Mirjam I. Lutz

Intracellular processing of disease-associated α-synuclein in the human brain suggests prion-like cell-to-cell spread.

Dementia with Lewy bodies (DLB), Parkinsons disease (PD) and multiple system atrophy are characterized by the deposition of disease-associated α-synuclein. In the present study we 1) examined the molecular specificity of the novel anti-α-synuclein 5G4 antibody; 2) evaluated immunoreactivity patterns and their correlation in human brain tissue with micro- and astrogliosis in 57 cases with PD or DLB; and 3) performed a systematic immunoelectron microscopical mapping of subcellular localizations. 5G4 strongly binds to the high molecular weight fraction of β-sheet rich oligomers, while no binding to primarily disordered oligomers or monomers was observed. We show novel localizations of disease-associated α-synuclein including perivascular macrophages, ependyma and cranial nerves. α-Synuclein immunoreactive neuropil dots and thin threads associate more with glial reaction than Lewy bodies alone. Astrocytic α-synuclein is an important component of the pathology. Furthermore, we document ultrastructurally the pathway of processing of disease-associated α-synuclein within neurons and astroglial cells. Interaction of mitochondria and disease-associated α-synuclein plays a key role in the molecular-structural cytopathogenesis of disorders with Lewy bodies. We conclude that 1) the 5G4 antibody has strong selectivity for β-sheet rich α-synuclein oligomers; 2) Lewy bodies themselves are not the most relevant morphological substrate that evokes tissue lesioning; 3) both neurons and astrocytes internalize disease-associated α-synuclein in the human brain, suggesting prion-like cell-to-cell spread of α-synuclein by uptake from surrounding structures, as shown previously in experimental observations.

Amyloid-β pathology and cerebral amyloid angiopathy are frequent in iatrogenic Creutzfeldt-Jakob disease after dural grafting.

QUESTIONS UNDER STUDY Alzheimer-type amyloid-β (Aβ) pathology was reported in brains of individuals developing iatrogenic Creutzfeldt-Jakob disease (iCJD) after treatment with human cadaveric growth hormone, and interpreted as evidence of human transmission of Aβ by the treatment. Here we investigated the prevalence of Aβ pathology in other instances of iCJD related to dura mater grafts. METHODS By use of immunohistochemistry for Aβ, we investigated seven brains of patients (age range 28-63) who succumbed to iCJD after dural grafting, which had been applied by means of neurosurgery between 11 and 25 years before death. For control, we examined a series of 21 brains of age-matched (40-63 years) patients with sporadic CJD (sCJD) and an additional series of 81 sCJD cases (55-85 years) with the same methods. RESULTS In five of seven iCJD brains, Aβ was deposited in meningeal vessels as congophilic amyloid angiopathy and brain parenchymal plaques. This was significantly (p <0.001) more frequent than in the age-matched sCJD controls and in the usual sCJD series. CONCLUSIONS We conclude that congophilic amyloid angiopathy and brain parenchymal Aβ plaques are frequent in iCJD after dural grafting. The presence of Aβ pathology in young individuals is highly unusual and suggests a causal relationship to the dural grafts. Further studies will be needed to elucidate whether such pathology resulted from the seeding of Aβ aggregates from the grafts to host tissues.

Distinct Patterns of Sirtuin Expression During Progression of Alzheimer’s Disease

Aging is one of the major risk factors for Alzheimer’s disease (AD). Sirtuins are associated with prolonged life span. To examine whether the expression levels of sirtuins associate with the progression of AD or not, we performed a comparative immunoblotting and immunohistochemical study of SIRT1, 3, and 5 in the entorhinal cortex and hippocampal subregions and white matter in 45 cases grouped according to Braak and Braak stages of neurofibrillary degeneration. In addition, we compared the expression levels with the local load of tau and amyloid-beta deposits, evaluated using morphometry. Our study revealed that (1) the neuronal subcellular redistribution of SIRT1 parallels the decrease in its expression, suggesting stepwise loss of neuroprotection dependent on the neuronal population; (2) in contrast to SIRT1 and 3, expression of SIRT5 increases during the progression of AD; (3) which might be related to its appearance in activated microglial cells. The complex patterns of the expression of sirtuins in relation to tissue damage should be taken into account when searching for therapies interacting with sirtuins.

Heroin abuse exaggerates age-related deposition of hyperphosphorylated tau and p62-positive inclusions

The observation of increased hyperphosphorylated tau levels correlating with microglial activation in opiate abusers has been interpreted as predisposition to accelerated Alzheimer disease-related changes. The present study focused on evaluating additional neurodegeneration-related proteins, including α-synuclein and TDP-43, and p62-positive deposits. We performed a systematic mapping of protein deposits in the brains of 27 individuals with documented heroin addiction (age: 19-40 years) and compared with 11 controls (age: 15-40 years). We confirm previous findings that heroin addiction associates with tau hyperphosphorylation in predilection brain areas for aging and Alzheimer disease. Furthermore, we show that this occurs also in areas implicated in the molecular disturbances and in vivo neuronal networks related to heroin abuse. There was, however, no presence of amyloid-beta deposits. We extend previous findings by showing the lack of TDP-43 or α-synuclein pathology and emphasize the independent effect of the duration of drug use on the appearance of age-related p62-positive neuritic profiles. These observations provide unique insights about neuropathological alterations in the brains of young heroin addicts and have implications about brain aging and the influences of environmental and toxic factors.

Tau Pathology in Creutzfeldt-Jakob Disease Revisited.

Creutzfeldt‐Jakob disease (CJD) is a human prion disease with different etiologies. To determine the spectrum of tau pathologies in CJD, we assessed phospho‐Tau (pTau) immunoreactivities in 75 sporadic CJD cases including an evaluation of the entorhinal cortex and six hippocampal subregions. Twelve cases (16%) showed only small tau‐immunoreactive neuritic profiles. Fifty‐two (69.3%) showed additional tau pathology in the medial temporal lobe compatible with primary age related tauopathy (PART). In 22/52 cases the lower pTau immunoreactivity load in the entorhinal cortex as compared to subiculum, dentate gyrus or CA4 region of the hippocampus was significantly different from the typical distribution of the Braak staging. A further 11 cases (14.7%) showed widespread tau pathologies compatible with features of primary tauopathies or the gray matter type of ageing‐related tau astrogliopathy (ARTAG). Prominent gray matter ARTAG was also observed in two out of three additionally examined V203I genetic CJD cases. Analysis of cerebrospinal fluid revealed prominent increase of total tau protein in cases with widespread tau pathology, while pTau (T181) level was increased only in four. This correlated with immunohistochemical observations showing less pathology with anti‐pTau T181 antibody when compared to anti‐pTau S202/T205, T212/S214 and T231. The frequency of tau pathologies is not unusually high in sporadic CJD and does not precisely relate to PrP deposition. However, the pattern of hippocampal tau pathology often deviates from the stages of Braak. Currently applied examination of cerebrospinal fluid pTau (T181) level does not reliably reflect primary tauopathies, PART and ARTAG seen in CJD brains.

Shared and Distinct Patterns of Oligodendroglial Response in α-Synucleinopathies and Tauopathies

Pathological protein deposits in oligodendroglia are common but variable features of various neurodegenerative conditions. To evaluate oligodendrocyte response in neurodegenerative diseases (NDDs) with different extents of oligodendroglial protein deposition we performed immunostaining for tubulin polymerization-promoting protein p25&agr; (TPPP/p25&agr;), &agr;-synuclein (&agr;-syn), phospho-tau, ubiquitin, myelin basic protein, and the microglial marker HLA-DR. We investigated cases of multiple system atrophy ([MSA] n = 10), Lewy body disease ([LBD] n = 10), globular glial tauopathy ([GGT] n = 7) and progressive supranuclear palsy ([PSP] n = 10). Loss of nuclear TPPP/p25&agr; immunoreactivity correlated significantly with the degree of microglial reaction and loss of myelin basic prtein density as a marker of tract degeneration. This was more prominent in MSA and GGT, which, together with enlarged cytoplasmic TPPP/p25&agr; immunoreactivity and inclusion burden allowed these disorders to be grouped as predominant oligodendroglial proteinopathies. However, distinct features, ie more colocalization of &agr;-syn than tau with TPPP/p25&agr;, more obvious loss of oligodendrocyte density in MSA, but more prominent association of tau protein inclusions in GGT to loss of nuclear TPPP/p25&agr; immunoreactivity, were also recognized. In addition, we observed previously underappreciated oligodendroglial &agr;-synuclein pathology in the pallidothalamic tract in LBD. Our study demonstrates common and distinct aspects of oligodendroglial involvement in the pathogenesis of diverse NDDs.

Familial early-onset dementia with complex neuropathologic phenotype and genomic background

Despite significant progress in our understanding of hereditary neurodegenerative diseases, the list of genes associated with early-onset dementia is not yet complete. In the present study, we describe a familial neurodegenerative disorder characterized clinically as the behavioral and/or dysexecutive variant of Alzheimers disease with neuroradiologic features of Alzheimers disease, however, lacking amyloid-β deposits in the brain. Instead, we observed a complex, 4 repeat predominant, tauopathy, together with a TAR DNA-binding protein of 43 kDa proteinopathy. Whole-exome sequencing on 2 affected siblings and 1 unaffected aunt uncovered a large number of candidate genes, including LRRK2 and SYNE2. In addition, DDI1, KRBA1, and TOR1A genes possessed novel stop-gain mutations only in the patients. Pathway, gene ontology, and network interaction analysis indicated the involvement of pathways related to neurodegeneration but revealed novel aspects also. This condition does not fit into any well-characterized category of neurodegenerative disorders. Exome sequencing did not disclose a single disease-specific gene mutation suggesting that a set of genes working together in different pathways may contribute to the etiology of the complex phenotype.

The role of proto-oncogene GLI1 in pituitary adenoma formation and cell survival regulation

The Hedgehog (Hh) pathway is an important regulator of early tissue patterning and stem cell propagation. It was found to be aberrantly activated in numerous types of human cancer and might be relevant in cancer stem cells. The identification of adult stem cells in the pituitary raised the question if tumor-initiating cells and Hh signaling are involved in pituitary adenoma formation. The present study aimed at the evaluation of Hh signaling in relation to stem cell and cell cycle markers in 30 human pituitary adenomas and in cultured murine adenoma cells. Therefore, expression levels of components of the Hh pathway, stem cell marker SOX2, cell cycle regulator tumor-protein 53 (TP53), proliferation marker Ki67 (MKI67) and superoxide dismutase 1 (SOD1) were evaluated in 30 human pituitary adenomas in comparison to control tissue. Modulation of cell function and target gene expression by the inhibition and activation of the Hh pathway were studied in murine adenoma cells. We show that transcription factor glioma-associated oncogene 1 (GLI1) is overexpressed in 87% of all pituitary adenomas. The expression of GLI1 significantly correlated with that of SOX2, TP53, MKI67 and SOD1. Inhibition of GLI1 resulted in the downregulation of the above genes and severe cell death in mouse adenoma cells. On the other hand, activation of the Hh pathway increased cell viability and target gene expression. In conclusion, our findings point toward an alternative, ligand-independent Hh pathway activation with GLI1 playing a major role in the cell survival of pituitary adenoma cells.

Secretagogin-dependent matrix metalloprotease-2 release from neurons regulates neuroblast migration

Significance Persisting proliferative capacity and regeneration in the adult brain are confined to a minority of regions. In the murine brain, the olfactory system is supplied by thousands of newly born neuroblasts daily to support sensory plasticity. Here, we reveal a neuronal scaffold that resides within and alongside this migratory route [termed the “rostral migratory stream” (RMS)] to guide forward migration of newly born neuroblasts. These neurons can externalize the enzyme matrix metalloprotease-2 to loosen the extracellular matrix, thus producing permissive corridors for migrating neuroblasts. This mechanism is likely phylogenetically conserved because it exists in the RMS equivalent in human fetal brains. This inducible mechanism might be pharmacologically targeted for therapeutic benefit. The rostral migratory stream (RMS) is viewed as a glia-enriched conduit of forward-migrating neuroblasts in which chemorepulsive signals control the pace of forward migration. Here we demonstrate the existence of a scaffold of neurons that receive synaptic inputs within the rat, mouse, and human fetal RMS equivalents. These neurons express secretagogin, a Ca2+-sensor protein, to execute an annexin V-dependent externalization of matrix metalloprotease-2 (MMP-2) for reconfiguring the extracellular matrix locally. Mouse genetics combined with pharmacological probing in vivo and in vitro demonstrate that MMP-2 externalization occurs on demand and that its loss slows neuroblast migration. Loss of function is particularly remarkable upon injury to the olfactory bulb. Cumulatively, we identify a signaling cascade that provokes structural remodeling of the RMS through recruitment of MMP-2 by a previously unrecognized neuronal constituent. Given the life-long presence of secretagogin-containing neurons in human, this mechanism might be exploited for therapeutic benefit in rescue strategies.

Plasma and cerebrospinal fluid tau and neurofilament concentrations in rapidly progressive neurological syndromes: a neuropathology-based cohort

Cerebrospinal fluid (CSF) tau and neurofilament light chain (NF‐L) proteins have proved to be reliable biomarkers for neuronal damage; however, there is a strong need for blood‐based tests.