A myelin gene causative of a catatonia-depression syndrome upon aging

Bioenergetics of Axon Integrity and Its Regulation by Oligodendrocytes and Schwann Cells

Axons are long slender portions of neurons that transmit electrical impulses to maintain proper physiological functioning. Axons in the central nervous system (CNS) and peripheral nervous system (PNS) do not exist in isolation but are found to form a complex association with their surrounding glial cells, oligodendrocytes and Schwann cells. These cells not only myelinate them for faster nerve impulse conduction but are also known to provide metabolic support. Due to their incredible length, continuous growth, and distance from the cell body (where major energy synthesis takes place), axons are in high energetic demand. The stability and integrity of axons have long been associated with axonal energy levels. The current mini-review is thus focused on how axons accomplish their high energetic requirement in a cell-autonomous manner and how the surrounding glial cells help them in maintaining their integrity by fulfilling their energy demands (non-cell autonomous trophic support). The concept that adjacent glial cells (oligodendrocytes and Schwann cells) provide trophic support to axons and assist them in maintaining their integrity comes from the conditional knockout research and the studies in which the metabolic pathways controlling metabolism in these glial cells are modulated and its effect on axonal integrity is evaluated. In the later part of the mini-review, the current knowledge of axon-glial metabolic coupling during various neurodegenerative conditions was discussed, along with the potential lacunae in our current understanding of axon-glial metabolic coupling.

Catatonia

Catatonia is a neuropsychiatric disorder characterized by motor, affective and cognitive-behavioural signs, which lasts from hours to days. Intensive research over the past two decades has led to catatonia being recognized as an independent diagnosis in the International Classification of Diseases, 11th Revision (ICD-11) since 2022. Catatonia is found in 5-18% of inpatients on psychiatric units and 3.3% of inpatients on medical units. However, in an unknown number of patients, catatonia remains unrecognized and these patients are at risk of life-threatening complications. Hence, recognizing the symptoms of catatonia early is crucial to initiate appropriate treatment to achieve a favourable outcome. Benzodiazepines such as lorazepam and diazepam, electroconvulsive therapy, and N-methyl-D-aspartate antagonists such as amantadine and memantine, are the cornerstones of catatonia therapy. In addition, dopamine-modulating second-generation antipsychotics (for example, clozapine and aripiprazole) are effective in some patient populations. Early and appropriate treatment combined with new screening assessments has the potential to reduce the high morbidity and mortality associated with catatonia in psychiatric and non-psychiatric settings.

Perinatal loss of galactosylceramidase in both oligodendrocytes and microglia is crucial for the pathogenesis of Krabbe disease in mice

Lysosomal galactosylceramidase (GALC) is expressed in all brain cells, including oligodendrocytes (OLs), microglia, and astrocytes, although the cell-specific function of GALC is largely unknown. Mutations in GALC cause Krabbe disease (KD), a fatal neurological lysosomal disorder that usually affects infants. To study how Galc ablation in each glial cell type contributes to Krabbe pathogenesis, we used conditional Galc-floxed mice. Here, we found that OL-specific Galc conditional knockout (CKO) in mice results in a phenotype that includes wasting, psychosine accumulation, and neuroinflammation. Microglia- or astrocyte-specific Galc deletion alone in mice did not show specific phenotypes. Interestingly, mice with CKO of Galc from both OLs and microglia have a more severe neuroinflammation with an increase in globoid cell accumulation than OL-specific CKO alone. Moreover, the enhanced phenotype occurred without additional accumulation of psychosine. Further studies revealed that Galc knockout (Galc-KO) microglia cocultured with Galc-KO OLs elicits globoid cell formation and the overexpression of osteopontin and monocyte chemoattractant protein-1, both proteins that are known to recruit immune cells and promote engulfment of debris and damaged cells. We conclude that OLs are the primary cells that initiate KD with an elevated psychosine level and microglia are required for the progression of neuroinflammation in a psychosine-independent manner.

Nanobodies against the myelin enzyme CNPase as tools for structural and functional studies

2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) is an abundant constituent of central nervous system non-compact myelin, frequently used as a marker antigen for myelinating cells. The catalytic activity of CNPase, the 3'-hydrolysis of 2',3'-cyclic nucleotides, is well characterised in vitro, but the in vivo function of CNPase remains unclear. CNPase interacts with the actin cytoskeleton to counteract the developmental closure of cytoplasmic channels that travel through compact myelin; its enzymatic activity may be involved in adenosine metabolism and RNA degradation. We developed a set of high-affinity nanobodies recognizing the phosphodiesterase domain of CNPase, and the crystal structures of each complex show that the five nanobodies have distinct epitopes. One of the nanobodies bound deep into the CNPase active site and acted as an inhibitor. Moreover, the nanobodies were characterised in imaging applications and as intrabodies, expressed in mammalian cells, such as primary oligodendrocytes. Fluorescently labelled nanobodies functioned in imaging of teased nerve fibers and whole brain tissue sections, as well as super-resolution microscopy. These anti-CNPase nanobodies provide new tools for structural and functional biology of myelination, including high-resolution imaging of nerve tissue.

Interaction between Oligodendrocytes and Interneurons in Brain Development and Related Neuropsychiatric Disorders

A variety of neurological and psychiatric disorders have recently been shown to be highly associated with the abnormal development and function of oligodendrocytes (OLs) and interneurons. OLs are the myelin-forming cells in the central nervous system (CNS), while interneurons are important neural types gating the function of excitatory neurons. These two types of cells are of great significance for the establishment and function of neural circuits, and they share similar developmental origins and transcriptional architectures, and interact with each other in multiple ways during development. In this review, we compare the similarities and differences in these two cell types, providing an important reference and further revealing the pathogenesis of related brain disorders.

Clinically approved immunomodulators ameliorate behavioral changes in a mouse model of hereditary spastic paraplegia type 11

We have previously demonstrated that neuroinflammation by the adaptive immune system acts as a robust and targetable disease amplifier in a mouse model of Spastic Paraplegia, type 11 (SPG11), a complicated form of Hereditary Spastic Paraplegia (HSP). While we identified an impact of neuroinflammation on distinct neuropathological changes and gait performance, neuropsychological features, typical and clinically highly relevant symptoms of complicated HSPs, were not addressed. Here we show that the corresponding SPG11 mouse model shows distinct behavioral abnormalities, particularly related to social behavior thus partially reflecting the neuropsychological changes in patients. We provide evidence that some behavioral abnormalities can be mitigated by genetic inactivation of the adaptive immune system. Translating this into a clinically applicable approach, we show that treatment with the established immunomodulators fingolimod or teriflunomide significantly attenuates distinct behavioral abnormalities, with the most striking effect on social behavior. This study links neuroinflammation to behavioral abnormalities in a mouse model of SPG11 and may thus pave the way for using immunomodulators as a treatment approach for SPG11 and possibly other complicated forms of HSP with neuropsychological involvement.

Homozygous CNP Mutation and Neurodegeneration in Weimaraners: Myelin Abnormalities and Accumulation of Lipofuscin-like Inclusions

A progressive neurological disorder was observed in a male neutered Weimaraner. Clinical signs included fecal incontinence, lethargy, moderate paraparesis, proprioceptive pelvic limb ataxia, falling, cognitive decline, incoordination, decreased interest in food, changes in posture, and episodes of trance-like behavior. Neurologic signs were first observed at approximately 4 years, 10 months of age and progressed slowly. Magnetic resonance imaging showed generalized brain atrophy with areas of white matter pathology. Humane euthanasia was elected at 6 years, 7 months of age due to increasing severity of the neurological signs. Autofluorescent intracellular granules were observed in the cerebral and cerebellar cortexes, optic nerve, and cardiac muscle of the affected dog. These abnormal inclusions in the cerebral cortex and cardiac muscle immunolabeled with antibodies to mitochondrial ATP synthase subunit c protein, like that observed in the neuronal ceroid lipofuscinosis group of lysosomal storage diseases. Immunolabeling also demonstrated pronounced neuroinflammation in brain tissues. The ultrastructural appearances of the disease-related inclusion bodies in the brain and optic nerve were quite variable. The ultrastructure and locations of many of the inclusions in the nervous tissues suggested that they were derived, at least in part, from the myelin surrounding axons. The storage bodies in the cardiac muscle were located in mitochondria-rich regions and consisted of parallel arrays of membrane-like components interspersed with electron-dense flocculent material. The disease was characterized by pronounced abnormalities in the myelin of the brain and optic nerve consisting of distinctive areas of ballooning between the layers of myelin. The whole genome sequence generated from the affected dog contained a homozygous G-to-A missense mutation in CNP, which encodes proteins with CNPase enzyme activity and a structural role in myelin. The mutation predicts a Thr42Met amino acid sequence substitution. Genotyping of archived Weimaraner DNA samples identified an additional G > A variant homozygote with a clinical history and brain lesions similar to those of the proband. Of 304 Weimaraners and over 4000 other dogs of various breeds, the proband and the other Weimaraner that exhibited similar signs were the only two that were homozygous for the CNP missense variant. CNPase immunolabeling was widespread in brain tissues from normal dogs but was undetectable in the same tissues from the proband. Based on the clinical history, fluorescence and electron-microscopy, immunohistochemistry, and molecular genetic findings, the late-onset Weimaraner disorder likely results from the missense mutation that results in CNPase deficiency, leading to myelin abnormalities, accumulation of lysosomal storage bodies, and brain atrophy. Similar disorders have been associated with different CNP variants in Dalmatians and in human subjects.

A systematic scoping review of rodent models of catatonia: Clinical correlations, translation and future approaches

Catatonia is a psychiatric disorder, which subsumes a plethora of affective, motor and behavioral symptoms. In the last two decades, the number of behavioral and neuroimaging studies on catatonia has steadily increased. The majority of behavioral and neuroimaging studies in psychiatric patients suggested aberrant higher-order frontoparietal networks which, on the biochemical level, are insufficiently modulated by gamma-aminobutyric acid (GABA)-ergic and glutamatergic transmission. However, the pathomechanisms of catatonic symptoms have rarely been studied using rodent models. Here, we performed a scoping review of literature available on PubMed for studies on rodent models of catatonia. We sought to identify what we could learn from pre-clinical animal models of catatonia-like symptoms, their underlying neuronal correlates, and the complex molecular (i.e. genes and neurotransmitter) mechanisms by which its modulation exerts its effects. What becomes evident is that although many transgenic models present catatonia-like symptoms, they have not been used to better understand the pathophysiological mechanisms underlying catatonia so far. However, the identified neuronal correlates of catatonia-like symptoms correlate to a great extent with findings from neuroscience research in psychiatric patients. This points us towards fundamental cortical-striatal-thalamocortical and associated networks modulated by white matter inflammation as well as aberrant dopaminergic, GABAergic, and glutamatergic neurotransmission that is involved in catatonia. Therefore, this scoping review opens up the possibility of finally using transgenic models to help with identifying novel target mechanisms for the development of new drugs for the treatment of catatonia.

Microstructural white matter biomarkers of symptom severity and therapy outcome in catatonia: Rationale, study design and preliminary clinical data of the whiteCAT study

The number of magnetic resonance imaging (MRI) studies on neuronal correlates of catatonia has dramatically increased in the last 10 years, but conclusive findings on white matter (WM) tracts alterations underlying catatonic symptoms are still lacking. Therefore, we conduct an interdisciplinary longitudinal MRI study (whiteCAT) with two main objectives: First, we aim to enroll 100 psychiatric patients with and 50 psychiatric patients without catatonia according to ICD-11 who will undergo a deep phenotyping approach with an extensive battery of demographic, psychopathological, psychometric, neuropsychological, instrumental and diffusion MRI assessments at baseline and 12 weeks follow-up. So far, 28 catatonia patients and 40 patients with schizophrenia or other primary psychotic disorders or mood disorders without catatonia have been studied cross-sectionally. 49 out of 68 patients have completed longitudinal assessment, so far. Second, we seek to develop and implement a new method for semi-automatic fiber tract delineation using active learning. By training supportive machine learning algorithms on the fly that are custom tailored to the respective analysis pipeline used to obtain the tractogram as well as the WM tract of interest, we plan to streamline and speed up this tedious and error-prone task while at the same time increasing reproducibility and robustness of the extraction process. The goal is to develop robust neuroimaging biomarkers of symptom severity and therapy outcome based on WM tracts underlying catatonia. If our MRI study is successful, it will be the largest longitudinal study to date that has investigated WM tracts in catatonia patients.

Molecular and immunological origins of catatonia

Catatonia occurs secondary to both primary psychiatric and neuromedical etiologies. Emerging evidence suggests possible linkages between causes of catatonia and neuroinflammation. These include obvious infectious and inflammatory etiologies, common neuromedical illnesses such as delirium, and psychiatric entities such as depression and autism-spectrum disorders. Symptoms of sickness behavior, thought to be a downstream effect of the cytokine response, are common in many of these etiologies and overlap significantly with symptoms of catatonia. Furthermore, there are syndromes that overlap with catatonia that some would consider variants, including neuroleptic malignant syndrome (NMS) and akinetic mutism, which may also have neuroinflammatory underpinnings. Low serum iron, a common finding in NMS and malignant catatonia, may be caused by the acute phase response. Cellular hits involving either pathogen-associated molecular patterns (PAMP) danger signals or the damage-associated molecular patterns (DAMP) danger signals of severe psychosocial stress may set the stage for a common pathway immunoactivation state that could lower the threshold for a catatonic state in susceptible individuals. Immunoactivation leading to dysfunction in the anterior cingulate cortex (ACC)/mid-cingulate cortex (MCC)/medial prefrontal cortex (mPFC)/paralimbic cortico-striato-thalamo-cortical (CSTC) circuit, involved in motivation and movement, may be particularly important in generating the motor and behavioral symptoms of catatonia.

Brain evolution and the meaning of catatonia - An update

Back in 2004, in a chapter titled "Brain Evolution and the Meaning of Catatonia", a case was made that the syndrome's core meaning is embedded in millions of years of vertebrate brain evolution. (Fricchione, 2004) In this update, advances over the last almost 20 years, in catatonia theory and research in particular, and pertinent neuropsychiatry in general, will be applied to this question of meaning. The approach will rely heavily on a number of thought leaders, including Nicos Tinbergen, Paul MacLean, John Bowlby, M. Marsel Mesulam, Bruce McEwen and Karl Friston. Their guidance will be supplemented with a selected survey of 21sty century neuropsychiatry, neurophysiology, molecular biology, neuroimaging and neurotherapeutics as applied to the catatonic syndrome. In an attempt to address the question of the meaning of the catatonic syndrome in human life, we will employ two conceptual networks representing the intersubjectivity of the quantitative conceptual network of physical terms and the subjectivity of the qualitative conceptual network of mental and spiritual terms. In the process, a common referent providing extensional identity may emerge (Goodman, 1991). The goal of this exercise is to enhance our attunement with the experience of patients suffering with catatonia. A deeper understanding of catatonia's origins in brain evolution and of the challenges of individual epigenetic development in the setting of environmental events coupled with appreciation of what has been described as the most painful mammalian condition, that of separation, has the potential to foster greater efforts on the part of clinicians to diagnose and treat patients who present with catatonia. In addition, in this ancient and extreme tactic, evolved to provide safety from extreme survival threat, one can speculate what is at the core of human fear and the challenge it presents to all of us. And when the biology, psychology and sociology of catatonia are examined, the nature of solutions to the challenge may emerge.

Expanding the function of oligodendrocytes to brain energy metabolism

Oligodendrocytes are best known for wrapping myelin, a unique specialization that enables energy-efficient and fast axonal impulse propagation in white matter tracts and fibers of the cortical circuitry. However, myelinating oligodendrocytes have additional metabolic functions that are only gradually understood, including the regulated release of pyruvate/lactate and extracellular vesicles, both of which are in support of the axonal energy balance. The axon-supportive functions of glial cells are older than myelin in nervous system evolution and implicate oligodendrocyte dysfunction and loss of myelin integrity as a risk factor for progressive neurodegeneration in brain diseases.

Uncovering oligodendrocyte enhancers that control Cnp expression

Oligodendrocytes (OLs) produce myelin sheaths around axons in the central nervous system (CNS). Myelin accelerates the propagation of action potentials along axons and supports the integrity of axons. Impaired myelination has been linked to neurological and neuropsychiatric disorders. As a major component of CNS myelin, 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) plays an indispensable role in the axon-supportive function of myelin. Notably, this function requires a high-level expression of CNP in OLs, as evidenced by downregulated expression of CNP in mental disorders and animal models. Little is known about how CNP expression is regulated in OLs. Especially, OL enhancers that govern CNP remain elusive. We have recently developed a powerful method that links OL enhancers to target genes in a principled manner. Here, we applied it to Cnp, uncovering two OL enhancers for it (termed Cnp-E1 and Cnp-E2). Epigenome editing analysis revealed that Cnp-E1 and Cnp-E2 are dedicated to Cnp. ATAC-seq and ChIP-seq data show that Cnp-E1 and Cnp-E2 are conserved OL-specific enhancers. Single cell multi-omics data that jointly profile gene expression and chromatin accessibility suggest that Cnp-E2 plays an important role in Cnp expression in the early stage of OL differentiation while Cnp-E1 sustains it in mature OLs.

The stability of the myelinating oligodendrocyte transcriptome is regulated by the nuclear lamina

Oligodendrocytes are specialized cells that insulate and support axons with their myelin membrane, allowing proper brain function. Here, we identify lamin A/C (LMNA/C) as essential for transcriptional and functional stability of myelinating oligodendrocytes. We show that LMNA/C levels increase with differentiation of progenitors and that loss of Lmna in differentiated oligodendrocytes profoundly alters their chromatin accessibility and transcriptional signature. Lmna deletion in myelinating glia is compatible with normal developmental myelination. However, altered chromatin accessibility is detected in fully differentiated oligodendrocytes together with increased expression of progenitor genes and decreased levels of lipid-related transcription factors and inner mitochondrial membrane transcripts. These changes are accompanied by altered brain metabolism, lower levels of myelin-related lipids, and altered mitochondrial structure in oligodendrocytes, thereby resulting in myelin thinning and the development of a progressively worsening motor phenotype. Overall, our data identify LMNA/C as essential for maintaining the transcriptional and functional stability of myelinating oligodendrocytes.

Recurrent Catatonia and Demyelinating Disorders

Catatonia, a neuropsychiatric syndrome characterized by psychomotor and behavioral symptoms, can be associated with various underlying conditions, including demyelinating diseases such as multiple sclerosis. This paper presents a case study of a 47-year-old female with recurrent catatonic relapses and an underlying demyelinating disease. The patient exhibited symptoms of confusion, decreased oral intake, and difficulty with movement and speech. Neurological examinations, brain imaging, and laboratory tests were conducted to evaluate the etiology and guide treatment. The patient showed improvement with lorazepam and electroconvulsive therapy (ECT). However, relapses occurred after the abrupt withdrawal of medication. The case study highlights the potential connection between demyelinating diseases and catatonia and emphasizes the importance of considering demyelinating diseases in the workup, treatment, and relapse prevention of catatonia. Further research is needed to explore the mechanisms underlying the relationship between demyelination and catatonia and to investigate how different etiologies may impact the recurrence rates of catatonic episodes.

The basolateral amygdala-anterior cingulate pathway contributes to depression-like behaviors and comorbidity with chronic pain behaviors in male mice

While depression and chronic pain are frequently comorbid, underlying neuronal circuits and their psychopathological relevance remain poorly defined. Here we show in mice that hyperactivity of the neuronal pathway linking the basolateral amygdala to the anterior cingulate cortex is essential for chronic pain-induced depression. Moreover, activation of this pathway in naive male mice, in the absence of on-going pain, is sufficient to trigger depressive-like behaviors, as well as transcriptomic alterations that recapitulate core molecular features of depression in the human brain. These alterations notably impact gene modules related to myelination and the oligodendrocyte lineage. Among these, we show that Sema4a, which was significantly upregulated in both male mice and humans in the context of altered mood, is necessary for the emergence of emotional dysfunction. Overall, these results place the amygdalo-cingulate pathway at the core of pain and depression comorbidity, and unravel the role of Sema4a and impaired myelination in mood control.

Isolated catatonia-like executive dysfunction in mice with forebrain-specific loss of myelin integrity

A key feature of advanced brain aging includes structural defects of intracortical myelin that are associated with secondary neuroinflammation. A similar pathology is seen in specific myelin mutant mice that model 'advanced brain aging' and exhibit a range of behavioral abnormalities. However, the cognitive assessment of these mutants is problematic because myelin-dependent motor-sensory functions are required for quantitative behavioral readouts. To better understand the role of cortical myelin integrity for higher brain functions, we generated mice lacking Plp1, encoding the major integral myelin membrane protein, selectively in ventricular zone stem cells of the mouse forebrain. In contrast to conventional Plp1 null mutants, subtle myelin defects were restricted to the cortex, hippocampus, and underlying callosal tracts. Moreover, forebrain-specific Plp1 mutants exhibited no defects of basic motor-sensory performance at any age tested. Surprisingly, several behavioral alterations reported for conventional Plp1 null mice (Gould et al., 2018) were absent and even social interactions appeared normal. However, with novel behavioral paradigms, we determined catatonia-like symptoms and isolated executive dysfunction in both genders. This suggests that loss of myelin integrity has an impact on cortical connectivity and underlies specific defects of executive function. These observations are likewise relevant for human neuropsychiatric conditions and other myelin-related diseases.

Oligodendroglial macroautophagy is essential for myelin sheath turnover to prevent neurodegeneration and death

Although macroautophagy deficits are implicated across adult-onset neurodegenerative diseases, we understand little about how the discrete, highly evolved cell types of the central nervous system use macroautophagy to maintain homeostasis. One such cell type is the oligodendrocyte, whose myelin sheaths are central for the reliable conduction of action potentials. Using an integrated approach of mouse genetics, live cell imaging, electron microscopy, and biochemistry, we show that mature oligodendrocytes require macroautophagy to degrade cell autonomously their myelin by consolidating cytosolic and transmembrane myelin proteins into an amphisome intermediate prior to degradation. We find that disruption of autophagic myelin turnover leads to changes in myelin sheath structure, ultimately impairing neural function and culminating in an adult-onset progressive motor decline, neurodegeneration, and death. Our model indicates that the continuous and cell-autonomous maintenance of the myelin sheath through macroautophagy is essential, shedding insight into how macroautophagy dysregulation might contribute to neurodegenerative disease pathophysiology.

Oligodendrocytes assemble myelin and support the axons they myelinate. Aber et al. report that oligodendrocytes coordinate autophagy and endocytosis to turn over myelin. The absence of oligodendroglial autophagy causes myelin abnormalities, behavioral dysfunction, glial and neurodegeneration, and death, demonstrating the importance of this process for a healthy CNS.

Molecular and cellular mechanisms leading to catatonia: an integrative approach from clinical and preclinical evidence

This review aims to describe the clinical spectrum of catatonia, in order to carefully assess the involvement of astrocytes, neurons, oligodendrocytes, and microglia, and articulate the available preclinical and clinical evidence to achieve a translational understanding of the cellular and molecular mechanisms behind this disorder. Catatonia is highly common in psychiatric and acutely ill patients, with prevalence ranging from 7.6% to 38%. It is usually present in different psychiatric conditions such as mood and psychotic disorders; it is also a consequence of folate deficiency, autoimmunity, paraneoplastic disorders, and even autistic spectrum disorders. Few therapeutic options are available due to its complexity and poorly understood physiopathology. We briefly revisit the traditional treatments used in catatonia, such as antipsychotics, electroconvulsive therapy, and benzodiazepines, before assessing novel therapeutics which aim to modulate molecular pathways through different mechanisms, including NMDA antagonism and its allosteric modulation, and anti-inflammatory drugs to modulate microglia reaction and mitigate oxidative stress, such as lithium, vitamin B12, and NMDAr positive allosteric modulators.

Activation of liver X receptors protects oligodendrocytes in CA3 of stress-induced mice

Depression is a complex disorder that is associated with various structural abnormalities. Oligodendrocyte (OL) dysfunction is associated with the pathogenesis of depression and the promotion of hippocampal oligodendrocyte maturation and myelination could be a novel therapeutic strategy for ameliorating depressive behaviors. Recent studies have shown that activation of liver X receptors (LXRs) by GW3965 improves depressive phenotypes, but the effects of GW3965 on OL function and myelination in the hippocampus of depression remain relatively unclear. To address this issue, we investigated the effects of GW3965 on mature OL in the hippocampus and on the myelin sheaths of mice subjected to chronic unpredictable stress (CUS). Behavioral tests were performed to assess depressive behaviors. Then, the number of mature OLs (CC1⁺) in each hippocampal subregion was precisely quantified with immunohistochemical and stereological methods, and the density of newborn mature OLs (BrdU⁺/Olig2⁺/CC1⁺ cells) in each hippocampal subregion was quantified with immunofluorescence. In addition, myelin basic protein (MBP) staining intensity in the cornu ammonis 3 (CA3) region was assessed by using immunofluorescence. We found that both the number of CC1⁺ OLs and the density of BrdU⁺/Olig2⁺/CC1⁺ cells were obviously decreased in each hippocampal subregion of mice subjected to CUS, and 4 weeks of GW3965 treatment reversed these effects only in the CA3 region. Furthermore, the decreased MBP expression in the CA3 region of mice subjected to CUS was ameliorated by GW3965 treatment. Collectively, these results suggested that improvement of OL maturation and enhancement of myelination may be structural mechanisms underlying the antidepressant effects of LXR agonists.

Lysosomal storage disease associated with a CNP sequence variant in Dalmatian dogs

A progressive neurological disorder was identified in purebred Dalmatian dogs. The disease is characterized by anxiety, pacing and circling, hypersensitivity, cognitive decline, sleep disturbance, loss of coordination, loss of control over urination and defecation, and visual impairment. Neurological signs first became apparent when the dogs were approximately 18 months of age and progressed slowly. Two affected littermates were euthanized at approximately 7 years, 5 months and 8 years, 2 months of age due to the severity of neurological impairment. The mother of the affected dogs and four other relatives exhibited milder, later-onset neurological signs. Pronounced accumulations of autofluorescent intracellular inclusions were found in cerebral cortex, cerebellum, optic nerve, and cardiac muscle of the affected dogs. These inclusions co-localized with immunolabeling of the lysosomal marker protein LAMP2 and bound antibodies to mitochondrial ATPase subunit c, indicating that the dogs suffered from a lysosomal storage disease with similarities to the neuronal ceroid lipofuscinoses. Ultrastructural analysis indicated that the storage bodies were surrounded by a single-layer membrane, but the storage granules were distinct from those reported for other lysosomal storage diseases. Whole genome sequences, generated with DNA from the two euthanized Dalmatians, both contained a rare, homozygous single-base deletion and reading-frame shift in CNP which encodes the enzyme CNPase (EC 3.1.4.37). The late-onset disease was exhibited by five of seven related Dalmatians that were heterozygous for the deletion allele and over 8 years of age, whereas none of 16 age-matched reference-allele homozygotes developed neurologic signs. No CNPase antigen could be detected with immunohistochemical labeling in tissues from the dogs with the earlier-onset disorder. Similar to the later-onset Dalmatians, autofluorescent storage granules were apparent in brain and cardiac tissue from transgenic mice that were nullizygous for Cnp. Based on the clinical signs, the histopathological, immunohistochemical, ultrastructural, and molecular-genetic findings, and the finding that nullizygous Cnp mice accumulate autofluorescent storage granules, we propose that the earlier-onset Dalmatian disorder is a novel lysosomal storage disease that results from a loss-of-function mutation in CNP and that shares features characteristic of the neuronal ceroid lipofuscinoses. That the later-onset disorder occurred only in dogs heterozygous for the CNP deletion variant suggests that this disorder is a result of the variant allele's presence.

Unraveling the mystery of white matter in depression: A translational perspective on recent advances

BACKGROUND

Numerous cortical and subcortical structures have been studied extensively concerning alterations of their integrity as well as their neurotransmitters in depression. However, connections between these structures have received considerably less attention.

OBJECTIVE

This systematic review presents results from recent neuroimaging as well as neuropathologic studies conducted on humans and other mammals. It aims to provide evidence for impaired white matter integrity in individuals expressing a depressive phenotype.

METHODS

A systematic database search in accordance with the PRISMA guidelines was conducted to identify imaging and postmortem studies conducted on humans with a diagnosis of major depressive disorder, as well as on rodents and primates subjected to an animal model of depression.

RESULTS

Alterations are especially apparent in frontal gyri, as well as in structures establishing interhemispheric connectivity between frontal regions. Translational neuropathological findings point to alterations in oligodendrocyte density and morphology, as well as to alterations in the expression of genes related to myelin synthesis. An important role of early life adversities in the development of depressive symptoms and white matter alterations across species is thereby revealed. Data indicating that stress can interfere with physiological myelination patterns is presented. Altered myelination is most notably present in regions that are subject to maturation during the developmental stage of exposure to adversities.

CONCLUSION

Translational studies point to replicable alterations in white matter integrity in subjects suffering from depression across multiple species. Impaired white matter integrity is apparent in imaging as well as neuropathological studies. Future studies should focus on determining to what extent influencing white matter integrity is able to improve symptoms of depression in animals as well as humans.

Ermin deficiency leads to compromised myelin, inflammatory milieu, and susceptibility to demyelinating insult

Ermin is an actin-binding protein found almost exclusively in the central nervous system (CNS) as a component of myelin sheaths. Although Ermin has been predicted to play a role in the formation and stability of myelin sheaths, this has not been directly examined in vivo. Here, we show that Ermin is essential for myelin sheath integrity and normal saltatory conduction. Loss of Ermin in mice caused de-compacted and fragmented myelin sheaths and led to slower conduction along with progressive neurological deficits. RNA sequencing of the corpus callosum, the largest white matter structure in the CNS, pointed to inflammatory activation in aged Ermin-deficient mice, which was corroborated by increased levels of microgliosis and astrogliosis. The inflammatory milieu and myelin abnormalities were further associated with increased susceptibility to immune-mediated demyelination insult in Ermin knockout mice. Supporting a possible role of Ermin deficiency in inflammatory white matter disorders, a rare inactivating mutation in the ERMN gene was identified in multiple sclerosis patients. Our findings demonstrate a critical role for Ermin in maintaining myelin integrity. Given its near-exclusive expression in myelinating oligodendrocytes, Ermin deficiency represents a compelling "inside-out" model of inflammatory dysmyelination and may offer a new paradigm for the development of myelin stability-targeted therapies.

Progressive axonopathy when oligodendrocytes lack the myelin protein CMTM5

Oligodendrocytes facilitate rapid impulse propagation along the axons they myelinate and support their long-term integrity. However, the functional relevance of many myelin proteins has remained unknown. Here, we find that expression of the tetraspan-transmembrane protein CMTM5 (chemokine-like factor-like MARVEL-transmembrane domain containing protein 5) is highly enriched in oligodendrocytes and central nervous system (CNS) myelin. Genetic disruption of the Cmtm5 gene in oligodendrocytes of mice does not impair the development or ultrastructure of CNS myelin. However, oligodendroglial Cmtm5 deficiency causes an early-onset progressive axonopathy, which we also observe in global and tamoxifen-induced oligodendroglial Cmtm5 mutants. Presence of the Wld^S mutation ameliorates the axonopathy, implying a Wallerian degeneration-like pathomechanism. These results indicate that CMTM5 is involved in the function of oligodendrocytes to maintain axonal integrity rather than myelin biogenesis.

NMDAR1 autoantibodies amplify behavioral phenotypes of genetic white matter inflammation: a mild encephalitis model with neuropsychiatric relevance

Encephalitis has an estimated prevalence of ≤0.01%. Even with extensive diagnostic work-up, an infectious etiology is identified or suspected in <50% of cases, suggesting a role for etiologically unclear, noninfectious processes. Mild encephalitis runs frequently unnoticed, despite slight neuroinflammation detectable postmortem in many neuropsychiatric illnesses. A widely unexplored field in humans, though clearly documented in rodents, is genetic brain inflammation, particularly that associated with myelin abnormalities, inducing primary white matter encephalitis. We hypothesized that "autoimmune encephalitides" may result from any brain inflammation concurring with the presence of brain antigen-directed autoantibodies, e.g., against N-methyl-D-aspartate-receptor NR1 (NMDAR1-AB), which are not causal of, but may considerably shape the encephalitis phenotype. We therefore immunized young female Cnp^-/- mice lacking the structural myelin protein 2'-3'-cyclic nucleotide 3'-phosphodiesterase (Cnp) with a "cocktail" of NMDAR1 peptides. Cnp^-/- mice exhibit early low-grade inflammation of white matter tracts and blood-brain barrier disruption. Our novel mental-time-travel test disclosed that Cnp^-/- mice are compromised in what-where-when orientation, but this episodic memory readout was not further deteriorated by NMDAR1-AB. In contrast, comparing wild-type and Cnp^-/- mice without/with NMDAR1-AB regarding hippocampal learning/memory and motor balance/coordination revealed distinct stair patterns of behavioral pathology. To elucidate a potential contribution of oligodendroglial NMDAR downregulation to NMDAR1-AB effects, we generated conditional NR1 knockout mice. These mice displayed normal Morris water maze and mental-time-travel, but beam balance performance was similar to immunized Cnp^-/-. Immunohistochemistry confirmed neuroinflammation/neurodegeneration in Cnp^-/- mice, yet without add-on effect of NMDAR1-AB. To conclude, genetic brain inflammation may explain an encephalitic component underlying autoimmune conditions.

A systematic review of the prognostic value of motor abnormalities on clinical outcome in psychosis

Schizophrenia spectrum disorders have heterogeneous outcomes and currently no marker predicts the course of illness. Motor abnormalities (MAs) are inherent to psychosis, the risk of psychosis, symptom severity, and brain alterations. However, the prognostic value of MAs is still unresolved. Here, we provide a systematic review of longitudinal studies on the prognostic role of MAs spanning individuals at clinical high risk for psychosis (CHR), patients with first-episode psychosis (FEP), and chronic schizophrenia. We included 68 studies for a total of 23,630 subjects that assessed neurological soft signs (NSS), hypo- or hyperkinetic movement disorders and/or catatonia as a prognostic factor on clinical and functional outcomes. We found increased levels of MAs, in particular NSS, parkinsonism, and dyskinesia, were related to deteriorating symptomatic and poor functional outcome over time. Collectively, the findings emphasize the clinical, prognostic and scientific relevance of MA assessment and detection in individuals with or at risk of psychosis. In the future, instrumental measures of MA are expected to further augment detection, early intervention and treatment strategies in psychosis.

Catatonia: Clinical Overview of the Diagnosis, Treatment, and Clinical Challenges

Catatonia is a syndrome that has been associated with several mental illness disorders but that has also presented as a result of other medical conditions. Schizophrenia and other psychiatric disorders such as mania and depression are known to be associated with catatonia; however, several case reports have been published of certain medical conditions inducing catatonia, including hyponatremia, cerebral venous sinus thrombosis, and liver transplantation. Neuroleptic Malignant Syndrome and anti-NMDA receptor encephalitis are also prominent causes of catatonia. Patients taking benzodiazepines or clozapine are also at risk of developing catatonia following the withdrawal of these medications—it is speculated that the prolonged use of these medications increases gamma-aminobutyric acid (GABA) activity and that discontinuation may increase excitatory neurotransmission, leading to catatonia. The treatment of catatonia often involves the use of benzodiazepines, such as lorazepam, that can be used in combination therapy with antipsychotics. Definitive treatment may be found with electroconvulsive therapy (ECT). Aberrant neuronal activity in different motor pathways, defective neurotransmitter regulation, and impaired oligodendrocyte function have all been proposed as the pathophysiology behind catatonia. There are many clinical challenges that come with catatonia and, as early treatment is associated with better outcomes, it becomes imperative to understand these challenges. The purpose of this manuscript is to provide an overview of these challenges and to look at clinical studies regarding the pathophysiology, diagnosis, and treatment of as well as the complications and risk factors associated with catatonia.

Residential surrounding greenness and DNA methylation: An epigenome-wide association study

BACKGROUND

DNA methylation is a potential biological mechanism through which residential greenness affects health, but little is known about its association with greenness and whether the association could be modified by genetic background. We aimed to evaluate the association between surrounding greenness and genome-wide DNA methylation and potential gene-greenness interaction effects on DNA methylation.

METHODS

We measured blood-derived DNA methylation using the HumanMethylation450 BeadChip array (Illumina) for 479 Australian women, including 66 monozygotic, 66 dizygotic twin pairs, and 215 sisters of these twins. Surrounding greenness was represented by Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) within 300, 500, 1000 or 2000 m surrounding participants' home addresses. For each cytosine-guanine dinucleotide (CpG), the associations between its methylation level and NDVI or EVI were evaluated by generalized estimating equations, after adjusting for age, education, marital status, area-level socioeconomic status, smoking behavior, cell-type proportions, and familial clustering. We used comb-p and DMRcate to identify significant differentially methylated regions (DMRs). For each significant CpG, we evaluated the interaction effects of greenness and single-nucleotide polymorphisms (SNPs) within ±1 Mb window on its methylation level.

RESULTS

We found associations between surrounding greenness and blood DNA methylation for one CpG (cg04720477, mapped to the promoter region of CNP gene) with false discovery rate [FDR] < 0.05, and for another 9 CpGs with 0.05 ≤ FDR < 0.10. For two of these CpGs, we found 33 SNPs significantly (FDR < 0.05) modified the greenness-methylation association. There were 35 significant DMRs related to surrounding greenness that were identified by both comb-p (Sidak p-value < 0.01) and DMRcate (FDR < 0.01). Those CpGs and DMRs were mapped to genes related to many human diseases, such as mental health disorders and neoplasms as well as nutritional and metabolic diseases.

CONCLUSIONS

Surrounding greenness was associated with blood DNA methylation of many loci across human genome, and this association could be modified by genetic variations.

Inducing sterile pyramidal neuronal death in mice to model distinct aspects of gray matter encephalitis

Up to one person in a population of 10,000 is diagnosed once in lifetime with an encephalitis, in 50-70% of unknown origin. Recognized causes amount to 20-50% viral infections. Approximately one third of affected subjects develops moderate and severe subsequent damage. Several neurotropic viruses can directly infect pyramidal neurons and induce neuronal death in cortex and hippocampus. The resulting encephalitic syndromes are frequently associated with cognitive deterioration and dementia, but involve numerous parallel and downstream cellular and molecular events that make the interpretation of direct consequences of sudden pyramidal neuronal loss difficult. This, however, would be pivotal for understanding how neuroinflammatory processes initiate the development of neurodegeneration, and thus for targeted prophylactic and therapeutic interventions. Here we utilized adult male NexCreERT2xRosa26-eGFP-DTA (= 'DTA') mice for the induction of a sterile encephalitis by diphtheria toxin-mediated ablation of cortical and hippocampal pyramidal neurons which also recruits immune cells into gray matter. We report multifaceted aftereffects of this defined process, including the expected pathology of classical hippocampal behaviors, evaluated in Morris water maze, but also of (pre)frontal circuit function, assessed by prepulse inhibition. Importantly, we modelled in encephalitis mice novel translationally relevant sequelae, namely altered social interaction/cognition, accompanied by compromised thermoreaction to social stimuli as convenient readout of parallel autonomic nervous system (dys)function. High resolution magnetic resonance imaging disclosed distinct abnormalities in brain dimensions, including cortical and hippocampal layering, as well as of cerebral blood flow and volume. Fluorescent tracer injection, immunohistochemistry and brain flow cytometry revealed persistent blood-brain-barrier perturbance and chronic brain inflammation. Surprisingly, blood flow cytometry showed no abnormalities in circulating major immune cell subsets and plasma high-mobility group box 1 (HMGB1) as proinflammatory marker remained unchanged. The present experimental work, analyzing multidimensional outcomes of direct pyramidal neuronal loss, will open new avenues for urgently needed encephalitis research.

Potential neuron-autonomous Purkinje cell degeneration by 2',3'-cyclic nucleotide 3'-phosphodiesterase promoter/Cre-mediated autophagy impairments

Studies of neuroglial interaction largely depend on cell-specific gene knockout (KO) experiments using Cre recombinase. However, genes known as glial-specific genes have recently been reported to be expressed in neuroglial stem cells, leading to the possibility that a glia-specific Cre driver results in unwanted gene deletion in neurons, which may affect sound interpretation. 2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) is generally considered to be an oligodendrocyte (OL) marker. Accordingly, Cnp promoter-controlled Cre recombinase has been used to create OL-specific gene targeting mice. However, in this study, using Rosa26-tdTomato-reporter/Cnp-Cre mice, we found that many forebrain neurons and cerebellar Purkinje neurons belong to the lineages of Cnp-expressing neuroglial stem cells. To answer whether gene targeting by Cnp-Cre can induce neuron-autonomous defects, we conditionally deleted an essential autophagy gene, Atg7, in Cnp-Cre mice. The Cnp-Cre-mediated Atg7 KO mice showed extensive p62 inclusion in neurons, including cerebellar Purkinje neurons with extensive neurodegeneration. Furthermore, neuronal areas showing p62 inclusion in Cnp-Cre-mediated Atg7 KO mice overlapped with the neuronal lineage of Cnp-expressing neuroglial stem cells. Moreover, Cnp-Cre-mediated Atg7-KO mice did not develop critical defects in myelination. Our results demonstrate that a large population of central neurons are derived from Cnp-expressing neuroglial stem cells; thus, conditional gene targeting using the Cnp promoter, which is known to be OL-specific, can induce neuron-autonomous phenotypes.

Protective Effects of Oroxylin A on Retinal Ganglion Cells in Experimental Model of Anterior Ischemic Optic Neuropathy

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common cause of acute vision loss in older people, and there is no effective therapy. The effect of the systemic or local application of steroids for NAION patients remains controversial. Oroxylin A (OA) (5,7-dihydroxy-6-methoxyflavone) is a bioactive flavonoid extracted from Scutellariae baicalensis Georgi. with various beneficial effects, including anti-inflammatory and neuroprotective effects. A previous study showed that OA promotes retinal ganglion cell (RGC) survival after optic nerve (ON) crush injury. The purpose of this research was to further explore the potential actions of OA in ischemic injury in an experimental anterior ischemic optic neuropathy (rAION) rat model induced by photothrombosis. Our results show that OA efficiently attenuated ischemic injury in rats by reducing optic disc edema, the apoptotic death of retinal ganglion cells, and the infiltration of inflammatory cells. Moreover, OA significantly ameliorated the pathologic changes of demyelination, modulated microglial polarization, and preserved visual function after rAION induction. OA activated nuclear factor E2 related factor (Nrf2) signaling and its downstream antioxidant enzymes NAD(P)H:quinone oxidoreductase (NQO-1) and heme oxygenase 1 (HO-1) in the retina. We demonstrated that OA activates Nrf2 signaling, protecting retinal ganglion cells from ischemic injury, in the rAION model and could potentially be used as a therapeutic approach in ischemic optic neuropathy.

Should Catatonia Be Conceptualized as a Pathological Response to Trauma?

ABSTRACT

Although catatonia is related to several medical conditions, catatonia as a response to trauma and posttraumatic stress disorder (PTSD) is less clear. The aim of this review is to explore the small emerging body of preliminary evidence that suggests a possible correlation between psychological trauma and catatonia. Initial data suggests a correlation between episodes of intense fear associated with trauma and PTSD and some forms of catatonic responses. Although this relationship is still speculative to be causative, it can have important implications if confirmed. This is especially salient when it is examined alongside existing studies of the response to fear in animals and the phenomenon of tonic immobility, which bears a striking resemblance to catatonia in humans. If prospective studies further support the initial findings, it could change our conceptual understanding of the etiology of a subtype of catatonia substantially while pointing to likely targets of further research to understand the biological mechanisms that underlie the illness.

Many roles for oligodendrocyte precursor cells in physiology and pathology

Oligodendrocyte precursor cells (OPCs) are a fourth resident glial cell population in the mammalian central nervous system. They are evenly distributed throughout the gray and white matter and continue to proliferate and generate new oligodendrocytes (OLs) throughout life. They were understudied until a few decades ago when immunolabeling for NG2 and platelet-derived growth factor receptor alpha revealed cells that are distinct from mature OLs, astrocytes, neurons, and microglia. In this review, we provide a summary of the known properties of OPCs with some historical background, followed by highlights from recent studies that suggest new roles for OPCs in certain pathological conditions.

Activated microglia drive demyelination via CSF1R signaling

Microgliosis is a prominent pathological feature in many neurological diseases including multiple sclerosis (MS), a progressive auto-immune demyelinating disorder. The precise role of microglia, parenchymal central nervous system (CNS) macrophages, during demyelination, and the relative contributions of peripheral macrophages are incompletely understood. Classical markers used to identify microglia do not reliably discriminate between microglia and peripheral macrophages, confounding analyses. Here, we use a genetic fate mapping strategy to identify microglia as predominant responders and key effectors of demyelination in the cuprizone (CUP) model. Colony-stimulating factor 1 (CSF1), also known as macrophage colony-stimulating factor (M-CSF) - a secreted cytokine that regulates microglia development and survival-is upregulated in demyelinated white matter lesions. Depletion of microglia with the CSF1R inhibitor PLX3397 greatly abrogates the demyelination, loss of oligodendrocytes, and reactive astrocytosis that results from CUP treatment. Electron microscopy (EM) and serial block face imaging show myelin sheaths remain intact in CUP treated mice depleted of microglia. However, these CUP-damaged myelin sheaths are lost and robustly phagocytosed upon-repopulation of microglia. Direct injection of CSF1 into CNS white matter induces focal microgliosis and demyelination indicating active CSF1 signaling can promote demyelination. Finally, mice defective in adopting a toxic astrocyte phenotype that is driven by microglia nevertheless demyelinate normally upon CUP treatment implicating microglia rather than astrocytes as the primary drivers of CUP-mediated demyelination. Together, these studies indicate activated microglia are required for and can drive demyelination directly and implicate CSF1 signaling in these events.

Oligodendrocyte lineage cells and depression

Depression is a common mental illness, affecting more than 300 million people worldwide. Decades of investigation have yielded symptomatic therapies for this disabling condition but have not led to a consensus about its pathogenesis. There are data to support several different theories of causation, including the monoamine hypothesis, hypothalamic-pituitary-adrenal axis changes, inflammation and immune system alterations, abnormalities of neurogenesis and a conducive environmental milieu. Research in these areas and others has greatly advanced the current understanding of depression; however, there are other, less widely known theories of pathogenesis. Oligodendrocyte lineage cells, including oligodendrocyte progenitor cells and mature oligodendrocytes, have numerous important functions, which include forming myelin sheaths that enwrap central nervous system axons, supporting axons metabolically, and mediating certain forms of neuroplasticity. These specialized glial cells have been implicated in psychiatric disorders such as depression. In this review, we summarize recent findings that shed light on how oligodendrocyte lineage cells might participate in the pathogenesis of depression, and we discuss new approaches for targeting these cells as a novel strategy to treat depression.

Molecular and neurocircuitry mechanisms of social avoidance

Humans and animals live in social relationships shaped by actions of approach and avoidance. Both are crucial for normal physical and mental development, survival, and well-being. Active withdrawal from social interaction is often induced by the perception of threat or unpleasant social experience and relies on adaptive mechanisms within neuronal networks associated with social behavior. In case of confrontation with overly strong or persistent stressors and/or dispositions of the affected individual, maladaptive processes in the neuronal circuitries and its associated transmitters and modulators lead to pathological social avoidance. This review focuses on active, fear-driven social avoidance, affected circuits within the mesocorticolimbic system and associated regions and a selection of molecular modulators that promise translational potential. A comprehensive review of human research in this field is followed by a reflection on animal studies that offer a broader and often more detailed range of analytical methodologies. Finally, we take a critical look at challenges that could be addressed in future translational research on fear-driven social avoidance.

Fear Deficits in Hypomyelinated Tppp Knock-Out Mice

Oligodendrocytes in the central nervous system (CNS) produce myelin sheaths that insulate axons to facilitate efficient electrical conduction. These myelin sheaths contain lamellar microtubules that enable vesicular transport into the inner sheath. Mechanistically, oligodendrocytes rely on Golgi outpost organelles and the associated protein tubulin polymerization promoting protein (TPPP) to nucleate or form new microtubules outside of the cell body. Consequently, elongation of lamellar microtubules is defective in Tppp knock-out (KO) mice, which have thinner and shorter myelin sheaths. We now explore the behavioral phenotypes of Tppp KO mice using a number of different assays. In open-field assays, Tppp KO mice display similar activity levels and movement patterns as wild-type mice, indicating that they do not display anxiety behavior. However, Tppp KO mice lack fear responses by two types of assays, traditional fear-conditioning assays and looming fear assays, which test for innate fear responses. Deficits in fear conditioning, which is a memory-dependent task, as well as in spatial memory tests, support possible short-term memory defects in Tppp KO mice. Together, our experiments indicate a connection between CNS myelination and behavioral deficits.

Higher Serum C-Reactive Protein Levels in Catatonic Patients: A Comparison to Non-catatonic Patients and Healthy Controls

Catatonia is a psychomotor syndrome defined by a constellation of predominantly motor symptoms. The aim of the present study was to determine whether recently admitted psychiatric patients with catatonia exhibited higher serum C-reactive protein (hs-CRP) levels compared to non-catatonic psychiatric patients and healthy controls (HCs). Recently admitted psychiatric patients were screened and evaluated for the catatonia syndrome using the Bush-Francis Catatonia Rating Scale and the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). The study sample was formed by 150 individuals (39 male and 111 female), including 51 catatonic patients, 55 non-catatonic patients, and 44 HCs. Serum hs-CRP levels were processed with the enzyme-linked immunosorbent assay. Serum levels of creatine kinase (CK), adrenocorticotropic hormone (ACTH), immunoglobulin G (IgG), complement component 3 (C3), and complement component 4 (C4) were also determined. There was a significantly higher percentage of patients with high inflammatory levels (hs-CRP > 3000ng/ml) in the catatonic (43.1%) than in the non-catatonic (14.5%) or HCs group (9.1%) (χ 2 =18.9, P < .001). Logistic regression showed that catatonic patients had significantly higher hs-CRP levels compared to non-catatonic patients even after controlling for other clinical and laboratory variables (OR = 3.52, P = .015, 95% CI 1.28-9.79). Multiple linear regression analysis revealed that log-transformed hs-CRP was independently predicted by body mass index and log-transformed C4, ACTH, and Cortisol in catatonic patients. Findings of the present study suggest that catatonia is specifically linked to a higher level of systemic inflammation, not merely attributable to the overall psychopathology, or alterations in the stress level and complement system.

Multiparametric mapping of white matter microstructure in catatonia

Catatonia is characterized by motor, affective and behavioral abnormalities. To date, the specific role of white matter (WM) abnormalities in schizophrenia spectrum disorders (SSD) patients with catatonia is largely unknown. In this study, diffusion magnetic resonance imaging (dMRI) data were collected from 111 right-handed SSD patients and 28 healthy controls. Catatonic symptoms were examined on the Northoff Catatonia Rating Scale (NCRS). We used whole-brain tract-based spatial statistics (TBSS), tractometry (along tract statistics using TractSeg) and graph analytics (clustering coefficient-CCO, local betweenness centrality-BC) to provide a framework of specific WM microstructural abnormalities underlying catatonia in SSD. Following a categorical approach, post hoc analyses showed differences in fractional anisotrophy (FA) measured via tractometry in the corpus callosum, corticospinal tract and thalamo-premotor tract as well as increased CCO as derived by graph analytics of the right superior parietal cortex (SPC) and left caudate nucleus in catatonic patients (NCRS total score ≥ 3; n = 30) when compared to non-catatonic patients (NCRS total score = 0; n = 29). In catatonic patients according to DSM-IV-TR (n = 43), catatonic symptoms were associated with FA variations (tractometry) of the left corticospinal tract and CCO of the left orbitofrontal cortex, primary motor cortex, supplementary motor area and putamen. This study supports the notion that structural reorganization of WM bundles connecting orbitofrontal/parietal, thalamic and striatal regions contribute to catatonia in SSD patients.

Altered diffusion in motor white matter tracts in psychosis patients with catatonia

Catatonia is a complex psychomotor symptom frequently observed in schizophrenia. Neural activity within the motor system is altered in catatonia. Likewise, white matter (WM) is also expected to be abnormal. The aim of this study was to test, if schizophrenia patients with catatonia show specific WM alterations. Forty-eight patients with schizophrenia and 43 healthy controls were included. Catatonia was currently present in 13 patients with schizophrenia. Tract-Based Spatial Statistics was used to test for differences in fractional anisotropy (FA) in the whole brain between the three groups. We detected a group effect (F-test) of WM within the corpus callosum (CC). In the t-test, patients with catatonia showed higher FA in many left lateralized WM clusters involved in motor behaviour compared to patients without catatonia, including the CC, internal and external capsule, superior longitudinal fascicle (SLF) and corticospinal tract (CST). Similarly, patients with catatonia showed also higher FA in the left internal capsule and left CST compared to healthy controls. In contrast, the group comparison between patients without catatonia and healthy controls revealed lower FA in many right lateralized clusters, comprising the CC, internal capsule, SLF, and inferior longitudinal fascicle in patients without catatonia. Our results are in line with the notion of an altered motor system in catatonia. Thus, our study provides evidence for increased WM connectivity, especially in motor tracts in schizophrenia patients with catatonia.

The effects of fluoxetine on oligodendrocytes in the hippocampus of chronic unpredictable stress-induced depressed model rats

Depression is a mental illness which is harmful seriously to the society. This study investigated the effects of fluoxetine on the CNPase⁺ oligodendrocytes in hippocampus of the depressed rats to explore the new target structure of antidepressants. Male Sprague-Dawley rats were used to build chronic unpredictable stress (CUS) depressed model of rats. Then, the depressed rats were divided into the CUS standard group and the CUS + fluoxetine (CUS/FLX) group. The CUS/FLX group was treated with fluoxetine at dose of 5 mg/(kg·d) from the fifth week to seventh week. After 7 weeks CUS intervention, the sucrose preference of the CUS standard group was significantly lower than that of the control group and the CUS/FLX group. The stereological results showed that the total number of the CNPase⁺ cells in the CA1, CA3, and DG subfield of the hippocampus in the CUS standard group were significantly decreased, when compared with the CNPase⁺ cells in the control group. However, the total number of the CNPase⁺ cells in the CA1 and CA3 subfield of the hippocampus in the CUS standard group was significantly decreased when it compared with CNPase⁺ cells in the CUS/FLX group. Therefore, fluoxetine might prevent the loss of CNPase⁺ oligodendrocytes in CA1 and CA3 subfields of hippocampus of the depressed rats. The oligodendrocytes in hippocampus may play an important role in the pathogenesis of depression. The current result might provide structural basis for the future studies that search for new antidepressant strategies.

Going Back to Kahlbaum's Psychomotor (and GABAergic) Origins: Is Catatonia More Than Just a Motor and Dopaminergic Syndrome?

In 1874, Karl Kahlbaum described catatonia as an independent syndrome characterized by motor, affective, and behavioral anomalies. In the following years, various catatonia concepts were established with all sharing the prime focus on motor and behavioral symptoms while largely neglecting affective changes. In 21st century, catatonia is a well-characterized clinical syndrome. Yet, its neurobiological origin is still not clear because methodological shortcomings of hitherto studies had hampered this challenging effort. To fully capture the clinical picture of catatonia as emphasized by Karl Kahlbaum, 2 decades ago a new catatonia scale was developed (Northoff Catatonia Rating Scale [NCRS]). Since then, studies have used NCRS to allow for a more mechanistic insight of catatonia. Here, we undertook a systematic review searching for neuroimaging studies using motor/behavioral catatonia rating scales/criteria and NCRS published up to March 31, 2019. We included 19 neuroimaging studies. Studies using motor/behavioral catatonia rating scales/criteria depict cortical and subcortical motor regions mediated by dopamine as neuronal and biochemical substrates of catatonia. In contrast, studies relying on NCRS found rather aberrant higher-order frontoparietal networks which, biochemically, are insufficiently modulated by gamma-aminobutyric acid (GABA)-ergic and glutamatergic transmission. This is further supported by the high therapeutic efficacy of GABAergic agents in acute catatonia. In sum, this systematic review points out the difference between motor/behavioral and NCRS-based classification of catatonia on both neuronal and biochemical grounds. That highlights the importance of Kahlbaum's original truly psychomotor concept of catatonia for guiding both research and clinical diagnosis and therapy.

Cingulate-basal ganglia-thalamo-cortical aspects of catatonia and implications for treatment

The catatonic syndrome is an example of a multifactorial neurobehavioral disorder that causes much morbidity and mortality but also has the potential to unlock the mystery of how motivation and movement interact to produce behavior. In this chapter, an attempt is made to understand better the catatonic syndrome through the lens of neurobiology and neuropathophysiology updated by recent studies in molecular biology, genomics, inflammasomics, neuroimaging, neural network theory, and neuropsychopathology. This will result in a neurostructural model for the catatonic syndrome that centers on paralimbic regions including the anterior and midcingulate cortices, as they interface with striatal and thalamic nodes in the salience decision-making network. Examination of neurologic disorders like the abulic syndrome, which includes in its extreme catatonic form, akinetic mutism, will identify the cingulate cortex and paralimbic neighbors as regions of interest. This exploration has the potential to unlock mysteries of the brain cascade from motivation to movement and to clarify catatonia therapeutics. Such a synthesis may also help us discern meaning inherent in this complex neurobehavioral syndrome.

Structure and neural mechanisms of catatonia

Catatonia is a psychomotor syndrome associated with several psychiatric and medical conditions. Psychomotor signs range from stupor to agitation, and include pathognomonic features such as verbigeration and waxy flexibility. Disturbances of volition led to the classification of catatonia as a subtype of schizophrenia, but changes in nosology now recognise the high prevalence in mood disorders, overlap with delirium, and comorbidity with medical conditions. Initial psychometric studies have revealed three behavioural factors, but the structure of catatonia is still unknown. Evidence from brain imaging studies of patients with psychotic disorders indicates increased neural activity in premotor areas in patients with hypokinetic catatonia. However, whether this localised hyperactivity is due to corticocortical inhibition or excess activity of inhibitory corticobasal ganglia loops is unclear. Current treatment of catatonia relies on benzodiazepines and electroconvulsive therapy-both effective, yet unspecific in their modes of action. Longitudinal research and treatment studies, with neuroimaging and brain stimulation techniques, are needed to advance our understanding of catatonia.

Catatonia and the immune system: a review

Catatonia is a psychomotor disorder featuring stupor, posturing, and echophenomena. This Series paper examines the evidence for immune dysregulation in catatonia. Activation of the innate immune system is associated with mutism, withdrawal, and psychomotor retardation, which constitute the neurovegetative features of catatonia. Evidence is sparse and conflicting for acute-phase activation in catatonia, and whether this feature is secondary to immobility is unclear. Various viral, bacterial, and parasitic infections have been associated with catatonia, but it is primarily linked to CNS infections. The most common cause of autoimmune catatonia is N-methyl-D-aspartate receptor (NMDAR) encephalitis, which can account for the full spectrum of catatonic features. Autoimmunity appears to cause catatonia less by systemic inflammation than by the downstream effects of specific actions on extracellular antigens. The specific association with NMDAR encephalitis supports a hypothesis of glutamatergic hypofunction in catatonia.

Genetically induced brain inflammation by Cnp deletion transiently benefits from microglia depletion

Reduced expression of 2'-3'-cyclic nucleotide 3'-phosphodiesterase (Cnp) in humans and mice causes white matter inflammation and catatonic signs. These consequences are experimentally alleviated by microglia ablation via colony-stimulating factor 1 receptor (CSF1R) inhibition using PLX5622. Here we address for the first time preclinical topics crucial for translation, most importantly 1) the comparison of 2 long-term PLX5622 applications (prevention and treatment) vs. 1 treatment alone, 2) the correlation of catatonic signs and executive dysfunction, 3) the phenotype of leftover microglia evading depletion, and 4) the role of intercellular interactions for efficient CSF1R inhibition. Based on our Cnp^-/- mouse model and in vitro time-lapse imaging, we report the unexpected discovery that microglia surviving under PLX5622 display a highly inflammatory phenotype including aggressive premortal phagocytosis of oligodendrocyte precursor cells. Interestingly, ablating microglia in vitro requires mixed glial cultures, whereas cultured pure microglia withstand PLX5622 application. Importantly, 2 extended rounds of CSF1R inhibition are not superior to 1 treatment regarding any readout investigated (magnetic resonance imaging and magnetic resonance spectroscopy, behavior, immunohistochemistry). Catatonia-related executive dysfunction and brain atrophy of Cnp^-/- mice fail to improve under PLX5622. To conclude, even though microglia depletion is temporarily beneficial and worth pursuing, complementary treatment strategies are needed for full and lasting recovery.-Fernandez Garcia-Agudo, L., Janova, H., Sendler, L. E., Arinrad, S., Steixner, A. A., Hassouna, I., Balmuth, E., Ronnenberg, A., Schopf, N., van der Flier, F. J., Begemann, M., Martens, H., Weber, M. S., Boretius, S., Nave, K.-A., Ehrenreich, H. Genetically induced brain inflammation by Cnp deletion transiently benefits from microglia depletion.

Wallerian degeneration in experimental focal cortical ischemia

Wallerian degeneration (WaD), commonly secondary to cerebral infarction, is the descending damage of fiber tracts with their accompanying myelin sheaths. However, whether this sequential injury can occur in non-ischemic corpus callosum (CC) and striatum in focal cortical ischemic model has not been fully demonstrated. The present study aimed to elucidate detailed histopathologic changes in CC and striatum after acute focal cortical infarction induced by permanent distal middle cerebral artery occlusion (dMCAO) in Sprague-Dawley rat. We found that myelin integrity, myelin-related proteins, MBP and MAG, and NF200-marked neurofilaments were all compromised in non-ischemic white matter regions, bilateral CC and ipsilateral striatum, along with cortical ischemia (all P < 0.05). Electron microscopy showed wide gaps between myelin sheath layers or between axon and myelin, with an abnormal folding of myelin sheath, and enlarged fluid-filled areas. APP accumulations were noted at 24 h post-dMCAO in those non-ischemic regions, and the deposition prolonged until 14 days after cortical ischemia (all P < 0.05). Moreover, in these areas, microglia and astrocytes were robustly and persistently activated in different patterns. No substantial changes were observed in contralateral striatum. In conclusion, our results suggest that WaD may be involved in non-ischemic CC and striatum after focal cortical infarction, accompanied by APP aggregation and neuroglia initiation forming the glial scar.

Conditional Mutagenesis in Oligodendrocyte Lineage Cells

Cell-type-specific gene targeting with the Cre/loxP system has become an indispensable technique in experimental neuroscience, particularly for the study of late-born glial cells that make myelin. A plethora of conditional mutants and Cre-expressing mouse lines is now available to the research community that allows laboratories to readily engage in in vivo analyses of oligodendrocytes and their precursor cells. This chapter summarizes concepts and strategies in targeting myelinating glial cells in mice for mutagenesis or imaging, and provides an overview of the most important Cre driver lines successfully used in this rapidly growing field.