Purkinje Cells Research Articles

SMPD4 mediated sphingolipid metabolism regulates brain and primary cilia development.

Genetic variants in multiple sphingolipid biosynthesis genes cause human brain disorders. A recent study collected patients from twelve unrelated families with variants in the gene SMPD4, a neutral sphingomyelinase which metabolizes sphingomyelin into ceramide at an early stage of the biosynthesis pathway. These patients have severe developmental brain malformations including microcephaly and cerebellar hypoplasia. The disease mechanism of SMPD4 was not known and we pursued a new mouse model. We hypothesized that the role of SMPD4 in producing ceramide is important for making primary cilia, a crucial organelle mediating cellular signaling. We found that the mouse model has cerebellar hypoplasia due to failure of Purkinje cell development. Human induced pluripotent stem cells exhibit neural progenitor cell death and have shortened primary cilia which is rescued by adding exogenous ceramide. SMPD4 production of ceramide is crucial for human brain development.

Comparative analysis of six adeno-associated viral vector serotypes in mouse inferior colliculus and cerebellum.

Adeno-associated viral vector (AAV) serotypes vary in how effectively they express genes across different cell types and brain regions. Here we report a systematic comparison of the AAV serotypes 1, 2, 5, 8, 9, and the directed evolution derived AAVrg, in the inferior colliculus and cerebellum. The AAVs were identical apart from their different serotypes, each having a synapsin promotor and expressing GFP (AAV-hSyn-GFP). Identical titers and volumes were injected into the inferior colliculus and cerebellum of adult male and female mice and brains were sectioned and imaged 2 weeks later. Transduction efficacy, anterograde labeling of axonal projections, and retrograde labeling of somata, were characterized and compared across serotypes. Cell-type tropism was assessed by analyzing the morphology of the GFP-labeled neurons in the cerebellar cortex. In both the cerebellum and inferior colliculus, AAV1 expressed GFP in more cells, labeled a larger volume, and produced significantly brighter labeling than all other serotypes, indicating superior transgene expression. AAV1 labeled more Purkinje cells, unipolar brush cells, and molecular layer interneurons than the other serotypes, while AAV2 labeled a greater number of granule cells. These results provide guidelines for the use of AAVs as gene delivery tools in these regions.Significance statement AAVs have become ubiquitous gene expression tools in neuroscience research and are becoming more common in clinical settings. Naturally occurring and engineered serotypes have varying abilities to infect neurons and cause them to produce proteins of interest. The efficacy of AAV transduction in specific cell types depends on many factors and remains difficult to predict, so an empirical approach is often required to determine the best performing serotype in each population of cells. In the present study we show that AAV1 produces the highest expression in these two regions, labels the most axonal projections, and labels Purkinje cells and unipolar brush cells better than the other serotypes tested, while AAV2 labels granule cells most effectively.

Effect of Experimental Litter Reduction on Cerebellum Development in Suckling Rats.

We studied morphological features of the cerebellum in 14-day-old Wistar rats from reduced litters (the number of pups was reduced from 10-12 to 6 on the next day after birth). The control group comprised 14-day-old animals from litters of medium size (10-12 rat pups). Rats from reduced litters had greater body weight and brain weight. The weight of the cerebellum, together with the weight of the adjacent part of the brain stem and the thickness of cerebellar cortex also significantly exceeded the corresponding parameters in control animals. The thickness of the molecular layer of the cerebellar cortex and the numerical density of Purkinje cells in these rats did not differ significantly from the control. The thickness of the external granular (neurogenic) layer of the cerebellar cortex in rats from reduced litters was smaller. This can indicate accelerated reduction of this layer that persists in rats until days 20-22 of age. Numerical density of cells in the external granular layer of control and experimental animals was similar. Numerical density Ki-67+ cells in this layer, as well as GFAP+ glial cells in the granular layer of the cerebellar cortex in rats from reduced litters significantly exceeded the corresponding parameters in control animals. The cerebellum of rats from litters reduced 1 day after birth had a number of differences in important indicators reflecting the rate of its development during the neonatal and suckling periods of ontogeny.

UHT Cow’s Milk Supplementation Affects Cell Niches and Functions of the Gut–Brain Axis in BALB/c Mice

Background/Objectives: Cow’s milk is a bioactive cocktail with essential nutritional factors that is widely consumed during early childhood development. However, it has been associated with allergic responses and immune cell activation. Here, we investigate whether cow’s milk consumption regulates gut–brain axis functions and affects patterns of behaviors in BALB/c mice, previously described by present low sociability, significant stereotypes, and restricted interest features. The major objectives consist of to investigate cow’s milk supplementation as possible triggers interfering with cellular niches of the gut–brain axis and behavioral patterns. Methods: Male BALB/c at 6 weeks were randomly divided into two groups, one supplemented with cow’s milk processed at ultra-high temperature (UHT) and another group receiving water (controls) three times per day (200 μL per dose) for one week. Results: Milk consumption disturbed histological compartments of the small intestine, including niches of KI67+-proliferating cells and CD138+ Ig-secreting plasma cells. In the liver, milk intake was associated with pro-inflammatory responses, oxidative stress, and atypical glycogen distribution. Milk-supplemented mice showed significant increase in granulocytes (CD11b+SSChigh cells) and CD4+ T cells in the blood. These mice also had neuroinflammatory signals, including an enhanced number of cortical Iba-1+ microglial cells in the brain and significant cerebellar expression of nitric oxide synthase 2 by Purkinje cells. These phenotypes and tissue disorders in milk-supplemented mice were associated with atypical behaviors, including low sociability, high restricted interest, and severe stereotypies. Moreover, synaptic niches were also disturbed after milk consumption, and Shank-3+ and Drebrin+ post-synaptic cells were significantly reduced in the brain of these mice. Conclusions: Together, these data suggest that milk consumption interfered with the gut–brain axis in BALB/c mice and increased atypical behaviors, at least in part, linked to synapse dysfunctions, neuroinflammation, and oxidative stress regulation.

Distinct functional classes of CA1 hippocampal interneurons are modulated by cerebellar stimulation in a coordinated manner.

There is mounting evidence that the cerebellum impacts hippocampal functioning, but the impact of the cerebellum on hippocampal interneurons remains obscure. Using miniscopes in freely behaving male and female mice, we find optogenetic stimulation of Purkinje cells alters the calcium activity of a large percentage of CA1 interneurons. This includes both increases and decreases in activity. Remarkably, this bidirectional impact occurs in a coordinated fashion, in line with interneurons' functional properties. Specifically, CA1 interneurons activated by cerebellar stimulation are commonly locomotion-active, while those inhibited by cerebellar stimulation are commonly rest-active interneurons. We additionally find that subsets of CA1 interneurons show altered activity during object investigations. Importantly, these interneurons also show coordinated modulation by cerebellar stimulation: CA1 interneurons that are activated by cerebellar stimulation are more likely to be activated, rather than inhibited, during object investigations, while interneurons that show decreased activity during cerebellar stimulation show the opposite profile. We examined two different stimulation locations (IV/V Vermis or Simplex) and two different stimulation approaches (7Hz or a single 1s light pulse) - in all cases, the cerebellum induces similar coordinated CA1 interneuron changes congruent with an explorative state. Overall, our data show that CA1 interneurons are impacted by cerebellar manipulation in a bidirectional and coordinated fashion, and are therefore likely to play an important role in cerebello-hippocampal communication.Significance Statement Acute manipulation of the cerebellum can affect the activity of cells in CA1, and perturbing normal cerebellar functioning can affect hippocampal-dependent spatial processing, including the processing of objects in space. Despite the importance of interneurons on the local hippocampal circuit, it was unknown how cerebellar activation impacts CA1 inhibitory neurons. We find that stimulating the cerebellum robustly affects multiple populations of CA1 interneurons in a bidirectional, coordinated manner, according to their functional profiles during behavior, including locomotion and object investigations.

α2δ-2 regulates synaptic GluK1 kainate receptors in Purkinje cells and motor coordination.

Gabapentin and pregabalin are inhibitory ligands of both α2δ-1 and α2δ-2 proteins (also known as subunits of voltage-activated Ca2+ channels) and are commonly prescribed for the treatment of neuropathic pain and epilepsy. However, these drugs can cause gait disorders and ataxia through unknown mechanisms. α2δ-2 and GluK1, a glutamate-gated kainate receptor subtype, are coexpressed in cerebellar Purkinje cells. In this study, we used a heterologous expression system and Purkinje cells to investigate the potential role of α2δ-2 in regulating GluK1-containing kainate receptor activity. Whole-cell patch clamp recordings showed that α2δ-2 coexpression augmented GluK1, but not GluK2, currents in HEK293 cells, and pregabalin abolished this augmentation. Pregabalin lost its inhibitory effect on GluK1 currents in HEK293 cells expressing both GluK1 and the α2δ-2(R282A) mutant. Blocking GluK1-containing receptors with UBP310 substantially reduced the amplitude of excitatory postsynaptic currents at parallel fiber-Purkinje cell synapses in mice. Also, pregabalin markedly attenuated the amplitude of excitatory postsynaptic currents and currents elicited by ATPA, a selective GluK1 receptor agonist, in Purkinje cells in Cacna2d1 knockout mice. Coimmunoprecipitation assays indicated that α2δ-2, but not α2δ-1, formed a protein complex with GluK1 in cerebellar tissues and HEK293 cells through its C terminus. Furthermore, α2δ-2 coexpression potentiated surface expression of GluK1 proteins in HEK293 cells, whereas pregabalin reduced GluK1 proteins in cerebellar synaptosomes. Disrupting α2δ-2-GluK1 interactions using α2δ-2 C-terminus peptide abrogated the potentiating effect of α2δ-2 on GluK1 currents and attenuated the amplitude of GluK1-mediated excitatory postsynaptic currents in Purkinje cells. However, neither pregabalin nor α2δ-2 C-terminus peptide had significant effect on P/Q-type currents in HEK293 cells. Additionally, CRISPR/Cas9-induced conditional knockdown of Cacna2d2 or Grik1 in Purkinje cells, as well as microinjection of α2δ-2 C-terminus peptide or UBP310 into the cerebellum, substantially impaired beam walking and rotarod performance in mice. Our study reveals that α2δ-2 directly interacts with GluK1 independently of its conventional role as a voltage-activated Ca2+ channel subunit. α2δ-2 regulates motor coordination by promoting synaptic expression and activity in GluK1-containing kainate receptors in Purkinje cells.

Nasal obstruction during development leads to defective synapse elimination, hypersynchrony, and impaired cerebellar function

Nasal respiratory disorders are linked to craniofacial anomalies and systemic dysfunctions. However, the implications of nasal respiratory disorders on brain development and their subsequent impact on brain functionalization remain largely unknown. Here, we describe that nasal obstruction from postnatal developmental stages in mice precipitates deficits in cerebellum-associated behaviors and compromised refinement and maturation of neural circuits in the cerebellum. We show that mice with nasal obstruction during developmental phases exhibit marked impairments in motor function and exhibit increased immobility time in forced swimming test. Additionally, we identified critical periods during which nasal respiration is essential for optimizing motor function and preserving mental health. Our study also reveals that nasal obstruction in mice disrupts the typical developmental process of synapse elimination in the cerebellum and hinders the normal transition of activity patterns in cerebellar Purkinje cell populations during development. Through comparing activity patterns in mouse models subjected to nasal obstruction at various stages, we suggest that the maturation of specific activity pattern among Purkinje cell populations is fundamental to the functional integrity of the cerebellum. Our findings highlight the indispensable role of adequate nasal respiration during development for the establishment and functional integrity of neural circuits, thereby significantly affecting brain function.

Neuronal SLC39A8 deficiency impairs cerebellar development by altering manganese homeostasis.

Solute carrier family 39, member 8 (SLC39A8), is a transmembrane transporter that mediates the cellular uptake of zinc, iron, and manganese (Mn). Human genetic studies document the involvement of SLC39A8 in Mn homeostasis, brain development, and function. However, the role and pathophysiological mechanisms of SLC39A8 in the central nervous system remain elusive. We generated Slc39a8 neuron-specific knockout (Slc39a8-NSKO) mice to study SLC39A8 function in neurons. The Slc39a8-NSKO mice displayed markedly decreased Mn levels in the whole brain and brain regions, especially the cerebellum. Radiotracer studies using 54Mn revealed that Slc39a8-NSKO mice had impaired brain uptake of Mn. Slc39a8-NSKO cerebellums exhibited morphological defects and abnormal dendritic arborization of Purkinje cells. Reduced neurogenesis and increased apoptotic cell death occurred in the cerebellar external granular layer of Slc39a8-NSKO mice. Brain Mn deficiency in Slc39a8-NSKO mice was associated with motor dysfunction. Unbiased RNA-Seq analysis revealed downregulation of key pathways relevant to neurodevelopment and synaptic plasticity, including cAMP signaling pathway genes. We further demonstrated that Slc39a8 was required for the optimal transcriptional response to the cAMP-mediated signaling pathway. In summary, our study highlighted the essential roles of SLC39A8 in brain Mn uptake and cerebellum development and functions.

Novel goose parvovirus in naturally infected ducks suffering from locomotor disorders: Molecular Detection, Histopathological examination, Immunohistochemical signals, and Full genome sequencing

In this study, we investigated the pathological effect of novel goose parvovirus (NGPV) infection on the skeletal muscle, brain, and intestine of naturally affected ducks suffering from locomotor dysfunction as a new approach for deeper understanding of such clinical form. For this purpose, a total of 97 diseased ducks, representing 24 flocks of different duck breeds (14-75 days old), were clinically examined. 72 tissue pools of intestine, brain, and skeletal muscle samples were submitted for molecular identification. Typical clinical signs among the examined ducks suggested the parvovirus infection. Regarding postmortem examination, all examined ducks showed muscle emaciation (100%) either accompanied by congestion (34%) or paleness (66%). Slight congestion, either in the brain (82.5%) or intestine (75.25%), was predominantly detected. Based on molecular identification, the intestine had the highest percentage of positive detection (91.7%), followed by the skeletal muscle (70.8%), and the brain (20.8%). The main histopathological alterations were myofiber atrophy and degeneration, marked enteritis accompanied by lymphocytic infiltration in the lamina propria and submucosa, while the affected brains showed vasculitis, diffuse gliosis, and Purkinje cell degeneration in the cerebellum. Next generation sequencing further confirmed the presence of a variant strain of goose parvovirus (vGPV) that is globally known as NGPV and closely related to Chinese NGPV isolates. Using immunohistochemistry, the NGPV antigen was positively detected in the muscle fibres, enterocytes, and Purkinje cells in the cerebellum. These findings provided proof of the involvement of virus replication in the locomotor disorders linked to NGPV infection in ducks.

Increased understanding of complex neuronal circuits in the cerebellar cortex

The prevailing belief has been that the fundamental structures of cerebellar neuronal circuits, consisting of a few major neuron types, are simple and well understood. Given that the cerebellum has long been known to be crucial for motor behaviors, these simple yet organized circuit structures seemed beneficial for theoretical studies proposing neural mechanisms underlying cerebellar motor functions and learning. On the other hand, experimental studies using advanced techniques have revealed numerous structural properties that were not traditionally defined. These include subdivided neuronal types and their circuit structures, feedback pathways from output Purkinje cells, and the multidimensional organization of neuronal interactions. With the recent recognition of the cerebellar involvement in non-motor functions, it is possible that these newly identified structural properties, which are potentially capable of generating greater complexity than previously recognized, are associated with increased information capacity. This, in turn, could contribute to the wide range of cerebellar functions. However, it remains largely unknown how such structural properties contribute to cerebellar neural computations through the regulation of neuronal activity or synaptic transmissions. To promote further research into cerebellar circuit structures and their functional significance, we aim to summarize the newly identified structural properties of the cerebellar cortex and discuss future research directions concerning cerebellar circuit structures and their potential functions.

Cerebellar cortical degeneration in ‘Cirneco dell'Etna’ dog: First case report

AbstractA 4‐month‐old, intact male, Cirneco dell'Etna dog was presented with clinical signs of cerebellar ataxia, hindlimb hypometry and short steps with rapid progression. No findings were obtained from blood examinations, magnetic resonance imaging and cerebrospinal fluid (CSF) examinations and the dog was euthanased when it was not able to walk. Histological examination and immunohistochemical staining of the cerebellum showed multifocal depletion of Purkinje cells, marked increase in cellularity (astrogliosis) and a moderate reduction of the cells of the granule layer and thinning of the molecular layer. This case report describes the first case of cerebellar cortical degeneration in a purebreed Cirneco dell'Etna dog.

Changes in the Cyto- and Fibroarchitectonics of the Cerebellar Cortex in Rats Subjected to Extreme Physical Activity.

Physical overexertion surpassing the functional capacity of the nervous system causes the hyperactivation of the neural structures of the cerebellum. In turn, it causes the depletion of intracellular resources and progressive structural changes in cerebellar cells and fibers. These degenerative changes may lead to cerebellar dysfunction, including the worsening of coordination, balance, and motor functions. In order to maintain the health and functioning of the cerebellum and the nervous system in general, one needs to avoid physical overexertion and have enough time to recover. Three major types of Purkinje cells were identified in control group animals. After the forced swimming test, animals had significant morphological changes in pyriform cells, granule cells, internuncial neurons, and neuroglial cells. In particular, the extreme degeneration of granule cells was manifested via their fusion into conglomerates. These changes demonstrate that neurodegeneration in the cerebellum takes place in response to physical overexertion.

In situ assessment of neuroinflammatory cytokines in different stages of ovine natural prion disease

IntroductionAccording to the neuroinflammatory hypothesis, a cytokine-mediated host innate immune response may be involved in the mechanisms that contribute to the process of neurodegeneration. Specifically, regarding prion diseases, some experimental murine models have evidenced an altered profile of inflammatory intermediaries. However, the local inflammatory response has rarely been assessed, and never in tissues from different natural models throughout the progression of neurodegeneration.MethodsThe aim of this study was to use immunohistochemistry (IHC) to in situ assess the temporal protein expression of several cytokines in the cerebellum of sheep suffering from various clinical stages of scrapie.Results and discussionClear changes in the expression of most of the assessed markers were observed in the affected sheep compared to the healthy control sheep, and from different stages. In summary, this preliminary IHC study focusing in the Purkinje cell layer changes demonstrate that all cytokines or respective receptors studied (IL-1, IL-1R, IL-2R, IL-6, IL-10R, and TNFαR) except for IFNγR are disease-associated signaling proteins showing an increase or decrease in relation to the progression of clinical disease. In the future, this study will be extended to other inflammatory mediators and brain regions, focusing in particular on the release of these inflammatory mediators by astroglial and microglial populations.

Cerebellar dysfunction in the mdx mouse model of Duchenne muscular dystrophy: An electrophysiological and behavioural study.

Patients with Duchenne muscular dystrophy (DMD) commonly show specific cognitive deficits in addition to a severe muscle impairment caused by the absence of dystrophin expression in skeletal muscle. These cognitive deficits have been related to the absence of dystrophin in specific regions of the central nervous system, notably cerebellar Purkinje cells (PCs). Dystrophin has recently been involved in GABAA receptors clustering at postsynaptic densities, and its absence, by disrupting this clustering, leads to decreased inhibitory input to PC. We performed an in vivo electrophysiological study of the dystrophin-deficient muscular dystrophy X-linked (mdx) mouse model of DMD to compare PC firing and local field potential (LFP) in alert mdx and control C57Bl/10 mice. We found that the absence of dystrophin is associated with altered PC firing and the emergence of fast (~160-200 Hz) LFP oscillations in the cerebellar cortex of alert mdx mice. These abnormalities were not related to the disrupted expression of calcium-binding proteins in cerebellar PC. We also demonstrate that cerebellar long-term depression is altered in alert mdx mice. Finally, mdx mice displayed a force weakness, mild impairment of motor coordination and balance during behavioural tests. These findings demonstrate the existence of cerebellar dysfunction in mdx mice. A similar cerebellar dysfunction may contribute to the cognitive deficits observed in patients with DMD.

Neuroprotective Efficacy of β-caryophyllene on Cerebellar Changes Caused by Bisphenol A in Rats via Alleviating Oxidative Stress

Exposure to bisphenol A (BP), an environmental pollutant, is potentially harmful to both human health and the environment. The purpose of the current research was to evaluate the effectiveness of β-caryophyllene (CF) (200 mg/kg) on rat cerebellar tissues exposed to BP (250 mg/kg). Thirty-five randomly selected male rats were split into five groups as: control (CON), olive oil (OL), BP, CF, and CF+BP. On day 15 of the experiment, all rats' cerebellar tissues were immediately extracted, followed by stereological and histological examination. Our results revealed that MDA level was significantly elevated in the BP group compared to the CON group (p<0.05). While no significant difference was detected in the mean cerebellar volume among the experimental groups, the BP group’s the Purkinje cell number was significantly reduced when compared to the CON group (p<0.05). In the CF+BP group, we found a significantly lower level of MDA and higher number of Purkinje cells compared to the BP group (p<0.05). Histopathological examination revealed that the BP group had the marked neuronal deterioration; however, in the CF+BP group, this structural alteration was not as severe than the BP group. Our findings showed that exposure to BP caused oxidative damage to cerebellar tissues, and administration of CF attenuated BP-induced toxicity via improvement of oxidative stress.

The zebrafish cerebellar neural circuits are involved in orienting behavior.

Deficits in social behavior are found in neurodevelopmental disorders, including autism spectrum disorders (ASDs). Since abnormalities in cerebellar morphology and function are observed in ASD patients, the cerebellum is thought to play a role in social behavior. However, it remains unknown whether the cerebellum is involved in social behavior in other animals and how cerebellar circuits control social behavior. To address this issue, we employed zebrafish stereotyped orienting behavior as a model of social behaviors, in which a pair of adult zebrafish in two separate tanks approach each other, with one swimming at synchronized angles (orienting angles) with the other. We harnessed transgenic zebrafish that express botulinum toxin, which inhibits the release of neurotransmitters, in either granule cells or Purkinje cells, and zebrafish mutants of reelin, which is involved in the positioning of cerebellar neurons, including Purkinje cells. These zebrafish, deficient in the function or formation of cerebellar neural circuits, showed a significantly shorter period of orienting behavior compared to their control siblings. We found an increase in c-fos and egr1 expression in the cerebellum after the orienting behavior. These results suggest that zebrafish cerebellar circuits play an important role in social orienting behavior.Significance Statement Abnormalities in cerebellar morphology and function are often observed in ASD patients. We describe the roles of cerebellar neural circuitry in social behavior using stereotyped orienting behavior in zebrafish, in which a pair of zebrafish in two separate tanks approach each other and show synchronous swimming. Neurotoxin-mediated inhibition of cerebellar neurons or mutations of the reelin gene, which is required for proper formation of cerebellar neural circuits, shortened the period of the orienting behavior. Furthermore, we found activation of the cerebellum in response to the orienting behavior. Our findings suggest that studies of zebrafish cerebellar neural circuits may provide a model for studying abnormalities in social behaviors, such as those seen in ASD.

Effects of Boron on Learning and Behavioral Disorders in Rat Autism Model Induced by Intracerebroventricular Propionic Acid.

Autism spectrum disorder is a neurodevelopmental disorder in which learning, communication, and social interaction are impaired. Research has sought to minimize the neural impairments associated with autism spectrum disorder and improve the quality of life. Recent studies suggest that boron may benefit nerve cells, with effects varying depending on the dosage. This study explored the impact of boron, administered as boric acid, on behavioral, biochemical, and histopathological parameters in a rat model of autism induced by propionic acid (PPA). Thirty-two male Sprague-Dawley rats were divided into control, autism model, and boron-treated groups. Behavioral tests were conducted pre- and post-PPA induction, with brain tissue analyzed post-euthanasia. Proinflammatory cytokines (tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), interleukin 6 (IL-6)) and brain-derived neurotrophic factor (BDNF) levels were assessed in the hippocampus. Histopathological evaluations were conducted on the hippocampus and cerebellum. Autism model rats displayed impaired learning, elevated BDNF and cytokine levels, microglial and astrocytic activation, and decreased Purkinje cell count. The boron-treated groups showed improvements, particularly with the 4mg/kg dose. This dose enhanced learning and social interaction, reduced proinflammatory cytokine levels, prevented microglial and astrocytic activation, and increased Purkinje cell count. Boron treatment exhibited neuroprotective potential, ameliorating autism spectrum disorder deficits by modulating cytokines, BDNF, microglia, and astrocytes, with low doses yielding pronounced effects.

Berberine alleviates cerebellar damage in global cerebral ischemia: A comprehensive study with stereological analysis, evaluation of the antioxidant response, and locomotor function in rat models

AbstractBackgroundGlobal cerebral ischemia (GCI) leads to significant oxidative damage in the cerebellum, mainly affecting Purkinje cells. This study aimed to investigate the neuroprotective effects of berberine chloride (BBR), a compound known for its antioxidant properties against GCI.Materials and methodsFourty‐two adult male Wistar rats were divided into three groups: Sham, GCI, and GCI + BBR. Rats received BBR (50 mg/kg) seven days before and six hours after inducing GCI via bilateral common carotid artery occlusion for 20 min. They were assessed for locomotor activity by the open‐field test, the cerebellar biochemical factors malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), cerebellum volume and Purkinje neuron count by stereological analysis.ResultsThe BBR treatment reduced the concentration of MDA and increased the activity of antioxidant enzymes SOD, CAT and GPx in the GCI + BBR group compared to the GCI group. Stereological analysis revealed higher Purkinje cell count, cerebellum, white matter, and gray matter volume in the GCI + BBR group compared to the GCI group. Furthermore, GCI + BBR showed enhanced locomotor function compared to the GCI group.ConclusionBBR showed therapeutic benefits and improved locomotor function. It demonstrated antioxidative effects by lowering MDA levels, boosting enzymatic activities, and significantly mitigating Purkinje cell death and cerebellar volume loss.

Reward-driven cerebellar climbing fiber activity influences both neural and behavioral learning.

The cerebellum plays a key role in motor coordination and learning. In contrast with classical supervised learning models, recent work has revealed that CFs can signal reward-predictive information in some behaviors. This raises the question of whether CFs may also operate according to principles similar to those described by reinforcement learning models. To test how CFs operate during reward-guided behavior, and evaluate the role of reward-related CF activity in learning, we have measured CF responses in Purkinje cells of the lateral cerebellum during a Pavlovian task using 2-photon calcium imaging. Specifically, we have performed multi-stimulus experiments to determine whether CF activity meets the requirements of a reward prediction error (rPE) signal for transfer from an unexpected reward to a reward-predictive cue. We find that once CF activity is transferred to a conditioned stimulus, and there is no longer a response to reward, CFs cannot generate learned responses to a second conditioned stimulus that carries the same reward prediction. In addition, by expressing the inhibitory opsin GtACR2 in neurons of the inferior olive, and optically inhibiting these neurons across behavioral training at the time of unexpected reward, we find that the transfer of CF signals to the conditioned stimulus is impaired. Moreover, this optogenetic inhibition also impairs learning, resulting in a deficit in anticipatory lick timing. Together, these results indicate that CF signals can exhibit several characteristics in common with rPEs during reinforcement learning, and that the cerebellum can harness these learning signals to generate accurately timed motor behavior.

Polyserine peptides are toxic and exacerbate tau pathology in mice.

Polyserine domains mediate the association of nuclear RNA binding proteins with cytoplasmic tau aggregates that occurs across tauopathy models and patient samples. In cell lines, polyserine peptides co-localize with and promote formation of tau aggregates suggesting the cytoplasmic mislocalization of polyserine-containing proteins might contribute to human disease. Moreover, polyserine can be produced by repeat associated non-AUG translation in CAG repeat expansion diseases. However, whether polyserine expressed in a mammalian brain is toxic and/or can exacerbate tau pathology is unknown. Here, we used AAV9-mediated delivery to express a 42-repeat polyserine protein in wild-type and tau transgenic mouse models. We observe that polyserine expression has toxic effects in wild-type animals indicated by reduced weight, behavioral abnormalities and a striking loss of Purkinje cells. Moreover, in the presence of a pathogenic variant of human tau, polyserine exacerbates disease markers such as phosphorylated and insoluble tau levels and the seeding capacity of brain extracts. These findings demonstrate that polyserine domains can promote tau-mediated pathology in a mouse model and are consistent with the hypothesis that cytoplasmic mislocalization of polyserine containing proteins might contribute to the progression of human tauopathies.