Widespread expression of alpha-synuclein and tau immunoreactivity in Hallervorden-Spatz syndrome with protracted clinical course

Parkinson's Disease and Metal Storage Disorders: A Systematic Review

Metal storage disorders (MSDs) are a set of rare inherited conditions with variable clinical pictures including neurological dysfunction. The objective of this study was, through a systematic review, to identify the prevalence of Parkinsonism in patients with MSDs in order to uncover novel pathways implemented in Parkinson’s disease. Human studies describing patients of any age with an MSD diagnosis were analysed. Foreign language publications as well as animal and cellular studies were excluded. Searches were conducted through PubMed and Ovid between April and September 2018. A total of 53 publications were identified including 43 case reports, nine cross-sectional studies, and one cohort study. The publication year ranged from 1981 to 2018. The most frequently identified MSDs were Pantothenate kinase-associated neurodegeneration (PKAN) with 11 papers describing Parkinsonism, Hereditary hemochromatosis (HH) (7 papers), and Wilson’s disease (6 papers). The mean ages of onset of Parkinsonism for these MSDs were 33, 53, and 48 years old, respectively. The Parkinsonian features described in the PKAN and HH patients were invariably atypical while the majority (4/6) of the Wilson’s disease papers had a typical picture. This paper has highlighted a relationship between MSDs and Parkinsonism. However, due to the low-level evidence identified, further research is required to better define what the relationship is.

Review: Spreading the word: precise animal models and validated methods are vital when evaluating prion-like behaviour of alpha-synuclein

Synucleinopathies are characterized by abnormal proteinaceous aggregates, mainly composed of fibrillar α-synuclein (α-syn). It is now believed that α-syn can form small aggregates in a restricted number of cells, that propagate to neighbouring cells and seed aggregation of endogenous α-syn, in a 'prion-like manner'. This process could underlie the stereotypical progression of Lewy bodies described by Braak and colleagues across different stages of Parkinson's disease (PD). This prion-like behaviour of α-syn has been recently investigated in animal models of PD or multiple system atrophy (MSA). These models investigate the cell-to-cell transfer of α-syn seeds, or the induction and spreading of α-syn pathology in transgenic or wild-type rodent brain. In this review, we first outline the involvement of α-syn in Lewy body diseases and MSA, and discuss how 'prion-like' mechanisms can contribute to disease. Thereon, we debate the relevance of animal models used to study prion-like propagation. Finally, we review current main histological methods used to assess α-syn pathology both in animal models and in human samples and their relevance to the disease. Specifically, we discuss using α-syn phosphorylated at serine 129 as a marker of pathology, and the novel methods available that allow for more sensitive detection of early pathology, which has relevance for modelling synucleinopathies.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

Protein kinases are one of the largest families of evolutionarily related proteins and the third most common protein class of human genome. All the protein kinases share the same structural organization. They are made up of an extracellular domain, transmembrane domain and an intra cellular kinase domain. Missense mutations in these kinases have been studied extensively and correlated with various neurological disorders. Individual mutations in the kinase domain affect the functions of protein. The enhanced or reduced expression of protein leads to hyperactivation or inactivation of the signalling pathways, resulting in neurodegeneration. Here, we present extensive analyses of missense mutations in the tyrosine kinase focussing on the neurodegenerative diseases encompassing structure function relationship. This is envisaged to enhance our understanding about the neurodegeneration and possible therapeutic measures.

The Synaptic Function of α-Synuclein

α-Synuclein is an abundant neuronal protein which localizes predominantly to presynaptic terminals, and is strongly linked genetically and pathologically to Parkinson's disease and other neurodegenerative diseases. While the accumulation of α-synuclein in the form of misfolded oligomers and large aggregates defines multiple neurodegenerative diseases called "synucleinopathies", its cellular function has remained largely unclear, and is the subject of intense investigation. In this review, I focus on the structural characteristics of α-synuclein, its cellular and subcellular localization, and discuss how this relates to its function in neurons, in particular at the neuronal synapse.

Hallervorden-Spatz disease

Hallervorden-Spatz disease (HSD) is a rare disorder characterized by progressive extrapyramidal dysfunction and dementia. Hallervorden and Spatz first described the disease, in 1922 as a form of familial brain degeneration characterized by iron deposition in the brain. Here we present four HSD cases with different clinical pictures.

Phenotypes and genotypes of patients with pantothenate kinase-associated neurodegeneration in Asian and Caucasian populations: 2 cases and literature review

Objectives. Pantothenate kinase-associated neurodegeneration (PKAN) is a rare disease caused by pantothenate kinase 2 (PANK2, OMIM 606157) mutations. This study is aimed to investigate clinical presentations, pathologies, and genetics in patients with PKAN. Methods. Two patients with PKAN were reported. We reviewed the literature to include additional 19 patients with PKAN in Eastern Asia. These patients were divided into classic and atypical groups by the age of onset. We compared the data on PKAN patients of Asian and Caucasian populations. Results. We found iron deposits in the globus pallidus in our Patient 1 and a heterozygous truncating mutation (c.1408insT) in Patient 2. Literature review shows that generalized dystonia and bulbar signs are more common in classic PKAN patients, whereas segmental dystonia and tremors are more specific to atypical ones. Asian patients have less complex presentations—lower prevalence of pyramidal signs, mental impairment, and parkinsonism—than Caucasians. D378G in exon 3 is the most frequent mutation (28%) in Asians. Conclusions. Our study demonstrates that the distribution of dystonia is the major distinction between subgroups of PKAN. Caucasian patients have more complex presentations than Asians. Exon 3 and 4 are hot spots for screening PANK2 mutations in Asian patients.

Genetics and Pathophysiology of Neurodegeneration with Brain Iron Accumulation (NBIA)

Our understanding of the syndromes of Neurodegeneration with Brain Iron Accumulation (NBIA) continues to grow considerably. In addition to the core syndromes of pantothenate kinase-associated neurodegeneration (PKAN, NBIA1) and PLA2G6-associated neurodegeneration (PLAN, NBIA2), several other genetic causes have been identified (including FA2H, C19orf12, ATP13A2, CP and FTL). In parallel, the clinical and pathological spectrum has broadened and new age-dependent presentations are being described. There is also growing recognition of overlap between the different NBIA disorders and other diseases including spastic paraplegias, leukodystrophies and neuronal ceroid lipofuscinosis which makes a diagnosis solely based on clinical findings challenging. Autopsy examination of genetically-confirmed cases demonstrates Lewy bodies, neurofibrillary tangles, and other hallmarks of apparently distinct neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease. Until we disentangle the various NBIA genes and their related pathways and move towards pathogenesis-targeted therapies, the treatment remains symptomatic. Our aim here is to provide an overview of historical developments of research into iron metabolism and its relevance in neurodegenerative disorders. We then focus on clinical features and investigational findings in NBIA and summarize therapeutic results reviewing reports of iron chelation therapy and deep brain stimulation. We also discuss genetic and molecular underpinnings of the NBIA syndromes.

Excess iron harms the brain: the syndromes of neurodegeneration with brain iron accumulation (NBIA)

Regulation of iron metabolism is crucial: both iron deficiency and iron overload can cause disease. In recent years, our understanding of the syndromes of Neurodegeneration with Brain Iron Accumulation (NBIA) continues to grow considerably. These are characterized by excessive iron deposition in the brain, mainly the basal ganglia. Pantothenate kinase-associated neurodegeneration (PKAN, NBIA1) and PLA2G6-associated neurodegeneration (PLAN, NBIA2) are the core syndromes, but several other genetic causes have been identified (including FA2H, C19orf12, ATP13A2, CP and FTL). These conditions show a wide clinical and pathological spectrum, with clinical overlap between the different NBIA disorders and other diseases including spastic paraplegias, leukodystrophies, and neuronal ceroid lipofuscinosis. Lewy body pathology was confirmed in some clinical subtypes (C19orf12-associated neurodegeneration and PLAN). Research aims at disentangling the various NBIA genes and their related pathways to move towards pathogenesis-targeted therapies. Until then treatment remains symptomatic. Here we will introduce the group of NBIA syndromes and review the main clinical features and investigational findings.

Syndromes of neurodegeneration with brain iron accumulation

In parallel to recent developments of genetic techniques, understanding of the syndromes of neurodegeneration with brain iron accumulation has grown considerably. The acknowledged clinical spectrum continues to broaden, with age-dependent presentations being recognized. Postmortem brain examination of genetically confirmed cases has demonstrated Lewy bodies and/or tangles in some forms, bridging the gap to more common neurodegenerative disorders, including Parkinson disease. In this review, the major forms of neurodegeneration with brain iron accumulation (NBIA) are summarized, concentrating on clinical findings and molecular insights. In addition to pantothenate kinase-associated neurodegeneration (PKAN) and phospholipase A2-associated neurodegeneration (PLAN), fatty acid hydroxylase-associated neurodegeneration (FAHN) NBIA, mitochondrial protein-associated neurodegeneration, Kufor-Rakeb disease, aceruloplasminemia, neuroferritinopathy, and SENDA syndrome (static encephalopathy of childhood with neurodegeneration in adulthood) are discussed.

Case report: MR spectroscopy in pantothenate kinase-2 associated neurodegeneration

We report a case of a 13-year-old girl with Hallervorden-Spatz disease (HSD) or pantothenate kinase-2 associated neurodegeneration (PKAN). HSD is a rare neurodegenerative disorder, which is characterized by a rapidly progressive extrapyramidal syndrome, dementia with optic atrophy, and retinal degeneration. It is associated with accumulation of cysteine-iron complex in the globus pallidi and substantia nigra. The MRI “eye of the tiger” sign is the characteristic. MRI spectroscopy is also characteristic. It shows markedly decreased NAA/Cr values in the globus pallidi and substantia nigra with increased mI/Cr values that suggest of gliosis.

Novel histopathologic findings in molecularly-confirmed pantothenate kinase-associated neurodegeneration

Pantothenate kinase-associated neurodegeneration is a form of neurodegeneration with brain iron accumulation, characterized by a progressive movement disorder and prominent iron deposition in the globus pallidus. Formerly referred to as Hallervorden-Spatz syndrome, the disorder was renamed pantothenate kinase-associated neurodegeneration after discovery of the causative gene, PANK2. Although the pathological features of clinically characterized Hallervorden-Spatz syndrome have been described, the literature is confounded by the historical use of this term for nearly all conditions with prominent basal ganglia iron accumulation and by the fact that this term encompasses a genetically heterogeneous group of disorders, now referred to as 'neurodegeneration with brain iron accumulation'. As a result, interpreting reports that precede molecular characterization of specific forms of neurodegeneration with brain iron accumulation is problematic. In the present studies, we describe neuropathological findings in six cases of molecularly confirmed pantothenate kinase-associated neurodegeneration. We identify prominent ubiquinated deposits in pantothenate kinase-associated neurodegeneration. We also characterize two distinct origins of spheroid bodies and delineate histological features of iron deposition. In so doing, we characterize fundamental features of the disease and redefine its nosological relationship to other neurodegenerative disorders.

Widespread Lewy body and tau accumulation in childhood and adult onset dystonia-parkinsonism cases with PLA2G6 mutations

The 2 major types of neurodegeneration with brain iron accumulation (NBIA) are the pantothenate kinase type 2 (PANK2)-associated neurodegeneration (PKAN) and NBIA2 or infantile neuroaxonal dystrophy (INAD) due to mutations in the phospholipase A2, group VI (PLA2G6) gene. We have recently demonstrated clinical heterogeneity in patients with mutations in the PLA2G6 gene by identifying a poorly defined subgroup of patients who present late with dystonia and parkinsonism. We report the clinical and genetic features of 7 cases with PLA2G6 mutations. Brain was available in 5 cases with an age of death ranging from 8 to 36 years and showed widespread alpha-synuclein-positive Lewy pathology, which was particularly severe in the neocortex, indicating that the Lewy pathology spread corresponded to Braak stage 6 and was that of the “diffuse neocortical type”. In 3 cases there was hyperphosphorylated tau accumulation in both cellular processes as threads and neuronal perikarya as pretangles and neurofibrillary tangles. Later onset cases tended to have less tau involvement but still severe alpha-synuclein pathology. The clinical and neuropathological features clearly represent a link between PLA2G6 and parkinsonian disorders.

Clinical and genetic delineation of neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) describes a group of progressive neurodegenerative disorders characterised by high brain iron and the presence of axonal spheroids, usually limited to the central nervous system. Mutations in the PANK2 gene account for the majority of NBIA cases and cause an autosomal recessive inborn error of coenzyme A metabolism called pantothenate kinase associated neurodegeneration (PKAN). More recently, it was found that mutations in the PLA2G6 gene cause both infantile neuroaxonal dystrophy (INAD) and, more rarely, an atypical neuroaxonal dystrophy that overlaps clinically with other forms of NBIA. High brain iron is also present in a portion of these cases. Clinical assessment, neuroimaging, and molecular genetic testing all play a role in guiding the diagnostic evaluation and treatment of NBIA.

Neuropathologic Findings in an Aged Albino Gorilla

Pallido-nigral spheroids associated with iron deposition have been observed in some aged clinically normal nonhuman primates. In humans, similar findings are observed in neurodegeneration with brain iron accumulation diseases, which, in some cases, show associated mutations in pantothenate kinase 2 gene (PANK2). Here we present an aged gorilla, 40 years old, suffering during the last 2 years of life from progressive tetraparesis, nystagmus, and dyskinesia of the arms, hands, and neck, with accompanying abnormal behavior. The postmortem neuropathologic examination revealed, in addition to aging-associated changes in the brain, numerous corpora amylacea in some brain areas, especially the substantia nigra, and large numbers of axonal spheroids associated with iron accumulation in the internal globus pallidus. Sequencing of the gorilla PANK2 gene failed to detect any mutation. The clinical, neuropathologic, and genetic findings in this gorilla point to an age-related pallido-nigral degeneration that presented PKAN-like neurologic deficits.

Disrupted membrane homeostasis and accumulation of ubiquitinated proteins in a mouse model of infantile neuroaxonal dystrophy caused by PLA2G6 mutations

Mutations in the PLA2G6 gene, which encodes group VIA calcium-independent phospholipase A2 (iPLA(2)beta), were recently identified in patients with infantile neuroaxonal dystrophy (INAD) and neurodegeneration with brain iron accumulation. A pathological hallmark of these childhood neurodegenerative diseases is the presence of distinctive spheroids in distal axons that contain accumulated membranes. We used iPLA(2)beta-KO mice generated by homologous recombination to investigate neurodegenerative consequences of PLA2G6 mutations. iPLA(2)beta-KO mice developed age-dependent neurological impairment that was evident in rotarod, balance, and climbing tests by 13 months of age. The primary abnormality underlying this neurological impairment was the formation of spheroids containing tubulovesicular membranes remarkably similar to human INAD. Spheroids were strongly labeled with anti-ubiquitin antibodies. Accumulation of ubiquitinated protein in spheroids was evident in some brain regions as early as 4 months of age, and the onset of motor impairment correlated with a dramatic increase in ubiquitin-positive spheroids throughout the neuropil in nearly all brain regions. Furthermore accumulating ubiquitinated proteins were observed primarily in insoluble fractions of brain tissue, implicating protein aggregation in this pathogenic process. These results indicate that loss of iPLA(2)beta causes age-dependent impairment of axonal membrane homeostasis and protein degradation pathways, leading to age-dependent neurological impairment. iPLA(2)beta-KO mice will be useful for further studies of pathogenesis and experimental interventions in INAD and neurodegeneration with brain iron accumulation.

Human-based studies on α-synuclein deposition and relationship to Parkinson's disease symptoms

This article reviews the current knowledge on alpha-synuclein and its cellular locations in studies using human brain tissue. Alterations in the conformation and distribution of alpha-synuclein are examined in Parkinson's disease and the relationship between clinical symptoms and pathology explored. alpha-Synuclein as a molecular chaperone has several isoforms and is known to have different environment-dependent conformations. Processing methods for studying human brain tissue significantly impact on the conformational type of alpha-synuclein analysed, and antibody species used for the in situ detection of alpha-synuclein give variable results depending on the epitope visualised. Human studies show that alpha-synuclein is not isolated to neurons, but is also found in glia, making the interpretation of studies using brain tissue homogenates less clearly related to neurons. These methodological issues impact significantly on our understanding of the form, location, and therefore function of alpha-synuclein in normal human brain tissue. There are less methodological issues regarding highly aggregated alpha-synuclein found in the major hallmark of Parkinson's disease, the Lewy body. However, it remains unclear whether these alpha-synuclein inclusions are harmful to host neurons or provide protection. Several correlations exist between the clinical symptoms of Parkinson's disease and the distribution of Lewy pathology, the strongest being the association between limbic and cortical Lewy bodies and well-formed visual hallucinations. Further correlation studies in prospectively-followed patients and, perhaps more importantly, controls are required in order to determine normal versus pathologic alpha-synuclein and how to detect such differences in clinical situations.

Tau-predominant-associated pathology in a sporadic late-onset Hallervorden-Spatz syndrome

Hallervorden-Spatz syndrome (HSS) is a heterogeneous clinicopathological disorder currently included within the broader title of neurodegeneration with brain iron accumulation (NBIA). The classic histological hallmarks of HSS are axonal spheroids and excessive iron-containing granules accompanied by neuronal loss and gliosis in the globus pallidus and substantia nigra reticulata. In the modern literature, attention has been drawn to the co-occurrence of two other histological markers: Lewy bodies mainly composed of abnormal alpha-synuclein, and neurofibrillary tangles due to hyperphosphorilated tau aggregation. Discrepancies exist regarding the importance of these molecular changes and its relevance for the nosology of HSS. Most authors have emphasized the importance of the Lewy body-like pathology, favoring the inclusion of HSS within the alpha-synucleinopathies. We report on a case of late-onset HSS, with the typical histological findings restricted to the basal ganglia and cerebellum in which tau pathology was exceedingly more abundant than alpha-synuclein pathology. This case contributes to the increasing evidence about the heterogeneity of HSS. We favor the view that the molecular changes and the protein misfolding underlying the Lewy body and tangle formation in HSS/NBIA are secondary to the main pathological process and should not be taken as the basis for its nosological classification.

Brain ferritin iron may influence age- and gender-related risks of neurodegeneration

BACKGROUND

Brain iron promotes oxidative damage and protein oligomerization that result in highly prevalent age-related proteinopathies such as Alzheimer's disease (AD), Parkinson's disease (PD), and Dementia with Lewy Bodies (DLB). Men are more likely to develop such diseases at earlier ages than women but brain iron levels increase with age in both genders. We hypothesized that brain iron may influence both the age- and gender-related risks of developing these diseases.

METHODS

The amount of iron in ferritin molecules (ferritin iron) was measured in vivo with MRI by utilizing the field dependent relaxation rate increase (FDRI) method. Ferritin iron was measured in four subcortical nuclei [caudate (C), putamen (P), globus pallidus (G), thalamus (T)], three white matter regions [frontal lobe (Fwm), genu and splenium of the corpus callosum (Gwm, Swm)] and hippocampus (Hipp) in 165 healthy adults aged 19-82.

RESULTS

There was a high correlation (r>0.99) between published post-mortem brain iron levels and FDRI. There were significant age-related changes in ferritin iron (increases in Hipp, C, P, G, and decreases in Fwm). Women had significantly lower ferritin iron than men in five regions (C, T, Fwm, Gwm, Swm).

CONCLUSIONS

This is the first demonstration of gender differences in brain ferritin iron levels. It is possible that brain iron accumulation is a risk factor that can be modified. MRI provides the opportunity to assess brain iron levels in vivo and may be useful in targeting individuals or groups for preventive therapeutic interventions.

Altered neuronal mitochondrial coenzyme A synthesis in neurodegeneration with brain iron accumulation caused by abnormal processing, stability, and catalytic activity of mutant pantothenate kinase 2

Mutations in the pantothenate kinase 2 (PANK2) gene have been identified in patients with neurodegeneration with brain iron accumulation (NBIA; formerly Hallervorden-Spatz disease). However, the mechanisms by which these mutations cause neurodegeneration are unclear, especially given the existence of multiple pantothenate kinase genes in humans and multiple PanK2 transcripts with potentially different subcellular localizations. We demonstrate that PanK2 protein is localized to mitochondria of neurons in human brain, distinguishing it from other pantothenate kinases that do not possess mitochondrial-targeting sequences. PanK2 protein translated from the most 5' start site is sequentially cleaved at two sites by the mitochondrial processing peptidase, generating a long-lived 48 kDa mature protein identical to that found in human brain extracts. The mature protein catalyzes the initial step in coenzyme A (CoA) synthesis but displays feedback inhibition in response to species of acyl CoA rather than CoA itself. Some, but not all disease-associated point mutations result in significantly reduced catalytic activity. The most common mutation, G521R, results in marked instability of the intermediate PanK2 isoform and reduced production of the mature isoform. These results suggest that NBIA is caused by altered neuronal mitochondrial lipid metabolism caused by mutations disrupting PanK2 protein levels and catalytic activity.

Mutations in the pantothenate kinase gene PANK2 are not associated with Parkinson disease

Pantothenate kinase-associated neurodegeneration (PKAN) may serve as a model for Parkinson disease (PD) since many PKAN patients suffer from parkinsonism and both conditions lead to iron accumulation in the basal ganglia. We screened the gene coding for pantothenate kinase 2 (PANK2) for sequence variants in PD. We found no mutations in 67 PD patients with affected sibs or early-onset disease. Moreover, PANK2 polymorphisms were not associated with late-onset idiopathic PD in 339 patients. We conclude that PANK2 variants exert, if any, only a very small effect in the genetic risk of PD.

Role of oxidative damage in protein aggregation associated with Parkinson's disease and related disorders

Parkinson's disease, the most common movement disorder, is characterized by the loss of brainstem neurons, specifically dopaminergic neurons in the substantia nigra, as well as the accumulation of neuronal cytoplasmic filamentous proteinaceous inclusions comprised of polymerized alpha-synuclein. It was reported recently that alpha-synuclein can induce the formation of filamentous tau inclusions, which are characteristic of disorders like Alzheimer's disease and Lewy body variant of Alzheimer's disease, suggesting that a similar mechanism may exist between alpha-synuclein fibrillogenesis and tau polymerization. Pathological brain inclusions comprised of alpha-synuclein or tau proteins are associated with a spectrum of neurodegenerative disorders, and oxidative and nitrative injury has been implicated in all of these diseases. However, the role of oxidative damage in alpha-synuclein and tau polymerization and pathological inclusion formation is complex. Differences in the level, type, and temporal sequence of the oxidative alterations appear to result in both inhibitory and stimulatory effects on the fibrillogenesis of these proteins.

The role of α-synuclein in neurodegenerative diseases

Alpha-synuclein is a 140 amino acid neuronal protein that has been associated with several neurodegenerative diseases. A point mutation in the gene coding for the alpha-synuclein protein was the first discovery linking this protein to a rare familial form of Parkinson's disease (PD). Subsequently, other mutations in the alpha-synuclein gene have been identified in familial PD. The aggregated proteinaceous inclusions called Lewy bodies found in PD and cortical Lewy body dementia (LBD) were discovered to be predominantly alpha-synuclein. Aberrant aggregation of alpha-synuclein has been detected in an increasing number of neurodegenerative diseases, collectively known as synucleopathies. Alpha-synuclein exists physiologically in both soluble and membrane-bound states, in unstructured and alpha-helical conformations, respectively. The physiological function of alpha-synuclein appears to require its translocation between these subcellular compartments and interconversion between the 2 conformations. Abnormal processing of alpha-synuclein is predicted to lead to pathological changes in its binding properties and function. In this review, genetic and environmental risk factors for alpha-synuclein pathology are described. Various mechanisms for in vitro and in vivo alpha-synuclein aggregation and neurotoxicity are summarized, and their relevance to neuropathology is explored.

Cloning, expression, purification, and spectroscopic analysis of the fragment 57–102 of human α-synuclein

The protein alpha-synuclein plays an important role in many neurodegenerative disorders, referred to as alpha-synucleinopathies, that include, among others, Parkinson's and Alzheimer's diseases. The central region of the wild type protein, known as the non-Abeta component of amyloid plaques (NAC, amino acids 61-95), seems to be responsible for its aggregation process. To structurally characterize this fragment by nuclear magnetic resonance, we produced it by DNA recombinant technology. This technique, unlike chemical synthesis, allows the production of labeled samples (13C, 15N) required for NMR studies. Because the NAC region is very sparingly soluble in aqueous buffer, we cloned a slightly larger portion of alpha-synuclein, alphasyn57-102, with the presence of several charged residues in both extremities of the NAC region. The conformational preferences of purified alphasyn57-102, in solution and bound to SDS micelles, was studied. Our results indicate that the protein is largely unfolded in solution but exhibits a helical conformation in the lipid-associated state. The methodology that we have used in this work for the cloning, expression, and purification of alphasyn57-102 can be easily applied to most small proteins, thus representing a powerful tool for structural NMR analysis of labeled peptides.

Consequences of NPC1 and NPC2 loss of function in mammalian neurons

Genetic deficiency of NPC1 or NPC2 results in a devastating cholesterol-glycosphingolipidosis of brain and other organs known as Niemann-Pick type C (NPC) disease. While NPC1 is a transmembrane protein believed involved in retroendocytic shuttling of substrate(s) to the Golgi and possibly elsewhere in cells as part of an essential recycling/homeostatic control mechanism, NPC2 is a soluble lysosomal protein known to bind cholesterol. The precise role(s) of NPC1 and NPC2 in endosomal-lysosomal function remain unclear, nor is it known whether the two proteins directly interact as part of this function. The pathologic features of NPC disease, however, are well documented. Brain cells undergo massive intracellular accumulation of glycosphingolipids (lactosylceramide, glucosylceramide, GM2 and GM3 gangliosides) and cholesterol and concomitant distortion of neuron shape (meganeurite formation). In neurons from humans with NPC disease the metabolic defects and storage often lead to extensive growth of new, ectopic dendrites (possibly linked to ganglioside sequestration) as well as formation of neurofibrillary tangles (NFTs) (possibly linked to dysregulation of cholesterol metabolism). Other features of cellular pathology in NPC disease include fragmentation of the Golgi apparatus and neuroaxonal dystrophy, though reasons for these changes remain largely unknown. As the disease progresses, neurodegeneration is also apparent for neurons in some brain regions, particularly Purkinje cells of the cerebellum, but the basis of this selective neuronal vulnerability is unknown. The NPC1 protein is evolutionarily conserved with homologues reported in yeast to humans; NPC2 is reported in C. elegans to humans. While neurons in mammalian models of NPC1 and NPC2 diseases exhibit many changes that are remarkably similar to those in humans (e.g., endosomal/lysosomal storage, Golgi fragmentation, neuroaxonal dystrophy, neurodegeneration), a reduced degree of ectopic dendritogenesis and an absence of NFTs in these species suggest important differences in the way lower mammalian neurons respond to NPC1/NPC2 loss of function.

Alpha-synuclein and Parkinson's disease

Alpha-synuclein (alpha-syn) is a small soluble protein expressed primarily at presynaptic terminals in the central nervous system. Interest in alpha-syn has increased dramatically after the discovery of a relationship between its dysfunction and several neurodegenerative diseases, including Parkinson's disease (PD). The physiological functions of alpha-syn remain to be fully defined, although recent data suggest a role in regulating membrane stability and neuronal plasticity. Various trigger factors, either environmental or genetic, can lead to a cascade of events involving misfolding or loss of normal function of alpha-syn. In dopaminergic neurons, this may promote a vicious cycle in which elevation in cytoplasmic dopamine, oxidative stress, alpha-syn dysfunction, and disruption of vesicle function lead to dopaminergic cell loss and PD. Alpha-syn dysfunction appears to be a common feature of all forms of PD. The mechanism by which alpha-syn induces neuronal cell toxicity may invoke multiple pathways, such as aggregation or interaction with other proteins and molecules, including synphilin-1, chaperone 14-3-3 protein, and dopamine itself. This complexity has hindered the development of models to study PD. The available animal models of PD, each present distinct advantages and limits. Findings to date suggest that alpha-syn-based models represent a paradigm, which is closest to the human pathology.

Aberrant phosphorylation of alpha-synuclein in human Niemann-Pick type C1 disease

Niemann-Pick type C1 disease (NPC1) is an autosomal recessive neurovisceral storage disease caused by the mutation of NPC1 gene, resulting in perturbed intracellular transport of unesterified cholesterol. In NPC1, early-onset tauopathy is a constant feature. In addition, in NPC1 patients with ApoE epsilon4 homozygosity, deposition of A beta occurs mimicking Alzheimer disease (AD). Since AD is frequently associated with neuronal expression of alpha-synuclein, we investigated phosphorylated alpha-synuclein (psyn) immunoreactivity in the brains of 12 NPC1 patients, ages at death ranging from 9 months to 55 years. Psyn immunoreactivity was demonstrated in the perikarya of storage neurons and oligodendroglia in 10 cases. The immunoreactivity appeared more intense in subjects who had the ApoE epsilon4 allele. Lewy bodies were found in the substantia nigra in 2 of these cases. The psyn immunoreactivity was most intense in the substantia nigra where tauopathy was most severe. Phosphorylated tau and alpha-synuclein frequently colocalized. This study first documents alpha-synucleinopathy in NPC1. This observation suggests that the defect in intracellular cholesterol trafficking in NPC1 may provoke aberrant phosphorylation of alpha-synuclein and tau, and that this phosphorylation is enhanced by the ApoE epsilon4 allele. Thus, elucidation of metabolic pathways in NPC1 could provide clues to common mechanisms associated with neurodegeneration.

α-Synuclein: Normal Function and Role in Neurodegenerative Diseases

Synucleins are a family of small, highly charged proteins expressed predominantly in neurons. Since their discovery and characterization during the last decade, much has been learned about their structure, potential functions, interactions with other proteins, and roles in disease. One of these proteins, alpha-synuclein (alpha-syn), is the major building block of pathological inclusions that characterize many neurodegenerative disorders, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and neurodegeneration with brain iron accumulation type 1 (NBIA-1), which collectively are termed synucleinopathies. Furthermore, genetic and biological studies support a role for alpha-syn in the pathophysiology of these diseases. Therefore, research must be continued in order to better understand the functions of the synuclein proteins under normal physiological conditions as well as their role in diseases.

Adult Hallervorden-Spatz syndrome simulating amyotrophic lateral sclerosis

Hallervorden-Spatz syndrome (HSS) is a neurodegenerative disorder characterized by progressive dementia, dystonia, ataxia, and rigidity. An atypical form of adult-onset HSS was observed in a 36-year-old man presenting with progressive dysarthria. Markedly dysarthric speech and a weak atrophic tongue associated with a neurogenic pattern of motor unit recruitment in bulbar-supplied muscles on electromyography led to an initial impression of bulbar amyotrophic lateral sclerosis (ALS). Lack of expected progression of symptoms, however, prompted reinvestigation. Repeat brain magnetic resonance imaging demonstrated an "eye-of-the-tiger" pattern in the basal ganglia, characteristic of HSS, thus requiring genetic studies. DNA analyses of the pantothenate kinase gene (PANK2) was conducted and revealed two novel, disease-causing exon 3 missense mutations (Cys231Ser and Tyr251Cys). This case broadens the genotypic and phenotypic spectrum of HSS to include a late-onset syndrome resembling bulbar-onset ALS.

Accumulation of phosphorylated alpha-synuclein in aging human brain

Alpha-synuclein in Lewy bodies (LBs) is phosphorylated at Ser129. We raised monoclonal and polyclonal antibodies to this phosphorylation site (psyn) and examined 157 serial autopsy brains from a geriatric hospital. Anti-psyn immunoreactivity was observed in 40 of these cases (25.5%). Immunohistochemistry revealed 4 novel types of pathology: diffuse neuronal cytoplasmic staining (pre-LB); neuropil thread-like structures (Lewy threads); dot-like structures similar to argyrophilic grains (Lewy dots); and axons in the white matter (Lewy axons). This novel pathology was abundantly present around LBs and also involved the limbic subcortical white matter, the cerebral cortical molecular layer, and the spongiform changes of the medial temporal lobe associated with cases of dementia with LBs (DLB). The phosphorylated alpha-synuclein was limited to the temporal lobe in cases of Parkinson disease, spread from the temporal lobe to the frontal lobe in cases of DLB transitional form and further spread to the parietal and occipital lobes in DLB neocortical form. Our findings suggest that LB-related pathology initially involves the neuronal perikarya, dendrites, and axons, causes impairment of axonal transport and synaptic transmission, and later leads to the formation of LBs, a hallmark of functional disturbance long before neuronal cell death.

Parkinson's genetics: molecular insights for the new millennium

In idiopathic Parkinson's disease and familial parkinsonism, the limited number of overlapping clinical and pathological outcomes argue that a common underlying molecular pathway is perturbed. Genetic methods are a powerful approach to identify molecular components of disease. We summarize recent attempts to identify the genetic components of familial parkinsonism, without a priori assumptions about disease causation. Much effort has been expended on mapping in families with early-onset disease, in which parkinsonism appears inherited as a Mendelian trait. More recently, association methods have been employed in late-onset disease using affected sib-pairs and population isolates. These findings have been extrapolated to Parkinson's disease in the community with some success. We review the molecular synthesis now emerging from a genetic perspective.

Severe involvement of ambient gyrus in dementia with grains

Argyrophilic grains are detected as punctate or filiform structures in the neuropil of the medial temporal lobe, and dementia with grains (DG) is defined as a form of dementia with argyrophilic grains as the only explainable cause. We found argyrophilic grains in 43.2% of our 190 serial autopsy brains (mean age, 79.7 yr) from a community-based geriatric hospital, but only 20% of these argyrophilic grain-positive brains fulfilled the criteria for DG. To determine if there are structural differences between cognitively normal cases with argyrophilic grains (CNG) and DG, we studied 14 brains with CNG and 15 brains with DG. All cases of DG had severe atrophy of the ambient gyrus (the junction between temporal lobe and amygdala) with spongiosis, neuronal loss, and gliosis, as well as many grains, pretangles, coiled bodies, and tau-immunoreactive astrocytes. Comparable changes were not present in the ambient gyrus of CNG brains. The temporal neocortex and hippocampus were relatively spared in DG, in contrast to Alzheimer disease. Our study suggests that selective severe involvement of the ambient gyrus may explain the clinical manifestations of a limbic-type dementia in DG.

The relationship between oxidative/nitrative stress and pathological inclusions in Alzheimer's and Parkinson's diseases

Alzheimer's (AD) and Parkinson's diseases (PD) are late-onset neurodegenerative diseases that have tremendous impact on the lives of affected individuals, their families, and society as a whole. Remarkable efforts are being made to elucidate the dominant factors that result in the pathogenesis of these disorders. Extensive postmortem studies suggest that oxidative/nitrative stresses are prominent features of these diseases, and several animal models support this notion. Furthermore, it is likely that protein modifications resulting from oxidative/nitrative damage contribute to the formation of intracytoplasmic inclusions characteristic of each disease. The frequent presentation of both AD and PD in individuals and the co-occurrence of inclusions characteristic of AD and PD in several other neurodegenerative diseases suggests the involvement of a common underlying aberrant process. It can be surmised that oxidative/nitrative stress, which is cooperatively influenced by environmental factors, genetic predisposition, and senescence, may be a link between these disorders.

Tau and alpha-synuclein pathology in amygdala of Parkinsonism-dementia complex patients of Guam

Amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) is a progressive neurodegenerative disorder of Chamorro residents of Guam and the Mariana Islands, characterized by abundant neuron loss and tau neurofibrillary pathology similar to that observed in Alzheimer's disease (AD). A variety of neurodegenerative diseases with tau pathology including ALS/PDC also have alpha-synuclein positive pathology, primarily in the amygdala. We further characterized the tau and alpha-synuclein pathology in the amygdala of a large series of 30 Chamorros using immunohistochemical and biochemical techniques. Tau pathology was readily detected in both affected and unaffected Chamorros. In contrast, alpha-synuclein pathology was detected in 37% of patients with PDC but not detected in Chamorros without PDC or AD. The alpha-synuclein aggregates often co-localized within neurons harboring neurofibrillary tangles suggesting a possible interaction between the two proteins. Tau and alpha-synuclein pathology within the amygdala is biochemically similar to that observed in AD and synucleinopathies, respectively. Thus, the amygdala may be selectively vulnerable to developing both tau and alpha-synuclein pathology or tau pathology may predispose it to synuclein aggregation. Furthermore, in PDC, tau and alpha-synuclein pathology occurs independent of beta-amyloid deposition in amygdala thereby implicating the aggregation of these molecules in the severe neurodegeneration frequently observed in this location.

Severe involvement of the ambient gyrus in a case of dementia with argyrophilic grain disease

We report here the severe involvement of the ambient gyrus in a case of argyrophilic grain (AG) dementia (AGD). The patient was a 78-year-old man who was first presented with prosopagnosia (agnosia of the face) at age 68, which was followed by progressive mental decline and the patient's death in a state of tetraplegia. The postmortem study showed severe atrophy of the medial temporal lobe with anterior gradient, most prominent in the ambient gyrus. Histologically, numerous AGs, pretangles and coiled bodies were detected by Gallyas-Braak (G-B) silver staining and also by immunostaining with various anti-tau antibodies in the affected area. Tau-immunoreactive ballooned neurons were also present. Neuronal loss and gliosis with laminar sponginess were evident in the ambient gyrus. Diffuse plaques were seen in the neocortex and frequently associated with clusters of AGs, which were morphologically distinct from neuritic plaques. Neurofibrillary tangles were localized in the entorhinal area. Vascular lesions were very scanty. Thus, this case fulfilled the morphological criteria of AGD. It is still unclear whether AG itself causes neuronal degeneration leading to dementia. The present case may reflect the importance of the ambient gyrus in the center of neuronal degeneration in AGD.

Visual hallucinations in Lewy body disease relate to Lewy bodies in the temporal lobe

Consensus opinion characterizes dementia with Lewy bodies (DLB) as a progressive dementing illness, with significant fluctuations in cognition, visual hallucinations and/or parkinsonism. When parkinsonism is an early dominant feature, consensus opinion recommends that dementia within the first year is necessary for a diagnosis of DLB. If dementia occurs later, a diagnosis of Parkinson's disease with dementia (PDD) is recommended. While many previous studies have correlated the neuropathology in DLB with dementia and parkinsonism, few have analysed the relationship between fluctuating cognition and/or well-formed visual hallucinations and the underlying neuropathology in DLB and PDD. The aim of the present study was to determine any relationship between these less-studied core clinical features of DLB, and the distribution and density of cortical Lewy bodies (LB). The brains of 63 cases with LB were obtained over 6 years following population-based studies of dementia and parkinsonian syndromes. Annual, internationally standardized, clinical assessment batteries were reviewed to determine the presence and onset of the core clinical features of DLB. The maximal density of LB, plaques and tangles in the amygdala, parahippocampal, anterior cingulate, superior frontal, inferior temporal, inferior parietal and visual cortices were determined. Current clinicopathological diagnostic criteria were used to classify cases into DLB (n = 29), PDD (n = 18) or parkinsonism without dementia (n = 16) groups. Predictive statistics were used to ascertain whether fluctuating cognition or visual hallucinations predicted the clinicopathological group. Analysis of variance and regressions were used to identify any significant relationship(s) between the presence and severity of neuropathological and clinical features. Cognitive fluctuations and/or visual hallucinations were not good predictors of DLB in pathologically proven patients, although the absence of these features early in the disease course was highly predictive of PDD. Cases with DLB had higher LB densities in the inferior temporal cortex than cases with PDD. There was no association across groups between any neuropathological variable and the presence or absence of fluctuating cognition. However, there was a striking association between the distribution of temporal lobe LB and well-formed visual hallucinations. Cases with well-formed visual hallucinations had high densities of LB in the amygdala and parahippocampus, with early hallucinations relating to higher densities in parahippocampal and inferior temporal cortices. These temporal regions have previously been associated with visual hallucinations in other disorders. Thus, our results suggest that the distribution of temporal lobe LB is more related to the presence and duration of visual hallucinations in cases with LB than to the presence, severity or duration of dementia.

Alpha-synuclein and the Lewy body disorders

alpha-Synuclein has risen to prominence during the past 5 years because of its association with several neurodegenerative diseases that have come to be known as the synucleinopathies. The clinical phenotype of the synucleinopathies is variable, with the most common being parkinsonism, autonomic dysfunction, and dementia. Progress has been made in clinical, neuropathologic and biochemical characterization of the synucleinopathies and their differentiation from other neurodegenerative disorders. At the molecular level, the synucleinopathies have conformational and post-translational modifications of synuclein that favor its fibrillization and aggregation in inclusions in neurons and glia. Whether inclusion body formation is an adaptive response or is directly related to degeneration of neuronal and glial cells is a topic of current research.