Brain Regions Of Mice Research Articles

Risperidone Induced DNA Methylation Changes in Dopamine Receptor and Stathmin Genes in Mice Exposed to Social Defeat Stress.

ObjectiveUnderstanding complex epigenetic mechanisms is necessary to fully elucidate the effects of antipsychotic drug. This study investigated DNA methylation and mRNA expression levels of dopamine D2 and D1 receptor (Drd2 and Drd1, respectively), nuclear receptor subfamily 3, group C, member 1 (Nr3c1) and stathmin 1 (Stmn1) in brain regions of mice exposed to social defeat stress (SDS) and effects of risperidone on altered methylation and mRNA expression levels induced by SDS.MethodsFollowing SDS for 10 days, risperidone (0.2 mg/kg) or vehicle was administered to adult mice for 7 days. Brain tissues from the prefrontal cortex (PFC), hippocampus (HIP) and amygdala (AMY) were processed to measure methylation and mRNA levels of Drd2, Drd1, Nr3c1 and Stmn1 using pyrosequencing and real time-polymerase chain reaction.ResultsWe found altered methylation status of Nr3c1 and Stmn1 in the HIP and AMY of mice exposed to SDS. These changes were reversed by risperidone treatment. In addition, different methylation patterns of Drd2 and Drd1 in the PFC and AMY between defeated and control mice were identified with risperidone treatment.ConclusionThese findings suggest that risperidone can cause epigenetic changes in Drd2, Drd1, Nr3c1 and Stmn1 in defeated mice. These changes could be epigenetic mechanisms underlying antipsychotic efficacy.

Coagulansin-A improves spatial memory in 5xFAD Tg mice by targeting Nrf-2/NF-κB and Bcl-2 pathway

The present study was designed to investigate the underlying molecular signaling of Coagulansin-A (Coag-A) as a therapeutic agent against Alzheimer’s disease (AD). Preliminarily, it exhibited a neuroprotective effect against H2O2-induced oxidative stress in HT-22 cells. The in vivo studies were performed by administering Coag-A (0.1, 1, and 10 mg/kg) intraperitoneally to 5xFAD transgenic (Tg) mouse model. Coag-A (10 mg/kg) significantly attenuated the cognitive decline compared to Tg mice group in the shallow water maze (SWM) and Y-maze test paradigms. The anti-aggregation potential of Coag-A was determined by performing Fourier transform-infrared (FT-IR) spectroscopy and differential scanning calorimeter (DSC) analysis in the prefrontal cortex (PFC) and hippocampal (HC) regions of mice brain. The FT-IR spectra demonstrated the inhibition of amyloid beta (Aβ) through a decrease in β-sheet aggregation, along with the inhibition of changes in the lipids, proteins, and phospholipids. The DSC analysis displayed a low-temperature exotherm associated with the reversible process of aggregation of soluble protein fractions prior to denaturation. Furthermore, Coag-A treatment displayed a regular density of granule cells in H&E stained sections, along with a reduced amyloid load and PAS-positive granules in all the regions of interest in mice brain. The real-time polymerase chain reaction (q-PCR), western blot and immunohistochemical (IHC) analysis demonstrated antioxidant, anti-inflammatory, and anti-apoptotic effect of Coag-A by enhancing the expression of nuclear factor erythroid-2-related factor (Nrf-2) and reducing nuclear factor kappa B (NF-κB) and Bax protein expression. In addition, Coag-A significantly increased the antioxidant enzymes and proteins level, along with a reduced pro-inflammatory cytokines production.

Ethanol concentration induces production of 3,4-dihydroxyphenylacetic acid and homovanillic acid in mouse brain through activation of monoamine oxidase pathway

First, we aimed to investigate ex vivo the effects of ethanol (EtOH) on levels of norepinephrine (NE), dopamine (DA), serotonin (5-HT), and their metabolites in the frontal cortex, hippocampus, and striatum of Aldh2-knockout (Aldh2-KO) and wild-type (WT) mice. Animals were treated intraperitoneally with saline (control) or EtOH (1.0, 2.0, or 3.0 g/kg). Brain samples were collected 60 and 120 min after EtOH injection, and monoamines and their metabolites were measured by HPLC-ECD. We found in both WT and Aldh2-KO mice that 3.0 g/kg EtOH increased the levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and decreased the level of 3-methoxytyramine (3-MT). A 2.0 g/kg dose of EtOH also increased HVA, but there was not a consistent effect within the brain regions of Aldh2-KO and WT mice. There were inconsistent findings of genotype differences in the levels of DA, 5-HT, and their metabolites in the brain regions tested. None of the EtOH doses altered NE, DA, 5-HT, or 5-hydroxyindoleacetic acid contents in any of the brain regions studied. Second, we tested whether EtOH-induced increases in DOPAC and HVA are mediated by increased monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT) activity. To test this, we used the MAO blocker clorgyline (2.0 and 4.0 mg/kg) and the COMT blocker tolcapone (15 and 30 mg/kg) alone or in combination with EtOH (3.0 g/kg). Clorgyline alone increased 3-MT and decreased DOPAC and HVA levels, whereas tolcapone alone increased DOPAC and decreased 3-MT and HVA levels. Surprisingly, the combination of EtOH with clorgyline (4.0 mg/kg) or tolcapone (30 mg/kg) further decreased 3-MT and increased DOPAC and HVA levels, an effect that reversed the inhibitor-induced decreases in HVA. These results suggest that a high concentration of EtOH can accelerate DA metabolism, as evidenced by the increase in DOPAC and HVA, and this effect is likely a consequence of increased degradation of DA by MAO.

Sex-Specific Neural Networks of Cued Threat Conditioning: A Pilot Study.

Cued threat conditioning is the most common preclinical model for emotional memory, which is dysregulated in anxiety disorders and post-traumatic stress disorder. Though women are twice as likely as men to develop these disorders, current knowledge of threat conditioning networks was established by studies that excluded female subjects. For unbiased investigation of sex differences in these networks, we quantified the neural activity marker c-fos across 112 brain regions in adult male and female mice after cued threat conditioning compared to naïve controls. We found that trained females engaged prelimbic cortex, lateral amygdala, cortical amygdala, dorsal peduncular cortex, and subparafasicular nucleus more than, and subparaventricular zone less than, trained males. To explore how these sex differences in regional activity impact the global network, we generated interregional cross-correlations of c-fos expression to identify regions that were co-active during conditioning and performed hub analyses to identify regional control centers within each neural network. These exploratory graph theory-derived analyses revealed sex differences in the functional coordination of the threat conditioning network as well as distinct hub regions between trained males and females. Hub identification across multiple networks constructed by sequentially pruning the least reliable connections revealed globus pallidus and ventral lateral septum as the most robust hubs for trained males and females, respectively. While low sample size and lack of non-associative controls are major limitations, these findings provide preliminary evidence of sex differences in the individual circuit components and broader global networks of threat conditioning that may confer female vulnerability to fear-based psychiatric disease.

Regulation of Neuroinflammatory Signaling by PPARγ Agonist in Mouse Model of Diabetes.

Many relevant studies, as well as clinical practice, confirm that untreated diabetes predisposes the development of neuroinflammation and cognitive impairment. Having regard for the fact that PPARγ are widely distributed in the brain and PPARγ ligands may regulate the inflammatory process, the anti-inflammatory potential of the PPARγ agonist, pioglitazone, was assessed in a mouse model of neuroinflammation related with diabetes. In this regard, the biochemical and molecular indicators of neuroinflammation were determined in the hippocampus and prefrontal cortex of diabetes mice. The levels of cytokines (IL-1β, IL-6, and TNF) and the expression of genes (Tnfrsf1a and Cav1) were measured. In addition, behavioral tests such as the open field test, the hole-board test, and the novel object recognition test were conducted. A 14-day treatment with pioglitazone significantly decreased IL-6 and TNFα levels in the prefrontal cortex and led to the downregulation of Tnfrsf1a expression and the upregulation of Cav1 expression in both brain regions of diabetic mice. Pioglitazone, by targeting neuroinflammatory signaling, improved memory and exploratory activity in behavioral tests. The present study provided a potential theoretical basis and therapeutic target for the treatment of neuroinflammation associated with diabetes. Pioglitazone may provide a promising therapeutic strategy in diabetes patients with muffled of behavioral activity.

Analysis of Cerebrovascular Architecture in Experimental Models of Hypertension and Chronic Neuroendocrine Stress

Cerebral small vessel disease and Alzheimer’s disease are leading causes of dementia. Psychological/social stress and associated hypertension are important drivers of brain vascular dysfunction and impaired perfusion. We set out to investigate if chronic neuroendocrine stress and hypertension have adverse effects on cerebrovascular architecture of various brain regions in two rodent models: 1) a rat model where HPA axis activation and hypertension were induced by brain derived neurotrophic factor (BDNF) overexpression in the paraventricular nucleus of the hypothalamus (PVN) for 5 wks, and 2) in a mouse model, where blood pressure and/or corticosterone levels were elevated by subcutaneous infusions of angiotensin II (AngII, 1.5mg/kg/day), adrenocorticotropic hormone (ACTH, 30ug/kg/day) or a combination of AngII and ACTH for 4 weeks. Cerebrovasculature was labeled by transcardiac perfusion of a liposome‑encapsulated fluorescent DiI dye. Brains were fixed in 4% PFA and transparency was increased with the SeeDB method. Vasculature of the hippocampus (HPC), sensory cortex (CTX), and PVN was evaluated using 2‐photon microscopy in 2mm thick coronal brain slices. 3D model of the vasculature was created by Imaris software (Oxford Instruments) yielding parameters such as vascular segment numbers, lengths, diameters, and number of branch points. 3D Euclidean distance mapping (EDM) was used to determine distribution of distances to nearest vessels (DNVs) within the extravascular space as a measure of accessibility to blood supply. We found that vascular densities were markedly elevated in the PVN relative to other brain regions in both rats and mice. In mice, HPC vascular density was significantly lower relative to CTX, whereas in rats, CTX and HPC densities were similar [vascular densities % (rats, mice): PVN:14.6±1.4, 17.0±0.6; CTX: 9.6±0.5, 8.6±0.4; HPC CA: 8.8±0.7, 6.2±0.3; HPC DG: 9.4±0.6, 5.4±0.3]. EDM analysis revealed that the proportion of short (<15μm) vs long DNVs was the highest in the PVN in both rats and mice. Distribution of DNVs shifted to longer distances in the CTX, and the proportion of short vs long DNVs was the lowest in HPC regions indicating an increased vulnerability to hypoperfusion. Interestingly, neuroendocrine stress and hypertension failed to significantly affect vascular densities and DNV statistics in either rats or mice in the analyzed brain regions. However, there was a notable sex difference in distribution of DNVs in HPC CA regions with male rats having a higher proportion of longer distances than females. In addition, analysis of vascular diameter distribution revealed that BDNF treatment decreased vessel diameters in the PVN of both male and female rats, and in the CTX of male, but not female rats. In summary, we found significant region‐specific variability in vascular structure, with the PVN demonstrating a uniquely dense vascular network. Cerebrovascular architecture was fairly resilient to treatments resembling chronic stress‐induced neuroendocrine and cardiovascular responses, but sex differences in HPC vasculature may promote a higher sensitivity to hypoperfusion in male vs female rats.

Optoception: Perception of Optogenetic Brain Perturbations.

How do animals experience brain manipulations? Optogenetics has allowed us to manipulate selectively and interrogate neural circuits underlying brain function in health and disease. However, little is known about whether mice can detect and learn from arbitrary optogenetic perturbations from a wide range of brain regions to guide behavior. To address this issue, mice were trained to report optogenetic brain perturbations to obtain rewards and avoid punishments. Here, we found that mice can perceive optogenetic manipulations regardless of the perturbed brain area, rewarding effects, or the stimulation of glutamatergic, GABAergic, and dopaminergic cell types. We named this phenomenon optoception, a perceptible signal internally generated from perturbing the brain, as occurs with interoception. Using optoception, mice can learn to execute two different sets of instructions based on the laser frequency. Importantly, optoception can occur either activating or silencing a single cell type. Moreover, stimulation of two brain regions in a single mouse uncovered that the optoception induced by one brain region does not necessarily transfer to a second not previously stimulated area, suggesting a different sensation is experienced from each site. After learning, they can indistinctly use randomly interleaved perturbations from both brain regions to guide behavior. Collectively taken, our findings revealed that mice’s brains could “monitor” perturbations of their self-activity, albeit indirectly, perhaps via interoception or as a discriminative stimulus, opening a new way to introduce information to the brain and control brain-computer interfaces.

Association of Mouse Vulnerability to Alzheimer’s Disease Pathology with Mutations of Gnb5: A Modulator of G‐protein Coupled Receptor Signaling

The prevalence and devastating effects of Alzheimer’s Disease (AD) and lack of effective treatments underscore the need to determine genes and molecular pathways with pathophysiologic relevance to develop targeted therapies. Prior unpublished bioinformatic analysis by our laboratory of genomic and brain transcript expression data from subjects with and without AD has identified hundreds of potential AD causative genes, one being GNB5, which encodes the protein Gβ5. Gβ5 is a divergent member of the G‐protein β subunit family and is primarily expressed in neuronal tissues. It is known to stabilize members of the R7‐Regulator of G‐protein Signaling (RGS) subfamily that exert GTPase Accelerating Protein (GAP) activities on Gαi/o proteins during G‐protein coupled receptor (GPCR) signaling. Homozygous lack of Gβ5 causes significant neuronal and behavioral impairments in both mice and humans; however, the impact of GNB5 heterozygosity requires further examination. For this project, we demonstrated through fear conditioning behavioral tasks involving hippocampus and amygdala function that learning and memory deficits existed in mice heterozygous for Gnb5. In addition, the potential relevance of GNB5 in AD pathogenesis was confirmed in an APP/PSEN1 double transgenic AD mouse model in which missing even one copy of the Gnb5 gene enhanced amyloid plaque and neurofibrillary tangle formations in multiple brain regions of mice including, the entorhinal cortex, hippocampus, and frontal cortex. These results were confirmed by traditional immunohistochemistry methods as well as immunostaining of transparent mouse brains cleared using the clear, unobstructed brain/body imaging cocktails and computational analysis (CUBIC) method. We further demonstrated that the exacerbated AD pathology may be caused, at least in part, by the increased vulnerability of heterozygous GNB5 mouse neurons to the toxicity of Aβ42 peptide oligomers which have been linked to beta‐amyloid plaque formation. Our data suggest the involvement of GNB5 regulated GPCR signaling in the progression of AD pathology and illustrates a potential new therapeutic target for attenuation of cellular pathology associated with AD.

Microglia Drive Pockets of Neuroinflammation in Middle Age.

During aging, microglia produce inflammatory factors, show reduced tissue surveillance, altered interactions with synapses, and prolonged responses to CNS insults, positioning these cells to have profound impact on the function of nearby neurons. We and others recently showed that microglial attributes differ significantly across brain regions in young adult mice. However, the degree to which microglial properties vary during aging is largely unexplored. Here, we analyze and manipulate microglial aging within the basal ganglia, brain circuits that exhibit prominent regional microglial heterogeneity and where neurons are vulnerable to functional decline and neurodegenerative disease. In male and female mice, we demonstrate that VTA and SNc microglia exhibit unique and premature responses to aging, compared with cortex and NAc microglia. This is associated with localized VTA/SNc neuroinflammation that may compromise synaptic function as early as middle age. Surprisingly, systemic inflammation, local neuron death, and astrocyte aging do not appear to underlie these early aging responses of VTA and SNc microglia. Instead, we found that microglial lysosome status was tightly linked to early aging of VTA microglia. Microglial ablation/repopulation normalized VTA microglial lysosome swelling and suppressed increases in VTA microglial density during aging. In contrast, CX3CR1 receptor KO exacerbated VTA microglial lysosome rearrangements and VTA microglial proliferation during aging. Our findings reveal a previously unappreciated regional variation in onset and magnitude of microglial proliferation and inflammatory factor production during aging and highlight critical links between microglial lysosome status and local microglial responses to aging.SIGNIFICANCE STATEMENT Microglia are CNS cells that are equipped to regulate neuronal health and function throughout the lifespan. We reveal that microglia in select brain regions begin to proliferate and produce inflammatory factors in late middle age, months before microglia in other brain regions. These findings demonstrate that CNS neuroinflammation during aging is not uniform. Moreover, they raise the possibility that local microglial responses to aging play a critical role in determining which populations of neurons are most vulnerable to functional decline and neurodegenerative disease.

Assessing the Role of Ependymal and Vascular Cells as Sources of Extracellular Cues Regulating the Mouse Ventricular-Subventricular Zone Neurogenic Niche.

Neurogenesis persists in selected regions of the adult mouse brain; among them, the ventricular-subventricular zone (V-SVZ) of the lateral ventricles represents a major experimental paradigm due to its conspicuous neurogenic output. Postnatal V-SVZ neurogenesis is maintained by a resident population of neural stem cells (NSCs). Although V-SVZ NSCs are largely quiescent, they can be activated to enter the cell cycle, self-renew and generate progeny that gives rise to olfactory bulb interneurons. These adult-born neurons integrate into existing circuits to modify cognitive functions in response to external stimuli, but cells shed by V-SVZ NSCs can also reach injured brain regions, suggesting a latent regenerative potential. The V-SVZ is endowed with a specialized microenvironment, which is essential to maintain the proliferative and neurogenic potential of NSCs, and to preserve the NSC pool from exhaustion by finely tuning their quiescent and active states. Intercellular communication is paramount to the stem cell niche properties of the V-SVZ, and several extracellular signals acting in the niche milieu have been identified. An important part of these signals comes from non-neural cell types, such as local vascular cells, ependymal and glial cells. Understanding the crosstalk between NSCs and other niche components may aid therapeutic approaches for neuropathological conditions, since neurodevelopmental disorders, age-related cognitive decline and neurodegenerative diseases have been associated with dysfunctional neurogenic niches. Here, we review recent advances in the study of the complex interactions between V-SVZ NSCs and their cellular niche. We focus on the extracellular cues produced by ependymal and vascular cells that regulate NSC behavior in the mouse postnatal V-SVZ, and discuss the potential implication of these molecular signals in pathological conditions.

Stress upregulates 2-arachidonoylglycerol levels in the hypothalamus, midbrain, and hindbrain, and it is sustained by green nut oil supplementation in SAMP8 mice revealed by DESI-MSI

The endocannabinoid 2-arachidonoylglycerol (2AG) is an important modulator of stress responses. Its level in the brain increases in response to stress, but region-specific effects of stress on brain 2AG are not well known yet. Moreover, green nut oil (GNO), oil extracted from the seeds of Plukenetia volubilis has several health benefits, but its effects on brain 2AG levels are unknown. Therefore, we conducted this study to explore the effects of stress and GNO supplementation on 2AG levels in specific brain regions of senescence-accelerated mouse prone 8 (SAMP8). In this study, desorption electrospray ionization-mass spectrometry imaging (DESI-MSI) revealed that water-immersion stress for three days significantly increased 2AG levels in several brain regions of SAMP8 mice, including the hypothalamus, midbrain, and hindbrain. No significant change was observed in the relative abundance of brain 2AG in stress given SAMP8 mice after eighteen days of removing stress load compared to control SAMP8 mice. GNO supplementation also increased brain 2AG in SAMP8 mice without stress load. Additionally, GNO supplementation sustained the increased brain 2AG levels in stress given SAMP8 mice after eighteen days of removing stress load. Among all brain regions, a relatively higher accumulation of 2AG was noted in the hypothalamus, midbrain, and hindbrain of GNO-fed SAMP8. Our data explored the potentiality of GNO supplementation to improve brain 2AG levels which might be used to treat anxiety and depressive behaviors.

Clostridioides difficile Infection Dysregulates Brain Dopamine Metabolism.

ABSTRACTGastrointestinal illnesses and dysbiosis are among the most common comorbidities reported in patients with neurodevelopmental disorders. The manuscript reports that C. difficile infection (CDI), predisposed by antibiotic-induced gut dysbiosis, causes significant alterations in dopamine metabolism in major dopaminergic brain regions in mice (P < 0.05). In addition, C. difficile infected mice exhibited significantly reduced dopamine beta-hydroxylase (DBH) activity compared to controls (P < 0.01). Moreover, a significantly increased serum concentration of p-cresol, a DBH inhibiting gut metabolite produced by C. difficile, was also observed in C. difficile infected mice (P < 0.05). Therefore, this study suggests a potential mechanistic link between CDI and alterations in the brain dopaminergic axis. Such alterations may plausibly influence the precipitation and aggravation of dopamine dysmetabolism-associated neurologic diseases in infected patients.IMPORTANCE The gut-brain axis is thought to play a significant role in the development and manifestation of neurologic diseases. This study reports significant alterations in the brain dopamine metabolism in mice infected with C. difficile, an important pathogen that overgrows in the gut after prolonged antibiotic therapy. Such alterations in specific brain regions may have an effect on the precipitation or manifestation of neurodevelopmental disorders in humans.

Regional variability and genotypic and pharmacodynamic effects on PrP concentration in the CNS

Prion protein (PrP) concentration controls the kinetics of prion replication and is a genetically and pharmacologically validated therapeutic target for prion disease. In order to evaluate PrP concentration as a pharmacodynamic biomarker and assess its contribution to known prion disease risk factors, we developed and validated a plate-based immunoassay reactive for PrP across 6 species of interest and applicable to brain and cerebrospinal fluid (CSF). PrP concentration varied dramatically across different brain regions in mice, cynomolgus macaques, and humans. PrP expression did not appear to contribute to the known risk factors of age, sex, or common PRNP genetic variants. CSF PrP was lowered in the presence of rare pathogenic PRNP variants, with heterozygous carriers of P102L displaying 55%, and D178N just 31%, of the CSF PrP concentration of mutation-negative controls. In rodents, pharmacologic reduction of brain Prnp RNA was reflected in brain parenchyma PrP and, in turn in CSF PrP, validating CSF as a sampling compartment for the effect of PrP-lowering therapy. Our findings support the use of CSF PrP as a pharmacodynamic biomarker for PrP-lowering drugs and suggest that relative reduction from individual baseline CSF PrP concentration may be an appropriate marker for target engagement.

Effects of Synaptotagmin1 gene knockout on the behavior of mice

Objective: To study the effects of Synaptotagmin1 gene knockout (Syt1+/-) on emotional behavior in mice and explore its possible mechanisms. Methods: Five 8-week-old male Syt1+/-mice and five wild-type (WT) mice in the same litter were selected. The expressions of Syt1 in 6 mice brain regions of prelimbic cortex (PL), hippocampus (HIP), amygdala (AMY), accumbens nucleus (ACB), caudoputamen (CP) and ventral tegmental area (VTA) were detected by Immunofluorescence staining. Nine 8-week-old male Syt1+/-mice and ten WT mice were selected as controls. The anxiety-like behaviors of adult Syt1+/- mice and WT mice were detected by open field test, elevated plus maze test and forced swim test. In addition, five 8-week-old male Syt1+/-mice and five WT mice were selected to detect the glutamate content in prelimbic cortex, hippocampus and amygdala. Results: Compared with WT mice, the number of Syt1 positive cells in PL, HIP, AMY, ACB, CP and VTA were decreased significantly in Syt1+/- mice (P＜0.01); Syt1+/- mice had less total movement distance in open field test (P＜0.01), more preference for peripheral area (P＜0.01) and less desire to explore the central platform (P＜0.01), while Syt1+/- mice preferred to stay in a closed and safe environment (P＜0.01); the number (P＜0.05) and the time spent in open-arm explorations (P＜0.01) were reduced significantly; the immobile time of Syt1+/- mice was increased in the forced swim test (P＜0.01). Meanwhile, the concentration of glutamate in the amygdala of Syt1+/- mice was increased significantly (P＜0.01). Conclusion: Syt1 gene knockout leads to significant anxiety-like behavior in mice, which is deduced that related to the increase of glutamate content in the amygdala.

A Semi-Automated Workflow for Brain Slice Histology Alignment, Registration, and Cell Quantification (SHARCQ).

Tools for refined cell-specific targeting have significantly contributed to understanding the characteristics and dynamics of distinct cellular populations by brain region. While advanced cell-labeling methods have accelerated the field of neuroscience, specifically in brain mapping, there remains a need to quantify and analyze the data. Here, by modifying a toolkit that localizes electrodes to brain regions (SHARP-Track; Slice Histology Alignment, Registration, and Probe-Track analysis), we introduce a post-imaging analysis tool to map histological images to established mouse brain atlases called SHARCQ (Slice Histology Alignment, Registration, and Cell Quantification). The program requires MATLAB, histological images, and either a manual or automatic cell count of the unprocessed images. SHARCQ simplifies the post-imaging analysis pipeline with a step-by-step GUI. We demonstrate that SHARCQ can be applied for a variety of mouse brain images, regardless of histology technique. In addition, SHARCQ rectifies discrepancies in mouse brain region borders between atlases by allowing the user to select between the Allen Brain Atlas or the digitized and modified Franklin-Paxinos Atlas for quantifying cell counts by region. SHARCQ produces quantitative and qualitative data, including counts of brain-wide region populations and a 3D model of registered cells within the atlas space. In summary, SHARCQ was designed as a neuroscience post-imaging analysis tool for cell-to-brain registration and quantification with a simple, accessible interface. All code is open-source and available for download (https://github.com/wildrootlab/SHARCQ).

A Progressive Build-up of Perineuronal Nets in the Somatosensory Cortex Is Associated with the Development of Chronic Pain in Mice.

Chronic pain is sustained by a maladaptive form of neuronal plasticity occurring in all stations of the pain neuraxis, including cortical regions of the pain matrix. We report that chronic inflammatory pain induced by unilateral injection of complete Freund's adjuvant (CFA) in the hindpaw of male mice was associated with a progressive build-up of perineuronal nets (PNNs) in the contralateral somatosensory cortex (SSC), medial prefrontal cortex (mPFC), and reticular thalamic nucleus. In the SSC, the density of PNNs labeled by Wisteria floribunda agglutinin (WFA) was increased at both 3 and 7 d following CFA injection, but only after 7 d in the mPFC. The number of parvalbumin (PV)-positive interneurons enwrapped by WFA+/PNNs was also increased in all three brain regions of mice injected with CFA. Remarkably, PNN degradation induced by intracortical infusion of chondroitinase-ABC significantly reduced mechanical and thermal pain, and also reversed the increased frequency of IPSCs recorded in layer 5 pyramidal neurons of the contralateral SSC in CFA-injected mice. These findings suggest a possible relationship between cortical PNNs and nociceptive sensitization, and support the hypothesis that PNNs maintain their plasticity in the adult life and regulate cortical responses to sensory inputs.SIGNIFICANCE STATEMENT The brain extracellular matrix not only provides structural support, but also regulates synapse formation and function, and modulates neuronal excitability. We found that chronic inflammatory pain in mice enhances the density of perineuronal nets (PNNs) in the somatosensory cortex and medial prefrontal cortex. Remarkably, enzymatic degradation of PNNs in the somatosensory cortex caused analgesia and reversed alterations of inhibitory synaptic transmission associated with chronic pain. These findings disclose a novel mechanism of nociceptive sensitization and support a role for PNNs in mechanisms of neuronal plasticity in the adult brain.

Profiling Microglia in a Mouse Model of Machado-Joseph Disease.

Microglia have been increasingly implicated in neurodegenerative diseases (NDs), and specific disease associated microglia (DAM) profiles have been defined for several of these NDs. Yet, the microglial profile in Machado–Joseph disease (MJD) remains unexplored. Here, we characterized the profile of microglia in the CMVMJD135 mouse model of MJD. This characterization was performed using primary microglial cultures and microglial cells obtained from disease-relevant brain regions of neonatal and adult CMVMJD135 mice, respectively. Machine learning models were implemented to identify potential clusters of microglia based on their morphological features, and an RNA-sequencing analysis was performed to identify molecular perturbations and potential therapeutic targets. Our findings reveal morphological alterations that point to an increased activation state of microglia in CMVMJD135 mice and a disease-specific transcriptional profile of MJD microglia, encompassing a total of 101 differentially expressed genes, with enrichment in molecular pathways related to oxidative stress, immune response, cell proliferation, cell death, and lipid metabolism. Overall, these results allowed us to define the cellular and molecular profile of MJD-associated microglia and to identify genes and pathways that might represent potential therapeutic targets for this disorder.

Impaired Oligodendrocyte Maturation Is an Early Feature in SCA3 Disease Pathogenesis.

Spinocerebellar ataxia Type 3 (SCA3), the most common dominantly inherited ataxia, is a polyglutamine neurodegenerative disease for which there is no disease-modifying therapy. The polyglutamine-encoding CAG repeat expansion in the ATXN3 gene results in expression of a mutant form of the ATXN3 protein, a deubiquitinase that causes selective neurodegeneration despite being widely expressed. The mechanisms driving neurodegeneration in SCA3 are unclear. Research to date, however, has focused almost exclusively on neurons. Here, using equal male and female age-matched transgenic mice expressing full-length human mutant ATXN3, we identified early and robust transcriptional changes in selectively vulnerable brain regions that implicate oligodendrocytes in disease pathogenesis. We mapped transcriptional changes across early, mid, and late stages of disease in two selectively vulnerable brain regions: the cerebellum and brainstem. The most significant disease-associated module through weighted gene coexpression network analysis revealed dysfunction in SCA3 oligodendrocyte maturation. These results reflect a toxic gain-of-function mechanism, as ATXN3 KO mice do not exhibit any impairments in oligodendrocyte maturation. Genetic crosses to reporter mice revealed a marked reduction in mature oligodendrocytes in SCA3-disease vulnerable brain regions, and ultrastructural microscopy confirmed abnormalities in axonal myelination. Further study of isolated oligodendrocyte precursor cells from SCA3 mice established that this impairment in oligodendrocyte maturation is a cell-autonomous process. We conclude that SCA3 is not simply a disease of neurons, and the search for therapeutic strategies and disease biomarkers will need to account for non-neuronal involvement in SCA3 pathogenesis.SIGNIFICANCE STATEMENT Despite advances in spinocerebellar ataxia Type 3 (SCA3) disease understanding, much remains unknown about how the disease gene causes brain dysfunction ultimately leading to cell death. We completed a longitudinal transcriptomic analysis of vulnerable brain regions in SCA3 mice to define the earliest and most robust changes across disease progression. Through gene network analyses followed up with biochemical and histologic studies in SCA3 mice, we provide evidence for severe dysfunction in oligodendrocyte maturation early in SCA3 pathogenesis. Our results advance understanding of SCA3 disease mechanisms, identify additional routes for therapeutic intervention, and may provide broader insight into polyglutamine diseases beyond SCA3.

Method for counting labeled neurons in mouse brain regions based on image representation and registration.

An important step in brain image analysis is to divide specific brain regions by matching brain slices to standard brain reference atlases, and perform statistical analysis on the labeled neurons in each brain region. Taking mouse fluorescently labeled brain slices as an example, due to the noise and distortion introduced during the preparation of brain slices, and the modal differences with standard brain atlas, the brain slices cannot directly establish an accurate one-to-one correspondence with the brain atlas, which in turn affects the accuracy of the number of labeled neurons in each brain region. This paper introduces the idea of image representation, uses neural networks to realize the registration of different modal mouse brain slices and brain atlas, completes the regional localization of the brain slices, and uses threshold segmentation to detect and count the labeled neurons in each brain region. The method proposed in this paper can effectively solve the problem of large deviation of neurons count caused by the inaccurate division of brain regions in large deformed brain slices, and can automatically realize accurate count of labeled neurons in each brain region of brain slices. The whole framework of method for counting labeled neurons in mouse brain regions based on image representation and registration.

Vascular and blood-brain barrier-related changes underlie stress responses and resilience in female mice and depression in human tissue

Prevalence, symptoms, and treatment of depression suggest that major depressive disorders (MDD) present sex differences. Social stress-induced neurovascular pathology is associated with depressive symptoms in male mice; however, this association is unclear in females. Here, we report that chronic social and subchronic variable stress promotes blood-brain barrier (BBB) alterations in mood-related brain regions of female mice. Targeted disruption of the BBB in the female prefrontal cortex (PFC) induces anxiety- and depression-like behaviours. By comparing the endothelium cell-specific transcriptomic profiling of the mouse male and female PFC, we identify several pathways and genes involved in maladaptive stress responses and resilience to stress. Furthermore, we confirm that the BBB in the PFC of stressed female mice is leaky. Then, we identify circulating vascular biomarkers of chronic stress, such as soluble E-selectin. Similar changes in circulating soluble E-selectin, BBB gene expression and morphology can be found in blood serum and postmortem brain samples from women diagnosed with MDD. Altogether, we propose that BBB dysfunction plays an important role in modulating stress responses in female mice and possibly MDD.