Missense mutations in the α-synuclein gene cause familial Parkinson's disease (PD), and α-synuclein is a major component of Lewy bodies (LBs) in sporadic PD, dementia with LBs (DLB), and the LB ...variant of Alzheimer's disease (AD). To determine whether α-synuclein is a component of LBs in familial AD (FAD) patients with known mutations in presenilin (
n = 65) or amyloid precursor protein (
n = 9) genes, studies were conducted with antibodies to α-, β-, and γ-synuclein. LBs were detected with α- but not β- or γ-synuclein antibodies in 22% of FAD brains, and α-synuclein-positive LBs were most numerous in amygdala where some LBs co-localized with tau-positive neurofibrillary tangles. As 12 (63%) of 19 FAD amygdala samples contained α-synuclein-positive LBs, these inclusions may be more common in FAD brains than previously reported. Furthermore, α-synuclein antibodies decorated LB filaments by immunoelectron microscopy, and Western blots revealed that the solubility of α-synuclein was reduced compared with control brains. The presence of α-synuclein-positive LBs was not associated with any specific FAD mutation. These studies suggest that insoluble α-synuclein aggregates into filaments that form LBs in many FAD patients, and we speculate that these inclusions may compromise the function and/or viability of affected neurons in the FAD brain.
Although axonal injury is a common feature of brain trauma, little is known of the immediate morphological responses of individual axons to mechanical injury. Here, we developed an in vitro model ...system that selectively stretches axons bridging two populations of human neurons derived from the cell line N-Tera2. We found that these axons demonstrated a remarkably high tolerance to dynamic stretch injury, with no primary axotomy at strains <65%. In addition, the axolemma remained impermeable to small molecules after injury unless axotomy had occurred. We also found that injured axons exhibited the behavior of "delayed elasticity" after injury, going from a straight orientation before injury to developing an undulating course as an immediate response to injury, yet gradually recovering their original orientation. Surprisingly, some portions of the axons were found to be up to 60% longer immediately after injury. Subsequent to returning to their original length, injured axons developed swellings of appearance remarkably similar to that found in brain-injured humans. These findings may offer insight into mechanical-loading conditions leading to traumatic axonal injury and into potential mechanisms of axon reassembly after brain trauma.
We investigated the distribution patterns of Lewy body-related pathology (LRP) and the effect of coincident Alzheimer disease (AD) pathology using a data-driven clustering approach that identified ...groups with different LRP pathology distributions without any diagnostic or researcher's input in two cohorts including: Parkinson disease patients without (PD, n = 141) and with AD (PD-AD, n = 80), dementia with Lewy bodies subjects without AD (DLB, n = 13) and demented subjects with AD and LRP pathology (Dem-AD-LB, n = 308). The Dem-AD-LB group presented two LRP patterns, olfactory-amygdala and limbic LRP with negligible brainstem pathology, that were absent in the PD groups, which are not currently included in the DLB staging system and lacked extracranial LRP as opposed to the PD group. The Dem-AD-LB individuals showed relative preservation of substantia nigra cells and dopamine active transporter in putamen. PD cases with AD pathology showed increased LRP. The cluster with occipital LRP was associated with non-AD type dementia clinical diagnosis in the Dem-AD-LB group and a faster progression to dementia in the PD groups. We found that (1) LRP pathology in Dem-AD-LB shows a distribution that differs from PD, without significant brainstem or extracranial LRP in initial phases; (2) coincident AD pathology is associated with increased LRP in PD indicating an interaction; (3) LRP and coincident AD pathology independently predict progression to dementia in PD, and (4) evaluation of LRP needs to acknowledge different LRP spreading patterns and evaluate substantia nigra integrity in the neuropathological assessment and consider the implications of neuropathological heterogeneity for clinical and biomarker characterization.
Abnormally hyperphosphorylated tau polymers known as paired helical filaments constitute one of the major characteristic lesions that lead to the demise of neurons in Alzheimer's disease. Here, we ...demonstrate that the environmental toxin arsenite causes a significant increase in the phosphorylation of several amino acid residues (Thr-181, Ser-202, Thr-205, Thr-231, Ser-262, Ser-356, Ser-396, and Ser-404) in tau, which are also hyperphosphorylated under pathological conditions. Complementary phosphopeptide mapping revealed a dramatic increase in the 32P-labeling of many peptides in tau following arsenite treatment. Although arsenite activates extracellular-signal regulated kinases-1/-2 and stress-activated protein kinases, these enzymes did not contribute to the arsenite-increased phosphorylation, nor did they appear to normally modify tau in vivo. Tau phosphorylation induced by arsenite did not involve glycogen synthase kinase-3 or protein phosphatase-1 or -2, but the activity responsible for tau hyperphosphorylation could be inhibited with the protein kinase inhibitor roscovitine. The effects of arsenite on the phosphorylation of some tau mutations (ΔΚ280, V337M, and R406W) associated with frontal-temporal dementia with parkinsonism linked to chromosome 17 was analyzed. The unchallenged and arsenite-induced phosphorylation of some mutant proteins, especially R406W, was altered at several phosphorylation sites, indicating that these mutations can significantly affect the structure of tau in vivo. Although the major kinase(s) involved in aberrant tau phosphorylation remains elusive, these results indicate that environmental factors, such as arsenite, may be involved in the cascade leading to deregulation of tau function associated with neurodegeneration.
Guam parkinsonism-dementia complex (PDC) is a neurodegenerative tauopathy in ethnic Chamorro residents of the Mariana Islands that manifests clinically with parkinsonism as well as dementia and is ...characterized neuropathologically by prominent cortical neuron loss in association with extensive telencephalic neurofibrillary tau pathology. To further characterize cortical gray and white matter tau, alpha-synuclein and lipid peroxidation pathologies in Guam PDC, we examined the brains of 17 Chamorro PDC and control subjects using biochemical and immunohistological techniques. We observed insoluble tau pathology in both gray and white matter of PDC and Guam control cases, with frontal and temporal lobes being most severely affected. Using phosphorylation dependent anti-tau antibodies, abundant tau inclusions were detected by immunohistochemistry in both neuronal and glial cells of the neocortex, while less alpha-synuclein pathology was observed in more limited brain regions. Further, in sharp contrast to Alzheimer's disease (AD), levels of the lipid peroxidation product 8, 12-iso-iPF(2alpha)-VI isoprostane were not elevated in Guam PDC brains relative to controls. Thus, although the tau pathologies of Guam PDC share similarities with AD, the composite Guam PDC neuropathology profile of tau, alpha-synuclein and 8, 12-iso-iPF(2alpha)-VI isoprostane reported here more closely resembles that seen in other tauopathies including frontotemporal dementias (FTDs), which may imply that Guam PDC and FTD tauopathies share underlying mechanisms of neurodegeneration.
BACKGROUND Abnormal neuronal inclusions composed of the transactivation response DNA-binding protein 43 (TDP-43) are characteristic neuropathologic lesions in sporadic and familial forms of ...amyotrophic lateral sclerosis (ALS). This makes TARDBP, the gene encoding for TDP-43, a candidate for genetic screening in ALS. OBJECTIVES To investigate the presence and frequency of TARDBP mutations in ALS. DESIGN Genetic analysis. SETTING Academic research. PARTICIPANTS One hundred thirty-four patients with sporadic ALS, 31 patients with familial non–superoxide dismutase 1 gene (non-SOD1) (OMIM 147450) ALS, and 400 healthy control subjects. MAIN OUTCOME MEASURES We identified 2 missense mutations (G348C and the novel N352S) in TARDBP in 2 small kindreds with a hereditary form of ALS with early spinal onset resulting in fatal respiratory insufficiency without clinical relevant bulbar symptoms or signs of cognitive impairment. RESULTS The mutations located in the C-terminus of TDP-43 were absent in 400 controls of white race/ethnicity. The novel identified N352S mutation is predicted to increase TDP-43 phosphorylation, while the G348C mutation might interfere with normal TDP-43 function by forming intermolecular disulfide bridges. CONCLUSIONS Mutations in TARDBP are a rare cause of familial non-SOD1 ALS. The identification of TARDBP mutations provides strong evidence for a direct link between TDP-43 dysfunction and neurodegeneration in ALS.Arch Neurol. 2008;65(9):1185-1189-->
OBJECTIVE:To compare the diagnostic accuracy of CSF biomarkers and amyloid PET for diagnosing early-stage Alzheimer disease (AD).
METHODS:From the prospective, longitudinal BioFINDER study, we ...included 122 healthy elderly and 34 patients with mild cognitive impairment who developed AD dementia within 3 years (MCI-AD). β-Amyloid (Aβ) deposition in 9 brain regions was examined with F-flutemetamol PET. CSF was analyzed with INNOTEST and EUROIMMUN ELISAs. The results were replicated in 146 controls and 64 patients with MCI-AD from the Alzheimerʼs Disease Neuroimaging Initiative study.
RESULTS:The best CSF measures for identifying MCI-AD were Aβ42/total tau (t-tau) and Aβ42/hyperphosphorylated tau (p-tau) (area under the curve AUC 0.93–0.94). The best PET measures performed similarly (AUC 0.92–0.93; anterior cingulate, posterior cingulate/precuneus, and global neocortical uptake). CSF Aβ42/t-tau and Aβ42/p-tau performed better than CSF Aβ42 and Aβ42/40 (AUC difference 0.03–0.12, p < 0.05). Using nonoptimized cutoffs, CSF Aβ42/t-tau had the highest accuracy of all CSF/PET biomarkers (sensitivity 97%, specificity 83%). The combination of CSF and PET was not better than using either biomarker separately.
CONCLUSIONS:Amyloid PET and CSF biomarkers can identify early AD with high accuracy. There were no differences between the best CSF and PET measures and no improvement when combining them. Regional PET measures were not better than assessing the global Aβ deposition. The results were replicated in an independent cohort using another CSF assay and PET tracer. The choice between CSF and amyloid PET biomarkers for identifying early AD can be based on availability, costs, and doctor/patient preferences since both have equally high diagnostic accuracy.
CLASSIFICATION OF EVIDENCE:This study provides Class III evidence that amyloid PET and CSF biomarkers identify early-stage AD equally accurately.
Accumulation of insoluble conformationally altered hyperphosphorylated tau occurs as part of the pathogenic process in Alzheimer's disease (AD) and other tauopathies. In most AD subjects, wild-type ...(WT) tau aggregates and accumulates in neurofibrillary tangles and dystrophic neurites in the brain; however, in some familial tauopathy disorders, mutations in the gene encoding tau cause disease.
We generated a mouse model, Tau4RTg2652, that expresses high levels of normal human tau in neurons resulting in the early stages of tau pathology. In this model, over expression of WT human tau drives pre-tangle pathology in young mice resulting in behavioral deficits. These changes occur at a relatively young age and recapitulate early pre-tangle stages of tau pathology associated with AD and mild cognitive impairment. Several features distinguish the Tau4RTg2652 model of tauopathy from previously described tau transgenic mice. Unlike other mouse models where behavioral and neuropathologic changes are induced by transgenic tau harboring MAPT mutations pathogenic for frontotemporal lobar degeneration (FTLD), the mice described here express the normal tau sequence.
Features of Tau4RTg2652 mice distinguishing them from other established wild type tau overexpressing mice include very early phenotypic manifestations, non-progressive tau pathology, abundant pre-tangle and phosphorylated tau, sparse oligomeric tau species, undetectable fibrillar tau pathology, stability of tau transgene copy number/expression, and normal lifespan. These results suggest that Tau4RTg2652 animals may facilitate studies of tauopathy target engagement where WT tau is driving tauopathy phenotypes.
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![Pathological [alpha]-synucl...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0001-6322/small "Pathological [alpha]-synuclein distribution in subjects with coincident Alzheimer's and Lewy body pathology")
