Promyelocytic leukemia protein is redistributed during the formation of intranuclear inclusions independent of polyglutamine expansion: an immunohistochemical study on Marinesco bodies

Clinical and Preclinical Neuroimaging Changes in Spinocerebellar Ataxia Type 12: A Study of Three Chinese Pedigrees

BACKGROUND

Spinocerebellar ataxia type 12 (SCA12) is a rare SCA subtype with unclear clinical and imaging features. Also, the radiological changes in prodromal and early stages remain unknown.

METHODS

Ten symptomatic and two pre-symptomatic cases from three Chinese pedigrees received clinical assessments and imaging studies including routine magnetic resonance imaging (MRI), diffusion kurtosis imaging (DKI), and positron emission tomography (PET) using 18F-flurodeoxyglucose (FDG) to investigate glucose metabolism in brain and 18F-vesicle monoamine transporter 2 (VMAT2) to inspect the integrity of the dopaminergic neuron. Seventy-two healthy individuals were recruited as controls in the quantitative FDG-PET analysis. Imaging parameters were compared between symptomatic and presymptomatic cases with different disease durations.

RESULTS

Patients displayed prominent action tremor, moderate ataxia, and subtle parkinsonism with poor levodopa-response. MRI showed extensive but heterogeneous cerebral atrophy, which was most evident in the frontoparietal lobes. Cerebellar atrophy was apparent in later stages. DKI detected impaired fibers in the cerebellar peduncles. In both symptomatic and pre-symptomatic cases, PET-CT showed an earlier FDG decline than atrophic changes in multiple regions, and the frontoparietal lobes were the earliest and most severe. However, the VMAT2 density were normal in the putamen and caudate nucleus of most cases (7/8).

CONCLUSIONS

We first found that hypometabolism in the cerebral cortex, but not cerebellum, is an early and prominent change in SCA12. The integrity of presynaptic dopaminergic neurons remains largely spared during the whole disease process.

Nuclear Architecture in the Nervous System

Neurons and glial cells in the nervous system exhibit different gene expression programs for neural development and function. These programs are controlled by the epigenetic regulatory layers in the nucleus. The nucleus is a well-organized subcellular organelle that includes chromatin, the nuclear lamina, and nuclear bodies. These subnuclear components operate together as epigenetic regulators of neural development and function and are collectively called the nuclear architecture. In the nervous system, dynamic rearrangement of the nuclear architecture has been observed in each cell type, especially in neurons, allowing for their specialized functions, including learning and memory formation. Although the importance of nuclear architecture has been debated for decades, the paradigm has been changing rapidly, owing to the development of new technologies. Here, we reviewed the latest studies on nuclear geometry, nuclear bodies, and heterochromatin compartments, as well as summarized recent novel insights regarding radial positioning, chromatin condensation, and chromatin interaction between genes and cis-regulatory elements.

PML-NB-dependent type I interferon memory results in a restricted form of HSV latency

Herpes simplex virus (HSV) establishes latent infection in long-lived neurons. During initial infection, neurons are exposed to multiple inflammatory cytokines but the effects of immune signaling on the nature of HSV latency are unknown. We show that initial infection of primary murine neurons in the presence of type I interferon (IFN) results in a form of latency that is restricted for reactivation. We also find that the subnuclear condensates, promyelocytic leukemia nuclear bodies (PML-NBs), are absent from primary sympathetic and sensory neurons but form with type I IFN treatment and persist even when IFN signaling resolves. HSV-1 genomes colocalize with PML-NBs throughout a latent infection of neurons only when type I IFN is present during initial infection. Depletion of PML prior to or following infection does not impact the establishment latency; however, it does rescue the ability of HSV to reactivate from IFN-treated neurons. This study demonstrates that viral genomes possess a memory of the IFN response during de novo infection, which results in differential subnuclear positioning and ultimately restricts the ability of genomes to reactivate.

Human brain pathology in myotonic dystrophy type 1: A systematic review

Brain involvement in myotonic dystrophy type 1 (DM1) is characterized by heterogeneous cognitive, behavioral, and affective symptoms and imaging alterations indicative of widespread grey and white matter involvement. The aim of the present study was to systematically review the literature on brain pathology in DM1. We conducted a structured search in EMBASE (index period 1974–2017) and MEDLINE (index period 1887–2017) on December 11, 2017, using free text and index search terms related to myotonic dystrophy type 1 and brain structures or regions. Eligible studies were full‐text studies reporting on microscopic brain pathology of DM1 patients without potentially interfering comorbidity. We discussed the findings based on the anatomical region and the nature of the anomaly. Neuropathological findings in DM1 can be classified as follows: (1) protein and nucleotide deposits; (2) changes in neurons and glial cells; and (3) white matter alterations. Most findings are unspecific to DM1 and may occur with physiological aging, albeit to a lesser degree. There are similarities and contrasts with Alzheimer's disease; both show the appearance of neurofibrillary tangles in the limbic system without plaque occurrence. Likewise, there is myelin loss and gliosis, and there are dilated perivascular spaces in the white matter resemblant of cerebral small vessel disease. However, we did not find evidence of lacunar infarction or microbleeding. The various neuropathological findings in DM1 are reflective of the heterogeneous clinical and neuroimaging features of the disease. The strength of conclusions from this study's findings is bounded by limited numbers of participants in studies, methodological constraints, and lack of assessed associations between histopathology and clinical or neuroimaging findings.

Parallel enlargement of Marinesco bodies and nuclei and progressive deposition of p62 in pigmented neurons of the substantia nigra

Marinesco bodies (MBs) are spherical nuclear inclusions found in pigmented neurons of the substantia nigra. Although MBs are abundant in senescent brains, how they are related to aging processes remains unclear. Here, we performed a morphometric analysis of midbrain pigmented neurons to identify the possible influence of MBs on nuclear size. The transected area of the nucleus (nuclear area) was larger in the presence of MBs and was correlated with the area of MB (MB area) in all tested brains. The MB-associated nuclear enlargement was significant even after MB areas were subtracted from nuclear areas. Moreover, higher MB immunoreactivity of p62 was detected in the nucleoplasm of the enlarged MB-associated nuclei. This study on human brains is the first quantitative approach demonstrating MB-associated nuclear enlargement and progressive accumulation of small nucleoplasmic materials. Although cellular hypertrophy is usually considered to be an indication of the upregulation of cellular function, this might not always be the case. These findings suggest that an age-related decline of ubiquitin-proteasome and autophagy system activity and stagnation of undegradable materials are one of the candidate mechanisms to explain the age-related decline of neural activity in the substantia nigra.

George Marinesco in the Constellation of Modern Neuroscience

George Marinesco is the founder of Romanian School of Neurology and one of the most remarkable neuroscientists of the last century. He was the pupil of Jean-Martin Charcot in Salpêtrière Hospital in Paris, France, but visited many other neurological centers where he met the entire constellation of neurologists of his time, including Camillo Golgi and Santiago Ramón y Cajal. The last made the preface of Nervous Cell, written in French by Marinesco. The original title was “La Cellule Nerveuse” and is considered even now a basic reference book for specialists in the field. He was a refined clinical observer with an integrative approach, as could be seen from the multitude of his discoveries. The descriptions of the succulent hand in syringomyelia, senile plaque in old subjects, palmar jaw reflex known as Marinesco-Radovici sign, or the application of cinematography in medicine are some of his important contributions. He was the first who described changes of locus niger in a patient affected by tuberculosis, as a possible cause in Parkinson disease. Before modern genetics, Marinesco and Sjögren described a rare and complex syndrome bearing their names. He was a hardworking man, focused on his scientific research, did not accepted flattering of others and was a great fighter against the injustice of the time.

Marinesco bodies and substantia nigra neuron density in Parkinson's disease

AIM

Marinesco bodies (MB) are intranuclear inclusions in pigmented neurons of the substantia nigra (SN). While rare in children, frequency increases with normal ageing and is high in Alzheimer's disease, dementia with Lewy bodies and other neurodegenerative disorders. Coinciding with the age-related rise in MB frequency is initiation of cell death among SN neurons. Whether MB have a role in this process is unknown. Our aim is to examine the association of MB with SN neuron density in Parkinson's disease (PD) in the Honolulu-Asia Aging Study.

METHODS

Data on MB and neuron density were measured in SN transverse sections in 131 autopsied men aged 73-99 years at the time of death from 1992 to 2007.

RESULTS

Marinesco body frequency was low in the presence vs. absence of PD (2.3% vs. 6.6%, P < 0.001). After PD onset, MB frequency declined as duration of PD increased (P = 0.006). Similar patterns were observed for SN neuron density. When MB frequency was low, neuron density was noticeably reduced in the SN ventrolateral quadrant, the region most vulnerable to PD neurodegeneration. Low MB frequency was unique to PD as its high frequency in non-PD cases was unrelated to parkinsonian signs and incidental Lewy bodies. Frequency was high in the presence of Alzheimer's disease and apolipoprotein ε4 alleles.

CONCLUSIONS

While findings confirm that MB frequency is low in PD, declines in MB frequency continue with PD duration. The extent to which MB have a distinct relationship with PD warrants clarification. Further studies of MB could be important in understanding PD processes.

Localization and regulation of PML bodies in the adult mouse brain

PML is a tumor suppressor protein involved in the pathogenesis of promyelocytic leukemia. In non-neuronal cells, PML is a principal component of characteristic nuclear bodies. In the brain, PML has been implicated in the control of embryonic neurogenesis, and in certain physiological and pathological phenomena in the adult brain. Yet, the cellular and subcellular localization of the PML protein in the brain, including its presence in the nuclear bodies, has not been investigated comprehensively. Because the formation of PML bodies appears to be a key aspect in the function of the PML protein, we investigated the presence of these structures and their anatomical distribution, throughout the adult mouse brain. We found that PML is broadly expressed across the gray matter, with the highest levels in the cerebral and cerebellar cortices. In the cerebral cortex PML is present exclusively in neurons, in which it forms well-defined nuclear inclusions containing SUMO-1, SUMO 2/3, but not Daxx. At the ultrastructural level, the appearance of neuronal PML bodies differs from the classic one, i.e., the solitary structure with more or less distinctive capsule. Rather, neuronal PML bodies have the form of small PML protein aggregates located in the close vicinity of chromatin threads. The number, size, and signal intensity of neuronal PML bodies are dynamically influenced by immobilization stress and seizures. Our study indicates that PML bodies are broadly involved in activity-dependent nuclear phenomena in adult neurons.

Accumulation of the sigma-1 receptor is common to neuronal nuclear inclusions in various neurodegenerative diseases

The sigma-1 receptor (SIGMAR1) is now known to be one of the endoplasmic reticulum (ER) chaperones, which participate in the degradation of misfolded proteins in cells via the ER-related degradation machinery linked to the ubiquitin-proteasome pathway. Mutations of the SIGMAR1 gene are implicated in the pathogenesis of familial frontotemporal lobar degeneration and motor neuron disease. Involvement of ER dysfunction in the formation of inclusion bodies in various neurodegenerative diseases has also become evident. We performed immunohistochemical staining to clarify the localization of SIGMAR1 in the brains of patients with neurodegenerative disorders, including trans-activation response DNA protein 43 (TDP-43) proteinopathy, tauopathy, α-synucleinopathy, polyglutamine disease and intranuclear inclusion body disease (INIBD). Double-immunocytofluorescence and Western blot analyses of cultured cells were also performed to investigate the role of SIGMAR1 using a specific exportin 1 inhibitor, leptomycin B and an ER stress inducer, thapsigargin. SIGMAR1 was consistently shown to be co-localized with neuronal nuclear inclusions in TDP-43 proteinopathy, five polyglutamine diseases and INIBD, as well as in intranuclear Marinesco bodies in aged normal controls. Cytoplasmic inclusions in neurons and glial cells were unreactive for SIGMAR1. In cultured cells, immunocytofluorescent study showed that leptomycin B and thapsigargin were shown to sequester SIGMAR1 within the nucleus, acting together with p62. This finding was also supported by immunoblot analysis. These results indicate that SIGMAR1 might shuttle between the nucleus and the cytoplasm. Neurodegenerative diseases characterized by neuronal nuclear inclusions might utilize the ER-related degradation machinery as a common pathway for the degradation of aberrant proteins.

The crowded nucleus

The principles that determine the organization of the nucleus have become clearer in recent years, largely because of new insights into polymer, colloid, and soft-matter science. Macromolecules, together with the giant linear polymers that form the chromosomes, are confined at high concentrations within the nuclear envelope and their interactions are influenced strongly by short-range depletion or entropic forces which are negligible in dilute systems, in addition to the more familiar van der Waals, electrostatic, steric, hydrogen bonding, and hydrophobic forces. The studies described in this volume are consistent with the model that this complex and concentrated mixture of macromolecules is maintained in a delicate equilibrium by quite simple although unsuspected physicochemical principles. The sensitivity of this equilibrium to perturbation may underlie the controversies about the existence of a nuclear matrix or scaffold. In this volume, we underline the importance for cell biologists of being familiar with current work in colloid, polymer, soft matter, and nanoscience. This chapter presents a brief background to the aspects of the nucleus that are considered in detail in subsequent chapters.

Immunohistochemical analysis of Marinesco bodies, using antibodies against proteins implicated in the ubiquitin-proteasome system, autophagy and aggresome formation

Marinesco bodies (MBs) are spherical eosinophilic intranuclear inclusions in pigmented neurons in the substantia nigra and locus ceruleus. Previous immunohistochemical studies have shown that MBs are positive for ubiquitin, p62 and SUMO-1, suggesting the involvement of ubiquitination and related proteins in the formation or disaggregation of MBs. However, the involvement is not thoroughly understood. Therefore, we immunohistochemically examined the midbrain from five control subjects ranged from 53 to 84 years old. MBs were positive for various proteins implicated in the ubiquitin-proteasome system (ubiquitin, p62, EDD1, NEDD8, NUB1, SUMO-1 and SUMO-2), aggresome formation (HDAC6) and autophagy (ubiquitin, p62, LC3, GABARAP and GATE-16). These findings suggest that proteins related to ubiquitination, proteasomal degradation and autophagy are involved in the formation or disaggregation of MBs.

The role of PML in the nervous system

The promyeloctic leukemia protein PML is a tumor suppressor that was originally identified due to its involvement in the (15;17) translocation of acute promyelocytic leukemia. While the majority of early research has focused upon the role of PML in the pathogenesis of leukemia, more recent evidence has identified important roles for PML in tissues outside the hemopoietic system, including the central nervous system (CNS). Here, we review recent literature on the role of PML in the CNS, with particular focus on the processes of neurodevelopment and neurodegeneration, and propose new lines of investigation.

Nuclear bodies in neurodegenerative disease

Neurodegenerative diseases are characterized by a relentlessly progressive loss of the functional and structural integrity of the central nervous system. In many cases, these diseases arise sporadically and the causes are unknown. The abnormal aggregation of protein within the cytoplasm or the nucleus of brain cells represents a unifying pathological feature of these diseases. There is increasing evidence for nuclear dysfunction in neurodegenerative diseases. How this relates to protein aggregation in the context of "cause and effect" remains to be determined in most cases. Co-ordinated nuclear function is predicated on the activity of distinct nuclear subdomains, or nuclear bodies, each responsible for a specific function. If nuclear dysfunction represents an important etiopathological feature in neurodegenerative disease, then this should be reflected by functional and/or morphological alterations in this nuclear compartmentalization. For most neurodegenerative diseases, evidence for nuclear dysfunction, with attendant consequences for nuclear architecture, is only beginning to emerge. In this review, I will discuss neurodegenerative diseases in the context of nuclear dysfunction and, more specifically, alterations in nuclear bodies. Although research in this field is in its infancy, identifying alterations in the nucleus in neurodegenerative disease has potentially profound implications for elucidating the pathogenesis of these disorders.

Ataxin-1 fusion partners alter polyQ lethality and aggregation

Intranuclear inclusion bodies (IBs) are the histopathologic markers of multiple protein folding diseases. IB formation has been extensively studied using fluorescent fusion products of pathogenic polyglutamine (polyQ) expressing proteins. These studies have been informative in determining the cellular targets of expanded polyQ protein as well as the methods by which cells rid themselves of IBs. The experimental thrust has been to intervene in the process of polyQ aggregation in an attempt to alleviate cytotoxicity. However new data argues against the notion that polyQ aggregation and cytotoxicity are inextricably linked processes. We reasoned that changing the protein context of a disease causing polyQ protein could accelerate its precipitation as an IB, potentially reducing its cytotoxicity. Our experimental strategy simply exploited the fact that conjoined proteins influence each others folding and aggregation properties. We fused a full-length pathogenic ataxin-1 construct to fluorescent tags (GFP and DsRed1-E5) that exist at different oligomeric states. The spectral properties of the DsRed1-E5-ataxin-1 transfectants had the additional advantage of allowing us to correlate fluorochrome maturation with cytotoxicity. Each fusion protein expressed a distinct cytotoxicity and IB morphology. Flow cytometric analyses of transfectants expressing the greatest fluorescent signals revealed that the DsRed1-E5-ataxin-1 fusion was more toxic than GFP fused ataxin-1 (31.8±4.5% cell death versus 12.85±3%), although co-transfection with the GFP fusion inhibited maturation of the DsRed1-E5 fluorochrome and diminished the toxicity of the DsRed1-E5-ataxin-1 fusion. These data show that polyQ driven aggregation can be influenced by fusion partners to generate species with different toxic properties and provide new opportunities to study IB aggregation, maturation and lethality.

Herpes simplex virus type 1 genomes are associated with ND10 nuclear substructures in quiescently infected human fibroblasts

Herpes simplex virus type 1 (HSV-1) genomes become associated with structures related to cellular nuclear substructures known as ND10 or promyelocytic leukemia nuclear bodies during the early stages of lytic infection. This paper describes the relationship between HSV-1 genomes and ND10 in human fibroblasts that maintain the viral genomes in a quiescent state. We report that quiescent HSV-1 genomes detected by fluorescence in situ hybridization (FISH) are associated with enlarged ND10-like structures, frequently such that the FISH-defined viral foci are apparently enveloped within a sphere of PML and other ND10 proteins. The number of FISH viral foci in each quiescently infected cell is concordant with the input multiplicity of infection, with each structure containing no more than a small number of viral genomes. A proportion of the enlarged ND10-like foci in quiescently infected cells contain accumulations of the heterochromatin protein HP1 but not other common markers of heterochromatin such as histone H3 di- or trimethylated on lysine residue 9. Many of the virally induced enlarged ND10-like structures also contain concentrations of conjugated ubiquitin. Quiescent infections can be established in cells that are highly depleted for PML. However, during the initial stages of establishment of a quiescent infection in such cells, other ND10 proteins (Sp100, hDaxx, and ATRX) are recruited into virally induced foci that are likely to be associated with HSV-1 genomes. These observations illustrate that the intimate connections between HSV-1 genomes and ND10 that occur during lytic infection also extend to quiescent infections.

Age-related accumulation of Marinesco bodies and lipofuscin in rhesus monkey midbrain dopamine neurons: relevance to selective neuronal vulnerability

Parkinson's disease (PD) is characterized by degeneration of nigrostriatal dopamine (DA) neurons. Although aging is a primary risk factor for PD, its role in DA neuron degeneration remains unknown. Neurodegeneration in PD is not uniform throughout the ventral midbrain: the ventral tier of the substantia nigra (vtSN) is most vulnerable, whereas the dorsal tier (dtSN) and ventral tegmental area (VTA) are relatively resistant. We studied young (9-10 years old), middle-aged (14-17 years old), and old-aged (22-29 years old) rhesus monkeys to identify factors potentially underlying selective vulnerability and their association with aging. We focused on markers relevant to the ubiquitin-proteasome (UPS) and lysosome systems. Unbiased stereological counting was performed on tyrosine hydroxylase-positive (TH+) neurons and TH+ neurons containing Marinesco bodies (TH+MB) or lipofuscin (TH+lipo), markers of UPS or lysosomal activity, respectively. TH+ neuron numbers were inversely correlated with advancing age specifically in the vtSN, not the dtSN or VTA. TH intensity decreased throughout the ventral midbrain with increasing age, an effect exacerbated in the vtSN. TH+MB neurons were localized in the vulnerable vtSN of old monkeys. The number of MBs per cell increased with age, and TH intensity of TH+MB neurons decreased in middle age. Conversely, TH+lipo neurons were primarily found in the resistant dtSN and VTA. These data suggest that particular age-related changes localize to DAergic subregions relevant to degenerative patterns in PD. Furthermore, the results begin to characterize the nature of the link between aging and PD, and they support the concept that aged monkeys represent a valuable model for studying specific events preceding PD.

PML and PML nuclear bodies: implications in antiviral defence

The establishment of an intracellular antiviral state is the defining activity of interferons (IFNs) as well as the property that permitted their discovery. Several pathways have been implicated in resistance to viral infection in IFN-treated cells, one of which implicates the ProMyelocytic Leukaemia (PML) protein and PML nuclear bodies (NBs, also known as ND10). PML NBs are dynamic intranuclear structures that require PML for their formation and which harbour numerous other transiently or permanently localised proteins. PML is expressed as a family of isoforms (PML I-VII) as a result of alternative splicing, most of which are found in the nucleus. IFN treatment directly induces transcription of the genes encoding both PML and Sp100, (another major component of PML NBs), resulting in higher levels of expression of these proteins and increases in both the size and number of PML NBs. These and other observations have encouraged the hypothesis that PML, PML NBs and a number of other constituents of these structures are involved in host antiviral defences. For example, exogenous expression of PML III or PML VI can impede infection by a number of RNA and DNA viruses, and certain viral proteins accumulate in PML NBs then cause their disruption by a variety of mechanisms. Although there are many other functions of PML NBs in a wide range of cellular pathways, there is accumulating evidence that they represent preferential targets for viral infections and that PML plays a role in the mechanism of the antiviral action of IFN. This article reviews the potential antiviral activities of PML NB constituent proteins, how RNA and DNA viruses overcome these defences, and the connections between these events and IFN pathways.

Abnormalities of the nucleus and nuclear inclusions in neurodegenerative disease: a work in progress

Neurodegenerative diseases are characterized pathologically by the abnormal accumulation of pathogenic protein species within the cell. Several neurodegenerative diseases feature intranuclear protein aggregation in the form of intranuclear inclusion bodies. Studies of these intranuclear inclusions are providing important clues regarding the cellular pathophysiology of these diseases, as exemplified by recent progress in defining the genetic basis of a subset of frontotemporal dementia cases. The precise role of intranuclear inclusion bodies in disease pathogenesis is currently a focus of debate. The present review provides an overview of the diverse family of neurodegenerative diseases in which nuclear inclusions form part of the neuropathological spectrum. In addition, current pathogenetic concepts relevant to these diseases will be reviewed and arguments for and against a protective role for intranuclear inclusions will be presented. The relationship of pathological intranuclear inclusions to functional intranuclear bodies will also be discussed. Finally, by analogy with pathological intranuclear inclusions, I will speculate on the possibility that intranuclear protein aggregation may represent a constitutive cellular protective mechanism occurring in neurons under physiological conditions.

Promyelocytic leukaemia-immunoreactive neuronal intranuclear rodlets in the human brain

In a previous study, we demonstrated immunoreactivity of a subset of neuronal intranuclear rodlets (INRs) in the human substantia nigra for promyelocytic leukaemia (PML) protein, the signature protein of PML bodies. In the present study, we extend these observations and describe the ultrastructural features, immunohistochemical staining characteristics, and topographical pattern of distribution of PML-immunoreactive intranuclear rodlets (PML-INRs). Consistent with a purported role for PML bodies in nuclear proteolysis and/or transcriptional regulation, PML-INRs are immunoreactive for components of the ubiquitin-proteasome system, the transcriptional regulator CREB-binding protein, acetylated histone H4, and the eukaryotic translation initiation factor eIF4E. Immunoelectron microscopy reveals that they all possess a filamentous core and, in some, this is surrounded by a granular shell. We further demonstrate that a proportion of INRs in extranigral sites also show partial immunoreactivity for PML. These observations indicate an intimate association between two neuronal nuclear bodies, PML bodies and INRs. Because both of these structures have been implicated in neurodegenerative disease, PML-INRs may provide a tool with which to study changes in nuclear substructure in disease.

Neurofibrillary tangles and deposition of oxidative products in the brain in cases of myotonic dystrophy

Myotonic dystrophy (MyD) is a neuromuscular degenerative disorder that is neuropathologically characterized by minor changes, such as the presence of neurofibrillary tangles (NFT), thalamic inclusions and functional brainstem lesions. In the current study, we conducted an immunohistochemical analysis to examine the distribution of NFT and formation of oxidative products in the brain specimens of 12 patients with MyD. Neurofibrillary tangles were found in the limbic system and/or the brainstem of all the cases examined but there were no senile plaques. The density of distribution of the NFT was not significantly correlated with clinicopathological findings, although cases with fewer NFTin the brain frequently showed sleep disturbances and lack of spontaneity. Nuclear and cytoplasmic immunoreactivities for 8-hydroxy-2'-deoxyguanosine and advanced glycation end products were observed in the glial cells and/or neurons in the brainstem, but not in the cerebral cortex. On the other hand, 10 out of the 12 cases showed cytoplasmic immunoreactivity for 4-hydroxy-2-nonenal-modified protein (4-HNE) in neurons of the temporal cortex and raphe nucleus. Deposition of 4-HNE was also recognized in the hippocampus and mesencephalic central gray matter, but not in the subiculum. The distribution pattern of the immunoreactivity for 4-HNE showed no clear correlation with either the psychological disturbances or the distribution of the NFT. Altered expression of monoaminergic neurons in the brainstem of MyD patients has already been reported, and it is worth noting that most of our cases showed NFT in the brainstem. The selective deposition of 4-HNE in the limbic system and brainstem suggests that lipid peroxidation may be involved in the neurodegenerative process in MyD. Using immunohistochemical analysis to determine the distribution of neurotransmitters in the mesencephalic central gray matter and/or pontine raphe nucleus may help elucidate the relationship between the clinical abnormalities, distribuion of NFT, and 4-HNE deposition in the brain in patients with MyD.

The PML-nuclear inclusion of human supraoptic neurons: a new compartment with SUMO-1- and ubiquitin-proteasome-associated domains

It is well known that the cell nucleus is organized in structural and functional compartments involved in transcription, RNA processing and protein modifications such as conjugation with SUMO-1 and proteolysis. Promyelocytic leukaemia (PML) bodies are dynamic nuclear structures that concentrate PML protein, SUMO-1 and several sumoylated and non-sumoylated protein regulators of nuclear functions. PML bodies and their associated CBP has been involved in neuronal survival. By light and electron microscopy immunocytochemistry and in situ hybridization we reported the presence, in non-pathological conditions, of a large PML-nuclear inclusion (PML-NI) in human supraoptic neurons. This inclusion appears as a single nuclear structure composed of a capsule enriched in PML, SUMO-1 and CBP proteins and a central lattice of filaments immunoreactive for class III beta-tubulin, ubiquitinated proteins and proteasomes. Furthermore, the PML-NI concentrates the SUMO-conjugating enzyme E2 (UBC9). The PML-NI may be considered a nuclear factory involved in sumoylation and proteolysis via ubiquitin-proteasome system, two nuclear pathways engaged in the control of the nucleoplasmic concentration of active transcriptional regulators. Interestingly, the structural and molecular organization of the PML-NI is related to the Marinesco bodies, age-associated ubiquitinated intranuclear inclusions, and to the intranuclear rodlets enriched in class III beta-tubulin, which are nuclear structures markedly decreased in Alzheimer's disease.

Defining the role of ubiquitin-interacting motifs in the polyglutamine disease protein, ataxin-3

Polyglutamine (polyQ) expansions cause neurodegeneration that is associated with protein misfolding and influenced by functional properties of the host protein. The polyQ disease protein, ataxin-3, has predicted ubiquitin-specific protease and ubiquitin-binding domains, which suggest that ataxin-3 functions in ubiquitin-dependent protein surveillance. Here we investigate direct links between the ubiquitin-proteasome pathway and ataxin-3. In neural cells we show that, through its ubiquitin interaction motifs (UIMs), normal or expanded ataxin-3 binds a broad range of ubiquitinated proteins that accumulate when the proteasome is inhibited. The expression of a catalytically inactive ataxin-3 (normal or expanded) causes ubiquitinated proteins to accumulate in cells, even in the absence of proteasome inhibitor. This accumulation of ubiquitinated proteins occurs primarily in the cell nucleus in transfected cells and requires intact UIMs in ataxin-3. We further show that both normal and expanded ataxin-3 can undergo oligoubiquitination. Although this post-translational modification occurs in a UIM-dependent manner, it becomes independent of UIMs when the catalytic cysteine residue of ataxin-3 is mutated, suggesting that ataxin-3 ubiquitination is itself regulated in trans by its own de-ubiquitinating activity. Finally, pulse-chase labeling reveals that ataxin-3 is degraded by the proteasome, with expanded ataxin-3 being as efficiently degraded as normal ataxin-3. Mutating the UIMs does not alter degradation, suggesting that UIM-mediated oligoubiquitination of ataxin-3 modulates ataxin-3 function rather than stability. The function of ataxin-3 as a de-ubiquitinating enzyme, its post-translational modification by ubiquitin, and its degradation via the proteasome link this polyQ protein to ubiquitin-dependent pathways already implicated in disease pathogenesis.

Ubiquitin immunoreactivity in the midbrain as a marker of stress to motor nervous systems in fatal injury

Previous studies showed an increase in the ubiquitin (Ub)-immunoreactive structures in the midbrain in acute deaths from asphyxiation and in fires in adult subjects. The present study examined the Ub-immunoreactivity in the midbrain as a marker of stress to motor nervous systems in fatal injury cases (over 35 years of age, n=140: blunt injuries, n=82; sharp injuries, n=58), compared with that in control groups (n=61) including death by strangulation, acute cardiac and cerebrovascular diseases. The intranuclear Ub-immunopositive inclusion of the pigmented dopaminergic neurons of the substantia nigra (inclusion Ub-index) and the granular 'dot-like' Ub-immunoreactivity area ('dot-like' Ub-area) in the crus cerebri were analyzed. In blunt injuries, those markers were high in abdomen and back injuries and low in head and chest injuries. The inclusion Ub-index was higher in the crush/pressure injury group than in those with injuries due to impact traffic accidents and falls. 'Dot-like' Ub-area was also low in falls. In sharp injury cases, cardiac injury with hemopericardium showed a higher inclusion Ub-index. These findings suggested that the stress to the motor nervous system may be very intense in crush/pressure injury and hemopericardium than in impact injury and fatal hemorrhages, respectively, and in abdomen and back injuries than in head and chest injuries.

Quantitative analysis of ubiquitin-immunoreactivity in the midbrain periaqueductal gray matter with regard to the causes of death in forensic autopsy

The aim of the present study was to examine Ub-immunoreactivity in the midbrain periaqueductal gray matter (PGM), which is involved in pain processing and modulation, in forensic autopsy cases (n=273) in relation to the causes of death: acute deaths from blunt injuries (n=75), sharp weapon injuries (n=36), fatal asphyxiation (n=22), drownings (n=16: freshwater, n=9; saltwater, n=7), fire fatalities (n=64), poisoning (n=12), hyperthermia (n=5), hypothermia (n=5), delayed deaths from blunt head injury (n=8), acute cardiac deaths (n=24), and acute cerebrovascular strokes (n=6). The Ub-immunoreactivity was clearly observed in the nuclei of the PGM neurons, showing no postmortem interference or age-dependency. A higher value was observed in blunt injuries, fire fatalities and also in saltwater drowning, hyperthermia and delayed head injury deaths. These findings suggest a complicated mechanism for the ubiquitination of PGM neurons, to which multiple factors including the intensity and duration of pains possibly under alert consciousness, traumatic and metabolic neurodegeneration may contribute.

Ubiquitin-immunoreactive structures in the midbrain of methamphetamine abusers

Ubiquitin (Ub) is involved in neurodegeneration and various stress responses in the brain. The present study investigated the Ub-immunoreactive structures in the midbrain of methamphetamine (MA) abusers as a marker of drug-induced neurodegeneration. Medico-legal autopsy cases were examined: fatal MA intoxication (n=14), other fatalities of MA abusers (n=23) including those due to injuries, asphyxiation, drowning, fire and natural diseases, and control groups (n=260). In the motor nervous systems, MA abusers showed a mild increase in the diffuse-type nuclear Ub-positivity in the pigmented neurons of the substantia nigra, depending on the blood MA level and irrespectively of the immediate causes of death. The intranuclear inclusion-type Ub-positivity of the nigral neurons and the granular 'dot-like' Ub-immunoreactivity area in the crus cerebri (cortico-spinal tracts) were usually low in MA abusers, and any increases were related to the immediate causes of death and the age of subjects. Acute MA fatality showed a higher neuronal Ub-positivity in the midbrain periaqueductal gray matter (PGM), which is involved in processing pain, fear and anxiety, and regulation of respiration and circulation. These findings suggest dysfunction of the nigral dopaminergic neurons and PGM neurons in the midbrain in MA abuse, which may account for the clinical symptoms.

Quantitative morphometry of granular ‘dot-like’ ubiquitin-immunoreactivity in the crus cerebri in asphyxiation and fire fatalities

In the central nervous system (CNS), a variety of ubiquitinated structures have been reported, usually as pathological alterations of the brain related to degenerative diseases or aging. However, previous studies showed an increase in the ubiquitin (Ub)-immunoreactive intranuclear inclusion of the pigmented neurons of the substantia nigra in the midbrain in asphyxiation and fire fatalities in the adult subjects. The aim of the present study was to examine granular 'dot-like' Ub-immunoreactivity in the crus cerebri (cortico-spinal tracts) in related fatalities (over 35 years of age, n=169), including fatal asphyxiation (n=27), drownings (n=14), fire fatalities (n=60), and control groups (n=68). Dot-like Ub-immunoreactivity was clearly observed in the descending tract of the crus cerebri. Morphometric analysis of the positive granular area (dot-like Ub-area) showed a higher value in strangulation and fire fatalities and a lower value in hemorrhagic and head injury deaths, as was observed for the inclusion-type neuronal Ub-positivity. However, there was a difference between those markers: a low value was seen for the inclusion-type neuronal Ub-positivity in hanging and drownings, and a difference in the dot-like Ub-area was detected between fire fatalities with lower and higher COHb levels. Our findings suggested the possible usefulness of these markers for examination of CNS stress responses in traumas, at least in middle-aged and elderly victims and a partial difference in stress reaction between the cortico-spinal tracts and dopaminergic neurons.

Intranuclear Rodlets in the Substantia Nigra: Interactions with Marinesco Bodies, Ubiquitin, and Promyelocytic Leukemia Protein

There is growing appreciation that the nucleus is organized into an array of discrete structural domains, each subserving a specific function. These functional nuclear bodies are to be distinguished from pathological intranuclear inclusions which have been described in a variety of neurodegenerative diseases. Marinesco bodies (MBs) are eosinophilic ubiquitinated intranuclear inclusions found in pigmented neurons of the human substantia nigra and locus coeruleus. Traditionally considered non-pathological entities, more recent studies have indicated that MBs are associated with the age-associated degenerative changes in the substantia nigra and striatal loss of dopaminergic terminals. In the present morphological study of the human substantia nigra, we demonstrate colocalization, contiguity, and focally shared immunoreactivity between MBs and neuronal intranuclear rodlets (INRs). The latter nuclear structures of uncertain function are markedly decreased in the cortex of Alzheimer's disease, but not dementia with Lewy bodies. In addition, we demonstrate an interaction between INRs and promyelocytic leukemia (PML) protein, the signature protein of PML nuclear bodies. These results suggest that structures which subserve the functional compartmentalization of the neuronal nucleus may be relevant to elucidating cellular mechanisms of age-related motor dysfunction.

Substantia nigra Marinesco bodies are associated with decreased striatal expression of dopaminergic markers

Marinesco bodies are nuclear inclusions found in pigmented neurons of the substantia nigra and locus ceruleus of humans and monkeys. It has long been known that the frequency of these inclusions increases with advancing age, but no pathologic associations have ever been established. We quantified Marinesco body frequency in human autopsy subjects, classified as young normal controls, elderly controls, dementia with Lewy bodies (DLB), Alzheimer disease (AD), and Parkinson disease (PD). Elderly controls, AD cases, and DLB cases had significantly increased Marinesco body frequencies relative to young controls and DLB cases had significantly increased frequencies relative to elderly controls, while PD cases did not differ from young controls; cases with AD did not differ from elderly controls. Lewy body-containing neurons had significantly higher Marinesco body frequencies than non-Lewy body-containing neurons. Marinesco body frequency in elderly control cases correlated significantly, in inverse fashion, with striatal concentrations of the dopaminergic neuron markers dopamine transporter and tyrosine hydroxylase. These statistical associations suggest that Marinesco bodies constitute or mark a pathologic process that may be related to, or contribute to, age-related motor dysfunction and/or Lewy body disorders. Further studies are needed to ascertain the molecular basis of Marinesco body formation; preliminary studies indicate that proteasome dysfunction can lead to similar abnormalities in cultured cells.

Pathogenesis of polyglutamine disorders: aggregation revisited

Expansion of CAG trinucleotide repeats coding for polyglutamine in unrelated proteins causes at least nine late-onset progressive neurodegenerative disorders, including Huntington's disease and a number of spinocerebellar ataxias. Expanded polyglutamine provokes a dominant gain-of-function neurotoxicity, regardless of the specific protein context within which it resides. Nevertheless, the protein context does modulate polyglutamine toxicity, as evidenced by the distinct clinical and pathological features of the various disorders. Importantly, polyglutamine toxicity might derive from its ability to aggregate. Indeed, aggregation probably underlies some defining attributes of the polyglutamine disorders, such as their late onset, progressive nature, and the dependence of onset age on polyglutamine length. However, the central role of aggregation in polyglutamine pathogenesis has been challenged by several studies, which instead argued that the soluble form of the disease proteins is responsible for neuronal damage. Thus, the question whether polyglutamine aggregates are deleterious, harmless or protective remains the most passionately disputed issue in the study of these diseases. In this review, we attempt to reconcile some of these controversies.