TDP-43 impairs sleep in Drosophila through Ataxin-2-dependent metabolic disturbance

Neurodegenerative diseases such as amyotrophic lateral sclerosis and frontotemporal dementia are associated with substantial sleep disruption, which may accelerate cognitive decline and brain degeneration. Here, we define a role for trans-activation response element (TAR) DNA binding protein 43 (TDP-43), a protein associated with human neurodegenerative disease, in regulating sleep using Drosophila. Expression of TDP-43 severely disrupts sleep, and the sleep deficit is rescued by Atx2 knockdown. Brain RNA sequencing revealed that Atx2 RNA interference regulates transcripts enriched for small-molecule metabolic signaling in TDP-43 brains. Focusing on these Atx2-regulated genes, we identified suppressors of the TDP-43 sleep phenotype enriched for metabolism pathways. Knockdown of Atx2 or treatment with rapamycin attenuated the sleep phenotype and mitigated the disruption of small-molecule glycogen metabolism caused by TDP-43. Our findings provide a connection between toxicity of TDP-43 and sleep disturbances and highlight key aspects of metabolism that interplay with TDP-43 toxicity upon Atx2 rescue.

Neurofibromin 1 regulates early developmental sleep in Drosophila

Sleep disturbances are common in neurodevelopmental disorders, but knowledge of molecular factors that govern sleep in young animals is lacking. Evidence across species, including Drosophila, suggests that juvenile sleep has distinct functions and regulatory mechanisms in comparison to sleep in maturity. In flies, manipulation of most known adult sleep regulatory genes is not associated with sleep phenotypes during early developmental (larval) stages. Here, we examine the role of the neurodevelopmental disorder-associated gene Neurofibromin 1 (Nf1) in sleep during numerous developmental periods. Mutations in Neurofibromin 1 (Nf1) are associated with sleep and circadian disorders in humans and adult flies. We find in flies that Nf1 acts to regulate sleep across the lifespan, beginning during larval stages. Nf1 is required in neurons for this function, as is signaling via the Alk pathway. These findings identify Nf1 as one of a small number of genes positioned to regulate sleep across developmental periods.

Stem cell-specific ecdysone signaling regulates the development and function of a Drosophila sleep homeostat

Complex behaviors arise from neural circuits that are assembled from diverse cell types. Sleep is a conserved and essential behavior, yet little is known regarding how the nervous system generates neuron types of the sleep-wake circuit. Here, we focus on the specification of Drosophila sleep-promoting neurons-long-field tangential input neurons that project to the dorsal layers of the fan-shaped body neuropil in the central complex (CX). We use lineage analysis and genetic birth dating to identify two bilateral Type II neural stem cells that generate these dorsal fan-shaped body (dFB) neurons. We show that adult dFB neurons express Ecdysone-induced protein E93, and loss of Ecdysone signaling or E93 in Type II NSCs results in the misspecification of the adult dFB neurons. Finally, we show that E93 knockdown in Type II NSCs affects adult sleep behavior. Our results provide insight into how extrinsic hormonal signaling acts on NSCs to generate neuronal diversity required for adult sleep behavior. These findings suggest that some adult sleep disorders might derive from defects in stem cell-specific temporal neurodevelopmental programs.

Energetic Demands Regulate Sleep-Wake Rhythm Circuit Development

Sleep and feeding patterns lack a clear daily rhythm during early life. As diurnal animals mature, feeding is consolidated to the day and sleep to the night. Circadian sleep patterns begin with formation of a circuit connecting the central clock to arousal output neurons; emergence of circadian sleep also enables long-term memory (LTM). However, the cues that trigger the development of this clock-arousal circuit are unknown. Here, we identify a role for nutritional status in driving sleep-wake rhythm development in Drosophila larvae. We find that in the 2nd instar (L2) period, sleep and feeding are spread across the day; these behaviors become organized into daily patterns by L3. Forcing mature (L3) animals to adopt immature (L2) feeding strategies disrupts sleep-wake rhythms and the ability to exhibit LTM. In addition, the development of the clock (DN1a)-arousal (Dh44) circuit itself is influenced by the larval nutritional environment. Finally, we demonstrate that larval arousal Dh44 neurons act through glucose metabolic genes to drive onset of daily sleep-wake rhythms. Together, our data suggest that changes to energetic demands in developing organisms triggers the formation of sleep-circadian circuits and behaviors.

Developmental emergence of sleep rhythms enables long-term memory in Drosophila

In adulthood, sleep-wake rhythms are one of the most prominent behaviors under circadian control. However, during early life, sleep is spread across the 24-hour day. The mechanism through which sleep rhythms emerge, and consequent advantage conferred to a juvenile animal, is unknown. In the second-instar Drosophila larvae (L2), like in human infants, sleep is not under circadian control. We identify the precise developmental time point when the clock begins to regulate sleep in Drosophila, leading to emergence of sleep rhythms in early third-instars (L3). At this stage, a cellular connection forms between DN1a clock neurons and arousal-promoting Dh44 neurons, bringing arousal under clock control to drive emergence of circadian sleep. Last, we demonstrate that L3 but not L2 larvae exhibit long-term memory (LTM) of aversive cues and that this LTM depends upon deep sleep generated once sleep rhythms begin. We propose that the developmental emergence of circadian sleep enables more complex cognitive processes, including the onset of enduring memories.

Intrinsic maturation of sleep output neurons regulates sleep ontogeny in Drosophila

The maturation of sleep behavior across a lifespan (sleep ontogeny) is an evolutionarily conserved phenomenon. Mammalian studies have shown that in addition to increased sleep duration, early life sleep exhibits stark differences compared with mature sleep with regard to sleep states. How the intrinsic maturation of sleep output circuits contributes to sleep ontogeny is poorly understood. The fruit fly Drosophila melanogaster exhibits multifaceted changes to sleep from juvenile to mature adulthood. Here, we use a non-invasive probabilistic approach to investigate the changes in sleep architecture in juvenile and mature flies. Increased sleep in juvenile flies is driven primarily by a decreased probability of transitioning to wake and characterized by more time in deeper sleep states. Functional manipulations of sleep-promoting neurons in the dorsal fan-shaped body (dFB) suggest that these neurons differentially regulate sleep in juvenile and mature flies. Transcriptomic analysis of dFB neurons at different ages and a subsequent RNAi screen implicate the genes involved in dFB sleep circuit maturation. These results reveal that the dynamic transcriptional states of sleep output neurons contribute to the changes in sleep across the lifespan.

Synaptic dysfunction connects autism spectrum disorder and sleep disturbances: A perspective from studies in model organisms

Sleep disturbances (SD) accompany many neurodevelopmental disorders, suggesting SD is a transdiagnostic process that can account for behavioral deficits and influence underlying neuropathogenesis. Autism Spectrum Disorder (ASD) comprises a complex set of neurodevelopmental conditions characterized by challenges in social interaction, communication, and restricted, repetitive behaviors. Diagnosis of ASD is based primarily on behavioral criteria, and there are no drugs that target core symptoms. Among the co-occurring conditions associated with ASD, SD are one of the most prevalent. SD often arises before the onset of other ASD symptoms. Sleep interventions improve not only sleep but also daytime behaviors in children with ASD. Here, we examine sleep phenotypes in multiple model systems relevant to ASD, e.g., mice, zebrafish, fruit flies and worms. Given the functions of sleep in promoting brain connectivity, neural plasticity, emotional regulation and social behavior, all of which are of critical importance in ASD pathogenesis, we propose that synaptic dysfunction is a major mechanism that connects ASD and SD. Common molecular targets in this interplay that are involved in synaptic function might be a novel avenue for therapy of individuals with ASD experiencing SD. Such therapy would be expected to improve not only sleep but also other ASD symptoms.

Randomized Noninferiority Trial of Telehealth Delivery of Cognitive Behavioral Treatment of Insomnia Compared to In-Person Care

Objective: Insomnia is prevalent and is associated with a range of negative sequelae. Cognitive behavioral treatment for insomnia (CBT-I) is the recommended intervention, but availability is limited. Telehealth provides increased access, but its efficacy is not certain. The objective of this study was to compare the efficacy of CBT-I delivered by telehealth to in-person treatment and to a waitlist control. Methods: Individuals with DSM-5 insomnia disorder (n = 60) were randomized to telehealth CBT-I, in-person CBT-I, or 8-week waitlist control. CBT-I was delivered over 6-8 weekly sessions by video telehealth or in-person in an outpatient clinic. Follow-up assessments were at 2 weeks and 3 months posttreatment. The Insomnia Severity Index (ISI) was the primary outcome. Change in ISI score was compared between the CBT-I group in an intent-to-treat, noninferiority analysis using an a priori margin of -3.0 points. All analyses were conducted using mixed-effects models. Data collection occurred from November 2017-July 2020. Results: The mean (SD) change in ISI score from baseline to 3-month follow-up was -7.8 (6.1) points for in-person CBT-I, -7.5 (6.9) points for telehealth, and -1.6 (2.1) for waitlist, and the difference between the CBT-I groups was not statistically significant (t₂₈ = -0.98, P = .33). The lower confidence limit of this between-group difference in the mean ISI changes was greater than the a priori margin of -3.0 points, indicating that telehealth treatment was not inferior to in-person treatment. There were significant improvements on most secondary outcome measures but no group differences. Conclusions: Telehealth CBT-I may produce clinically significant improvements in insomnia severity that are noninferior to in-person treatment. CBT-I is also associated with significant gains across a range of domains of functioning. Telehealth is a promising option for increasing access to treatment without loss of clinical gains. Trial Registration: ClinicalTrials.gov identifier: NCT03328585.

Getting into rhythm: developmental emergence of circadian clocks and behaviors

Circadian clocks keep time to coordinate diverse behaviors and physiological functions. While molecular circadian rhythms are evident during early development, most behavioral rhythms, such as sleep-wake, do not emerge until far later. Here, we examine the development of circadian clocks, outputs, and behaviors across phylogeny, with a particular focus on Drosophila. We explore potential mechanisms for how central clocks and circadian output loci establish communication, and discuss why from an evolutionary perspective sleep-wake and other behavioral rhythms emerge long after central clocks begin keeping time.

Treatment of Insomnia with Zaleplon in HIV+ Significantly Improves Sleep and Depression

More than 50% of individuals who are HIV positive report insomnia, which can reduce HIV treatment adherence, impair quality of life, and contribute to metabolic dysfunction. Major depressive disorder is also highly comorbid in this population, leading to further impairment. There is evidence that treating insomnia may improve not only sleep, but depression and metabolic function, as well. The present study aimed to examine the effects of pharmacotherapeutic treatment of insomnia on sleep, depression, and metabolic functioning in individuals with HIV. 20 individuals with asymptomatic seropositive HIV and comorbid insomnia and depression were administered zaleplon for 6 weeks. Insomnia severity was assessed using the Insomnia Severity Index and Epworth Sleepiness Scale, and depression severity was assessed using the Quick Inventory of Depression, both prior to treatment and 6 weeks post treatment. Metabolomic changes were assessed using a comprehensive platform measuring ~2000 lipid features and polar metabolites. Linear mixed effects models demonstrated that 6 weeks of treatment with zaleplon significantly improved symptoms of both insomnia and depression. Metabolomic analyses also demonstrated that changes in insomnia severity were associated with significant changes in key branched chain amino acid metabolites. Our results show that improvement in insomnia is associated with reduced depressive symptoms and beneficial metabolomic changes. Additionally, changes in key branched chain amino acid metabolites following treatment may serve as useful biomarkers of treatment response.

The CHD8/CHD7/Kismet family links blood-brain barrier glia and serotonin to ASD-associated sleep defects

Sleep disturbances in autism and neurodevelopmental disorders are common and adversely affect patient's quality of life, yet the underlying mechanisms are understudied. We found that individuals with mutations in CHD8, among the highest-confidence autism risk genes, or CHD7 suffer from disturbed sleep maintenance. These defects are recapitulated in Drosophila mutants affecting kismet, the sole CHD8/CHD7 ortholog. We show that Kismet is required in glia for early developmental and adult sleep architecture. This role localizes to subperineurial glia constituting the blood-brain barrier. We demonstrate that Kismet-related sleep disturbances are caused by high serotonin during development, paralleling a well-established but genetically unsolved autism endophenotype. Despite their developmental origin, Kismet's sleep architecture defects can be reversed in adulthood by a behavioral regime resembling human sleep restriction therapy. Our findings provide fundamental insights into glial regulation of sleep and propose a causal mechanistic link between the CHD8/CHD7/Kismet family, developmental hyperserotonemia, and autism-associated sleep disturbances.

Pathogenic variants in SMARCA5, a chromatin remodeler, cause a range of syndromic neurodevelopmental features

Intellectual disability encompasses a wide spectrum of neurodevelopmental disorders, with many linked genetic loci. However, the underlying molecular mechanism for more than 50% of the patients remains elusive. We describe pathogenic variants in SMARCA5, encoding the ATPase motor of the ISWI chromatin remodeler, as a cause of a previously unidentified neurodevelopmental disorder, identifying 12 individuals with de novo or dominantly segregating rare heterozygous variants. Accompanying phenotypes include mild developmental delay, frequent postnatal short stature and microcephaly, and recurrent dysmorphic features. Loss of function of the SMARCA5 Drosophila ortholog Iswi led to smaller body size, reduced sensory dendrite complexity, and tiling defects in larvae. In adult flies, Iswi neural knockdown caused decreased brain size, aberrant mushroom body morphology, and abnormal locomotor function. Iswi loss of function was rescued by wild-type but not mutant SMARCA5. Our results demonstrate that SMARCA5 pathogenic variants cause a neurodevelopmental syndrome with mild facial dysmorphia.

Social Behavioral Deficits with Loss of Neurofibromin Emerge from Peripheral Chemosensory Neuron Dysfunction

Neurofibromatosis type 1 (NF1) is a neurodevelopmental disorder associated with social and communicative disabilities. The cellular and circuit mechanisms by which loss of neurofibromin 1 (Nf1) results in social deficits are unknown. Here, we identify social behavioral dysregulation with Nf1 loss in Drosophila. These deficits map to primary dysfunction of a group of peripheral sensory neurons. Nf1 regulation of Ras signaling in adult ppk23⁺ chemosensory cells is required for normal social behaviors in flies. Loss of Nf1 attenuates ppk23⁺ neuronal activity in response to pheromones, and circuit-specific manipulation of Nf1 expression or neuronal activity in ppk23⁺ neurons rescues social deficits. This disrupted sensory processing gives rise to persistent changes in behavior beyond the social interaction, indicating a sustained effect of an acute sensory misperception. Together our data identify a specific circuit mechanism through which Nf1 regulates social behaviors and suggest social deficits in NF1 arise from propagation of sensory misinformation.

A Drosophila model of sleep restriction therapy for insomnia

Insomnia is the most common sleep disorder among adults, especially affecting individuals of advanced age or with neurodegenerative disease. Insomnia is also a common comorbidity across psychiatric disorders. Cognitive behavioral therapy for insomnia (CBT-I) is the first-line treatment for insomnia; a key component of this intervention is restriction of sleep opportunity, which optimizes matching of sleep ability and opportunity, leading to enhanced sleep drive. Despite the well-documented efficacy of CBT-I, little is known regarding how CBT-I works at a cellular and molecular level to improve sleep, due in large part to an absence of experimentally-tractable animals models of this intervention. Here, guided by human behavioral sleep therapies, we developed a Drosophila model for sleep restriction therapy (SRT) of insomnia. We demonstrate that restriction of sleep opportunity through manipulation of environmental cues improves sleep efficiency in multiple short-sleeping Drosophila mutants. The response to sleep opportunity restriction requires ongoing environmental inputs, but is independent of the molecular circadian clock. We apply this sleep opportunity restriction paradigm to aging and Alzheimer's disease fly models, and find that sleep impairments in these models are reversible with sleep restriction, with associated improvement in reproductive fitness and extended lifespan. This work establishes a model to investigate the neurobiological basis of CBT-I, and provides a platform that can be exploited toward novel treatment targets for insomnia.

The chromatin remodeler ISWI acts during Drosophila development to regulate adult sleep

Sleep disruptions are among the most commonly reported symptoms across neurodevelopmental disorders (NDDs), but mechanisms linking brain development to normal sleep are largely unknown. From a Drosophila screen of human NDD-associated risk genes, we identified the chromatin remodeler Imitation SWItch/SNF (ISWI) to be required for adult fly sleep. Loss of ISWI also results in disrupted circadian rhythms, memory, and social behavior, but ISWI acts in different cells and during distinct developmental times to affect each of these adult behaviors. Specifically, ISWI expression in type I neuroblasts is required for both adult sleep and formation of a learning-associated brain region. Expression in flies of the human ISWI homologs SMARCA1 and SMARCA5 differentially rescues adult phenotypes, while de novo SMARCA5 patient variants fail to rescue sleep. We propose that sleep deficits are a primary phenotype of early developmental origin in NDDs and point toward chromatin remodeling machinery as critical for sleep circuit formation.

0023 Neuropeptidergic Regulation of Drosophila Larval Sleep

Introduction

Sleep during early life is thought to be important for brain development. Indeed, disruptions in sleep during development have long-lasting effects on cognitive functioning. Recently, our lab has developed the LarvaLodge platform for monitoring sleep in developing Drosophila larvae. Using this system we can investigate the neural circuits and signals controlling sleep during early neurodevelopmental periods. Neuropeptides play critical roles in regulating many behaviors in both larvae and adult flies.While several neuropeptides modulate sleep in adult flies, it is not known what role neuropeptides play in controlling larval sleep.

Methods

To identify peptidergic neurons that regulate 2nd instar larval sleep, we activated neurons labeled by 34 independent Gal4 driver lines corresponding to 25 different neuropeptide genes using the heat-sensitive cation channel, TrpA1.

Results

Of the 34 Gal4 driver lines, we determined that 2 lines are wake-promoting and 7 lines are sleep-promoting. A subset of these exert effects on sleep without associated changes in wake activity levels. We also observed sleep fragmentation (increase in sleep bout number and decrease in sleep bout length) in 3 lines. Subsequent analysis indicated that manipulation of activity in Diuretic hormone 44 (Dh44)-labeled neurons bidirectionally modulates sleep-wake. Additionally, pan-neuronal knockdown of Dh44 altered sleep duration.

Conclusion

This work indicates that neuropeptidergic signaling modulates sleep during early development and provides a platform to examine how neuropeptidergic regulation of sleep/wake changes throughout the lifespan.

Support

NIH T32

0069 Sleep in Drosophila is Regulated by the Chromatin Remodeling Factor ISWI

Introduction

Sleep is commonly disrupted in patients with neurodevelopmental disorders (NDDs). Despite strong clinical associations between disrupted sleep and other NDD symptoms, we lack an understanding of how these are pathophysiologically related. Drosophila melanogaster exhibit essential characteristics of human sleep and have well-defined neural circuits underlying learning and social behaviors. This represents an ideal system to investigate the mechanistic interaction between disrupted sleep and other behavioral dysfunctions in NDDs.

Methods

We performed a reverse genetic RNAi-based screen targeting Drosophila homologs of human genes within NDD-associated risk loci. Pan-neuronal knockdown of risk genes was achieved using the Gal4-UAS system.

Results

Pan-neuronal knockdown of ISWI led to dramatic deficits in sleep and circadian arrhythmicity in the adult fly. Across species, ISWI and its homologs are ATP-dependent chromatin remodelers that regulate gene expression important for neural differentiation. We found that depleting ISWI also leads to memory and social deficits. ISWI functions during dissociable temporal windows of pre-adult development and in different circuits to establish different adult behaviors. The sleep phenotype associated with ISWI knockdown mapped to a specific population of cells. RNA-Seq of developing brains during the window important for sleep deficits revealed significant transcriptional changes in genes associated with nervous system development, suggesting ISWI acts in the development of sleep regulatory circuits. Finally, mutations in the human homologs of ISWI, SMARCA1/5, have been implicated in NDDs. Expressing either SMARCA1/5 in the setting of ISWI knockdown differentially rescued adult deficits.

Conclusion

Identification of ISWI provides a platform for unraveling pleiotropic behavioral effects from an NDD risk gene. Sleep, circadian rhythms, memory, and social behaviors are affected by ISWI knockdown, and map to different developmental periods and circuits. In addition, SMARCA1/5 differentially rescue adult behaviors, suggesting NDD-causing mutations in these genes may affect different behaviors. Current work aims to determine how human mutations in SMARCA1/5 affect behaviors.

Support

This work was supported by NIH K08 NS090461 (MSK) and T32 HL007953 (NNG), Hearst Foundation Fellowship 2018 (NNG), Burroughs Welcome Career Award for Medical Scientists, March of Dimes Basil O’Connor Scholar Award, and Sloan Research Fellowship (MSK).

Identification of a molecular basis for the juvenile sleep state

Across species, sleep in young animals is critical for normal brain maturation. The molecular determinants of early life sleep remain unknown. Through an RNAi-based screen, we identified a gene, pdm3, required for sleep maturation in Drosophila. Pdm3, a transcription factor, coordinates an early developmental program that prepares the brain to later execute high levels of juvenile adult sleep. PDM3 controls the wiring of wake-promoting dopaminergic (DA) neurites to a sleep-promoting region, and loss of PDM3 prematurely increases DA inhibition of the sleep center, abolishing the juvenile sleep state. RNA-Seq/ChIP-Seq and a subsequent modifier screen reveal that pdm3 represses expression of the synaptogenesis gene Msp300 to establish the appropriate window for DA innervation. These studies define the molecular cues governing sleep behavioral and circuit development, and suggest sleep disorders may be of neurodevelopmental origin.

Sleep: The Balm of Hurt Minds

Two new studies use Drosophila to unravel the role of sleep in clearance of damaged neural processes.

Exploring phylogeny to find the function of sleep

During sleep, animals do not eat, reproduce or forage. Sleeping animals are vulnerable to predation. Yet, the persistence of sleep despite evolutionary pressures, and the deleterious effects of sleep deprivation, indicate that sleep serves a function or functions that cannot easily be bypassed. Recent research demonstrates sleep to be phylogenetically far more pervasive than previously appreciated; it is possible that the very first animals slept. Here, we give an overview of sleep across various species, with the aim of determining its original purpose. Sleep exists in animals without cephalized nervous systems and can be influenced by non-neuronal signals, including those associated with metabolic rhythms. Together, these observations support the notion that sleep serves metabolic functions in neural and non-neural tissues.

Precision Medicine for Insomnia

Insomnia affects up to 15% of the US population. There are effective pharmacologic and behavioral treatments for insomnia; however, there is often no one-size-fits-all intervention. This article discusses the leading behavioral treatment of insomnia, cognitive behavioral therapy for insomnia, and its ability to be tailored to an individual's specific symptoms. It then discusses pharmacologic options for treating insomnia, and offers some guidance on medication selection to enhance personalized care. In addition, it discusses how the current evidence base can help providers make choices between pharmacologic and behavioral treatments.

Quantitative imaging of sleep behavior in Caenorhabditis elegans and larval Drosophila melanogaster

Sleep is nearly universal among animals, yet remains poorly understood. Recent work has leveraged simple model organisms, such as Caenorhabditis elegans and Drosophila melanogaster larvae, to investigate the genetic and neural bases of sleep. However, manual methods of recording sleep behavior in these systems are labor intensive and low in throughput. To address these limitations, we developed methods for quantitative imaging of individual animals cultivated in custom microfabricated multiwell substrates, and used them to elucidate molecular mechanisms underlying sleep. Here, we describe the steps necessary to design, produce, and image these plates, as well as analyze the resulting behavioral data. We also describe approaches for experimentally manipulating sleep. Following these procedures, after ~2 h of experimental preparation, we are able to simultaneously image 24 C. elegans from the second larval stage to adult stages or 20 Drosophila larvae during the second instar life stage at a spatial resolution of 10 or 27 µm, respectively. Although this system has been optimized to measure activity and quiescence in Caenorhabditis larvae and adults and in Drosophila larvae, it can also be used to assess other behaviors over short or long periods. Moreover, with minor modifications, it can be adapted for the behavioral monitoring of a wide range of small animals.

Behavioral and genetic features of sleep ontogeny in Drosophila

The fruit fly Drosophila melanogaster, like most organisms, exhibits increased sleep amount and depth in young compared to mature animals. While the fly has emerged as a powerful model for studying sleep during development, qualitative behavioral features of sleep ontogeny and its genetic control are poorly understood. Here we find that, in addition to increased sleep time and intensity, young flies sleep with less place preference than mature adults, and, like mammals, exhibit more motor twitches during sleep. In addition, we show that ontogenetic changes in sleep amount, twitch, and place preference are preserved across sleep mutants with lesions in distinct molecular pathways. Our results demonstrate that sleep ontogeny is characterized by multifaceted behavioral changes, including quantitative and qualitative alterations to sleep as animals mature. Further, the preservation of sleep ontogenetic changes despite mutations that alter sleep time suggests independent genetic control mechanisms for sleep maturation.

Starvation resistance is associated with developmentally specified changes in sleep, feeding and metabolic rate

Food shortage represents a primary challenge to survival, and animals have adapted diverse developmental, physiological and behavioral strategies to survive when food becomes unavailable. Starvation resistance is strongly influenced by ecological and evolutionary history, yet the genetic basis for the evolution of starvation resistance remains poorly understood. The fruit fly Drosophila melanogaster provides a powerful model for leveraging experimental evolution to investigate traits associated with starvation resistance. While control populations only live a few days without food, selection for starvation resistance results in populations that can survive weeks. We have previously shown that selection for starvation resistance results in increased sleep and reduced feeding in adult flies. Here, we investigate the ontogeny of starvation resistance-associated behavioral and metabolic phenotypes in these experimentally selected flies. We found that selection for starvation resistance resulted in delayed development and a reduction in metabolic rate in larvae that persisted into adulthood, suggesting that these traits may allow for the accumulation of energy stores and an increase in body size within these selected populations. In addition, we found that larval sleep was largely unaffected by starvation selection and that feeding increased during the late larval stages, suggesting that experimental evolution for starvation resistance produces developmentally specified changes in behavioral regulation. Together, these findings reveal a critical role for development in the evolution of starvation resistance and indicate that selection can selectively influence behavior during defined developmental time points.

Sleep and Metabolism: Eaat-ing Your Way to ZZZs

A new study in fruit flies identifies a molecule, Eaat2, that regulates both sleep and metabolic rate. Surprisingly, Eaat2 acts in a specific glial subtype to modulate both processes, suggesting a cellular link in the brain between sleep and metabolism.

A sleep state in Drosophila larvae required for neural stem cell proliferation

Sleep during development is involved in refining brain circuitry, but a role for sleep in the earliest periods of nervous system elaboration, when neurons are first being born, has not been explored. Here we identify a sleep state in Drosophila larvae that coincides with a major wave of neurogenesis. Mechanisms controlling larval sleep are partially distinct from adult sleep: octopamine, the Drosophila analog of mammalian norepinephrine, is the major arousal neuromodulator in larvae, but dopamine is not required. Using real-time behavioral monitoring in a closed-loop sleep deprivation system, we find that sleep loss in larvae impairs cell division of neural progenitors. This work establishes a system uniquely suited for studying sleep during nascent periods, and demonstrates that sleep in early life regulates neural stem cell proliferation.

Nearly all animals sleep more while they are still developing, suggesting that sleep is important in early life. Previous studies have shown that sleep may be required for building connections in the brain. However, it has been difficult to study the effects of sleep in earlier stages of brain development, when stem cells divide to create brain cells in a process known as “neurogenesis”. This is partly because, in mammals, most neurogenesis occurs in the womb.

Scientists have successfully studied sleep using the common fruit fly. But these studies have so far focused on adult flies, in which neurogenesis is mostly complete. Fly larvae, on the other hand, are widely used to study brain development and neurogenesis. Compared to mammals in the womb, fruit fly larvae are very easy to access and manipulate. However, unlike adult flies, no one had previously looked to see if larvae even display a behaviour that would fit the definition of sleep.

To see if fruit fly larvae do sleep, Szuperak et al. created the “LarvaLodge”, an apparatus in which individual larvae can be housed while having their activity monitored over time. In these lodges, a bright light was used to test how hard it is to arouse inactive fruit fly larvae, and further experiments asked what happens when larvae are prevented from resting. Then, to look at neurogenesis in the larvae, Szuperak et al. used a stain that labels dividing stem cells within the nervous system. Those cells could then be seen and counted when a larva was dissected and examined under a microscope.

The results from the LarvaLodge showed that fruit fly larvae do indeed sleep: they have extended periods of rest during which they react less to outside disturbances and adopt a particular posture (they retract their heads towards their bodies). Also when larvae were deprived of sleep, by shining a light or shaking, they compensated by sleeping more afterwards. Importantly, depriving the larvae of sleep also led to lower levels of neurogenesis. These findings establish the fruit fly larva as a new and useful system for studying the role of sleep in early development, and may help shed light on the role sleep plays in disorders affecting brain development.

Anti-NMDA Receptor Encephalitis, Autoimmunity, and Psychosis

(Reprinted with permission from Schizophrenia Research 2013; 176:36-40).

Changes in Female Drosophila Sleep following Mating Are Mediated by SPSN-SAG Neurons

Female Drosophila melanogaster, like many other organisms, exhibit different behavioral repertoires after mating with a male. These postmating responses (PMRs) include increased egg production and laying, increased rejection behavior (avoiding further male advances), decreased longevity, altered gustation and decreased sleep. Sex Peptide (SP), a protein transferred from the male during copulation, is largely responsible for many of these behavioral responses, and acts through a specific circuit to induce rejection behavior and alter dietary preference. However, less is known about the mechanisms and neurons that influence sleep in mated females. In this study, we investigated postmating changes in female sleep across strains and ages and on different media, and report that these changes are robust and relatively consistent under a variety of conditions. We find that female sleep is reduced by male-derived SP acting through the canonical sex peptide receptor (SPR) within the same neurons responsible for altering other PMRs. This circuit includes the SPSN-SAG neurons, whose silencing by DREADD induces postmating behaviors including sleep. Our data are consistent with the idea that mating status is communicated to the central brain through a common circuit that diverges in higher brain centers to modify a collection of postmating sensorimotor processes.

Anti-NMDA receptor encephalitis, autoimmunity, and psychosis

Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is a recently-discovered synaptic autoimmune disorder in which auto-antibodies target NMDARs in the brain, leading to their removal from the synapse. Patients manifest with prominent psychiatric symptoms - and in particular psychosis - early in the disease course. This presentation converges with long-standing evidence on multiple fronts supporting the glutamatergic model of schizophrenia. We review mechanisms underlying disease in anti-NMDAR encephalitis, and discuss its role in furthering our understanding of neural circuit dysfunction in schizophrenia.

Sleep deprivation suppresses aggression in Drosophila

Sleep disturbances negatively impact numerous functions and have been linked to aggression and violence. However, a clear effect of sleep deprivation on aggressive behaviors remains unclear. We find that acute sleep deprivation profoundly suppresses aggressive behaviors in the fruit fly, while other social behaviors are unaffected. This suppression is recovered following post-deprivation sleep rebound, and occurs regardless of the approach to achieve sleep loss. Genetic and pharmacologic approaches suggest octopamine signaling transmits changes in aggression upon sleep deprivation, and reduced aggression places sleep-deprived flies at a competitive disadvantage for obtaining a reproductive partner. These findings demonstrate an interaction between two phylogenetically conserved behaviors, and suggest that previous sleep experiences strongly modulate aggression with consequences for reproductive fitness.

A critical period of sleep for development of courtship circuitry and behavior in Drosophila

Most animals sleep more early in life than in adulthood, but the function of early sleep is not known. Using Drosophila, we found that increased sleep in young flies was associated with an elevated arousal threshold and resistance to sleep deprivation. Excess sleep results from decreased inhibition of a sleep-promoting region by a specific dopaminergic circuit. Experimental hyperactivation of this circuit in young flies results in sleep loss and lasting deficits in adult courtship behaviors. These deficits are accompanied by impaired development of a single olfactory glomerulus, VA1v, which normally displays extensive sleep-dependent growth after eclosion. Our results demonstrate that sleep promotes normal brain development that gives rise to an adult behavior critical for species propagation and suggest that rapidly growing regions of the brain are most susceptible to sleep perturbations early in life.

Frequency and characteristics of isolated psychiatric episodes in anti–N-methyl-d-aspartate receptor encephalitis

IMPORTANCE

Patients with anti–N-methyl-D-aspartate receptor (NMDAR) encephalitis often develop prominent psychiatric manifestations. The frequency and type of isolated psychiatric episodes (pure psychiatric symptoms without neurological involvement) either as initial presentation of the disease or as relapse are unknown.

OBJECTIVE

To determine the frequency, symptoms, and outcome of isolated psychiatric episodes in a cohort of patients with anti-NMDAR encephalitis.

DESIGN, SETTING, AND PARTICIPANTS

Observational cohort of patients diagnosed during a5-year period (median follow-up, 2 years). A total of 571 patients with IgG antibodies against the NR1 subunit of the NMDAR were included in the study. Antibody studies were performed at the University of Pennsylvania and the University of Barcelona, and clinical information was obtained by us or referring physicians.

MAIN OUTCOMES AND MEASURES

Frequency, type of symptoms, and outcome of patients with anti-NMDAR encephalitis and isolated psychiatric manifestations.

RESULTS

Of 571 patients, 23 (4%) developed isolated psychiatric episodes, 5 at disease onset and 18 during relapse. For all 23 patients, age (median, 20 years), sex (91%female), and tumor association (43%; ovarian teratoma in all cases) were similar to the population at large.Predominant symptoms included delusional thinking (74%), mood disturbances (70%,usually manic), and aggression (57%). Brain magnetic resonance imaging findings were abnormal in 10 of 22 patients (45%) and cerebrospinal fluid analysis showed pleocytosis in 17 of 22 patients (77%). Eighty-three percent of the patients had full or substantial recovery after immunotherapy and tumor resection when appropriate. After relapse, 17 of 18 patients(94%) returned to a similar or better prerelapse functional level.

CONCLUSIONS AND RELEVANCE

Isolated psychiatric episodes are rare but can occur as initial onset or relapse of anti-NMDAR encephalitis. Recognition of these episodes is important because they respond to immunotherapy. In patients with new-onset psychosis, having a history of encephalitis, subtle neurological symptoms, and/or abnormal results on ancillary tests should prompt screening for NMDAR antibodies.

The emerging link between autoimmune disorders and neuropsychiatric disease

Abnormal autoimmune activity has been implicated in a number of neuropsychiatric disorders. In this review, the authors discuss a newly recognized class of synaptic autoimmune encephalitides as well as behavioral and cognitive manifestations of systemic autoimmune diseases.

Anti-NMDA Receptor Encephalitis in Psychiatry

Anti-NMDA receptor encephalitis is an autoimmune disorder in which antibodies attack NMDA (N-methyl-D-aspartate)-type glutamate receptors at central neuronal synapses. Symptoms include a highly characteristic set of neurologic deficits, but also prominent psychiatric manifestations that often bring mental health professionals into the course of care. Distinct phases of illness have become increasingly appreciated, and include a range of psychotic symptoms early in the course of the disease followed by more severe fluctuations in consciousness with neurologic involvement, and ultimately protracted cognitive and behavioral deficits. Young women are most commonly impacted and an ovarian teratoma is sometimes associated with the syndrome. Patients respond well to immunotherapy, but psychiatric symptoms can be challenging to manage. We provide an up to date review of this disorder and highlight the role of psychiatry in diagnosis, symptomatology, and treatment.

Preferential control of basal dendritic protrusions by EphB2

The flow of information between neurons in many neural circuits is controlled by a highly specialized site of cell-cell contact known as a synapse. A number of molecules have been identified that are involved in central nervous system synapse development, but knowledge is limited regarding whether these cues direct organization of specific synapse types or on particular regions of individual neurons. Glutamate is the primary excitatory neurotransmitter in the brain, and the majority of glutamatergic synapses occur on mushroom-shaped protrusions called dendritic spines. Changes in the morphology of these structures are associated with long-lasting modulation of synaptic strength thought to underlie learning and memory, and can be abnormal in neuropsychiatric disease. Here, we use rat cortical slice cultures to examine how a previously-described synaptogenic molecule, the EphB2 receptor tyrosine kinase, regulates dendritic protrusion morphology in specific regions of the dendritic arbor in cortical pyramidal neurons. We find that alterations in EphB2 signaling can bidirectionally control protrusion length, and knockdown of EphB2 expression levels reduces the number of dendritic spines and filopodia. Expression of wild-type or dominant negative EphB2 reveals that EphB2 preferentially regulates dendritic protrusion structure in basal dendrites. Our findings suggest that EphB2 may act to specify synapse formation in a particular subcellular region of cortical pyramidal neurons.

The emerging link between autoimmune disorders and neuropsychiatric disease

Abnormal autoimmune activity has been implicated in a number of neuropsychiatric disorders. In this review, the authors discuss a newly recognized class of synaptic autoimmune encephalitides as well as behavioral and cognitive manifestations of systemic autoimmune diseases.

Psychiatric manifestations of paraneoplastic disorders

Paraneoplastic disorders of the CNS result from immune responses to neuronal proteins expressed by tumors found elsewhere in the body. Limbic encephalitis, one of the most common manifestations of paraneoplastic disorders, is characterized by rapid onset of psychiatric and neurological symptoms that often culminate in severe neurological deterioration. Recent work has described paraneoplastic syndromes with prominent, and sometimes isolated, psychiatric symptoms for which patients are fi rst seen by a psychiatrist. Here the authors review the existing literature on psychiatric and behavioral manifestations of paraneoplastic disorders, the cellular mechanisms underlying these syndromes, and current treatment and outcomes. They also discuss the broad behavioral findings that highlight the need for psychiatrists to be aware of initial presentations of paraneoplastic disorders.

Cell adhesion molecules: signalling functions at the synapse

Many cell adhesion molecules are localized at synaptic sites in neuronal axons and dendrites. These molecules bridge pre- and postsynaptic specializations but do far more than simply provide a mechanical link between cells. In this review, we will discuss the roles these proteins have during development and at mature synapses. Synaptic adhesion proteins participate in the formation, maturation, function and plasticity of synaptic connections. Together with conventional synaptic transmission mechanisms, these molecules are an important element in the trans-cellular communication mediated by synapses.

Intracellular and trans-synaptic regulation of glutamatergic synaptogenesis by EphB receptors

The majority of mature excitatory synapses in the CNS are found on dendritic spines and contain AMPA- and NMDA-type glutamate receptors apposed to presynaptic specializations. EphB receptor tyrosine kinase signaling has been implicated in both NMDA-type glutamate receptor clustering and dendritic spine formation, but it remains unclear whether EphB plays a broader role in presynaptic and postsynaptic development. Here, we find that EphB2 is involved in organizing excitatory synapses through the independent activities of particular EphB2 protein domains. We demonstrate that EphB2 controls AMPA-type glutamate receptor localization through PDZ (postsynaptic density-95/Discs large/zona occludens-1) binding domain interactions and triggers presynaptic differentiation via its ephrin binding domain. Knockdown of EphB2 in dissociated neurons results in decreased functional synaptic inputs, spines, and presynaptic specializations. Mice lacking EphB1-EphB3 have reduced numbers of synapses, and defects are rescued with postnatal reexpression of EphB2 in single neurons in brain slice. These results demonstrate that EphB2 acts to control the organization of specific classes of mature glutamatergic synapses.

Role for rapid dendritic protein synthesis in hippocampal mGluR-dependent long-term depression

A hippocampal pyramidal neuron receives more than 10(4) excitatory glutamatergic synapses. Many of these synapses contain the molecular machinery for messenger RNA translation, suggesting that the protein complement (and thus function) of each synapse can be regulated on the basis of activity. Here, local postsynaptic protein synthesis, triggered by synaptic activation of metabotropic glutamate receptors, was found to modify synaptic transmission within minutes.