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Systemic exposure to nanoparticles (NPs) adversely affects different organs, including the nervous system. We systematically extracted data from publication on PubMed and Embase database up to the year 2020, and analyzed in vitro and in vivo neurotoxicity of 4 of the most well studied NPs (silver NPs, carbon-based NPs, iron NPs and silica NPs). A relatively good correlation was observed between in vitro and in vivo effects, including genotoxicity, oxidative stress, apoptosis and pro-inflammatory effects. However, crucial knowledge gap exists in current understanding of the underlying mechanisms. Some of the critical knowledge gaps and research needs identified in relation to neurotoxicity of nanoparticles include (1) lack of physio-chemical characteristics of NPs used, (2) cellular/tissue uptake of NP, (3) NP translocation across the blood-brain barrier (BBB), (4) Effect of exposure routes. [ABSTRACT FROM AUTHOR]

In eukaryotes, most intracellular membrane fusion reactions are mediated by the interaction of SNARE proteins that are present in both fusing membranes. However, the minimal number of SNARE complexes needed for membrane fusion is not known. Here we show unambiguously that one SNARE complex is sufficient for membrane fusion. We performed controlled in vitro Förster resonance energy transfer (FRET) experiments and found that liposomes bearing only a single SNARE molecule are still capable of fusion with other liposomes or with purified synaptic vesicles. Furthermore, we demonstrated that multiple SNARE complexes do not act cooperatively, showing that synergy between several SNARE complexes is not needed for membrane fusion. Our findings shed new light on the mechanism of SNARE-mediated membrane fusion and call for a revision of current views of fusion events such as the fast release of neurotransmitters. [ABSTRACT FROM AUTHOR]

Parkinson's Disease (PD) is the second most common neurodegenerative disorder. The pathological hallmark of PD is loss of dopaminergic neurons and the presence of aggregated α-synuclein, primarily in the substantia nigra pars compacta (SNpc) of the midbrain. However, the molecular mechanisms that underlie the pathology in different cell types is not currently understood. Here, we present a single nucleus transcriptome analysis of human post-mortem SNpc obtained from 15 sporadic Parkinson's Disease (PD) cases and 14 Controls. Our dataset comprises ∼84K nuclei, representing all major cell types of the brain, allowing us to obtain a transcriptome-level characterization of these cell types. Importantly, we identify multiple subpopulations for each cell type and describe specific gene sets that provide insights into the differing roles of these subpopulations. Our findings reveal a significant decrease in neuronal cells in PD samples, accompanied by an increase in glial cells and T cells. Subpopulation analyses demonstrate a significant depletion of tyrosine hydroxylase (TH) enriched astrocyte, microglia and oligodendrocyte populations in PD samples, as well as TH enriched neurons, which are also depleted. Moreover, marker gene analysis of the depleted subpopulations identified 28 overlapping genes, including those associated with dopamine metabolism (e.g., ALDH1A1, SLC6A3 & SLC18A2). Overall, our study provides a valuable resource for understanding the molecular mechanisms involved in dopaminergic neuron degeneration and glial responses in PD, highlighting the existence of novel subpopulations and cell type-specific gene sets. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-plasmid approach with multiple expression modules (including self-excising piggyBac transposase). • Allows simultaneous loss- (shRNA, CRISPR/Cas9) and gain-of-function (protein overexpression) experiments. • Applicable across diverse (non-transgenic) species including mouse, rat, ferret and Xenopus tropicalis. • Cell-type specific and temporal (CreERT2) control. Advances in single cell sequencing have enabled the identification of a large number of genes, expressed in many different cell types, and across a variety of model organisms. In particular, the nervous system harbors an immense number of interacting cell types, which are poorly characterized. Future loss- and gain-of-function experiments will be essential in determining how novel genes play critical roles in diverse cellular, as well as evolutionarily adapted, contexts. However, functional analysis across species is often hampered by technical limitations, in non-genetic animal systems. Here, we describe a new single plasmid system, misPiggy. The system is based around the hyperactive piggyBac transposon system, which combines stable genomic integration of transgenes (for long-term expression) with large cargo capacity. Taking full advantage of these characteristics, we engineered novel expression modules into misPiggy that allow for cell-type specific loss- and gain-of-gene function. These modules work widely across species from frog to ferret. As a proof of principle, we present a loss-of-function analysis of the neuronal receptor Deleted in Colorectal Cancer (DCC) in retinal ganglion cells (RGCs) of Xenopus tropicalis tadpoles. Single axon tracings of mosaic knock-out cells reveal a specific cell-intrinsic requirement of DCC, specifically in axonal arborization within the frog tectum, rather than retina-to-brain axon guidance. Furthermore, we report additional technical advances that enable temporal control of knock-down or gain-of-function analysis. We applied this to visualize and manipulate labeled neurons, astrocytes and other glial cells in the central nervous system (CNS) of mouse, rat and ferret. We propose that misPiggy will be a valuable tool for rapid, flexible and cost-effective screening of gene function across a variety of animal models. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Unravelling cell type-specific responses to Parkinson's Disease at single cell resolution" published in the journal Molecular Neurodegeneration. The correction addresses an error in the original article where the affiliation of company #8, 'bit.bio', was mistakenly omitted. The correction has been made to include the correct affiliation information. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. The authors of the article are listed as Araks Martirosyan, Rizwan Ansari, Francisco Pestana, and several others. [Extracted from the article]

• Neuronal circuits in the adult cortex are plastic. • Astrocytes are essential for circuit remodeling. • Astrocytes perform multiple roles associated with plasticity. • Boosting astrocyte activity enhances plasticity and may be beneficial therapeutically. Plasticity is a fundamental property of neuronal circuits, allowing them to adapt to alterations in activation. Generally speaking, plasticity has been viewed from a 'neuron-centric' perspective, with changes in circuit function attributed to alterations in neuronal excitability, synaptic strength or neuronal connectivity. However, it is now clear that glial cells, in particular astrocytes, are key regulators of neuronal plasticity. This article reviews recent progress made in understanding astrocyte function and attempts to summarize these functions into a coherent framework that positions astrocytes as central players in the plasticity process. [ABSTRACT FROM AUTHOR]

Background: Three amino acid differences between rodent and human APP affect medically important features, including β-secretase cleavage of APP and Aβ peptide aggregation (De Strooper et al., EMBO J 14:4932-38, 1995; Ueno et al., Biochemistry 53:7523-30, 2014; Bush, 2003, Trends Neurosci 26:207–14). Most rodent models for Alzheimer's disease (AD) are, therefore, based on the human APP sequence, expressed from artificial mini-genes randomly inserted in the rodent genome. While these models mimic rather well various biochemical aspects of the disease, such as Aβ-aggregation, they are also prone to overexpression artifacts and to complex phenotypical alterations, due to genes affected in or close to the insertion site(s) of the mini-genes (Sasaguri et al., EMBO J 36:2473-87, 2017; Goodwin et al., Genome Res 29:494-505, 2019). Knock-in strategies which introduce clinical mutants in a humanized endogenous rodent APP sequence (Saito et al., Nat Neurosci 17:661-3, 2014) represent useful improvements, but need to be compared with appropriate humanized wildtype (WT) mice. Methods: Computational modelling of the human β-CTF bound to BACE1 was used to study the differential processing of rodent and human APP. We humanized the three pivotal residues we identified G676R, F681Y and R684H (labeled according to the human APP770 isoform) in the mouse and rat genomes using a CRISPR-Cas9 approach. These new models, termed mouse and rat Apphu/hu, express APP from the endogenous promotor. We also introduced the early-onset familial Alzheimer's disease (FAD) mutation M139T into the endogenous Rat Psen1 gene. Results: We show that introducing these three amino acid substitutions into the rodent sequence lowers the affinity of the APP substrate for BACE1 cleavage. The effect on β-secretase processing was confirmed as both humanized rodent models produce three times more (human) Aβ compared to the original WT strain. These models represent suitable controls, or starting points, for studying the effect of transgenes or knock-in mutations on APP processing (Saito et al., Nat Neurosci 17:661-3, 2014). We introduced the early-onset familial Alzheimer's disease (FAD) mutation M139T into the endogenous Rat Psen1 gene and provide an initial characterization of Aβ processing in this novel rat AD model. Conclusion: The different humanized APP models (rat and mouse) expressing human Aβ and PSEN1 M139T are valuable controls to study APP processing in vivo allowing the use of a human Aβ ELISA which is more sensitive than the equivalent system for rodents. These animals will be made available to the research community. [ABSTRACT FROM AUTHOR]

Astrocytes are a major cell type in the mammalian CNS. Astrocytes are now known to play a number of essential roles in processes including synapse formation and function, as well as blood-brain barrier formation and control of cerebral blood flow. However, our understanding of the molecular mechanisms underlying astrocyte development and function is still rudimentary. This lack of knowledge is at least partly due to the lack of tools currently available for astrocyte biology. ACSA-2 is a commercially available antibody originally developed for the isolation of astrocytes from young postnatal mouse brain, using magnetic cell-sorting methods, but its utility in isolating cells from adult tissue has not yet been published. Using a modified protocol, we now show that this tool can also be used to isolate ultrapure astrocytes from the adult brain. Furthermore, using a variety of techniques (including single-cell sequencing, overexpression and knockdown assays, immunoblotting, and immunohistochemistry), we identify the ACSA-2 epitope for the first time as ATP1B2 and characterize its distribution in the CNS. Finally, we show that ATP1B2 is stably expressed in multiple models of CNS injury and disease. Hence, we show that the ACSA-2 antibody possesses the potential to be an extremely valuable tool for astrocyte research, allowing the purification and characterization of astrocytes (potentially including injury and disease models) without the need for any specialized and expensive equipment. In fact, our results suggest that ACSA-2 should be a first-choice method for astrocyte isolation and characterization. [ABSTRACT FROM AUTHOR]

Astrocytes are ubiquitous in the central nervous system (CNS). These cells possess thousands of individual processes, which extend out into the neuropil, interacting with neurons, other glia and blood vessels. Paralleling the wide diversity of their interactions, astrocytes have been reported to play key roles in supporting CNS structure, metabolism, blood-brain-barrier formation and control of vascular blood flow, axon guidance, synapse formation and modulation of synaptic transmission. Traditionally, astrocytes have been studied as a homogenous group of cells. However, recent studies have uncovered a surprising degree of heterogeneity in their development and function, in both the healthy and diseased brain. A better understanding of astrocyte heterogeneity is urgently needed to understand normal brain function, as well as the role of astrocytes in response to injury and disease. [ABSTRACT FROM AUTHOR]

Astrocytes are a major cell type in the mammalian nervous system, are in close proximity to neurons, and show rich Ca2+ activity thought to mediate cellular outputs. Astrocytes show activity linked to sensory [ 1, 2 ] and motor [ 3, 4 ] events, reflecting local neural activity and brain-wide neuromodulatory inputs. Sensory responses are highly variable [ 5–10 ], which may reflect interactions between distinct input types [ 6, 7, 9 ]. However, the diversity of inputs generating astrocyte activity, particularly during sensory stimulation and behavior, is not fully understood [ 11, 12 ]. Using a combination of Ca2+ imaging, a treadmill assay, and visual stimulation, we examined the properties of astrocyte activity in mouse visual cortex associated with motor or sensory events. Consistent with previous work, motor activity activated astrocytes across the cortex with little specificity, reflecting a diffuse neuromodulatory mechanism. In contrast, moving visual stimuli generated specific activity patterns that reflected the stimulus' trajectory within the visual field, precisely as one would predict if astrocytes reported local neural activity. Visual responses depended strongly on behavioral state, with astrocytes showing high amplitude Ca2+ transients during locomotion and little activity during stillness. Furthermore, the amplitudes of visual responses were highly correlated with pupil size, suggesting a role of arousal. Interestingly, while depletion of cortical noradrenaline abolished locomotor responses, visual responses were only reduced in amplitude and their spatiotemporal organization remained intact, suggesting two distinct types of inputs underlie visual responses. We conclude that cortical astrocytes integrate local sensory information and behavioral state, suggesting a role in information processing. • Astrocytes of moving mice display robust retinotopic responses to visual stimuli • Sensory responses are distinguishable from responses to locomotion • Vision-driven responses are correlated to arousal • Vision- and arousal-driven responses are differentially regulated by noradrenaline Slezak et al. reveal robust sensory-induced calcium transients in visual cortex astrocytes of locomoting mice. They dissociate spatiotemporal properties of these transients from global events elicited by arousal and demonstrate their differential regulation by noradrenaline. [ABSTRACT FROM AUTHOR]