Expression of mutant DISC1 in Purkinje cells increases their spontaneous activity and impairs cognitive and social behaviors in mice

Spliceosomal GTPase Eftud2 deficiency-triggered ferroptosis leads to Purkinje cell degeneration

Spliceosomal GTPase elongation factor Tu GTP binding domain containing 2 (EFTUD2) is a causative gene for mandibulofacial dysostosis with microcephaly (MFDM) syndrome comprising cerebellar hypoplasia and motor dysfunction. How EFTUD2 deficiency contributes to these symptoms remains elusive. Here, we demonstrate that specific ablation of Eftud2 in cerebellar Purkinje cells (PCs) in mice results in severe ferroptosis, PC degeneration, dyskinesia, and cerebellar atrophy, which recapitulates phenotypes observed in patients with MFDM. Mechanistically, Eftud2 promotes Scd1 and Gch1 expression, upregulates monounsaturated fatty acid phospholipids, and enhances antioxidant activity, thereby suppressing PC ferroptosis. Importantly, we identified transcription factor Atf4 as a downstream target to regulate anti-ferroptosis effects in PCs in a p53-independent manner. Inhibiting ferroptosis efficiently rescued cerebellar deficits in Eftud2 cKO mice. Our data reveal an important role of Eftud2 in maintaining PC survival, showing that pharmacologically or genetically inhibiting ferroptosis may be a promising therapeutic strategy for EFTUD2 deficiency-induced disorders.

Converging and Diverging Cerebellar Pathways for Motor and Social Behaviors in Mice

Evidence from clinical and preclinical studies has shown that the cerebellum contributes to cognitive functions, including social behaviors. Now that the cerebellum's role in a wider range of behaviors has been confirmed, the question arises whether the cerebellum contributes to social behaviors via the same mechanisms with which it modulates movements. This review seeks to answer whether the cerebellum guides motor and social behaviors through identical pathways. It focuses on studies in which cerebellar cells, synapses, or genes are manipulated in a cell-type specific manner followed by testing of the effects on social and motor behaviors. These studies show that both anatomically restricted and cerebellar cortex-wide manipulations can lead to social impairments without abnormal motor control, and vice versa. These studies suggest that the cerebellum employs different cellular, synaptic, and molecular pathways for social and motor behaviors. Future studies warrant a focus on the diverging mechanisms by which the cerebellum contributes to a wide range of neural functions.

Impairments of cerebellar structure and function in a zebrafish KO of neuropsychiatric risk gene znf536

Genetic variants in ZNF536 contribute to the risk for neuropsychiatric disorders such as schizophrenia, autism, and others. The role of this putative transcriptional repressor in brain development and function is, however, largely unknown. We generated znf536 knockout (KO) zebrafish and studied their behavior, brain anatomy, and brain function. Larval KO zebrafish showed a reduced ability to compete for food, resulting in decreased total body length and size. This phenotype can be rescued by segregating the homozygous KO larvae from their wild-type and heterozygous siblings, enabling studies of adult homozygous KO animals. In adult KO zebrafish, we observed significant reductions in anxiety-like behavior and social interaction. These znf536 KO zebrafish have decreased cerebellar volume, corresponding to decreased populations of specific neuronal cells, especially in the valvular cerebelli (Va). Finally, using a Tg[mbp:mgfp] line, we identified a previously undetected myelin structure located bilaterally within the Va, which also displayed a reduction in volume and disorganization in KO zebrafish. These findings indicate an important role for ZNF536 in brain development and implicate the cerebellum in the pathophysiology of neuropsychiatric disorders.

Oxytocin Receptor in Cerebellar Purkinje Cells Does Not Engage in Autism-Related Behaviors

The classical motor center cerebellum is one of the most consistent structures of abnormality in autism spectrum disorders (ASD), and neuropeptide oxytocin is increasingly explored as a potential pharmacotherapy for ASD. However, whether oxytocin targets the cerebellum for therapeutic effects remains unclear. Here, we report a localization of oxytocin receptor (OXTR) in Purkinje cells (PCs) of cerebellar lobule Crus I, which is functionally connected with ASD-implicated circuits. OXTR activation neither affects firing activities, intrinsic excitability, and synaptic transmission of normal PCs nor improves abnormal intrinsic excitability and synaptic transmission of PCs in maternal immune activation (MIA) mouse model of autism. Furthermore, blockage of OXTR in Crus I in wild-type mice does not induce autistic-like social, stereotypic, cognitive, and anxiety-like behaviors. These results suggest that oxytocin signaling in Crus I PCs seems to be uninvolved in ASD pathophysiology, and contribute to understanding of targets and mechanisms of oxytocin in ASD treatment.

Adult mice with noise-induced hearing loss exhibited temporal ordering memory deficits accompanied by microglia-associated neuroplastic changes in the medial prefrontal cortex

Acquired peripheral hearing loss in midlife is considered the primary modifiable risk factor for dementia, while the underlying pathological mechanism remains poorly understood. Excessive noise exposure is the most common cause of acquired peripheral hearing loss in modern society. This study was designed to investigate the impact of noise-induced hearing loss (NIHL) on cognition, with a focus on the medial prefrontal cortex (mPFC), a brain region that is involved in both auditory and cognitive processes and is highly affected in patients with cognitive impairment. Adult C57BL/6 J mice were randomly assigned to a control group and seven noise groups: 0HPN, 12HPN, 1DPN, 3DPN, 7DPN, 14DPN, and 28DPN, which were exposed to broadband noise at a 123 dB sound pressure level (SPL) for 2 h and sacrificed immediately (0 h), 12 h, or 1, 3, 7, 14, or 28 days post-noise exposure (HPN, DPN), respectively. Hearing assessment, behavioral tests, and neuromorphological studies in the mPFC were performed in control and 28DPN mice. All experimental animals were included in the time-course analysis of serum corticosterone (CORT) levels and mPFC microglial morphology. The results illustrated that noise exposure induced early-onset transient serum CORT elevation and permanent moderate-to-severe hearing loss in mice. 28DPN mice, in which permanent NIHL has been verified, exhibited impaired performance in temporal order object recognition tasks concomitant with reduced structural complexity of mPFC pyramidal neurons. The time-course immunohistochemical analysis in the mPFC revealed significantly higher morphological microglial activation at 14 and 28 DPN, preceded by a remarkably higher amount of microglial engulfed postsynaptic marker PSD95 at 7 DPN. Additionally, lipid accumulation in microglia was observed in 7DPN, 14DPN and 28DPN mice, suggesting a driving role of lipid handling deficits following excessive phagocytosis of synaptic elements in delayed and sustained microglial abnormalities. These findings provide fundamentally novel information concerning mPFC-related cognitive impairment in mice with NIHL and empirical evidence suggesting the involvement of microglial malfunction in the mPFC neurodegenerative consequences of NIHL.

Early dynamics of glial fibrillary acidic protein and extracellular DNA in plasma of mice after closed head traumatic brain injury

BACKGROUND

Glial fibrillary acidic protein (GFAP) in plasma is an established biomarker of traumatic brain injury (TBI) in humans. Plasma extracellular DNA (ecDNA) is a very sensitive, although nonspecific marker of tissue damage including TBI. Whether plasma GFAP or ecDNA could be used as an early non-invasive biomarker in the mouse model of closed head injury is unknown. The aim of this paper was to describe the early dynamics of plasma GFAP and ecDNA in the animal model of closed head TBI.

METHODS

Closed head TBI was induced using the weight-drop method in 40 adult CD1 mice and blood was collected in different time points (1, 2 or 3h) after TBI in different groups of mice. Plasma GFAP and ecDNA and ecDNA fragmentation from the experimental groups were compared to healthy controls. In the surviving mice, a static rods test was performed 30 days after TBI to assess the neurological outcome of TBI.

RESULTS

Despite a trend of higher plasma GFAP after TBI the differences between the groups were not statistically significant. Plasma ecDNA was higher by 50% after 1h (P<0.05) and 2h (P<0.05) after TBI and was highly variable after 3h. Plasma ecDNA, but not GFAP, was partially predictive of the neurological impairment of the mice.

CONCLUSION

In this study, we have described the early dynamics of plasma GFAP and ecDNA after TBI in mice. According to our results, ecDNA in plasma is a more sensitive early marker of TBI than GFAP. Analysis of tissue-specific ecDNA might improve its predictive value regarding the survival and neurobehavioral outcome.

Social behavior and spatial orientation in rat strains with genetic predisposition to catatonia (GC) and stereotypes (PM)

Various psychopathologies, including schizophrenia, bipolar disorder and major depression, are associated with abnormalities in social behavior and learning. One of the syndromes that may also take place in these disorders is catatonia. Catatonia is a psychomotor syndrome in which motor excitement, stereotypy, stuporous state, including the phenomenon of “waxy flexibility” (catalepsy), can be observed. Rats with genetic catatonia (GC) and pendulum-like movements (PM) of the anterior half of the body have physiological and behavioral changes similar to those observed in schizophrenia and depression in humans and can be considered as incomplete experimental models of these pathologies. The social behavior of the GC and PM rats has not been previously studied, and the cognitive abilities of animals of these strains are also insufficiently studied. To determine whether the GC and PM rats have changes in social behavior and spatial learning, behavioral phenotyping was performed in the residentintruder test, three-chamber test, Barnes maze test. Some deviations in social behavior, such as increased offensive aggression in PM rats in the resident-intruder test, increased or decreased social interactions depending on the environment in different tests in GC, were shown. In addition, principal component analysis revealed a negative association between catatonic freezing and the socialization index in the three-chamber test. Decreased locomotor activity of GС rats can adversely affect the performance of tasks on spatial memory. It has been shown that PM rats do not use a spatial strategy in the Barnes maze, which may indicate impairment of learning and spatial memory.

Methylmercury exposure during prenatal and postnatal neurodevelopment promotes oxidative stress associated with motor and cognitive damages in rats: an environmental-experimental toxicology study

The environmental contamination by methylmercury (MeHg) is a major concern for public health. The effects of MeHg in the central nervous system (CNS) of adult animals have been extensively investigated; however, little is known about the effects of MeHg exposure during intrauterine and lactation periods on motor and cognitive functions of adolescent rats. Therefore, this study aimed to investigate the effect of MeHg exposure during intrauterine life and lactation on both motor and cognitive functions of offspring rats. Ten female Wistar rats were exposed to 40 μg/kg/day of MeHg through cookie treats from the first day of pregnancy until the last day of breastfeeding. Both motor and cognitive functions of offspring male rats were assessed by open field, rotarod, and step-down inhibitory avoidance tests. Forty-one days after birth, the hippocampus and cerebellum were collected to determine total Hg content, antioxidant capacity against peroxyl radicals (ACAP), reduced glutathione (GSH) levels, lipid peroxidation (LPO), and nitrite levels. MeHg exposure during CNS development increased Hg levels in both hippocampal and cerebellar parenchymas, triggered oxidative stress throughout ACAP and GSH decrease, increased LPO and nitrite levels. These alterations resulted in reduced spontaneous and stimulated locomotion and short- and long-term memory deficits. Therefore, damages triggered by MeHg exposure during intrauterine life and lactation had detrimental effects on oxidative biochemistry and motor and cognitive functions of offspring rats.

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The MeHg exposure during CNS development increased mercury levels in hippocampal and cerebellar parenchyma.

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The MeHg intoxication during pregnancy and lactation impairs the redox status of hippocampus and cerebellum of the offspring.

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MeHg exposure causes behavioral effects in motor ability and cognition of offspring rats.

Astrocyte Bioenergetics and Major Psychiatric Disorders

Ongoing research continues to add new elements to the emerging picture of involvement of astrocyte energy metabolism in the pathophysiology of major psychiatric disorders, including schizophrenia, mood disorders, and addictions. This review outlines what is known about the energy metabolism in astrocytes, the most numerous cell type in the brain, and summarizes the recent work on how specific perturbations of astrocyte bioenergetics may contribute to the neuropsychiatric conditions. The role of astrocyte energy metabolism in mental health and disease is reviewed on the organism, organ, and cell level. Data arising from genomic, metabolomic, in vitro, and neurobehavioral studies is critically analyzed to suggest future directions in research and possible metabolism-focused therapeutic interventions.

Behavioral Tasks Evaluating Schizophrenia-like Symptoms in Animal Models: A Recent Update

BACKGROUND

Schizophrenia is a serious mental illness that affects more than 21 million people worldwide. Both genetics and the environment play a role in its etiology and pathogenesis. Symptoms of schizophrenia are mainly categorized into positive, negative, and cognitive. One major approach to identify and understand these diverse symptoms in humans has been to study behavioral phenotypes in a range of animal models of schizophrenia.

OBJECTIVE

We aimed to provide a comprehensive review of the behavioral tasks commonly used for measuring schizophrenia-like behaviors in rodents together with an update of the recent study findings.

METHODS

Articles describing phenotypes of schizophrenia-like behaviors in various animal models were collected through a literature search in Google Scholar, PubMed, Web of Science, and Scopus, with a focus on advances over the last 10 years.

RESULTS

Numerous studies have used a range of animal models and behavioral paradigms of schizophrenia to develop antipsychotic drugs for improved therapeutics. In establishing animal models of schizophrenia, the candidate models were evaluated for schizophrenia-like behaviors using several behavioral tasks for positive, negative, and cognitive symptoms designed to verify human symptoms of schizophrenia. Such validated animal models were provided as rapid preclinical avenues for drug testing and mechanistic studies.

CONCLUSION

Based on the most recent advances in the field, it is apparent that a myriad of behavior tests are needed to confirm and evaluate the congruency of animal models with the numerous behaviors and clinical signs exhibited by patients with schizophrenia.

MCT1 Deletion in Oligodendrocyte Lineage Cells Causes Late-Onset Hypomyelination and Axonal Degeneration

Oligodendrocytes (OLs) are important for myelination and shuttling energy metabolites lactate and pyruvate toward axons through their expression of monocarboxylate transporter 1 (MCT1). Recent studies suggest that loss of OL MCT1 causes axonal degeneration. However, it is unknown how widespread and chronic loss of MCT1 in OLs specifically affects neuronal energy homeostasis with aging. To answer this, MCT1 conditional null mice were generated that allow for OL-specific MCT1 ablation. We observe that MCT1 loss from OL lineage cells is dispensable for normal myelination and axonal energy homeostasis early in life. By contrast, loss of OL lineage MCT1 expression with aging leads to significant axonal degeneration with concomitant hypomyelination. These data support the hypothesis that MCT1 is important for neuronal energy homeostasis in the aging central nervous system (CNS). The reduction in OL MCT1 that occurs with aging may enhance the risk for axonal degeneration and atrophy in neurodegenerative diseases.

Using conditional cell-specific deletion of MCT1, Philips et al. learn that oligodendrocyte lineage cells are actually dispensable for normal myelination and axonal energy homeostasis during early life but that the oligodendroglial lactate/MCT1-based support is critical for the aging of the nervous system.

Transient effects of chemotherapy for testicular cancer on mouse behaviour

The treatment of testicular cancer includes unilateral orchiectomy and chemotherapy and is curative for most patients. However, observational studies revealed an association with depression, anxiety and cognitive impairment. It is unclear whether these side effects are caused by chemotherapy, hemicastration or the disease itself. The aim of our study was to analyse the behavioural effects of hemicastration and chemotherapy in adult male mice. The animals were randomly divided into four groups – control, chemotherapy, hemicastration and hemicastration with chemotherapy. After chemotherapy that included three cycles of bleomycin, etoposide, cisplatin mice underwent a battery of behavioural tests. To assess the long-term effects animals were tested also 3 months after the end of treatment. Chemotherapy led to lower locomotor- and exploratory activity, higher anxiety-like behaviour and worse spatial memory immediately after treatment. These behavioural effects were not present three months later. Hemicastration had no effect on most of the observed outcomes. In conclusion, adverse behavioural effects induced by chemotherapy in mice are transient and disappear later in life. Further studies are needed to elucidate the mechanisms responsible for the observed effects.

Spaced training improves learning in Ts65Dn and Ube3a mouse models of intellectual disabilities

Benefits of distributed learning strategies have been extensively described in the human literature, but minimally investigated in intellectual disability syndromes. We tested the hypothesis that training trials spaced apart in time could improve learning in two distinct genetic mouse models of neurodevelopmental disorders characterized by intellectual impairments. As compared to training with massed trials, spaced training significantly improved learning in both the Ts65Dn trisomy mouse model of Down syndrome and the maternally inherited Ube3a mutant mouse model of Angelman syndrome. Spacing the training trials at 1 h intervals accelerated acquisition of three cognitive tasks by Ts65Dn mice: (1) object location memory, (2) novel object recognition, (3) water maze spatial learning. Further, (4) spaced training improved water maze spatial learning by Ube3a mice. In contrast, (5) cerebellar-mediated rotarod motor learning was not improved by spaced training. Corroborations in three assays, conducted in two model systems, replicated within and across two laboratories, confirm the strength of the findings. Our results indicate strong translational relevance of a behavioral intervention strategy for improving the standard of care in treating the learning difficulties that are characteristic and clinically intractable features of many neurodevelopmental disorders.

Is there an "antisocial" cerebellum? Evidence from disorders other than autism characterized by abnormal social behaviours

The cerebellum is a hindbrain structure which involvement in functions not related to motor control and planning is being increasingly recognized in the last decades. Studies on Autism Spectrum Disorders (ASD) have reported cerebellar involvement on these conditions characterized by social deficits and repetitive motor behavior patterns. Although such an involvement hints at a possible cerebellar participation in the social domain, the fact that ASD patients present both social and motor deficits impedes drawing any firm conclusion regarding cerebellar involvement in pathological social behaviours, probably influenced by the classical view of the cerebellum as a purely "motor" brain structure. Here, we suggest the cerebellum can be a key node for the production and control of normal and particularly aberrant social behaviours, as indicated by its involvement in other neuropsychiatric disorders which main symptom is deregulated social behaviour. Therefore, in this work, we briefly review cerebellar involvement in social behavior in rodent models, followed by discussing the findings linking the cerebellum to those other psychiatric conditions characterized by defective social behaviours. Finally, possible commonalities between the studies and putative underlying impaired functions will be discussed and experimental approaches both in patients and experimental animals will also be proposed, aimed at stimulating research on the role of the cerebellum in social behaviours and disorders characterized by social impairments, which, if successful, will definitely help reinforcing the proposed cerebellar involvement in the social domain.

Anxiogenic-like behavior and deficient attention/working memory in rats expressing the human DISC1 gene

In humans, mutations in the Disrupted-in-schizophrenia 1 (DISC1) gene have been related to psychiatric disorders, including symptoms of abnormal cognitive and emotional behaviors. In our previous studies, overexpression of the human DISC1 gene in rats resulted in schizophrenia-like phenotypes showing deficits in motor learning, impaired cognitive function and dysfunctions of the dopamine system. Here we asked, whether the DISC1 overexpression affects locomotor activity in the open field (OF), anxiety in the elevated plus-maze (EPM), depression-related behavior in the forced swim test (FST), and attention-like/short-term working-memory in the spontaneous alternation behavior (SAB) in the T-maze in transgenic DISC1 (tgDISC1) rats and littermate controls (WT). TgDISC1 rats showed enhanced anxiety behavior in the EPM and an impairment in attention-like/short-term working-memory in the SAB. However, tgDISC1 animals showed no locomotor impairments or depression-like behavior in the OF and FST. These results suggest that DISC1 overexpression leads to higher anxiety level and an attention-like/working-memory deficit. These findings may expand the causal role of DISC1 in its contribution to multiple symptom dimensions of psychiatric disorders.

Cerebellum and cognition: Does the rodent cerebellum participate in cognitive functions?

There is a widespread, nearly complete consensus that the human and non-human primate cerebellum is engaged in non-motor, cognitive functions. This body of research has implicated the lateral portions of lobule VII (Crus I and Crus II) and the ventrolateral dentate nucleus. With rodents, however, it is not so clear. We review here approximately 40 years of experiments using a variety of cerebellar manipulations in rats and mice and measuring the effects on executive functions (working memory, inhibition, and cognitive flexibility), spatial navigation, discrimination learning, and goal-directed and stimulus-driven instrumental conditioning. Our conclusion is that there is a solid body of support for engagement of the rodent cerebellum in tests of cognitive flexibility and spatial navigation, and some support for engagement in working memory and certain types of discrimination learning. Future directions will involve determining the relevant cellular mechanisms, cerebellar regions, and precise cognitive functions of the rodent cerebellum.

Neurobiology and treatment of social cognition in schizophrenia: Bridging the bed-bench gap

Social cognition refers to the psychological processes involved in the perception, encoding, storage, retrieval, and regulation of information about others and ourselves. This process is essential for survival and reproduction in complex social environments. Recent evidence suggests that impairments in social cognition frequently occur in schizophrenia, mainly contributing to poor functional outcomes, including the inability to engage in meaningful work and maintain satisfying interpersonal relationships. With the ambiguous definition of social cognition, the neurobiology underlying impaired social cognition remains unknown, and the effectiveness of currently available intervention strategies in schizophrenia remain limited. Considering the advances and challenges of translational research for schizophrenia, social cognition has been considered a high-priority domain for treatment development. Here, we describe the current state of the framework, clinical concerns, and intervention approaches for social cognition in schizophrenia. Next, we introduce translatable rodent models associated with schizophrenia that allow the evaluation of different components of social behaviors, providing deeper insights into the neural substrates of social cognition in schizophrenia. Our review presents a valuable perspective that indicates the necessity of building bridges between basic and clinical science researchers for the development of novel therapeutic approaches in impaired social cognition in schizophrenia.

Modelling the neuromotor abnormalities of psychotic illness: Putative mechanisms and systems dysfunction

Limitations in access to antipsychotic-naïve patients and in the incisiveness of studies that can be conducted on them, together with the inevitability of subsequent antipsychotic treatment, indicate an enduring role for animal models that can inform on the pathobiology of neuromotor abnormalities in schizophrenia and related psychotic illness. This review focusses particularly on genetically modified mouse models that involve genes associated with risk for schizophrenia and with mechanisms implicated in the neuromotor abnormalities evident in psychotic patients, as well as developmental models that seek to mirror the trajectory, phenomenology and putative pathophysiology of psychotic illness. Such abnormalities are inconsistent and subtle in mice mutant for some schizophrenia risk genes but more evident for others. The phenotype of dopaminergic and glutamatergic mutants indicates the involvement of these mechanisms, informs on the roles of specific receptor subtypes, and implicates the interplay of cortical and subcortical processes. Developmental models suggest a criticality in the timing of early adversity for diversity in the relative emergence of psychological symptoms vis-à-vis neuromotor abnormalities in the overall psychosis phenotype. These findings elaborate current concepts of dysfunction in a neuronal network linking the cerebral cortex, basal ganglia, thalamus and cerebellum. Both findings in model systems and clinical evidence converge in indicating that any distinction between 'psychomotor' and 'neuromotor' abnormality is artificial and arbitrary due to a unitary origin in developmentally determined systems/network dysfunction that underlies the lifetime trajectory of psychotic illness.