Neuronal nuclear tau and neurodegeneration

Chronic Vanadium Exposure Promotes Aggregation of Alpha-Synuclein, Tau and Amyloid Beta in Mouse Brain

The interaction of toxic environmental metals and metalloids with brain proteins and polypeptides can result in pathological aggregations and formation of toxic oligomers, which are key features of many neurodegenerative diseases. Occupational and environmental exposure to vanadium is connected to a neurological syndrome that includes psychiatric symptoms, cognitive decline, and neurodegeneration. In this study, we hypothesized that prolonged vanadium exposure may be a potential risk factor for Alzheimer's and Parkinson's diseases. A total of 72 male BALB/c mice, each 4 weeks' old, were used. Vanadium-treated groups received intraperitoneal injections of 3 mg/kg body weight of vanadium three times a week for 6, 12, or 18 months. The control group received sterile water while the withdrawal group were given vanadium injection for 3 months, followed by withdrawal of the metal, but treatment with sterile water only, and were sacrificed at 3-, 9-, or 15-months post vanadium exposure. Sagittal sections of brain paraffin-embedded tissue were prepared and analyzed using immunofluorescence to study the immunoreactivity and cellular localization of α-synuclein (α-syn), amyloid-β (Aβ), and tau proteins. Our findings revealed pathological aggregation of these proteins in the frontoparietal cortices and the dorsal CA1 and CA3 regions. Double immunolabeling with glial cells and neurons showed neuronal degeneration, functional gliosis, and activation of astrocytes and microglia at sites of α-synuclein immunoreactivity. We observed increased immunoreactivity of phosphorylated nuclei tau both in the parietal cortices and corpus callosum white matter while we observed intraneuronal accumulation of Aβ deposits in the cortex and dorsal hippocampal regions in vanadium treated brains. These cellular changes and proteinopathies, although persisting, were significantly attenuated after vanadium withdrawal. Our findings show that prolonged vanadium exposure promotes abnormal accumulation of neurodegeneration-associated proteins (α-syn, Tau, and Aβ) in the brain, which is further exacerbated by aging in the context of extended exposure to the metal.

Phosphorylation-Induced Self-Coacervation versus RNA-Assisted Complex Coacervation of Tau Proteins

In this study, the role of phosphorylation in the liquid-liquid phase separation (LLPS) of tau, the underlying driving forces, and the potential implications of this separation on protein conformation and subsequent protein aggregation were investigated. We compared in vivo-produced phosphorylated tau (p-tau) and nonphosphorylated tau under different coacervation conditions without adding crowding agents. Our findings revealed that spontaneous phase separation occurs exclusively in p-tau, triggered by a temperature shift from 4 °C to room temperature, and is driven by electrostatic and hydrophobic interactions. The p-tau self-acervation is reversible with temperature changes. Native mass spectrometry detects only two to nine phosphate groups per p-tau molecule, highlighting the impact of phosphorylation on tau's structural flexibility. Cross-linking mass spectrometry showed fewer long-range contacts in p-tau, suggesting a looser conformation induced by phosphorylation. Phosphorylation-induced LLPS and RNA-induced LLPS occurred at different timeframes. However, neither tau nor p-tau formed fibrils without the addition of dextran sulfate or RNA as inducers. Using human kidney epithelial cells expressing the tau R domain fused with fluorescent proteins as reporter cells, we observed aggregates in the nuclear envelope (NE) only in the cells treated with LLPS-state p-tau, which correlates with NE occurrences reported in Alzheimer's disease brain sections. These findings provide deeper insights into the impact of phosphorylation on tau aggregation through an intermediate condensation phase, offering novel perspectives on neurodegenerative disease mechanisms.

A Focus on the Link Between Metal Dyshomeostasis, Norepinephrine, and Protein Aggregation

Neurodegenerative disorders are one of the main public health problems worldwide and, for this reason, they have attracted the attention of several researchers who aim to better understand the molecular processes linked to the etiology of these disorders, including Alzheimer's and Parkinson's diseases. In this review, we describe both the beneficial and toxic effect of norepinephrine (NE) and its connected ROS/metal-mediated pathways, which end in neuromelanin (NM) formation and protein aggregation. In particular, we emphasize the importance of stabilizing the delicate homeostatic balance that regulates (i) the metal/ROS-promoted oxidation of catecholamines, as NE, and (ii) the generation of oxidative by-products capable of covalently and non-covalently modifying neuroproteins, thus altering their stability and their oligomerization; these processes may end in (iii) the incorporation of protein conjugates into vesicles, which then evolve into neuromelanin (NM) organelles. In general, we aim to provide an up-to-date overview of the challenges and controversies emerging from the current literature to delineate a direction for future research.

Nuclear Alpha-Synuclein in Parkinson's Disease and the Malignant Transformation in Melanoma

Background: Alpha-synuclein (ASyn), a marker of Parkinson's disease (PD) and other neurodegenerative processes, plays pivotal roles in neuronal nuclei and synapses. ASyn and its phosphorylated form at Serine 129 (p-ASyn) are involved in DNA protection and repair, processes altered in aging, neurodegeneration, and cancer. Objective: To analyze the localization of p-ASyn in skin biopsies of PD patients and melanoma. Methods: Biopsies from 26 PD patients, 20 melanoma patients, and 31 control subjects were probed and analyzed with a p-ASyn antibody by immunohistochemistry and immunofluorescence. Nuclear positivity was quantified by image analysis. Results: Peripheral nerve endings from healthy subjects show little p-ASyn immunopositivity but notable axonal presence in PD. Control subjects show immunopositivity to p-ASyn along all epidermic strata and scarce presence in their cytoplasm. In contrast, its nuclear presence in PD is weaker, with a higher cytoplasmic and intercellular presence. Nuclear p-ASyn in melanoma varied from similar to control skin in early stage melanoma to a higher rate of empty nuclei in the intermediate stage and total absence of nuclear p-ASyn in severe cases. Interpretation: These findings support the nuclear localization of p-ASyn in skin cells and show that its presence decreases PD and almost disappears in the malignant transformation of melanocytes, redistributing to the cytoplasm and intercellular spaces. This confirms the association between PD and melanoma, providing crucial insights into the role of p-ASyn in both diseases. Trial Registration: ClinicalTrials.gov identifier: NCT01380899.

Cellular and pathological functions of tau

Tau protein is involved in various cellular processes, including having a canonical role in binding and stabilization of microtubules in neurons. Tauopathies are neurodegenerative diseases marked by the abnormal accumulation of tau protein aggregates in neurons, as seen, for example, in conditions such as frontotemporal dementia and Alzheimer disease. Mutations in tau coding regions or that disrupt tau mRNA splicing, tau post-translational modifications and cellular stress factors (such as oxidative stress and inflammation) increase the tendency of tau to aggregate and interfere with its clearance. Pathological tau is strongly implicated in the progression of neurodegenerative diseases, and the propagation of tau aggregates is associated with disease severity. Recent technological advancements, including cryo-electron microscopy and disease models derived from human induced pluripotent stem cells, have increased our understanding of tau-related pathology in neurodegenerative conditions. Substantial progress has been made in deciphering tau aggregate structures and the molecular mechanisms that underlie protein aggregation and toxicity. In this Review, we discuss recent insights into the diverse cellular functions of tau and the pathology of tau inclusions and explore the potential for therapeutic interventions.

Molecular Insights into Tau Pathology and its Therapeutic Strategies in Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia. The two major hallmarks of this disease are extracellular amyloid plaques and intracellular neurofibrillary tangles in the brain, accompanied by loss of neurons and synapses. The plaques and tangles mainly consist of amyloid-β (Aβ) and tau protein, respectively. Most of the therapeutic strategies for AD to date have focused on Aβ. However, there is still no effective therapy available. In recent years, the clinical therapeutic failure of targeting Aβ pathology has resulted in increased interest towards tau-based therapeutics. In the current review, we focus on the research progress regarding the pathological mechanisms of tau protein in this disease and discuss tau-targeting therapeutic strategies.

HSV-1 infection induces phosphorylated tau propagation among neurons via extracellular vesicles

Extracellular vesicles (EV), key players in cell-to-cell communication, may contribute to disease propagation in several neurodegenerative diseases, including Alzheimer's disease (AD), by favoring the dissemination of neurotoxic proteins within the brain. Interestingly, growing evidence supports the role of herpes simplex virus type 1 (HSV-1) infection in the pathogenesis of AD. Here, we investigated whether HSV-1 infection could promote the spread of phosphorylated tau (ptau) among neurons via EV. We analyzed the ptau species that were secreted via EV following HSV-1 infection in neuroblastoma cells and primary neurons, focusing particularly on T205, T181, and T217, the phosphorylation sites mainly associated with AD. Moreover, by overexpressing human tau tagged with GFP (htauGFP), we found that recipient tau knockout (KO) neurons uptook EV that are loaded with HSV-1-induced phtauGFP. Finally, we exploited an in vivo model of acute infection and assessed that cerebral HSV-1 infection promotes the release of ptau via EV in the brain of infected mice. Overall, our data suggest that, following HSV-1 infection, EV play a role in tau spreading within the brain, thus contributing to neurodegeneration.IMPORTANCEHerpes simplex virus type 1 (HSV-1) infection that reaches the brain has been repeatedly linked with the appearance of the pathognomonic markers of Alzheimer's disease (AD), including accumulation of amyloid beta and hyperphosphorylated tau proteins, and cognitive deficits. AD is a multifactorial neurodegenerative disease representing the most common form of dementia in the elderly, and no cure is currently available, thus prompting additional investigation on potential risk factors and pathological mechanisms. Here, we demonstrate that the virus exploits the extracellular vesicles (EV) to disseminate phosphorylated tau (ptau) among brain cells. Importantly, we provide evidence that the HSV-1-induced EV-bearing ptau can be undertaken by recipient neurons, thus likely contributing to misfolding and aggregation of native tau, as reported for other AD models. Hence, our data highlight a novel mechanism exploited by HSV-1 to propagate tau-related damage in the brain.

Phosphorylated Tau at T181 accumulates in the serum of hibernating Syrian hamsters and rapidly disappears after arousal

The search for biomarkers for the early diagnosis of neurodegenerative diseases is a growing area. Numerous investigations are exploring minimally invasive and cost-effective biomarkers, with the detection of phosphorylated Tau (pTau) protein emerging as one of the most promising fields. pTau is the main component of the paired helical filaments found in the brains of Alzheimer's disease cases and serves as a precursor in the formation of neurofibrillary tangles (NFTs). Recent research has revealed that analysis of p-Tau181, p-Tau217 and p-Tau231 in blood may be an option for detecting the preclinical stage of Alzheimer's disease. In this study, we have analyzed the values of pTau 181 in the serum of Syrian hamsters during hibernation. Naturally, over the course of hibernation, these animals exhibit a reversible accumulation of pTau in the brain tissue, which rapidly disappears upon awakening. A biosensing system based on the interferometric optical detection method was used to measure the concentration of pTau181 protein in serum samples from Syrian hamsters. This method eliminates the matrix effect and amplifies the signal obtained by using silicon dioxide nanoparticles (SiO2 NPs) biofunctionalized with the αpTau181 antibody. Our results indicate a substantial increase in the serum concentration of pTau in threonine-181 during hibernation, which disappears completely 2-3 h after awakening. Investigating the mechanism by which pTau protein appears in the blood non-pathologically may enhance current diagnostic techniques. Furthermore, since this process is reversible, and no tangles are detected in the brains of hibernating hamsters, additional analysis may contribute to the discovery of improved biomarkers. Additionally, exploring drugs targeting pTau to prevent the formation of tangles or studying the outcomes of any pTau-targeted treatment could be valuable.

Lamivudine modulates the expression of neurological impairment-related genes and LINE-1 retrotransposons in brain tissues of a Down syndrome mouse model

Elevated activity of retrotransposons is increasingly recognized to be implicated in a wide range of neurodegenerative and neurodevelopmental diseases, including Down syndrome (DS), which is the most common chromosomal condition causing intellectual disability globally. Previous research by our group has revealed that treatment with lamivudine, a reverse transcriptase inhibitor, improved neurobehavioral phenotypes and completely rescued hippocampal-dependent recognition memory in a DS mouse model, Ts65Dn. We hypothesized that retrotransposition rates would increase in the Ts65Dn mouse model, and lamivudine could block retrotransposons. We analyzed the differentially expressed long interspersed element-1 (LINE-1 or L1) mapping on MMU16 and 17, and showed for the first time that retrotransposition could be associated with Ts65Dn's pathology, as misregulation of L1 was found in brain tissues associated with trisomy. In the cerebral cortex, 6 out of 26 upregulated L1s in trisomic treated mice were located in the telomeric region of MMU16 near Ttc3, Kcnj6, and Dscam genes. In the hippocampus, one upregulated L1 element in trisomic treated mice was located near the Fgd4 gene on MMU16. Moreover, two downregulated L1s rescued after treatment with lamivudine were located in the intronic region of Nrxn1 (MMU17) and Snhg14 (MMU7), implicated in a variety of neurodegenerative disorders. To gain further insight into the mechanism of this improvement, we here analyzed the gene expression profile in the hippocampus and cerebral cortex of trisomic mice treated and no-treated with lamivudine compared to their wild-type littermates. We found that treatment with lamivudine rescued the expression of 24% of trisomic genes in the cortex (located on mouse chromosome (MMU) 16 and 17) and 15% in the hippocampus (located in the human chromosome 21 orthologous regions), with important DS candidate genes such as App and Ets2, rescued in both regions.

Norepinephrine Drives Sleep Fragmentation Activation of Asparagine Endopeptidase, Locus Ceruleus Degeneration, and Hippocampal Amyloid-β42 Accumulation

Chronic sleep disruption (CSD), from insufficient or fragmented sleep and is an important risk factor for Alzheimer's disease (AD). Underlying mechanisms are not understood. CSD in mice results in degeneration of locus ceruleus neurons (LCn) and CA1 hippocampal neurons and increases hippocampal amyloid-β42 (Aβ42), entorhinal cortex (EC) tau phosphorylation (p-tau), and glial reactivity. LCn injury is increasingly implicated in AD pathogenesis. CSD increases NE turnover in LCn, and LCn norepinephrine (NE) metabolism activates asparagine endopeptidase (AEP), an enzyme known to cleave amyloid precursor protein (APP) and tau into neurotoxic fragments. We hypothesized that CSD would activate LCn AEP in an NE-dependent manner to induce LCn and hippocampal injury. Here, we studied LCn, hippocampal, and EC responses to CSD in mice deficient in NE [dopamine β-hydroxylase (Dbh)-/-] and control male and female mice, using a model of chronic fragmentation of sleep (CFS). Sleep was equally fragmented in Dbh -/- and control male and female mice, yet only Dbh -/- mice conferred resistance to CFS loss of LCn, LCn p-tau, and LCn AEP upregulation and activation as evidenced by an increase in AEP-cleaved APP and tau fragments. Absence of NE also prevented a CFS increase in hippocampal AEP-APP and Aβ42 but did not prevent CFS-increased AEP-tau and p-tau in the EC. Collectively, this work demonstrates AEP activation by CFS, establishes key roles for NE in both CFS degeneration of LCn neurons and CFS promotion of forebrain Aβ accumulation, and, thereby, identifies a key molecular link between CSD and specific AD neural injuries.

Nuclear Tau accumulation in Alzheimer's disease

Tau is a well-known microtubule-associated protein and is located in the cytoplasm of neurons, which play a crucial role in Alzheimer's diseases. Due to its preferred binding to DNA sequences found in the nucleolus and pericentromeric heterochromatin, Tau has been found within the cell nucleus, where it may be a nucleic acid-associated protein. Tau has the ability to directly interact with nuclear pore complex nucleoporins, influencing both their structural and functional integrity. The interaction between Tau and NUPs highlights a potential mechanism underlying NPC dysfunction in AD pathogenesis. Pathological Tau hinders the import and export of nucleus through RAN mediated cascades. Nuclear Tau aggregates colocalize with membrane less organelles called nuclear speckles, which are involved in pre-mRNA splicing, and modify their dynamics, composition, and structure. Additionally, SRRM2 and other nuclear speckle proteins including MSUT2 and PABPN1 mislocalize to cytosolic Tau aggregates, and causes propagation of Tau aggregates. Research highlights, Extracellular Tau Oligomers induce significant nuclear invagination. They act as a key player in the transformation of healthy neurons into sick neurons in AD. The mechanism behind this phenomenon depends on intracellular Tau and is linked to changes in chromatin structure, nucleocytoplasmic transport, and gene transcription. This review highlights the vital roles of nuclear Tau protein in the context of nuclear pore complex functioning and, modulation of nuclear speckles in Alzheimer's diseases. Addressing these pathways is essential for formulating focused therapeutics intended to alleviate Tau-induced neurodegeneration.

Potential Application of MicroRNAs and Some Other Molecular Biomarkers in Alzheimer's Disease

Alzheimer's disease (AD) is the world's most common neurodegenerative disease, expected to affect up to one-third of the elderly population in the near future. Among the major challenges in combating AD are the inability to reverse the damage caused by the disease, expensive diagnostic tools, and the lack of specific markers for the early detection of AD. This paper highlights promising research directions for molecular markers in AD diagnosis, including the diagnostic potential of microRNAs. The latest molecular methods for diagnosing AD are discussed, with particular emphasis on diagnostic techniques prior to the appearance of full AD symptoms and markers detectable in human body fluids. A collection of recent studies demonstrates the promising potential of molecular methods in AD diagnosis, using miRNAs as biomarkers. Up- or downregulation in neurodegenerative diseases may not only provide a new diagnostic tool but also serve as a marker for differentiating neurodegenerative diseases. However, further research in this direction is needed.

Intrathecal production of anti-Epstein-Barr virus viral capsid antigen IgG is associated with neurocognition and tau proteins in people with HIV

OBJECTIVE

HIV and Epstein-Barr virus (EBV) co-infection has been linked to increased immune activation and larger HIV reservoir. We assessed whether anti-EBV humoral responses are associated with increased cerebrospinal fluid (CSF) inflammation and with neurocognitive impairment (NCI) in people with HIV (PWH).

DESIGN

Cross-sectional analysis in 123 EBV-seropositive PWH either on antiretroviral therapy ( n  = 70) or not.

METHODS

Serum and CSF anti-EBV viral capsid antigen immunoglobulin G (anti-EVI) and CSF EBV DNA were measured by commercial immunoassay and RT-PCR. Seventy-eight participants without neurological confounding factors underwent neurocognitive assessment (Global Deficit Score, GDS). CSF total tau and 181-phosphorylated-tau (ptau) were measured by immunoassays together with biomarkers of blood-brain barrier (BBB) integrity, immune activation, astrocytosis, and intrathecal synthesis. Logistic and linear regressions and moderation analysis were used to investigate the relationships between CSF anti-EVI, GDS, and biomarkers.

RESULTS

Twenty-one (17.1%) and 22 participants (17.9%) had detectable CSF anti-EVI (10.5-416.0 U/ml) and CSF EBV DNA (25-971 copies/ml). After adjusting for BBB integrity, age, and clinical factors, the presence of CSF anti-EVI was only associated with serum levels of anti-EVI, and not with CSF EBV DNA. CSF anti-EVI, tau and ptau showed reciprocal interactions affecting their associations with GDS. After adjusting for demographics and clinical parameters, higher CSF anti-EVI levels were associated with worse GDS (aβ 0.45, P  < 0.001), and CSF levels of tau and ptau had a moderation effect on the strength of this association (models' P  < 0.001).

CONCLUSION

Humoral immune responses against EBV within the central nervous system may contribute to NCI in PWH through mechanisms that involve neuronal injury.

Delaying Brain Aging or Decreasing Tau Levels as Strategies to Prevent Alzheimer's Disease: In Memoriam of Mark A. Smith

Aging is the main risk for neurodegenerative disorders like Alzheimer's disease. In this short review, I will comment on how delaying brain aging through the addition of Yamanaka Factors or small compounds that bind to the folate receptor alpha, which promote the expression of the Yamanaka Factors or by the decrease tau levels in brain cells from older subjects could serve as strategies to prevent Alzheimer's disease.

Nuclear face of Tau: an inside player in neurodegeneration

Tau (Tubulin associated unit) protein is a major hallmark of Alzheimer's disease (AD) and tauopathies. Tau is predominantly an axonal protein with a crucial role in the stabilization and dynamics of the microtubules. Since the discovery of Tau protein in 1975, research efforts were concentrated on the pathophysiological role of Tau protein in the context of the microtubules. Although, for more than three decades, different localizations of Tau protein have been discovered e.g., in the nuclear compartments. Discovery of the role of Tau protein in various cellular compartments especially in the nucleus opens up a new fold of complexity in tauopathies. Data from cellular models, animal models, and the human brain indicate that nuclear Tau is crucial for genome stability and to cope with cellular distress. Moreover, it's nature of nuclear translocation, its interactions with the nuclear DNA/RNA and proteins suggest it could play multiple roles in the nucleus. To comprehend Tau pathophysiology and efficient Tau-based therapies, there is an urgent need to understand whole repertoire of Tau species (nuclear and cytoplasmic) and their functional relevance. To complete the map of Tau repertoire, understanding of various species of Tau in the nucleus and cytoplasm, identification if specific transcripts of Tau, isoforms and post-translational modifications could foretell Tau's localizations and functions, and how they are modified in neurodegenerative diseases like AD, is urgently required. In this review, we explore the nuclear face of Tau protein, its nuclear localizations and functions and its linkage with Alzheimer's disease.

Recent Advances in High-Content Imaging and Analysis in iPSC-Based Modelling of Neurodegenerative Diseases

In the field of neurodegenerative pathologies, the platforms for disease modelling based on patient-derived induced pluripotent stem cells (iPSCs) represent a valuable molecular diagnostic/prognostic tool. Indeed, they paved the way for the in vitro recapitulation of the pathological mechanisms underlying neurodegeneration and for characterizing the molecular heterogeneity of disease manifestations, also enabling drug screening approaches for new therapeutic candidates. A major challenge is related to the choice and optimization of the morpho-functional study designs in human iPSC-derived neurons to deeply detail the cell phenotypes as markers of neurodegeneration. In recent years, the specific combination of high-throughput screening with subcellular resolution microscopy for cell-based high-content imaging (HCI) screening allowed in-depth analyses of cell morphology and neurite trafficking in iPSC-derived neuronal cells by using specific cutting-edge microscopes and automated computational assays. The present work aims to describe the main recent protocols and advances achieved with the HCI analysis in iPSC-based modelling of neurodegenerative diseases, highlighting technical and bioinformatics tips and tricks for further uses and research. To this end, microscopy requirements and the latest computational pipelines to analyze imaging data will be explored, while also providing an overview of the available open-source high-throughput automated platforms.

Transcriptomic Analysis in the Hippocampus and Retina of Tg2576 AD Mice Reveals Defective Mitochondrial Oxidative Phosphorylation and Recovery by Tau 12A12mAb Treatment

Increasing evidence implicates decreased energy metabolism and mitochondrial dysfunctions among the earliest pathogenic events of Alzheimer's disease (AD). However, the molecular mechanisms underlying bioenergetic dysfunctions in AD remain, to date, largely unknown. In this work, we analyzed transcriptomic changes occurring in the hippocampus and retina of a Tg2576 AD mouse model and wild-type controls, evaluating their functional implications by gene set enrichment analysis. The results revealed that oxidative phosphorylation and mitochondrial-related pathways are significantly down-regulated in both tissues of Tg2576 mice, supporting the role of these processes in the pathogenesis of AD. In addition, we also analyzed transcriptomic changes occurring in Tg2576 mice treated with the 12A12 monoclonal antibody that neutralizes an AD-relevant tau-derived neurotoxic peptide in vivo. Our analysis showed that the mitochondrial alterations observed in AD mice were significantly reverted by treatment with 12A12mAb, supporting bioenergetic pathways as key mediators of its in vivo neuroprotective and anti-amyloidogenic effects. This study provides, for the first time, a comprehensive characterization of molecular events underlying the disrupted mitochondrial bioenergetics in AD pathology, laying the foundation for the future development of diagnostic and therapeutic tools.

Cell-specific MAPT gene expression is preserved in neuronal and glial tau cytopathologies in progressive supranuclear palsy

Microtubule-associated protein tau (MAPT) aggregates in neurons, astrocytes and oligodendrocytes in a number of neurodegenerative diseases, including progressive supranuclear palsy (PSP). Tau is a target of therapy and the strategy includes either the elimination of pathological tau aggregates or reducing MAPT expression, and thus the amount of tau protein made to prevent its aggregation. Disease-associated tau affects brain regions in a sequential manner that includes cell-to-cell spreading. Involvement of glial cells that show tau aggregates is interpreted as glial cells taking up misfolded tau assuming that glial cells do not express enough MAPT. Although studies have evaluated MAPT expression in human brain tissue homogenates, it is not clear whether MAPT expression is compromised in cells accumulating pathological tau. To address these perplexing aspects of disease pathogenesis, this study used RNAscope combined with immunofluorescence (AT8), and single-nuclear(sn) RNAseq to systematically map and quantify MAPT expression dynamics across different cell types and brain regions in controls (n = 3) and evaluated whether tau cytopathology affects MAPT expression in PSP (n = 3). MAPT transcripts were detected in neurons, astrocytes and oligodendrocytes, and varied between brain regions and within each cell type, and were preserved in all cell types with tau aggregates in PSP. These results propose a complex scenario in all cell types, where, in addition to the ingested misfolded tau, the preserved cellular MAPT expression provides a pool for local protein production that can (1) be phosphorylated and aggregated, or (2) feed the seeding of ingested misfolded tau by providing physiological tau, both accentuating the pathological process. Since tau cytopathology does not compromise MAPT gene expression in PSP, a complete loss of tau protein expression as an early pathogenic component is less likely. These observations provide rationale for a dual approach to therapy by decreasing cellular MAPT expression and targeting removal of misfolded tau.

Drosophila melanogaster as a model to study autophagy in neurodegenerative diseases induced by proteinopathies

Proteinopathies are a large group of neurodegenerative diseases caused by both genetic and sporadic mutations in particular genes which can lead to alterations of the protein structure and to the formation of aggregates, especially toxic for neurons. Autophagy is a key mechanism for clearing those aggregates and its function has been strongly associated with the ubiquitin-proteasome system (UPS), hence mutations in both pathways have been associated with the onset of neurodegenerative diseases, particularly those induced by protein misfolding and accumulation of aggregates. Many crucial discoveries regarding the molecular and cellular events underlying the role of autophagy in these diseases have come from studies using Drosophila models. Indeed, despite the physiological and morphological differences between the fly and the human brain, most of the biochemical and molecular aspects regulating protein homeostasis, including autophagy, are conserved between the two species.In this review, we will provide an overview of the most common neurodegenerative proteinopathies, which include PolyQ diseases (Huntington's disease, Spinocerebellar ataxia 1, 2, and 3), Amyotrophic Lateral Sclerosis (C9orf72, SOD1, TDP-43, FUS), Alzheimer's disease (APP, Tau) Parkinson's disease (a-syn, parkin and PINK1, LRRK2) and prion diseases, highlighting the studies using Drosophila that have contributed to understanding the conserved mechanisms and elucidating the role of autophagy in these diseases.

Sleep matters: Neurodegeneration spectrum heterogeneity, combustion and friction ultrafine particles, industrial nanoparticle pollution, and sleep disorders-Denial is not an option

Sustained exposures to ubiquitous outdoor/indoor fine particulate matter (PM_2.5), including combustion and friction ultrafine PM (UFPM) and industrial nanoparticles (NPs) starting in utero, are linked to early pediatric and young adulthood aberrant neural protein accumulation, including hyperphosphorylated tau (p-tau), beta-amyloid (Aβ_{1 - 42}), α-synuclein (α syn) and TAR DNA-binding protein 43 (TDP-43), hallmarks of Alzheimer's (AD), Parkinson's disease (PD), frontotemporal lobar degeneration (FTLD), and amyotrophic lateral sclerosis (ALS). UFPM from anthropogenic and natural sources and NPs enter the brain through the nasal/olfactory pathway, lung, gastrointestinal (GI) tract, skin, and placental barriers. On a global scale, the most important sources of outdoor UFPM are motor traffic emissions. This study focuses on the neuropathology heterogeneity and overlap of AD, PD, FTLD, and ALS in older adults, their similarities with the neuropathology of young, highly exposed urbanites, and their strong link with sleep disorders. Critical information includes how this UFPM and NPs cross all biological barriers, interact with brain soluble proteins and key organelles, and result in the oxidative, endoplasmic reticulum, and mitochondrial stress, neuroinflammation, DNA damage, protein aggregation and misfolding, and faulty complex protein quality control. The brain toxicity of UFPM and NPs makes them powerful candidates for early development and progression of fatal common neurodegenerative diseases, all having sleep disturbances. A detailed residential history, proximity to high-traffic roads, occupational histories, exposures to high-emission sources (i.e., factories, burning pits, forest fires, and airports), indoor PM sources (tobacco, wood burning in winter, cooking fumes, and microplastics in house dust), and consumption of industrial NPs, along with neurocognitive and neuropsychiatric histories, are critical. Environmental pollution is a ubiquitous, early, and cumulative risk factor for neurodegeneration and sleep disorders. Prevention of deadly neurological diseases associated with air pollution should be a public health priority.

Pathological Nuclear Hallmarks in Dentate Granule Cells of Alzheimer’s Patients: A Biphasic Regulation of Neurogenesis

The dentate gyrus (DG) of the human hippocampus is a complex and dynamic structure harboring mature and immature granular neurons in diverse proliferative states. While most mammals show persistent neurogenesis through adulthood, human neurogenesis is still under debate. We found nuclear alterations in granular cells in autopsied human brains, detected by immunohistochemistry. These alterations differ from those reported in pyramidal neurons of the hippocampal circuit. Aging and early AD chromatin were clearly differentiated by the increased epigenetic markers H3K9me3 (heterochromatin suppressive mark) and H3K4me3 (transcriptional euchromatin mark). At early AD stages, lamin B2 was redistributed to the nucleoplasm, indicating cell-cycle reactivation, probably induced by hippocampal nuclear pathology. At intermediate and late AD stages, higher lamin B2 immunopositivity in the perinucleus suggests fewer immature neurons, less neurogenesis, and fewer adaptation resources to environmental factors. In addition, senile samples showed increased nuclear Tau interacting with aged chromatin, likely favoring DNA repair and maintaining genomic stability. However, at late AD stages, the progressive disappearance of phosphorylated Tau forms in the nucleus, increased chromatin disorganization, and increased nuclear autophagy support a model of biphasic neurogenesis in AD. Therefore, designing therapies to alleviate the neuronal nuclear pathology might be the only pathway to a true rejuvenation of brain circuits.