Mouse Brain Research Articles

The Effect of Donepezil Hydrochloride in the Twitcher Mouse Model of Krabbe Disease.

Krabbe disease (KD) is a rare demyelinating disorder characterized by demyelination caused by mutations in the GALC gene, resulting in toxic accumulation of psychosine. Psychosine has been identified as detrimental to oligodendrocytes, leading to demyelination through diverse hypothesized pathways. Reducing demyelination is essential to maintain neurological function in KD; however, therapeutic interventions are currently limited. Acetylcholinesterase inhibitors (AChEi) are commonly used for symptomatic management of Alzheimer's Disease and are suggested to have potential disease-modifying effects, including regulating myelin state. In particular, donepezil, an AChEi, has demonstrated promising effects in cellular and animal models, including promotion of the expression of myelin-related genes and reduction of glial cell reactivity. This drug also acts as an agonist for sigma-1 receptors (Sig-1R), which are implicated in demyelination diseases. In the context of drug repurposing, here, we demonstrate that administration of donepezil has protective effects in the twitcher mouse model of KD. We provide data showing that donepezil preserves myelin and reduces glial cell reactivity in the brains of twitcher mice. Moreover, donepezil also improves behavioral phenotypes and increases lifespan in twitcher animals. These findings suggest that donepezil, with its dual activity as an AChE inhibitor and Sig-1R agonist, may hold promise as a therapeutic candidate for demyelinating diseases, including KD.

Apolipoprotein C3-rich low-density lipoprotein (AC3RL) exacerbates cerebral ischaemic stroke injury by increasing BBB leakage via LOX-1

Abstract Background Ischaemic stroke causes the abrupt reduction or cessation of blood flow to the brain results in a cascade of events that can compromise blood-brain barrier (BBB) integrity. We revealed that an increase in apolipoprotein C3 (ApoC3)-rich low-density lipoprotein (AC3RL) is associated with endothelial cell apoptosis and inflammatory responses, indicating that AC3RL is one of the risk factors for cardiovascular events. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) triggers a cascade of events within endothelial cells that leads to endothelial dysfunction. Purpose We aimed to investigate whether AC3RL affects BBB permeability via the LOX-1, and thus increases brain damage. Methods We collected the whole blood from normal and patients with ischaemic events and separated them by centrifugation. AC3RL were collected using FPLC. We performed middle cerebral artery occlusion (MCAO) surgery to induce ischaemic stroke using B6 (C57BL/6) and LOX-1-/- mice injected with AC3RL. Triphenyl tetrazolium chloride (TTC) and Evans blue stains were accessed to confirm brain injury and BBB permeability. Results FPLC results showed that patients with ischaemic events presented higher levels of AC3RL compared to normal people. TTC stain showed the increased area of ischaemic penumbra damage in B6 mice with AC3RL injection, and LOX-1-/- mice with AC3RL injection were significantly protected. Evans blue dye leakage was observed in the brain tissues of B6 mice with AC3RL injection. LOX-1-/- mice with AC3RL injection revealed a decrease in BBB permeability. The modified neurological severity score (mNSS) method revealed a significant rise in B6 mice with AC3RL injection, which suggested a decline in motor and nervous function. LOX-1-/- mice with AC3RL injection significantly improved in motor and neurological functioning. Conclusions We demonstrate that AC3RL, through its effects on LOX-1, is associated with an increased risk of BBB damage after stroke. Therefore, pharmacological inhibition of AC3RL-LOX-1 interaction will be the main strategy to reduce severe brain damage. Figure 1: (A) AC3RL percentage (%) in individuals. Normal: healthy people, Ischemic event: patients who have experienced an ischemic event. **p < 0.001 vs. Normal group. (B, C) TTC stain of brain tissue after euthanasia to pinpoint the site of brain damage. The white portion of the mice brains indicated the site of the injury. (D, E) Evans blue dye leakage study in mice brains exhibited BBB permeability changes. (F) Assessment of mice's motor and neurological performance using the mNSS. Data are expressed as the mean ± SEM. **p < 0.001, ****p < 0.0001 vs. sham group, ##p < 0.001 vs. B6 I.V. AC3RL group.Graphical abstractFigure 1.

Japanese encephalitis virus-induced DNA methylation contributes to blood-brain barrier permeability by modulating tight junction protein expression

Japanese encephalitis virus (JEV) is a neurotropic and neuroinvasive flavivirus causing viral encephalitis, which seriously threatens the development of animal husbandry and human health. DNA methylation is a major epigenetic modification involved in viral pathogenesis, yet how DNA methylation affects JEV infection remains unknown. Here, we show genome-wide DNA methylation profiles in the brains of JEV-infected mice compared to mock-infected mice. JEV can significantly increase the overall DNA methylation levels in JEV-infected mouse brains. A total of 14,781 differentially methylated regions associated genes (DMGs) have been identified. Subsequently, KEGG pathway analysis suggested that DNA methylation modulates the tight junction signaling pathway, which can potentially impact the permeability of the blood-brain barrier (BBB). We demonstrate that hypermethylation of the tight junction gene Afdn promoter inhibited AFDN expression and increased monolayer permeability of mouse brain microvascular endothelial (bEnd.3) cells in an in vitro transwell assay. Collectively, this study reveals that DNA methylation is increased in a murine Japanese encephalitis model and that modulation of Afdn expression promotes BBB permeability.

Tissue-Specific Immune Transcriptional Signatures in the Bordering Tissues of the Mouse Retina and Brain.

Bordering the central nervous system (CNS) parenchyma are the choroid (underlying the retina) and the leptomeninges (the inner layers of the meninges enveloping the brain). Although near the neural parenchyma, the choroid and leptomeninges are external to the immune privileged environment of the retina and brain and thus are distinct immune compartments. This study aimed to characterize the transcriptomic signatures of immune cells within the choroid and leptomeninges bordering the healthy adult mouse CNS. Eyes and brains were obtained from 7-week-old C57Bl/6J mice. Choroid and leptomeninges were processed for isolation of CD45+ immune cells and single cell RNA-sequencing. Additionally, single cell RNA-sequencing was performed on immune cells isolated from choroid obtained from human donor eye tissue. Immunostaining and confocal microscopy of wholemount tissue were used to validate selected immune cell populations in situ. A total of 3606 cells were sequenced from mouse tissues, including 2125 CD45+ cells from choroid and 1481 CD45+ cells from leptomeninges. Clustering and differential gene expression analysis revealed heterogeneous subtypes of monocytes/macrophages, dendritic cells, T cells, and B cells. Whereas some clusters were common to both choroid and leptomeninges, others exhibited tissue-specific gene expression profiles and potential functional specializations. Analysis of 6501 CD45+ cells sequenced from human choroid identified similar immune cell populations to mouse choroid. This study provides a detailed characterization of the molecular signatures of immune cells within the vascular connective tissues bordering the healthy retina and brain, and their potential roles in immune protection.

A Novel Mouse Model for Cerebral Inflammatory Demyelination in X-Linked Adrenoleukodystrophy: Insights into Pathogenesis and Potential Therapeutic Targets.

X-linked adrenoleukodystrophy (ALD) is caused by mutations in ABCD1, a peroxisomal gene. More than half of males with an ABCD1 mutation develop inflammatory cerebral demyelination (cALD), but underlying mechanisms remain unknown and therapies are limited. We sought to develop and characterize a mouse model of cALD to facilitate study of disease mechanisms and therapy development. We used immunoassays and immunohistochemistry to assess novel (interleukin 18 [IL-18]) and established molecular markers in cerebrospinal fluid (CSF) and postmortem brain tissue from cALD patients. We generated a cALD phenotype in Abcd1-knockout mice using a 2-hit method that combines cuprizone and experimental autoimmune encephalomyelitis models. We then used magnetic resonance imaging (MRI) and immunohistochemistry to assess the fidelity of cALD molecular markers in the mice. Human and mouse cALD lesions shared histologic features of myelin phagocytosis, myelin loss, abundant microglial activation, T and B-cell infiltration, and astrogliosis. Compared to wild-type controls, Abcd1-knockout mice displayed more cerebral demyelination, blood-brain barrier disruption, and perivascular immune cell infiltration. This enhanced inflammatory response was associated with higher levels of fibrin deposition, oxidative stress, demyelination, and axonal injury. IL-18 immunoreactivity co-localized with perivascular monocytes/macrophages in both human and mouse brain tissue. In cALD patients, CSF IL-18 levels correlated with MRI lesion severity. Our results suggest loss of Abcd1 function in mice predisposes to more severe blood-brain barrier disruption, cerebral inflammation driven by the infiltration of peripheral immune cells, demyelination, and axonal damage, replicating human cALD features. This novel mouse model could shed light on cALD mechanisms and accelerate cALD therapy development. ANN NEUROL 2024.

Highly demarcated structural alterations in the brain and impaired social incentive learning in Tbx1 heterozygous mice.

Copy number variants (CNVs) are robustly associated with psychiatric disorders and changes in brain structures. However, because CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how each gene encoded in the 22q11.2 region contributes to structural alterations, associated mental illnesses, and their dimensions. Our previous studies identified Tbx1, a T-box family transcription factor encoded in the 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes and behavioral alterations relevant to affected structures in congenic Tbx1 heterozygous mice. Our data showed that the volumes of the anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were most robustly reduced in Tbx1 heterozygous mice. In an amygdala-dependent task, Tbx1 heterozygous mice were impaired in their ability to learn the incentive value of a social partner. The volumes of the primary and secondary auditory cortexes were increased, and acoustic, but not non-acoustic, sensorimotor gating was impaired in Tbx1 heterozygous mice. Our findings identify the brain's regional volume alterations and their relevant behavioral dimensions associated with Tbx1 heterozygosity.

Therapeutic potential of 4-phenylbutyric acid against methylmercury-induced neuronal cell death in mice.

Methylmercury (MeHg) is an environmental neurotoxin that induces damage to the central nervous system and is the causative agent in Minamata disease. The mechanisms underlying MeHg neurotoxicity remain largely unknown, and there is a need for effective therapeutic agents, such as those that target MeHg-induced endoplasmic reticulum (ER) stress and the unfolded protein response (UPR), which is activated as a defense mechanism. We investigated whether intraperitoneal administration of the chemical chaperone, 4-phenylbutyric acid (4-PBA), at 120mg/kg/day can alleviate neurotoxicity in the brains of mice administered 50ppm MeHg in drinking water for 5weeks. 4-PBA significantly reduced MeHg-induced ER stress, neuronal apoptosis, and neurological symptoms. Furthermore, 4-PBA was effective even when administered 2weeks after the initiation of exposure to 30ppm MeHg in drinking water. Our results strongly indicate that ER stress and the UPR are key processes involved in MeHg toxicity, and that 4-PBA is a novel therapeutic candidate for MeHg-induced neurotoxicity.

6-Methoxyflavone improves anxiety, depression, and memory by increasing monoamines in mice brain: HPLC analysis and in silico studies

Abstract 6-Methoxyflavone (6-MOF) is a flavonoid that has been reported to be a GABA-A receptor agonist and reverses cisplatin-induced hyperalgesia and allodynia. Considering the varied neuropharmacological profile of 6-MOF, this study was intended to determine the pharmacological effects of 6-MOF on locomotion, anxiety, novel object recognition (NOR), depression, spatial memory, socialization behavior, nest-building behavior, and depression in various groups of mice. Selected groups of mice were injected with 25, 50, and 75 mg/kg 6-MOF. Using HPLC-UV, the frontal cortex, striatum, and hippocampus of the sacrificed mice were analyzed for the levels of vitamin C, dopamine, serotonin, noradrenaline, adenosine, and its metabolites. Statistical analysis showed significant results in socialization behavior and elevated plus maze with 75 mg/kg. In Y-maze, NOR 6-MOF showed significant results at all three doses, while in tail suspension test (TST), 50 and 75 mg/kg showed significant results; however, no statistical significance was observed in nest-building behavior; 50 and 75 mg/kg 6-MOF showed significant results in the Morris water maze. 6-MOF raised vitamin C levels in the frontal cortex and hippocampus. Serotonin, dopamine, and nor-adrenaline levels were raised in the hippocampus and striatum. It has also imparted region-specific neuroprotection by improving adenosine and its metabolite levels. In silico studies performed using PyRx have shown that the minimum binding energy of 6-MOF with antioxidant enzyme is −7.1 k/cal/mol. The binding energy showed that 6-MOF was successfully docked with an anti-oxidant enzyme. In conclusion, in silico and behavioral studies showed that 6-MOF can be a potential candidate for the treatment of cognitive decline, anxiety, and depression.

Aberrance of GAP43/p-GAP43 Closely Associates with the Pathology of Neuron Loss in Prion-Infected Rodent Models.

Prion diseases are fatal neurodegenerative disorders characterized by neuron damage and loss. Growth-associated protein 43 (GAP43) functions in neuronal plasticity and synaptic function, but its role in prion diseases is not fully elucidated. In this study, we investigated the changes of GAP43 in the central nerve system (CNS) of several prion-infected rodent models and explored the potential relationship of GAP43 with PrPSc deposit and neuron loss using various methods. We found that GAP43 levels were significantly decreased in the brain tissues of scrapie-infected rodent models at the terminal stage of the disease. Immunohistochemical analysis showed that GAP43 colocalized with NeuN-positive cells morphologically, indicating the presence of GAP43 in mature neurons. On contrary, the levels of GAP43 and p-GAP43 increased in a prion-infected cell line SMB-S15 in vitro, accompanying with the increase of intracellular calcium. Stimulation of lipopolysaccharide (LPS) upregulated while removal of PrPSc propagation downregulated the level of GAP43 in SMB-S15 cells. Morphological colocalization and molecular interaction between GAP43 and PrPSc have been addressed in the brains of prion-infected rodents and prion-infected cell line. Histological assays of the serial sections of the whole brains of prion-infected mice proposed that the reduced GAP43 level correlated with large amount of PrPSc deposits and notable neuron damage and loss showing cell crumpled and nuclear pyknosis. The impairment of GAP43 signaling and disturbance of calcium homeostasis by aberrance of brain GAP43/p-GAP43 not only reflect but also likely contribute to the pathology of severe neuron loss at the end of prion disease.

Repetitive transcranial magnetic stimulation alleviates motor impairment in Parkinson’s disease: association with peripheral inflammatory regulatory T-cells and SYT6

BackgroundRepetitive transcranial magnetic stimulation (rTMS) has been used to treat various neurological disorders. However, the molecular mechanism underlying the therapeutic effect of rTMS on Parkinson’s disease (PD) has not been fully elucidated. Neuroinflammation like regulatory T-cells (Tregs) appears to be a key modulator of disease progression in PD. If rTMS affects the peripheral Tregs in PD remains unknown.MethodsHere, we conducted a prospective clinical study (Chinese ClinicalTrials. gov: ChiCTR 2100051140) involving 54 PD patients who received 10-day rTMS (10 Hz) stimulation on the primary motor cortex (M1) region or sham treatment. Clinical and function assessment as well as flow cytology study were undertaken in 54 PD patients who were consecutively recruited from the department of neurology at Zhujiang hospital between September 2021 and January 2022. Subsequently, we implemented flow cytometry analysis to examine the Tregs population in spleen of MPTP-induced PD mice that received rTMS or sham treatment, along with quantitative proteomic approach reveal novel molecular targets for Parkinson's disease, and finally, the RNA interference method verifies the role of these new molecular targets in the treatment of PD.ResultsWe demonstrated that a 10-day rTMS treatment on the M1 motor cortex significantly improved motor dysfunction in PD patients. The beneficial effects persisted for up to 40 days, and were associated with an increase in peripheral Tregs. There was a positive correlation between Tregs and motor improvements in PD cases. Similarly, a 10-day rTMS treatment on the brains of MPTP-induced PD mice significantly ameliorated motor symptoms. rTMS reversed the downregulation of circulating Tregs and tyrosine hydroxylase neurons in these mice. It also increased anti-inflammatory mediators, deactivated microglia, and decreased inflammatory cytokines. These effects were blocked by administration of a Treg inhibitor anti-CD25 antibody in MPTP-induced PD mice. Quantitative proteomic analysis identified TLR4, TH, Slc6a3 and especially Syt6 as the hub node proteins related to Tregs and rTMS therapy. Lastly, we validated the role of Treg and rTMS-related protein syt6 in MPTP mice using the virus interference method.ConclusionsOur clinical and experimental studies suggest that rTMS improves motor function by modulating the function of Tregs and suppressing toxic neuroinflammation. Hub node proteins (especially Syt6) may be potential therapeutic targets.Trial registrationChinese ClinicalTrials, ChiCTR2100051140. Registered 15 December 2021, https://www.chictr.org.cn/bin/project/edit?pid=133691Graphical rTMS is a safe and non-invasive method for Parkinson's disease. In this study, we showed the proportion of CD4+CD25+CD127- regulatory T-cells (Tregs) in the peripheral blood was significantly increased after rTMS treatment. Similar effects of rTMS treatment were verified in MPTP-induced PD mice. Proteomic analysis and RNA interference analyses identified TLR4, TH, Slc6a3 and especially Syt6 as hub node proteins that can be modulated by rTMS therapy in PD.

Human TRPV1 is an efficient thermogenetic actuator for chronic neuromodulation

Thermogenetics is a promising neuromodulation technique based on the use of heat-sensitive ion channels. However, on the way to its clinical application, a number of questions have to be addressed. First, to avoid immune response in future human applications, human ion channels should be studied as thermogenetic actuators. Second, heating levels necessary to activate these channels in vivo in brain tissue should be studied and cytotoxicity of these temperatures addressed. Third, the possibility and safety of chronic neuromodulation has to be demonstrated. In this study, we present a comprehensive framework for thermogenetic neuromodulation in vivo using the thermosensitive human ion channel hTRPV1. By targeting hTRPV1 expression to excitatory neurons of the mouse brain and activating them within a non-harmful temperature range with a fiber-coupled infrared laser, we not only induced neuronal firing and stimulated locomotion in mice, but also demonstrated that thermogenetics can be employed for repeated neuromodulation without causing evident brain tissue injury. Our results lay the foundation for the use of thermogenetic neuromodulation in brain research and therapy of neuropathologies.

Toward quantitative CEST imaging of glutamate in the mouse brain using a multi-pool exchange model calibrated by 1H-MRS.

To develop a CEST quantification model to map glutamate concentration in the mouse brain at 11.7 T, overcoming the limitations of conventional glutamate-weighted CEST (gluCEST) contrast (magnetization transfer ratio with asymmetric analysis). 1H-MRS was used as a gold standard for glutamate quantification to calibrate a CEST-based quantitative pipeline. Joint localized measurements of Z-spectra at B1 = 5 μT and quantitative 1H-MRS were carried out in two voxels of interest in the mouse brain. A six-pool Bloch-McConnell model was found appropriate to fit experimental data. Glutamate exchange rate was estimated in both regions with this dedicated multi-pool fitting model and using glutamate concentration determined by 1H-MRS. Glutamate exchange rate was estimated to be ˜1300 Hz in the mouse brain. Using this calibrated value, maps of glutamate concentration in the mouse brain were obtained by pixel-by-pixel fitting of Z-spectra at B1 = 5 μT. A complementary study of simulations, however, showed that the quantitative model has high sensitivity to noise, and therefore, requires high-SNR acquisitions. Interestingly, fitted [Glu] seemed to be overestimated compared to 1H-MRS measurements, although it was estimated with simulations that the model has no intrinsic fitting bias with our experimental level of noise. The hypothesis of an unknown proton-exchanging pool contributing to gluCEST signal is discussed. High-resolution mapping of glutamate in the brain was made possible using the proposed calibrated quantification model of gluCEST data. Further studying of the in vivo molecular contributions to gluCEST signal could improve modeling.

SPOT: spatial proteomics through on-site tissue-protein-labeling

BackgroundSpatial proteomics seeks to understand the spatial organization of proteins in tissues or at different subcellular localization in their native environment. However, capturing the spatial organization of proteins is challenging. Here, we present an innovative approach termed Spatial Proteomics through On-site Tissue-protein-labeling (SPOT), which combines the direct labeling of tissue proteins in situ on a slide and quantitative mass spectrometry for the profiling of spatially-resolved proteomics.Materials and MethodsEfficacy of direct TMT labeling was investigated using seven types of sagittal mouse brain slides, including frozen tissues without staining, formalin-fixed paraffin-embedded (FFPE) tissues without staining, deparaffinized FFPE tissues, deparaffinized and decrosslinked FFPE tissues, and tissues with hematoxylin & eosin (H&E) staining, hematoxylin (H) staining, eosin (E) staining. The ability of SPOT to profile proteomes at a spatial resolution was further evaluated on a horizontal mouse brain slide with direct TMT labeling at eight different mouse brain regions. Finally, SPOT was applied to human prostate cancer tissues as well as a tissue microarray (TMA), where TMT tags were meticulously applied to confined regions based on the pathological annotations. After on-site direct tissue-protein-labeling, tissues were scraped off the slides and subject to standard TMT-based quantitative proteomics analysis.ResultsTissue proteins on different types of mouse brain slides could be directly labeled with TMT tags. Moreover, the versatility of our direct-labeling approach extended to discerning specific mouse brain regions based on quantitative outcomes. The SPOT was further applied on both frozen tissues on slides and FFPE tissues on TMAs from prostate cancer tissues, where a distinct proteomic profile was observed among the regions with different Gleason scores.ConclusionsSPOT is a robust and versatile technique that allows comprehensive profiling of spatially-resolved proteomics across diverse types of tissue slides to advance our understanding of intricate molecular landscapes.

Widespread Gene Editing in the Brain via In Utero Delivery of mRNA Using Acid-Degradable Lipid Nanoparticles.

In utero gene editing with mRNA-based therapeutics has the potential to revolutionize the treatment of neurodevelopmental disorders. However, a critical bottleneck in clinical application has been the lack of mRNA delivery vehicles that can efficiently transfect cells in the brain. In this report, we demonstrate that in utero intracerebroventricular (ICV) injection of densely PEGylated lipid nanoparticles (ADP-LNPs) containing an acid-degradable PEG-lipid can safely and effectively deliver mRNA for gene editing enzymes to the fetal mouse brain, resulting in successful transfection and editing of brain cells. ADP-LNPs containing Cre mRNA transfected 30% of the fetal brain cells in Ai9 mice and had no detectable adverse effects on fetal development and postnatal growth. In addition, ADP-LNPs efficiently transfected neural stem and progenitor cells in Ai9 mice with Cre mRNA, which subsequently proliferated and caused over 40% of the cortical neurons and 60% of the hippocampal neurons to be edited in treated mice 10 weeks after birth. Furthermore, using Angelman syndrome, a paradigmatic neurodevelopmental disorder, as a disease model, we demonstrate that ADP-LNPs carrying Cas9 mRNA and gRNA induced indels in 21% of brain cells within 7 days postpartum, underscoring the precision and potential of this approach. These findings demonstrate that LNP/mRNA complexes have the potential to be a transformative tool for in utero treatment of neurodevelopmental disorders and set the stage for a frontier in treating neurodevelopmental disorders that focuses on curing genetic diseases before birth.

Deep-Learning-Based Segmentation of Cells and Analysis (DL-SCAN)

With the recent surge in the development of highly selective probes, fluorescence microscopy has become one of the most widely used approaches to studying cellular properties and signaling in living cells and tissues. Traditionally, microscopy image analysis heavily relies on manufacturer-supplied software, which often demands extensive training and lacks automation capabilities for handling diverse datasets. A critical challenge arises if the fluorophores employed exhibit low brightness and a low signal-to-noise ratio (SNR). Consequently, manual intervention may become a necessity, introducing variability in the analysis outcomes even for identical samples when analyzed by different users. This leads to the incorporation of blinded analysis, which ensures that the outcome is free from user bias to a certain extent but is extremely time-consuming. To overcome these issues, we developed a tool called DL-SCAN that automatically segments and analyzes fluorophore-stained regions of interest such as cell bodies in fluorescence microscopy images using deep learning. We demonstrate the program’s ability to automate cell identification and study cellular ion dynamics using synthetic image stacks with varying SNR. This is followed by its application to experimental Na+ and Ca2+ imaging data from neurons and astrocytes in mouse brain tissue slices exposed to transient chemical ischemia. The results from DL-SCAN are consistent, reproducible, and free from user bias, allowing efficient and rapid analysis of experimental data in an objective manner. The open-source nature of the tool also provides room for modification and extension to analyze other forms of microscopy images specific to the dynamics of different ions in other cell types.

Differential temporal decline of cerebral oxytocin and μ-opioid receptor density during the aging process in mice.

Aging is often associated with changes in social, sexual, emotional and pain functioning, as well as with the increased prevalence of certain psychopathologies. However, the neurodevelopmental basis underpinning these age-related changes remains to be determined. Considering the key roles of oxytocin (OTR) and μ-opioid (MOPr) receptor systems in regulating social, sexual, pain, reward and emotional processing, it seems plausible that they are also implicated in age-related behavioural alterations. Although the ontogeny of both receptors has been well characterized in rodent brains from early development till adulthood, little is known concerning the neuroadaptations occurring from middle age to old age. Therefore, we mapped the neuroadaptations in OTR and MOPr in the brains of mice at those developmental endpoints. Quantitative OTR and MOPr autoradiographic binding was carried out in the brains of male mice at 2, 6, 9, 12 and 18 months of age. A significant whole brain decline in OTR density was detected between 2 and 6months of age, with no additional decline thereafter. Interestingly, for MOPrs, the decline in density was not detected until 9months of age. Region-specific age-related decline in OTR density was concentrated in the lateral anterior olfactory nuclei (AOL) and, for MOPr, in the AOL and the nucleus accumbens for MOPr. Identifying the tipping point of these age-related variations in both receptors may assist with our understanding of the neurobiology underlining age-related changes in social, pain and emotional functioning/processing. It may also help us target interventions to specific developmental windows to abrogate certain age-related psychopathologies.

Transcription factor 4 expression in the developing non-human primate brain: a comparative analysis with the mouse brain

Transcription factor 4 (TCF4) has been implicated in a range of neuropsychiatric disorders, including major depressive disorder, bipolar disorder, and schizophrenia. Mutations or deletions in TCF4 cause Pitt-Hopkins syndrome (PTHS), a rare neurodevelopmental disorder. A detailed understanding of its spatial expression across the developing brain is necessary for comprehending TCF4 biology and, by extension, to develop effective treatments for TCF4-associated disorders. However, most current knowledge is derived from mouse models, which are invaluable for preclinical studies but may not fully capture the complexities of human neuropsychiatric phenotypes. This study compared TCF4 expression in the developing mouse brain to its regional and cellular expression patterns in normal prenatal, neonatal, and young adult rhesus macaque brains, a species more relevant to human neurodevelopment. While the general developmental expression of TCF4 is largely conserved between macaques and mice, we saw several interspecies differences. Most notably, a distinct layered pattern of TCF4 expression was clear in the developing macaque neocortex but largely absent in the mouse brain. High TCF4 expression was seen in the inner dentate gyrus of adult mice but not in macaques. Conversely, TCF4 expression was higher in the adult macaque striatum compared to the mouse striatum. Further research is needed to show the significance of these interspecies differences. Still, they underscore the importance of integrating rodent and primate studies to comprehensively understand TCF4 function and its implications for human disorders. Moreover, the primate-specific expression patterns of TCF4 will inform genetic and other therapeutic strategies to treat TCF4-associated disorders.

Comparative Validation of Scintillator Materials for X-Ray-Mediated Neuronal Control in the Deep Brain

When exposed to X-rays, scintillators emit visible luminescence. X-ray-mediated optogenetics employs scintillators for remotely activating light-sensitive proteins in biological tissue through X-ray irradiation. This approach offers advantages over traditional optogenetics, allowing for deeper tissue penetration and wireless control. Here, we assessed the short-term safety and efficacy of candidate scintillator materials for neuronal control. Our analyses revealed that lead-free halide scintillators, such as Cs3Cu2I5, exhibited significant cytotoxicity within 24 h and induced neuroinflammatory effects when injected into the mouse brain. In contrast, cerium-doped gadolinium aluminum gallium garnet (Ce:GAGG) nanoparticles showed no detectable cytotoxicity within the same period, and injection into the mouse brain did not lead to observable neuroinflammation over four weeks. Electrophysiological recordings in the cerebral cortex of awake mice showed that X-ray-induced radioluminescence from Ce:GAGG nanoparticles reliably activated 45% of the neuronal population surrounding the implanted particles, a significantly higher activation rate than europium-doped GAGG (Eu:GAGG) microparticles, which activated only 10% of neurons. Furthermore, we established the cell-type specificity of this technique by using Ce:GAGG nanoparticles to selectively stimulate midbrain dopamine neurons. This technique was applied to freely behaving mice, allowing for wireless modulation of place preference behavior mediated by midbrain dopamine neurons. These findings highlight the unique suitability of Ce:GAGG nanoparticles for X-ray-mediated optogenetics. The deep tissue penetration, short-term safety, wireless neuronal control, and cell-type specificity of this system offer exciting possibilities for diverse neuroscience applications and therapeutic interventions.

Loss of CLN3 in microglia leads to impaired lipid metabolism and myelin turnover

Loss-of-function mutations in CLN3 cause juvenile Batten disease, featuring neurodegeneration and early-stage neuroinflammation. How loss of CLN3 function leads to early neuroinflammation is not yet understood. Here, we have comprehensively studied microglia from Cln3∆ex7/8 mice, a genetically accurate disease model. Loss of CLN3 function in microglia leads to lysosomal storage material accumulation and abnormal morphology of subcellular organelles. Moreover, pathological proteomic signatures are indicative of defects in lysosomal function and abnormal lipid metabolism. Consistent with these findings, CLN3-deficient microglia are unable to efficiently turnover myelin and metabolize the associated lipids, showing defects in lipid droplet formation and cholesterol accumulation. Accordingly, we also observe impaired myelin integrity in aged Cln3∆ex7/8 mouse brain. Autophagy inducers and cholesterol-lowering drugs correct the observed microglial phenotypes. Taken together, these data implicate a cell-autonomous defect in CLN3-deficient microglia that impacts their ability to support neuronal cell health, suggesting microglial targeted therapies should be considered for CLN3 disease.

Aging and senescent fates of oligodendrocyte precursor cells in the mouse brain

Age-related changes in oligodendrocyte precursor cells (OPCs) contribute to white matter dysfunction. In aged mice, we hypothesized that myelin-dense fimbria OPCs possess niche-specific properties, compared to hippocampal OPCs. Aged fimbria OPCs were fewer, larger, and localized to neighboring microglia. We identified age-increased p16/Cdkn2a-expressing OPCs enriched for senescence-related pathways and distinct senescence signatures between hippocampus and fimbria. Aged brain OPC populations differ in microenvironment properties and responses to senescence-directed intervention.