Adrian L. Oblak

Invited review: Frontotemporal dementia caused by microtubule-associated protein tau gene (MAPT) mutations: a chameleon for neuropathology and neuroimaging.

Hereditary frontotemporal dementia associated with mutations in the microtubule‐associated protein tau gene (MAPT) is a protean disorder. Three neuropathologic subtypes can be recognized, based on the presence of inclusions made of tau isoforms with three and four repeats, predominantly three repeats and mostly four repeats. This is relevant for establishing a correlation between structural magnetic resonance imaging and positron emission tomography using tracers specific for aggregated tau. Longitudinal studies will be essential to determine the evolution of anatomical alterations from the asymptomatic stage to the various phases of disease following the onset of symptoms.

Cytosolic Fc receptor TRIM21 inhibits seeded tau aggregation

Significance The mammalian cell cytoplasm contains numerous proteins with direct antimicrobial activity. Although these have been extensively studied in the context of viral and bacterial infection, it is unknown whether pathogenic self-propagating proteins, proposed to underlie common neurodegenerative diseases, can be targeted in a similar manner. We studied the ability of tripartite motif protein 21 (TRIM21), a newly identified intracellular antibody receptor, to intercept assemblies of misfolded tau, a cytoplasmic protein that aggregates in patients with Alzheimer’s disease. We developed tau “seeding” assays in human cells and found that TRIM21 could intercept and potently neutralize antibody-labeled tau assemblies. These findings demonstrate that the intracellular immune system can act against self-propagating misfolded proteins, with implications for ongoing attempts to develop antibody-based therapies for neurodegenerative disorders. Alzheimer’s disease (AD) and other neurodegenerative disorders are associated with the cytoplasmic aggregation of microtubule-associated protein tau. Recent evidence supports transcellular transfer of tau misfolding (seeding) as the mechanism of spread within an affected brain, a process reminiscent of viral infection. However, whereas microbial pathogens can be recognized as nonself by immune receptors, misfolded protein assemblies evade detection, as they are host-derived. Here, we show that when misfolded tau assemblies enter the cell, they can be detected and neutralized via a danger response mediated by tau-associated antibodies and the cytosolic Fc receptor tripartite motif protein 21 (TRIM21). We developed fluorescent, morphology-based seeding assays that allow the formation of pathological tau aggregates to be measured in situ within 24 h in the presence of picomolar concentrations of tau seeds. We found that anti-tau antibodies accompany tau seeds into the cell, where they recruit TRIM21 shortly after entry. After binding, TRIM21 neutralizes tau seeds through the activity of the proteasome and the AAA ATPase p97/VCP in a similar manner to infectious viruses. These results establish that intracellular antiviral immunity can be redirected against host-origin endopathogens involved in neurodegeneration.

Rapid-onset dystonia-parkinsonism associated with the I758S mutation of the ATP1A3 gene: a neuropathologic and neuroanatomical study of four siblings

Rapid-onset dystonia-parkinsonism (RDP) is a movement disorder associated with mutations in the ATP1A3 gene. Signs and symptoms of RDP commonly occur in adolescence or early adulthood and can be triggered by physical or psychological stress. Mutations in ATP1A3 are also associated with alternating hemiplegia of childhood (AHC). The neuropathologic substrate of these conditions is unknown. The central nervous system of four siblings, three affected by RDP and one asymptomatic, all carrying the I758S mutation in the ATP1A3 gene, was analyzed. This neuropathologic study is the first carried out in ATP1A3 mutation carriers, whether affected by RDP or AHC. Symptoms began in the third decade of life for two subjects and in the fifth for another. The present investigation aimed at identifying, in mutation carriers, anatomical areas potentially affected and contributing to RDP pathogenesis. Comorbid conditions, including cerebrovascular disease and Alzheimer disease, were evident in all subjects. We evaluated areas that may be relevant to RDP separately from those affected by the comorbid conditions. Anatomical areas identified as potential targets of I758S mutation were globus pallidus, subthalamic nucleus, red nucleus, inferior olivary nucleus, cerebellar Purkinje and granule cell layers, and dentate nucleus. Involvement of subcortical white matter tracts was also evident. Furthermore, in the spinal cord, a loss of dorsal column fibers was noted. This study has identified RDP-associated pathology in neuronal populations, which are part of complex motor and sensory loops. Their involvement would cause an interruption of cerebral and cerebellar connections which are essential for maintenance of motor control.

Amyloid polymorphisms constitute distinct clouds of conformational variants in different etiological subtypes of Alzheimer’s disease

Significance The clinical and pathological variability among patients with Alzheimer’s disease (AD) remains largely unexplained. Evidence is growing that this heterogeneity may be influenced by the heterogeneous molecular architecture of misfolded amyloid-β peptide (Aβ) in the brain. To test this hypothesis, we used unique fluorescent ligands to interrogate the molecular structure of Aβ in amyloid plaques from patients who had died with etiologically distinct subtypes of AD. We found that Aβ-amyloid plaques in the brain cluster as clouds of conformational variants that differ among certain subtypes of AD. The conformational features of AD plaques were partially transmissible to transgenic mice in a seeding paradigm, suggesting a mechanism whereby different molecular strains of Aβ propagate their features within the brain. The molecular architecture of amyloids formed in vivo can be interrogated using luminescent conjugated oligothiophenes (LCOs), a unique class of amyloid dyes. When bound to amyloid, LCOs yield fluorescence emission spectra that reflect the 3D structure of the protein aggregates. Given that synthetic amyloid-β peptide (Aβ) has been shown to adopt distinct structural conformations with different biological activities, we asked whether Aβ can assume structurally and functionally distinct conformations within the brain. To this end, we analyzed the LCO-stained cores of β-amyloid plaques in postmortem tissue sections from frontal, temporal, and occipital neocortices in 40 cases of familial Alzheimer’s disease (AD) or sporadic (idiopathic) AD (sAD). The spectral attributes of LCO-bound plaques varied markedly in the brain, but the mean spectral properties of the amyloid cores were generally similar in all three cortical regions of individual patients. Remarkably, the LCO amyloid spectra differed significantly among some of the familial and sAD subtypes, and between typical patients with sAD and those with posterior cortical atrophy AD. Neither the amount of Aβ nor its protease resistance correlated with LCO spectral properties. LCO spectral amyloid phenotypes could be partially conveyed to Aβ plaques induced by experimental transmission in a mouse model. These findings indicate that polymorphic Aβ-amyloid deposits within the brain cluster as clouds of conformational variants in different AD cases. Heterogeneity in the molecular architecture of pathogenic Aβ among individuals and in etiologically distinct subtypes of AD justifies further studies to assess putative links between Aβ conformation and clinical phenotype.

Visuoperception test predicts pathologic diagnosis of Alzheimer disease in corticobasal syndrome

Objective: To use the Visual Object and Space Perception Battery (VOSP) to distinguish Alzheimer disease (AD) from non-AD pathology in corticobasal syndrome (CBS). Methods: This clinicopathologic study assessed 36 patients with CBS on the VOSP. All were autopsied. The primary dependent variable was a binary pathologic outcome: patients with CBS who had primary pathologic diagnosis of AD (CBS-AD, n = 10) vs patients with CBS without primary pathologic diagnosis of AD (CBS-nonAD, n = 26). We also determined sensitivity and specificity of individual VOSP subtests. Results: Patients with CBS-AD had younger onset (54.5 vs 63.6 years, p = 0.001) and lower memory scores on the Mattis Dementia Rating Scale–2 (16 vs 22 points, p = 0.003). Failure on the VOSP subtests Incomplete Letters (odds ratio [OR] 11.5, p = 0.006), Position Discrimination (OR 10.86, p = 0.008), Number Location (OR 12.27, p = 0.026), and Cube Analysis (OR 45.71 p = 0.0001) had significantly greater odds of CBS-AD than CBS-nonAD. These associations remained when adjusting for total Mattis Dementia Rating score, disease laterality, education, age, and sex. Receiver operating characteristic curves demonstrated significant accuracy for Incomplete Letters and all VOSP spatial subtests, with Cube Analysis performing best (area under the curve 0.91, p = 0.0004). Conclusions: In patients with CBS, failure on specific VOSP subtests is associated with greater odds of having underlying AD. There may be preferential involvement of the dorsal stream in CBS-AD. Classification of evidence: This study provides Class II evidence that some subtests of the VOSP accurately distinguish patients with CBS-AD from those without AD pathology (e.g., Cube Analysis sensitivity 100%, specificity 77%).

Clinicopathological Correlates in a PRNP P102L Mutation Carrier with Rapidly Progressing Parkinsonism-dystonia

Parkinsonism‐dystonia is rare in carriers of the prion protein (PrP) gene (PRNP) proline‐to‐leucine substitution at codon 102 (P102L mutation). The severity and distribution of PrP deposition may influence the clinical presentation. The authors present such clinicopathological correlation in a 56‐year‐old man who had a PRNP P102L mutation associated with a phenotype characterized by rapidly progressing parkinsonism‐dystonia. The patient was studied clinically (videotaped examinations, brain magnetic resonance images [MRIs]) and was analyzed using molecular genetics (gene sequence analysis) and neuropathology (histology, immunohistochemistry) during his 7‐month disease course. The patient had parkinsonism, apraxia, aphasia, and dystonia, which progressed rapidly. Molecular genetic analysis revealed his PRNP P102L mutation carrier status. Brain MRIs revealed progressive, global volume loss and T2‐weighted/fluid‐attenuated inversion recovery hyperintensity in the neocortex and basal ganglia. Postmortem examination showed neuronal loss, gliosis, spongiform changes, and PrP deposition in the striatum. PrP immunohistochemistry revealed widespread, severe PrP deposition in the thalamus and cerebellar cortex. Based on the neuropathological and molecular‐genetic analyses, the rapidly progressing parkinsonism‐dystonia was correlated with nigrostriatal, thalamic, and cerebellar pathology.

THE MODEL-AD CONSORTIUM PRECLINICAL TESTING PIPELINE: PHARMACOKINETICS AND PHARMACODYNAMICS OF PROPHYLACTIC TREATMENT WITH LEVETIRACETAM IN THE 5XFAD MOUSE MODEL OF ALZHEIMER’S DISEASE

restrictive barrier properties controlled by tight junctions and polarized expression of selective transporters, the endothelial cells that form the BBB effectively regulates movement of metabolites and nutrients between blood and brain parenchyma. Any changes in the BBB may impair the clearance of neurotoxic molecules allowing their accumulation and deposition in brain parenchyma and vasculature, leading to neuronal dysfunction and degeneration, and contribute to the onset and progression of Alzheimer’s disease (AD). In AD and CAA, accumulation of amyloid-b (Ab) on microvessels results in a rupture of vessels wall and cerebral hemorrhage, which contribute to, and aggravate, dementia. Accumulation of Ab depends on the imbalance between the production and clearance of Ab. Several pathways for Ab clearance from the brain have been reported including transport across the BBB and enzymatic degradation. Despite our understanding of the pathways responsible for BBB dysfunction and clearance of Ab, the availability of drugs to treat CAA or AD remains lacking. Identifying strategies to rectify BBB integrity and function, and maximize clearance of Ab from the brain is of high clinical importance for the development of interventions, which prevent or delay onset of CAA and AD.Methods:In my lab, we developed a novel BBB model consisting of cerebrovascular endothelial cells and high-throughput screening (HTS) methodologies to screen for hit compounds that ameliorate Ab induced increases in endothelial cell permeability and enhance Ab clearance. Identified hits were then tested in vivo in AD mouse model for BBB tightness, Ab brain levels and Ab related pathology. Results:Multiple hit compounds were identified from the screening that were ranked for their potencies. Most potent compounds were in vivo evaluated in ADmouse model for their therapeutic effect against AD pathology. Our in vitro to in vivo studies have successfully identified candidate therapeutic molecules to test in future clinical studies. Conclusions:Our findings demonstrated the BBB as a therapeutic target to prevent and/or slow the progression of the amyloid pathogenesis disorders CAA and AD.

MODEL-AD: CHARACTERIZATION OF FAMILIAL AD MODELS (5XFAD, APP/PS1, HTAU, 3XTG-AD)

function (rotarod and pole tests), memory (8-arm radial arm maze), and anxiety (open field). In addition, brain, spinal cord, and muscle were evaluated by histology and biochemistry. Results:Our results indicate mild motor deficits on the grip strength test from the NEFH/A315Tmice. Rotarod and 8-arm radial maze showed no significant deficiencies comparing the hTDP-43 and A315T expressing mice. We do see an accumulation of phosphorylated TDP-43 positive neurons and some change in muscle organization present in the A315T mouse, though little motor deficit is evident in the mice at 10-months of age. Conclusions:Although we observe just moderate changes in motor function, this model may provide insight into understanding the early pathological markers associated with the pathogenesis of ALS.

MODEL-AD: LATE-ONSET ALZHEIMER’S DISEASE MODELS

function (rotarod and pole tests), memory (8-arm radial arm maze), and anxiety (open field). In addition, brain, spinal cord, and muscle were evaluated by histology and biochemistry. Results:Our results indicate mild motor deficits on the grip strength test from the NEFH/A315Tmice. Rotarod and 8-arm radial maze showed no significant deficiencies comparing the hTDP-43 and A315T expressing mice. We do see an accumulation of phosphorylated TDP-43 positive neurons and some change in muscle organization present in the A315T mouse, though little motor deficit is evident in the mice at 10-months of age. Conclusions:Although we observe just moderate changes in motor function, this model may provide insight into understanding the early pathological markers associated with the pathogenesis of ALS.

NOVEL MODELS OF LATE-ONSET ALZHEIMER’S DISEASE BASED ON GWAS

amyloid beta(Ab) and protecting nerve cells. Furthermore, 6MSITC has been reported to be absorbed a high rate in the body, which is considered to be about from 40 to 60%. Other isothiocyanate, as an analog of 6-MSITC, has been reported to permeate the brain blad barrier. Therefore, 6-MSITC can be considered as an effective compound for brain function. Methods: The doubleblinded clinical study was conducted using 6-MSITC (25 placebo, 25 subjects, 8 weeks ingestion), and the rat pheochromocytoma cell line, PC12, were used to study the synergistic effects for the neurite outgrowth, dopamine secretion and Ab toxicity by 6-MSITC, DHA, curcumin, isorhamnetin. Results:Significant results were obtained by the clinical test. Furthermore, we found that 6-MSITC reduced the toxicity from Ab, increased secretion of dopamine on nerve cells. 6-MSITC also has synergistic effects of DHA, curcumin, and ginkgo biloba compound, which are considered to be good compounds for improvement of brain function. Conclusions: Thus, 6-MSITC may be used a compound to prevent Alzheimer’s disease.