Kinase signalling in excitatory neurons regulates sleep quantity and depth.

Progress has been made in the elucidation of sleep and wakefulness regulation at the neurocircuit level1,2. However, the intracellular signalling pathways that regulate sleep and the neuron groups in which these intracellular mechanisms work remain largely unknown. Here, using a forward genetics approach in mice, we identify histone deacetylase 4 (HDAC4) as a sleep-regulating molecule. Haploinsufficiency of Hdac4, a substrate of salt-inducible kinase 3 (SIK3)3, increased sleep. By contrast, mice that lacked SIK3 or its upstream kinase LKB1 in neurons or with a Hdac4S245A mutation that confers resistance to phosphorylation by SIK3 showed decreased sleep. These findings indicate that LKB1-SIK3-HDAC4 constitute a signalling cascade that regulates sleep and wakefulness. We also performed targeted manipulation of SIK3 and HDAC4 in specific neurons and brain regions. This showed that SIK3 signalling in excitatory neurons located in the cerebral cortex and the hypothalamus positively regulates EEG delta power during non-rapid eye movement sleep (NREMS) and NREMS amount, respectively. A subset of transcripts biased towards synaptic functions was commonly regulated in cortical glutamatergic neurons through the expression of a gain-of-function allele of Sik3 and through sleep deprivation. These findings suggest that NREMS quantity and depth are regulated by distinct groups of excitatory neurons through common intracellular signals. This study provides a basis for linking intracellular events and circuit-level mechanisms that control NREMS.

Enhancement of Haloperidol-Induced Catalepsy by GPR143, an L-Dopa Receptor, in Striatal Cholinergic Interneurons.

Dopamine neurons play crucial roles in pleasure, reward, memory, learning, and fine motor skills and their dysfunction is associated with various neuropsychiatric diseases. Dopamine receptors are the main target of treatment for neurologic and psychiatric disorders. Antipsychotics that antagonize the dopamine D2 receptor (DRD2) are used to alleviate the symptoms of these disorders but may also sometimes cause disabling side effects such as parkinsonism (catalepsy in rodents). Here we show that GPR143, a G-protein-coupled receptor for L-3,4-dihydroxyphenylalanine (L-DOPA), expressed in striatal cholinergic interneurons enhances the DRD2-mediated side effects of haloperidol, an antipsychotic agent. Haloperidol-induced catalepsy was attenuated in male Gpr143 gene-deficient (Gpr143-/y ) mice compared with wild-type (Wt) mice. Reducing the endogenous release of L-DOPA and preventing interactions between GPR143 and DRD2 suppressed the haloperidol-induced catalepsy in Wt mice but not Gpr143-/y mice. The phenotypic defect in Gpr143-/y mice was mimicked in cholinergic interneuron-specific Gpr143-/y (Chat-cre;Gpr143flox/y ) mice. Administration of haloperidol increased the phosphorylation of ribosomal protein S6 at Ser240/244 in the dorsolateral striatum of Wt mice but not Chat-cre;Gpr143flox/y mice. In Chinese hamster ovary cells stably expressing DRD2, co-expression of GPR143 increased cell surface expression level of DRD2, and L-DOPA application further enhanced the DRD2 surface expression. Shorter pauses in cholinergic interneuron firing activity were observed after intrastriatal stimulation in striatal slice preparations from Chat-cre;Gpr143flox/y mice compared with those from Wt mice. Together, these findings provide evidence that GPR143 regulates DRD2 function in cholinergic interneurons and may be involved in parkinsonism induced by antipsychotic drugs.

Forward-genetics analysis of sleep in randomly mutagenized mice.

Sleep is conserved from invertebrates to vertebrates, and is tightly regulated in a homeostatic manner. The molecular and cellular mechanisms that determine the amount of rapid eye movement sleep (REMS) and non-REMS (NREMS) remain unknown. Here we identify two dominant mutations that affect sleep and wakefulness by using an electroencephalogram/electromyogram-based screen of randomly mutagenized mice. A splicing mutation in the Sik3 protein kinase gene causes a profound decrease in total wake time, owing to an increase in inherent sleep need. Sleep deprivation affects phosphorylation of regulatory sites on the kinase, suggesting a role for SIK3 in the homeostatic regulation of sleep amount. Sik3 orthologues also regulate sleep in fruitflies and roundworms. A missense, gain-of-function mutation in the sodium leak channel NALCN reduces the total amount and episode duration of REMS, apparently by increasing the excitability of REMS-inhibiting neurons. Our results substantiate the use of a forward-genetics approach for studying sleep behaviours in mice, and demonstrate the role of SIK3 and NALCN in regulating the amount of NREMS and REMS, respectively.

Sequencing of selected chromatin remodelling genes reveals increased burden of rare missense variants in ASD patients from the Japanese population.

Chromatin remodelling is an important process in neural development and is related to autism spectrum disorder (ASD) and schizophrenia (SCZ) aetiology. To further elucidate the involvement of chromatin remodelling genes in the genetic aetiology of ASD and SCZ in the Japanese population, we performed a case-control study. Targeted sequencing was conducted on coding regions of four BAF chromatin remodelling complex genes: SMARCA2, SMARCA4, SMARCC2, and ARID1B in 185 ASD, 432 SCZ patients, and 517 controls. 27 rare non-synonymous variants were identified in ASD and SCZ patients, including 25 missense, one in-frame deletion in SMRACA4, and one frame-shift variant in SMARCC2. Association analysis was conducted to investigate the burden of rare variants in BAF genes in ASD and SCZ patients. Significant enrichment of rare missense variants in BAF genes, but not synonymous variants, was found in ASD compared to controls. Rare pathogenic variants indicated by in silico tools were significantly enriched in ASD, but not statistically significant in SCZ. Pathogenic-predicted variants were located in disordered binding regions and may confer risk for ASD and SCZ by disrupting protein-protein interactions. Our study supports the involvement of rare missense variants of BAF genes in ASD and SCZ susceptibility.

Striatal-Inoculation of α-Synuclein Preformed Fibrils Aggravated the Phenotypes of REM Sleep without Atonia in A53T BAC-SNCA Transgenic Mice.

Accumulation of α-synuclein (α-syn) is the pathological hallmark of α-synucleinopathy. Rapid eye movement (REM) sleep behavior disorder (RBD) is a pivotal manifestation of α-synucleinopathy including Parkinson's disease (PD). RBD is clinically confirmed by REM sleep without atonia (RWA) in polysomnography. To accurately characterize RWA preceding RBD and their underlying α-syn pathology, we inoculated α-syn preformed fibrils (PFFs) into the striatum of A53T human α-syn BAC transgenic (A53T BAC-SNCA Tg) mice which exhibit RBD-like phenotypes with RWA. RWA phenotypes were aggravated by PFFs-inoculation in A53T BAC-SNCA Tg mice at 1 month after inoculation, in which prominent α-syn pathology in the pedunculopontine nucleus (PPN) was observed. The intensity of RWA phenotype could be dependent on the severity of the underlying α-syn pathology.

Thalamic NMDA receptor function is necessary for patterning of the thalamocortical somatosensory map and for sensorimotor behaviors.

NMDARs play a major role in patterning of topographic sensory maps in the brain. Genetic knock-out of the essential subunit of NMDARs in excitatory cortical neurons prevents whisker-specific neural pattern formation in the barrel cortex. To determine the role of NMDARs en route to the cortex, we generated sensory thalamus-specific NR1 (Grin1)-null mice (ThNR1KO). A multipronged approach, using histology, electrophysiology, optical imaging, and behavioral testing revealed that, in these mice, whisker patterns develop in the trigeminal brainstem but do not develop in the somatosensory thalamus. Subsequently, there is no barrel formation in the neocortex yet a partial afferent patterning develops. Whisker stimulation evokes weak cortical activity and presynaptic neurotransmitter release probability is also affected. We found several behavioral deficits in tasks, ranging from sensorimotor to social and cognitive. Collectively, these results show that thalamic NMDARs play a critical role in the patterning of the somatosensory thalamic and cortical maps and their impairment may lead to pronounced behavioral defects.

Caffeoylquinic Acid Mitigates Neuronal Loss and Cognitive Decline in 5XFAD Mice Without Reducing the Amyloid-ß Plaque Burden.

Background: Caffeoylquinic acid (CQA), which is abundant in coffee beans and Centella asiatica, reportedly improves cognitive function in Alzheimer's disease (AD) model mice, but its effects on neuroinflammation, neuronal loss, and the amyloid-ß (Aß) plaque burden have remained unclear. Objective: To assess the effects of a 16-week treatment with CQA on recognition memory, working memory, Aß levels, neuronal loss, neuroinflammation, and gene expression in the brains of 5XFAD mice, a commonly used mouse model of familial AD. Methods: 5XFAD mice at 7 weeks of age were fed a 0.8% CQA-containing diet for 4 months and then underwent novel object recognition (NOR) and Y-maze tests. The Aß levels and plaque burden were analyzed by enzyme-linked immunosorbent assay and immunofluorescent staining, respectively. Immunostaining of markers of mature neurons, synapses, and glial cells was analyzed. AmpliSeq transcriptome analysis and quantitative reverse-transcription-polymerase chain reaction were performed to assess the effect of CQA on gene expression levels in the cerebral cortex of the 5XFAD mice. Results: CQA treatment for 4 months improved recognition memory and ameliorated the reduction of mature neurons and synaptic function-related gene mRNAs. The Aß levels, plaque burden, and glial markers of neuroinflammation seemed unaffected. Conclusions: These findings suggest that CQA treatment mitigates neuronal loss and improves cognitive function without reducing Aß levels or neuroinflammation. Thus, CQA is a potential therapeutic compound for AD, improving cognitive function via as-yet unknown mechanisms independent of reductions in Aß or neuroinflammation.

Study of the genetic association between selected 3q29 region genes and schizophrenia and autism spectrum disorder in the Japanese population.

Psychiatric disorders are highly inheritable, and most psychiatric disorders exhibit genetic overlap. Recent studies associated the 3q29 recurrent deletion with schizophrenia (SCZ) and autism spectrum disorder (ASD). In this study, we investigated the association of genes in the 3q29 region with SCZ and ASD. TM4SF19 and PAK2 were chosen as candidate genes for this study based on evidence from previous research. We sequenced TM4SF19 and PAK2 in 437 SCZ cases, 187 ASD cases and 524 controls in the Japanese population. Through targeted sequencing, we identified 6 missense variants among the cases (ASD & SCZ), 3 missense variants among controls, and 1 variant common to both cases and controls; however, no loss-of-function variants were identified. Fisher's exact test showed a significant association of variants in TM4SF19 among cases (p=0.0160). These results suggest TM4SF19 variants affect the etiology of SCZ and ASD in the Japanese population. Further research examining 3q29 region genes and their association with SCZ and ASD is thus needed.

Analysis of human neuronal cells carrying ASTN2 deletion associated with psychiatric disorders.

Recent genetic studies have found common genomic risk variants among psychiatric disorders, strongly suggesting the overlaps in their molecular and cellular mechanism. Our research group identified the variant in ASTN2 as one of the candidate risk factors across these psychiatric disorders by whole-genome copy number variation analysis. However, the alterations in the human neuronal cells resulting from ASTN2 variants identified in patients remain unknown. To address this, we used patient-derived and genome-edited iPS cells with ASTN2 deletion; cells were further differentiated into neuronal cells. A comprehensive gene expression analysis using genome-edited iPS cells with variants on both alleles revealed that the expression level of ZNF558, a gene specifically expressed in human forebrain neural progenitor cells, was greatly reduced in ASTN2-deleted neuronal cells. Furthermore, the expression of the mitophagy-related gene SPATA18, which is repressed by ZNF558, and mitophagy activity were increased in ASTN2-deleted neuronal cells. These phenotypes were also detected in neuronal cells differentiated from patient-derived iPS cells with heterozygous ASTN2 deletion. Our results suggest that ASTN2 deletion is related to the common pathogenic mechanism of psychiatric disorders by regulating mitophagy via ZNF558.

Crucial role of TFAP2B in the nervous system for regulating NREM sleep.

The AP-2 transcription factors are crucial for regulating sleep in both vertebrate and invertebrate animals. In mice, loss of function of the transcription factor AP-2ß (TFAP2B) reduces non-rapid eye movement (NREM) sleep. When and where TFAP2B functions, however, is unclear. Here, we used the Cre-loxP system to generate mice in which Tfap2b was specifically deleted in the nervous system during development and mice in which neuronal Tfap2b was specifically deleted postnatally. Both types of mice exhibited reduced NREM sleep, but the nervous system-specific deletion of Tfap2b resulted in more severe sleep phenotypes accompanied by defective light entrainment of the circadian clock and stereotypic jumping behavior. These findings indicate that TFAP2B in postnatal neurons functions at least partly in sleep regulation and imply that TFAP2B also functions either at earlier stages or in additional cell types within the nervous system.

Phenotypes for general behavior, activity, and body temperature in 3q29 deletion model mice.

Whole genome analysis has identified rare copy number variations (CNV) that are strongly involved in the pathogenesis of psychiatric disorders, and 3q29 deletion has been found to have the largest effect size. The 3q29 deletion mice model (3q29-del mice) has been established as a good pathological model for schizophrenia based on phenotypic analysis; however, circadian rhythm and sleep, which are also closely related to neuropsychiatric disorders, have not been investigated. In this study, our aims were to reevaluate the pathogenesis of 3q29-del by recreating model mice and analyzing their behavior and to identify novel new insights into the temporal activity and temperature fluctuations of the mouse model using a recently developed small implantable accelerometer chip, Nano-tag. We generated 3q29-del mice using genome editing technology and reevaluated common behavioral phenotypes. We next implanted Nano-tag in the abdominal cavity of mice for continuous measurements of long-time activity and body temperature. Our model mice exhibited weight loss similar to that of other mice reported previously. A general behavioral battery test in the model mice revealed phenotypes similar to those observed in mouse models of schizophrenia, including increased rearing frequency. Intraperitoneal implantation of Nano-tag, a miniature acceleration sensor, resulted in hypersensitive and rapid increases in the activity and body temperature of 3q29-del mice upon switching to lights-off condition. Similar to the 3q29-del mice reported previously, these mice are a promising model animals for schizophrenia. Successive quantitative analysis may provide results that could help in treating sleep disorders closely associated with neuropsychiatric disorders.

Forward genetic screen of Caenorhabditis elegans mutants with impaired sleep reveals a crucial role of neuronal diacylglycerol kinase DGK-1 in regulating sleep.

The sleep state is widely observed in animals. The molecular mechanisms underlying sleep regulation, however, remain largely unclear. In the nematode Caenorhabditis elegans, developmentally timed sleep (DTS) and stress-induced sleep (SIS) are 2 types of quiescent behaviors that fulfill the definition of sleep and share conserved sleep-regulating molecules with mammals. To identify novel sleep-regulating molecules, we conducted an unbiased forward genetic screen based on DTS phenotypes. We isolated 2 mutants, rem8 and rem10, that exhibited significantly disrupted DTS and SIS. The causal gene of the abnormal sleep phenotypes in both mutants was mapped to dgk-1, which encodes diacylglycerol kinase. Perhaps due to the diminished SIS, dgk-1 mutant worms exhibited decreased survival following exposure to a noxious stimulus. Pan-neuronal and/or cholinergic expression of dgk-1 partly rescued the dgk-1 mutant defects in DTS, SIS, and post-stress survival. Moreover, we revealed that pkc-1/nPKC participates in sleep regulation and counteracts the effect of dgk-1; the reduced DTS, SIS, and post-stress survival rate were partly suppressed in the pkc-1; dgk-1 double mutant compared with the dgk-1 single mutant. Excessive sleep observed in the pkc-1 mutant was also suppressed in the pkc-1; dgk-1 double mutant, implying that dgk-1 has a complicated mode of action. Our findings indicate that neuronal DGK-1 is essential for normal sleep and that the counterbalance between DGK-1 and PKC-1 is crucial for regulating sleep and mitigating post-stress damage.

Bidirectional relationship between sleep and depression.

Patients with depression almost inevitably exhibit abnormalities in sleep, such as shortened latency to enter rapid eye movement (REM) sleep and decrease in electroencephalogram delta power during non-REM sleep. Insufficient sleep can be stressful, and the accumulation of stress leads to the deterioration of mental health and contributes to the development of psychiatric disorders. Thus, it is likely that depression and sleep are bidirectionally related, i.e. development of depression contributes to sleep disturbances and vice versa. However, the relation between depression and sleep seems complicated. For example, acute sleep deprivation can paradoxically improve depressive symptoms. Thus, it is difficult to conclude whether sleep has beneficial or harmful effects in patients with depression. How antidepressants affect sleep in patients with depression might provide clues to understanding the effects of sleep, but caution is required considering that antidepressants have diverse effects other than sleep. Recent animal studies support the bidirectional relation between depression and sleep, and animal models of depression are expected to be beneficial for the identification of neuronal circuits that connect stress, sleep, and depression. This review provides a comprehensive overview regarding the current knowledge of the relationship between depression and sleep.

Reverse genetic screening during L1 arrest reveals a role of the diacylglycerol kinase 1 gene dgk-1 and sphingolipid metabolism genes in sleep regulation.

Sleep is a fundamental state of behavioral quiescence and physiological restoration. Sleep is controlled by environmental conditions, indicating a complex regulation of sleep by multiple processes. Our knowledge of the genes and mechanisms that control sleep during various conditions is, however, still incomplete. In Caenorhabditis elegans, sleep is increased when development is arrested upon starvation. Here, we performed a reverse genetic sleep screen in arrested L1 larvae for genes that are associated with metabolism. We found over 100 genes that are associated with a reduced sleep phenotype. Enrichment analysis revealed sphingolipid metabolism as a key pathway that controls sleep. A strong sleep loss was caused by the loss of function of the diacylglycerol kinase 1 gene, dgk-1, a negative regulator of synaptic transmission. Rescue experiments indicated that dgk-1 is required for sleep in cholinergic and tyraminergic neurons. The Ring Interneuron S (RIS) neuron is crucial for sleep in C. elegans and activates to induce sleep. RIS activation transients were abolished in dgk-1 mutant animals. Calcium transients were partially rescued by a reduction-of-function mutation of unc-13, suggesting that dgk-1 might be required for RIS activation by limiting synaptic vesicle release. dgk-1 mutant animals had impaired L1 arrest survival and dampened expression of the protective heat shock factor gene hsp-12.6. These data suggest that dgk-1 impairment causes broad physiological deficits. Microcalorimetry and metabolomic analyses of larvae with impaired RIS showed that RIS is broadly required for energy conservation and metabolic control, including for the presence of sphingolipids. Our data support the notion that metabolism broadly influences sleep and that sleep is associated with profound metabolic changes. We thus provide novel insights into the interplay of lipids and sleep and provide a rich resource of mutants and metabolic pathways for future sleep studies.

Fully automatic REM sleep stage-specific intervention systems using single EEG in mice.

Sleep stage-specific intervention is widely used to elucidate the functions of sleep and their underlying mechanisms. For this intervention, it is imperative to accurately classify rapid-eye-movement (REM) sleep. However, the proof of fully automatic real-time REM sleep classification in vivo has not been obtained in mice. Here, we report the in vivo implementation of a system that classifies sleep stages in real-time from a single-channel electroencephalogram (EEG). It enabled REM sleep-specific intervention with 90 % sensitivity and 86 % precision without prior configuration to each mouse. We further derived systems capable of classification with higher frequency sampling and time resolution. This attach-and-go sleep staging system provides a fully automatic accurate and scalable tool for investigating the functions of sleep.

ER proteostasis regulators cell-non-autonomously control sleep.

Sleep is regulated by peripheral tissues under fatigue. The molecular pathways in peripheral cells that trigger systemic sleep-related signals, however, are unclear. Here, a forward genetic screen in C. elegans identifies 3 genes that strongly affect sleep amount: sel-1, sel-11, and mars-1. sel-1 and sel-11 encode endoplasmic reticulum (ER)-associated degradation components, whereas mars-1 encodes methionyl-tRNA synthetase. We find that these machineries function in non-neuronal tissues and that the ER unfolded protein response components inositol-requiring enzyme 1 (IRE1)/XBP1 and protein kinase R-like ER kinase (PERK)/eukaryotic initiation factor-2α (eIF2α)/activating transcription factor-4 (ATF4) participate in non-neuronal sleep regulation, partly by reducing global translation. Neuronal epidermal growth factor receptor (EGFR) signaling is also required. Mouse studies suggest that this mechanism is conserved in mammals. Considering that prolonged wakefulness increases ER proteostasis stress in peripheral tissues, our results suggest that peripheral ER proteostasis factors control sleep homeostasis. Moreover, based on our results, peripheral tissues likely cope with ER stress not only by the well-established cell-autonomous mechanisms but also by promoting the individual's sleep.

Intracellular Ca2+ dynamics in the ALA neuron reflect sleep pressure and regulate sleep in Caenorhabditis elegans.

The mechanisms underlying sleep homeostasis are poorly understood. The nematode Caenorhabditis elegans exhibits 2 types of sleep: lethargus, or developmentally timed, and stress-induced sleep. Lethargus is characterized by alternating cycles of sleep and motion bouts. Sleep bouts are homeostatically regulated, i.e., prolonged active bouts lead to prolonged sleep bouts. Here we reveal that the interneuron ALA is crucial for homeostatic regulation during lethargus. Intracellular Ca2+ in ALA gradually increased during active bouts and rapidly decayed upon transitions to sleep bouts. Longer active bouts were accompanied by higher intracellular Ca2+ peaks. Optogenetic activation of ALA during active bouts caused transitions to sleep bouts. Dysfunction of CEH-17, which is an LIM homeodomain transcription factor selectively expressed in ALA, impaired the characteristic patterns of ALA intracellular Ca2+ and abolished the homeostatic regulation of sleep bouts. These findings indicate that ALA encodes sleep pressure and contributes to sleep homeostasis.

Spectroscopic second and third harmonic generation microscopy using a femtosecond laser source in the third near-infrared (NIR-III) optical window.

In this study, second harmonic generation (SHG) and third harmonic generation (THG) spectroscopic imaging were performed on biological samples using a femtosecond laser source in the third near-infrared (NIR) optical window (NIR-III). Using a visible-NIR spectrometer, the SHG and THG signals were simultaneously detected and were extracted using spectral analysis. Visualization of biological samples such as cultured cells (HEK293 T), mouse brain slices, and the nematode Caenorhabditis elegans was performed in a label-free manner. In particular, in an SHG image of an entire coronal brain section (8 × 6 mm2), we observed mesh-like and filamentous structures in the arachnoid mater and wall of the cerebral ventricle, probably corresponding to the collagen fibers, cilia, and rootlet. Moreover, the THG images clearly depicted the densely packed axons in the white matter and cell nuclei at the cortex of the mouse brain slice sample and lipid-rich granules such as lipid droplets inside the nematode. The observations and conclusions drawn from this technique confirm that it can be utilized for various biological applications, including in vivo label-free imaging of living animals.

Long-Term Effects of Repeated Social Defeat Stress on Brain Activity during Social Interaction in BALB/c Mice.

Understanding the long-term effects of stress on brain function is crucial for understanding the mechanisms of depression. The BALB/c mouse strain has high susceptibility to stress and is thus an effective model for depression. The long-term effects of repeated social defeat stress (SDS) on BALB/c mice, however, are not clear. Here, we investigated the effects of repeated SDS in male BALB/c mice over the subsequent two weeks. Some defeated mice immediately exhibited social avoidance, whereas anxiety-like behavior was only evident at later periods. Furthermore, defeated mice segregated into two groups based on the level of social avoidance, namely, avoidant and nonavoidant mice. The characteristic of avoidance or nonavoidance in each individual was not fixed over the two weeks. In addition, we developed a semi-automated method for analyzing c-Fos expression in the mouse brain to investigate the effect of repeated SDS on brain activity more than two weeks after the end of the stress exposure. Following social interaction, c-Fos expression was reduced in several brain regions in the defeated mice compared with control mice. The correlation of c-Fos expression among these brain areas, with exception of the medial prefrontal cortex (mPFC) and central amygdala (CeA), was increased in defeated mice, suggesting increased synchrony. Notably, c-Fos expression in the lateral habenula (LHb) was different between mice that exhibited social avoidance from immediately after the repeated SDS and those that exhibited social avoidance only at later periods. These observations provide insight into the long-term effects of social stress on behavior and brain activity.