
62 subjects with PD, 84 with ET, and 291 controls were included. Women were more prevalent in control (69%) compared to PD (44%) and ET (44%) groups, and mean age was significantly younger in PD (73 yrs) and older in ET (83) compared to controls (81). The mean SCOPA-Aut Total score in PD was significantly higher than controls, with no difference in ET. No autonomic dysfunction was found in any domain in ET but in PD there were significant abnormalities in gastrointestinal, cardiovascular, urinary, and thermoregulatory domains. Individual question data revealed a significantly higher percentage of subjects with dysfunction on 11/23 questions in the PD group but only 1 question (sialorrhea) in the ET group compared with controls.
Autonomic scores, particularly gastrointestinal, cardiovascular, urinary, and thermoregulatory were increased in patients with PD, as assessed by SCOPA-Aut. Patients with ET did not exhibit autonomic dysfunction, with the exception of sialorrhea.
Autonomic dysfunction; Parkinson’s disease; Essential tremor
Identifying biomarkers that distinguish Parkinson’s disease (PD) from normal control (NC) individuals has the potential to increase diagnostic sensitivity for the detection of early-stage PD. A previous proteomic study identified potential biomarkers in postmortem ventricular cerebrospinal fluid (V-CSF) from neuropathologically diagnosed PD subjects lacking Alzheimer’s disease (AD) neuropathology. In the present study, we assessed these biomarkers as well as p-tau181, Aβ42, and S100B by ELISA in PD (n = 43) and NC (n = 49) cases. The p-tau181/Aβ42 ratio and ApoA-1 showed statistically significant differences between groups. Multiple regression analysis demonstrated that p-tau181/Aβ42 had a significant odds ratio: OR = 1.42 (95% confidence interval [CI], 1.12–1.84), P = 0.006. Among the molecules investigated, intriguing correlations were observed that require further investigation. Our results suggest coexistent AD CSF biomarkers within the PD group notwithstanding that it was selected to minimize AD neuropathological lesions.
Parkinson’s disease; biomarkers; ventricular cerebrospinal fluid; apolipoprotein A-1; p-tau181/Aβ42 ratio
The pathology of essential tremor is increasingly being studied; however, there are limited studies of biochemical changes in this condition.
We studied several candidate biochemical/anatomical systems in the brainstem, striatum and cerebellum of 23 essential tremor subjects who came to autopsy, comparing them to a control population.
Striatal tyrosine hydroxylase, a marker of dopaminergic neurons, was 91.7 ±113.2 ng/mg versus 96.4±102.7 ng/mg (not significant) in cases and controls. Locus ceruleus dopamine beta-hydroxylase, a marker of noradrenergic neurons, was not significantly different between essential tremor and control groups. Parvalbumin, a marker of GABAergic neurons, was 199.3±42.0 versus 251.4±74.8 ng/mg (p=0.025) in the pons in the region of the locus ceruleus of essential tremor versus controls, while there was no difference in cerebellar parvalbumin.
These results are supportive of a possible role for reduced GABAergic function within the locus ceruleus in essential tremor. The hypothesis that essential tremor represents early Parkinson’s disease was not supported as striatal dopaminergic markers were not reduced compared to control subjects.
tremor; pathology; GABA; norepinephrine
The current consensus criteria for the neuropathologic diagnosis of Alzheimer’s disease (AD), known as the National Institute on Aging/Reagan Institute of the Alzheimer Association Consensus Recommendations for the Postmortem Diagnosis of AD or NIA-Reagan Criteria , were published in 1997 (hereafter referred to as “1997 Criteria”). Knowledge of AD and the tools used for clinical investigation of cognitive impairment and dementia have advanced substantially since then and have prompted this update on the neuropathologic assessment of AD.
We present a practical guide for the implementation of recently revised National Institute on Aging-Alzheimer’s Association guidelines for the neuropathologic assessment of Alzheimer’s disease (AD). Major revisions from previous consensus criteria are: (i) recognition that AD neuropathologic changes may occur in the apparent absence of cognitive impairment, (ii) an “ABC” score for AD neuropathologic change that incorporates histopathologic assessments of amyloid β deposits (A), staging of neurofibrillary tangles (B), and scoring of neuritic plaques (C), and (iii) more detailed approaches for assessing commonly co-morbid conditions such as Lewy body disease, vascular brain injury, hippocampal sclerosis, and TAR DNA binding protein (TDP)-43 immunoreactive inclusions. Recommendations also are made for the minimum sampling of brain, preferred staining methods with acceptable alternatives, reporting of results, and clinico-pathologic correlations.
Florbetapir F 18 (18F-AV-45) is a positron emission tomography (PET) imaging ligand for the detection of amyloid aggregation associated with Alzheimer’s disease. Earlier data showed that florbetapir F 18 binds with high affinity to β-amyloid plaques in human brain homogenates (Kd = 3.7 nM) and has favorable imaging pharmacokinetic properties, including rapid brain penetration and washout. The present study used human autopsy brain tissue to evaluate the correlation between in vitro florbetapir F 18 binding and β-amyloid density measured by established neuropathological methods.
The localization and density of florbetapir F 18 binding in frozen and formalin-fixed paraffin-embedded sections of postmortem brain tissue from 40 subjects with a varying degree of neurodegenerative pathology was assessed by standard florbetapir F 18 autoradiography and correlated with the localization and density of β-amyloid identified by silver staining, thioflavin S staining, and immunohistochemistry.
There were strong quantitative correlations between florbetapir F 18 tissue binding and both β-amyloid plaques identified by light microscopy (sliver staining and thioflavin S fluorescence) and by immunohistochemical measurements of β-amyloid using three antibodies recognizing different epitopes of the β-amyloid peptide (Aβ). Florbetapir F 18 did not bind to neurofibrillary tangles.
Florbetapir F 18 selectively binds β-amyloid in human brain tissue. The binding intensity was quantitatively correlated with the density of β-amyloid plaques identified by standard neuropathological techniques and correlated with the density of Aβ measured by immunohistochemistry. Since β-amyloid plaques are a defining neuropathological feature for Alzheimer’s disease, these results support the use of florbetapir F 18 as an amyloid PET ligand to identify the presence of AD pathology in patients with signs and symptoms of progressive late-life cognitive impairment.
PET imaging; Alzheimer’s disease; β-amyloid plaque; autoradiography; β-amyloid; amyloid PET imaging; florbetapir F 18; 18F-AV-45; postmortem
Dementia is a frequent complication of Parkinson’s disease (PD). About half of PD dementia (PDD) is hypothesized to be due to progression of the underlying Lewy body pathology into limbic regions and the cerebral cortex while the other half is thought to be due to coexistent Alzheimer’s disease. Clinically, however, these are indistinguishable. The spread of amyloid plaques to the striatum has been reported to be a sensitive and specific indicator of dementia due to Alzheimer’s disease (AD). The purpose of the present study was to determine if the presence of striatal plaques might also be a useful indicator of the presence of diagnostic levels of AD pathology within PD subjects. We analyzed neuropathologically-confirmed cases of PD without dementia (PDND, N = 31), PDD without AD (PDD, N = 31) and PD with dementia meeting clinicopathological criteria for AD (PDAD, N =40). The minimum diagnostic criterion for AD was defined as including a clinical history of dementia, moderate or frequent CERAD cortical neuritic plaque density and Braak neurofibrillary stage III–VI. Striatal amyloid plaque densities were determined using Campbell-Switzer and Thioflavine S stains. Striatal plaque densities were significantly higher in PDAD compared to PDD (p<0.001). The presence of striatal plaques was approximately 80% sensitive and 80% specific for predicting AD. In comparison, the presence of cerebral cortex plaques alone was highly sensitive (100%) but had poor specificity (48% to 55%). The results suggest that striatal amyloid imaging may be clinically useful for making the distinction between PDD and PDAD.
striatum; Lewy body; diagnosis; autopsy; neuropathology; biomarker
Evaluate electrophysiologic findings in incidental Lewy Body disease (ILBD).
ILBD, Control, and Parkinson's disease (PD) subjects had electrophysiological evaluation within two years prior to autopsy. Data analyzed included surface electromyography (EMG) of upper extremity muscles during rest and muscle activation, and electroencephalography (EEG) recording at rest. For EMG, gross tracings and spectral peaks were analyzed. EEG measures analyzed were background frequency and power in delta, theta, alpha, and beta bands.
Three of ten ILBD subjects (30%) showed unilateral rhythmic EMG discharges at rest without a visually apparent rest tremor. The ILBD resting EMG frequency was lower than in the Control group with no overlap (P=0.03) and close to that of the PD group. The ILBD group had significantly lower background rhythm frequency than the Control group (P=0.001) but was greater than the PD group (P=0.01).
The electrophysiologic changes in ILBD cases are between those of Control and PD, suggesting that these findings may reflect changes correlating with ILBD as a possible precursor to PD.
Electrophysiologic changes in ILBD may assist with the identification of a preclinical stage for Lewy body disorders and help the development of a therapeutic agent for modifying Lewy body disease progression.
Lewy body; Electromyography; Electroencephalography; Pathology; Parkinson's disease; Tremor
Amyloid-β (Aβ) peptides are intimately involved in the inflammatory pathology of atherosclerotic vascular disease (AVD) and Alzheimer's disease (AD). Although substantial amounts of these peptides are produced in the periphery, their role and significance to vascular disease outside the brain requires further investigation.
Amyloid-β peptides present in the walls of human aorta atherosclerotic lesions as well as activated and non-activated human platelets were isolated using sequential size-exclusion columns and HPLC reverse-phase methods. The Aβ peptide isolates were quantified by ELISA and structurally analyzed using MALDI-TOF mass spectrometry procedures.
Our experiments revealed that both aorta and platelets contained Aβ peptides, predominately Aβ40. The source of the Aβ pool in aortic atherosclerosis lesions is probably the activated platelets and/or vascular wall cells expressing APP/PN2. Significant levels of Aβ42 are present in the plasma, suggesting that this reservoir makes a minor contribution to atherosclerotic plaques.
Our data reveal that although aortic atherosclerosis and AD cerebrovascular amyloidosis exhibit clearly divergent end-stage manifestations, both vascular diseases share some key pathophysiological promoting elements and pathways. Whether they happen to be deposited in vessels of the central nervous system or atherosclerotic plaques in the periphery, Aβ peptides may promote and perhaps synergize chronic inflammatory processes which culminate in the degeneration, malfunction and ultimate destruction of arterial walls.
atherosclerosis; platelets; amyloid-beta; vascular inflammation; Alzheimer's disease; coagulation cascade
Banked tissue is essential to the study of neurological disease but using postmortem tissue introduces a number of possible confounds. Foremost amongst these are factors relating to variation in postmortem interval (PMI). Currently there are conflicting reports on how PMI affects overall RNA integrity, and very few reports of how gene expression is affected by PMI. We analyzed total RNA extracted from frozen cerebellar cortex from 79 deceased human subjects enrolled in the Banner Sun Health Research Institute Brain and Body Donation Program. The PMI, which ranged from 1.5 to 45 hours, correlated with overall RNA quality measures including RNA Integrity Number (RIN) (r = − 0.34, p = 0.002) and RNA quantitative yield (r = − 0.25, p = 0.02). Additionally, we determined the expression of 89 genes using a PCR-based gene expression array (RT2 ProfilerTM PCR Array: Human Alzheimer’s Disease; SABiosciencesTM, Frederick, MD). A greater proportion of genes had decreased rather than increased expression with increasing PMI (65/89 vs 20/89; p < 0.0001). Of these, transcripts from the genes ADAM9, LPL, PRKCG, and SERPINA3 had significantly decreased expression with increasing PMI (p < 0.01). No individual gene transcripts had significantly increased expression with increasing PMI. In conclusion, it is apparent that RNA degrades progressively with increasing PMI and that measurement of gene expression in brain tissue with longer PMI may give artificially low values. For tissue derived from autopsy, a short PMI optimizes its utility for molecular research.
RIN; RNA; postmortem; brain; gene expression; Alzheimer’s disease; neurological disease; research; methods
Down syndrome appears to be associated with a virtually certain risk of fibrillar amyloid-β (Aβ) pathology by the age of 40 and a very high risk of dementia at older ages. The positron emission tomography (PET) ligand florbetapir F18 has been shown to characterize fibrillar Aβ in the living human brain and to provide a close correlation with subsequent Aβ neuropathology in individuals proximate to and after the end of life. The extent to which the most frequently used PET ligands can be used to detect fibrillar Aβ in patients with Down syndrome remains to be determined.
To characterize PET estimates of fibrillar Aβ burden in a Down syndrome patient very close to the end of life and to compare them with neuropathologic assessment made after his death.
With the family’s informed consent, florbetapir PET was used to study a 55-year-old Down syndrome patient with Alzheimer disease near the end of life; his brain was donated for neuropathologic assessment when he died 14 days later. Visual ratings of cerebral florbetapir uptake were performed by trained readers who were masked to the patient’s diagnosis as part of a larger study, and an automated algorithm was used to characterize regional-to-cerebellar standard uptake value ratios in 6 cerebral regions of interest. Neuropathologic assessments were performed masked to the patient’s diagnosis or PET measurements.
Visual ratings and automated analyses of the PET image revealed a heavy fibrillar Aβ burden in cortical, striatal, and thalamic regions, similar to that reported for patients with late-onset Alzheimer disease. This matched neuropathologic findings of frequent neuritic and diffuse plaques, as well as frequent amyloid angiopathy, except for neuropathologically demonstrated frequent cerebellar diffuse plaques and amyloid angiopathy that were not detected by the PET scan.
Florbetapir PET can be used to detect increased cerebral-to-cerebellar fibrillar Aβ burden in a Down syndrome patient with Alzheimer disease, even in the presence of frequent amyloid angiopathy and diffuse plaques in the cerebellum. Additional studies are needed to determine the extent to which PET could be used to detect and to track fibrillar Aβ and to evaluate investigational Aβ-modifying treatments in the presymptomatic and symptomatic stages of Alzheimer disease.
The recent Parkinson Disease GWAS Consortium meta-analysis and replication study reports association at several previously confirmed risk loci SNCA, MAPT, GAK/DGKQ, and HLA and identified a novel risk locus at RIT2. To further explore functional consequences of these associations, we investigated modification of gene expression in prefrontal cortex brain samples of pathologically confirmed PD cases (N = 26) and controls (N = 24) by 67 associated SNPs in these 5 loci. Association between the eSNPs and expression was evaluated using a 2-degrees of freedom test of both association and difference in association between cases and controls, adjusted for relevant covariates. SNPs at each of the 5 loci were tested for cis-acting effects on all probes within 250 kb of each locus. Trans-effects of the SNPs on the 39,122 probes passing all QC on the microarray were also examined. From the analysis of cis-acting SNP effects, several SNPs in the MAPT region show significant association to multiple nearby probes, including two strongly correlated probes targeting the gene LOC644246 and the duplicated genes LRRC37A and LRRC37A2, and a third uncorrelated probe targeting the gene DCAKD. Significant cis-associations were also observed between SNPs and two probes targeting genes in the HLA region on chromosome 6. Expanding the association study to examine trans effects revealed an additional 23 SNP-probe associations reaching statistical significance (p<2.8×10−8) including SNPs from the SNCA, MAPT and RIT2 regions. These findings provide additional context for the interpretation of PD associated SNPs identified in recent GWAS as well as potential insight into the mechanisms underlying the observed SNP associations.
Maxillary sinus carcinoma (MSC) is a rare cancer of the head and neck region. Patients are treated with surgery, radiation therapy, and chemotherapy and the treatment regimen is based on patient’s age, general health condition, disease stage, and its extent of spread. There is very little information available on the genetics of this disease. DNA content based flow sorting of tumor cells followed by array comparative genomic hybridization allows for high definition global assessment of distinct clonal changes within tumor populations.
We applied this technique to primary and metastatic samples collected from a patient with radio- and chemotherapy refractory maxillary sinus carcinoma to gauge the progression of this disease.
A clonal KIT amplicon was present in aneuploid populations sorted from the primary tumor and in divergent subclones arising in metastatic foci found in the brain, lung, and jejunum. The evolution of these subclones was associated with distinct genetic aberrations and DNA ploidies.
The information presented here paves the path to understanding the development and progression of this disease.
Human induced pluripotent stem cells (iPSCs) have become an intriguing approach for neurological disease modeling, because neural lineage-specific cell types that retain the donors' complex genetics can be established in vitro. The statistical power of these iPSC-based models, however, is dependent on accurate diagnoses of the somatic cell donors; unfortunately, many neurodegenerative diseases are commonly misdiagnosed in live human subjects. Postmortem histopathological examination of a donor's brain, combined with premortem clinical criteria, is often the most robust approach to correctly classify an individual as a disease-specific case or unaffected control. In this study, we describe iPSCs generated from a skin biopsy collected postmortem during the rapid autopsy of a 75-year-old male, whole body donor, defined as an unaffected neurological control by both clinical and histopathological criteria. These iPSCs were established in a feeder-free system by lentiviral transduction of the Yamanaka factors, Oct3/4, Sox2, Klf4, and c-Myc. Selected iPSC clones expressed both nuclear and surface antigens recognized as pluripotency markers of human embryonic stem cells (hESCs) and were able to differentiate in vitro into neurons and glia. Statistical analysis also demonstrated that fibroblast proliferation was significantly affected by biopsy site, but not donor age (within an elderly cohort). These results provide evidence that autopsy donor-derived fibroblasts can be successfully reprogrammed into iPSCs, and may provide an advantageous approach for generating iPSC-based neurological disease models.
induced pluripotent stem cells; genetic disease models; diagnostics; neurodegenerative diseases; postmortem; autopsy; neural differentiation
Normal pressure hydrocephalus (NPH) is considered potentially treatable with the placement of a cerebrospinal fluid (CSF) shunt. Yet, the procedure has had variable success, particularly with respect to improving the cognitive impairment in NPH. The presence of neurologic co-morbidities, particularly Alzheimer's Disease (AD), may contribute to shunt responsiveness. Uncovering the extent to which AD and NPH co-occur has implications for diagnosis and treatment of NPH. Autopsy studies of patients with NPH during life would elucidate the frequency of such co-morbidities.
We conducted a search of the Sun Health Research Institute Brain Donation Program database between 1/1/1997 and 4/1/09 to identify all cases with neuropathologic evidence of dementia as well as those cases of clinically diagnosed NPH. We reviewed the medical records and brain findings of each NPH case.
Of the 761 cases autopsied over the study interval, 563 cases were found to have neuropathological evidence meeting criteria for a dementing illness. AD was found exclusively in 313/563 (56%) cases with 94/563 cases having a secondary diagnosis of dementia.
We identified 9/761 cases with a clinical diagnosis of NPH, all nine cases were among the 563 cases with neuropathology of dementing illness at autopsy, representing 1.6% (9/563). Upon review of brain autopsy reports, 8/9 (89%) cases were found to have AD and 1/9 (11%) had progressive supranuclear palsy. Review of the medical records of the nine NPH cases revealed the following clinical co-morbidities: 5/9 with AD; 1/9 with Parkinson's Disease (PD); 1/9 with Mild Cognitive Impairment (MCI); 1/9 with seizure disorder.
Given the findings of our study, we support the AD-NPH theory and posit that AD is a common pathological co-morbidity in the setting of NPH and may preclude cognitive improvement post-shunt placement. This may have influence on selection of cases for shunting in the future.
normal pressure hydrocephalus; Alzheimer's disease; cerebrospinal fluid shunt; autopsy study; dementia
Multiple lines of evidence suggest cardiovascular co-morbidities hasten the onset of Alzheimer’s disease (AD) or accelerate its course.
To evaluate the utility of cerebral vascular physical function/condition parameters as potential systemic indicators of AD, we employed transcranial Doppler (TCD) ultrasound to assess cerebral blood flow and vascular resistance of the 16 arterial segments comprising the circle of Willis and its major tributaries.
Our study revealed decreased arterial mean flow velocity (MFV) and increased pulsatility index (PI) are associated with a clinical diagnosis of presumptive AD. Cerebral blood flow impairment revealed by these parameters reflects the global hemodynamic and structural consequences of a multifaceted disease process yielding diffuse congestive microvascular pathology, increased arterial rigidity, and decreased arterial compliance combined with putative age-associated cardiovascular output declines.
TCD evaluation offers direct physical confirmation of brain perfusion impairment and may ultimately provide a convenient, noninvasive means to assess the efficacy of medical interventions on cerebral blood flow or reveal incipient AD. In the near term, TCD-based direct assessments of brain perfusion may offer the prospect of preventing or mitigating AD simply by revealing patients who would benefit from interventions to improve circulatory system function.
Alzheimer’s disease; transcranial Doppler ultrasonography; cerebral blood flow; brain hypoperfusion; mean flow velocity; pulsatility index
Compare the frequency of REM sleep behavior disorder (RBD) and excessive daytime sleepiness (EDS) in Parkinson’s disease (PD), restless legs syndrome (RLS), essential tremor (ET), and control subjects.
Subjects enrolled in a longitudinal clinicopathologic study, and when available an informant, completed the Mayo Sleep Questionnaire, which asks “Have you ever been told that you act out your dreams?”, and the Epworth Sleepiness Scale (ESS).
Probable RBD (based on informant response to the questionnaire) was much more frequent in PD (34/49, 69%, p<0.001) than in RLS (6/30, 20%), ET (7/53, 13%), or control subjects (23/175, 13%), with an odds ratio of 11 for PD compared to controls. The mean ESS and the number of subjects with an ESS ≥ 10 was higher in PD (29/60, 48%, p<0.001) and RLS (12/39, 31%, p<0.001) compared with ET (12/93, 13%) and Controls (34/296, 11%).
Probable RBD is much more frequent in PD with no evidence to suggest an increase in either RLS or ET. Given the evidence that RBD is a synucleinopathy, the lack of an increased frequency of RBD in subjects with ET or RLS suggests the majority of ET and RLS subjects are unlikely to be at increased risk for developing PD.
Parkinson’s disease; REM sleep behavior disorder; essential tremor; restless legs syndrome; excessive daytime sleepiness
A substantial body of evidence amassed from epidemiologic, correlative and experimental studies strongly associates atherosclerotic vascular disease (AVD) with Alzheimer's disease (AD). Depending on the precise interrelationship between AVD and AD, systematic application of interventions to maintain vascular health and function as a component of standard AD therapy offers the prospect of mitigating what is presently the inexorable course of dementia. To assess this hypothesis it is vital to rigorously establish the measures of AVD that are most strongly associated with an AD diagnosis.
A precise neuropathological diagnosis was established for all subjects using a battery of genetic, clinical, and histological methods. The severity of atherosclerosis in the circle of Willis (CW) was quantified by direct digitized measurement of arterial occlusion in postmortem specimens and compared between AD and non-demented control (NDC) groups by calculating a corresponding index of occlusion.
Atherosclerotic occlusion of the CW arteries was more extensive in the AD group than the NDC group. Statistically significant differences were also observed between control and AD groups with regard to Braak stage, total plaque score, total NFT score, total white matter rarefaction score, brain weight, MMSE scores and apolipoprotein E allelic frequencies.
Our results, combined with a consideration of the multifaceted impacts of impaired cerebral circulation, suggest an immediate need for prospective clinical trials to assess the efficacy of AD prevention using anti-atherosclerotic agents.
Alzheimer's disease; vascular dementia; intracranial atherosclerosis; circle of Willis; brain hypoperfusion
The ability to understand how Parkinson’s disease (PD) neurodegeneration leads to cortical dysfunction will be critical for developing therapeutic advances in PD dementia (PD-D). The overall purpose of this project was to study the small amplitude cortical myoclonus in PD as an in vivo model of focal cortical dysfunction secondary to PD neurodegeneration. The objectives were to test the hypothesis that cortical myoclonus in PD is linked to abnormal levels of α-synuclein in primary motor cortex and to define its relationship to various biochemical, clinical, and pathological measures.
Primary motor cortex was evaluated for 11 PD subjects with (PD+Myoclonus group) and 8 without (PD group) electrophysiologically confirmed cortical myoclonus who had premortem movement and cognitive testing. Similarly assessed 9 controls were used for comparison. Measurements for α-synuclein, Aβ-42 peptide, and other biochemical measures were made in primary motor cortex.
A 36% increase in α-synuclein was found in the motor cortex of PD+Myoclonus cases when compared to PD without myoclonus. This occurred without significant differences in insoluble α-synuclein, phosphorylated to total α-synuclein ratio, or Aβ-42 peptide levels. Higher total motor cortex α-synuclein levels significantly correlated with the presence of cortical myoclonus but did not correlate with multiple clinical or pathological findings.
These results suggest an association between elevated α-synuclein and the dysfunctional physiology arising from the motor cortex in PD+Myoclonus cases. Alzheimer’s disease pathology was not associated with cortical myoclonus in PD. Cortical myoclonus arising from motor cortex is a model to study cortical dysfunction in PD.