Epigenetic silencing of selected hypothalamic neuropeptides in narcolepsy with cataplexy.

Narcolepsy with cataplexy is a sleep disorder caused by deficiency in the hypothalamic neuropeptide hypocretin/orexin (HCRT), unanimously believed to result from autoimmune destruction of hypocretin-producing neurons. HCRT deficiency can also occur in secondary forms of narcolepsy and be only temporary, suggesting it can occur without irreversible neuronal loss. The recent discovery that narcolepsy patients also show loss of hypothalamic (corticotropin-releasing hormone) CRH-producing neurons suggests that other mechanisms than cell-specific autoimmune attack, are involved. Here, we identify the HCRT cell-colocalized neuropeptide QRFP as the best marker of HCRT neurons. We show that if HCRT neurons are ablated in mice, in addition to Hcrt, Qrfp transcript is also lost in the lateral hypothalamus, while in mice where only the Hcrt gene is inactivated Qrfp is unchanged. Similarly, postmortem hypothalamic tissues of narcolepsy patients show preserved QRFP expression, suggesting the neurons are present but fail to actively produce HCRT. We show that the promoter of the HCRT gene of patients exhibits hypermethylation at a methylation-sensitive and evolutionary-conserved PAX5:ETS1 transcription factor-binding site, suggesting the gene is subject to transcriptional silencing. We show also that in addition to HCRT, CRH and Dynorphin (PDYN) gene promoters, exhibit hypermethylation in the hypothalamus of patients. Altogether, we propose that HCRT, PDYN, and CRH are epigenetically silenced by a hypothalamic assault (inflammation) in narcolepsy patients, without concurrent cell death. Since methylation is reversible, our findings open the prospect of reversing or curing narcolepsy.

Orexin 2 receptor-selective agonist danavorexton improves narcolepsy phenotype in a mouse model and in human patients.

Narcolepsy type 1 (NT1) is a sleep disorder caused by a loss of orexinergic neurons. Narcolepsy type 2 (NT2) is heterogeneous; affected individuals typically have normal orexin levels. Following evaluation in mice, the effects of the orexin 2 receptor (OX2R)-selective agonist danavorexton were evaluated in single- and multiple-rising-dose studies in healthy adults, and in individuals with NT1 and NT2. In orexin/ataxin-3 narcolepsy mice, danavorexton reduced sleep/wakefulness fragmentation and cataplexy-like episodes during the active phase. In humans, danavorexton administered intravenously was well tolerated and was associated with marked improvements in sleep latency in both NT1 and NT2. In individuals with NT1, danavorexton dose-dependently increased sleep latency in the Maintenance of Wakefulness Test, up to the ceiling effect of 40 min, in both the single- and multiple-rising-dose studies. These findings indicate that OX2Rs remain functional despite long-term orexin loss in NT1. OX2R-selective agonists are a promising treatment for both NT1 and NT2.

Bi-allelic variants in HCRT cause autosomal recessive narcolepsy.

Narcolepsy with cataplexy is a complex disease with both genetic and environmental risk factors. To gain further insight into the homozygous HCRT-related narcolepsy, we present a case series of five patients from two consanguineous families, each harboring a novel homozygous variant of HCRT c.17_18del. All affected individuals exhibited severe cataplexy accompanied by narcolepsy symptoms during infancy. Additionally, cataplexy symptoms improved or disappeared in the majority of patients over time. Pathogenic variants in HCRT cause autosomal recessive narcolepsy with cataplexy. Genetic testing of the HCRT gene should be conducted in specific subgroups of narcolepsy, particularly those with early onset, familial cases, and a predominantly cataplexy phenotype.

A Discrete Glycinergic Neuronal Population in the Ventromedial Medulla That Induces Muscle Atonia during REM Sleep and Cataplexy in Mice.

During rapid eye movement (REM) sleep, anti-gravity muscle tone and bodily movements are mostly absent, because somatic motoneurons are inhibited by descending inhibitory pathways. Recent studies showed that glycine/GABA neurons in the ventromedial medulla (VMM; GlyVMM neurons) play an important role in generating muscle atonia during REM sleep (REM-atonia). However, how these REM-atonia-inducing neurons interconnect with other neuronal populations has been unknown. In the present study, we first identified a specific subpopulation of GlyVMM neurons that play an important role in induction of REM-atonia by virus vector-mediated tracing in male mice in which glycinergic neurons expressed Cre recombinase. We found these neurons receive direct synaptic input from neurons in several brain stem regions, including glutamatergic neurons in the sublaterodorsal tegmental nucleus (SLD; GluSLD neurons). Silencing this circuit by specifically expressing tetanus toxin light chain (TeTNLC) resulted in REM sleep without atonia. This manipulation also caused a marked decrease in time spent in cataplexy-like episodes (CLEs) when applied to narcoleptic orexin-ataxin-3 mice. We also showed that GlyVMM neurons play an important role in maintenance of sleep. This present study identified a population of glycinergic neurons in the VMM that are commonly involved in REM-atonia and cataplexy.SIGNIFICANCE STATEMENT We identified a population of glycinergic neurons in the ventral medulla that plays an important role in inducing muscle atonia during rapid eye movement (REM) sleep. It sends axonal projections almost exclusively to motoneurons in the spinal cord and brain stem except to those that innervate extraocular muscles, while other glycinergic neurons in the same region also send projections to other regions including monoaminergic nuclei. Furthermore, these neurons receive direct inputs from several brainstem regions including glutamatergic neurons in the sublaterodorsal tegmental nucleus (SLD). Genetic silencing of this pathway resulted in REM sleep without atonia and a decrease of cataplexy when applied to narcoleptic mice. This work identified a neural population involved in generating muscle atonia during REM sleep and cataplexy.

GABAergic Neurons of the Central Amygdala Promote Cataplexy.

Narcolepsy is characterized by chronic sleepiness and cataplexy-sudden muscle paralysis triggered by strong, positive emotions. This condition is caused by a lack of orexin (hypocretin) signaling, but little is known about the neural mechanisms that mediate cataplexy. The amygdala regulates responses to rewarding stimuli and contains neurons active during cataplexy. In addition, lesions of the amygdala reduce cataplexy. Because GABAergic neurons of the central nucleus of the amygdala (CeA) target brainstem regions known to regulate muscle tone, we hypothesized that these cells promote emotion-triggered cataplexy. We injected adeno-associated viral vectors coding for Cre-dependent DREADDs or a control vector into the CeA of orexin knock-out mice crossed with vGAT-Cre mice, resulting in selective expression of the excitatory hM3 receptor or the inhibitory hM4 receptor in GABAergic neurons of the CeA. We measured sleep/wake behavior and cataplexy after injection of saline or the hM3/hM4 ligand clozapine-N-oxide (CNO) under baseline conditions and under conditions that should elicit positive emotions. In mice expressing hM3, CNO approximately doubled the amount of cataplexy in the first 3 h after dosing under baseline conditions. Rewarding stimuli (chocolate or running wheels) also increased cataplexy, but CNO produced no further increase. In mice expressing hM4, CNO reduced cataplexy in the presence of chocolate or running wheels. These results demonstrate that GABAergic neurons of the CeA are sufficient and necessary for the production of cataplexy in mice, and they likely are a key part of the mechanism through which positive emotions trigger cataplexy.SIGNIFICANCE STATEMENT Cataplexy is one of the major symptoms of narcolepsy, but little is known about how strong, positive emotions trigger these episodes of muscle paralysis. Prior research shows that amygdala neurons are active during cataplexy and cataplexy is reduced by lesions of the amygdala. We found that cataplexy is substantially increased by selective activation of GABAergic neurons in the central nucleus of the amygdala (CeA). We also demonstrate that inhibition of these neurons reduces reward-promoted cataplexy. These results build upon prior work to establish the CeA as a crucial element in the neural mechanisms of cataplexy. These results demonstrate the importance of the CeA in regulating responses to rewarding stimuli, shedding light on the broader neurobiology of emotions and motor control.

Rare missense mutations in P2RY11 in narcolepsy with cataplexy.

The sleep disorder narcolepsy with cataplexy is characterized by a highly specific loss of hypocretin (orexin) neurons, leading to the hypothesis that the condition is caused by an immune or autoimmune mechanism. All genetic variants associated with narcolepsy are immune-related. Among these are single nucleotide polymorphisms in the P2RY11-EIF3G locus. It is unknown how these genetic variants affect narcolepsy pathogenesis and whether the effect is directly related to P2Y11 signalling or EIF3G function. Exome sequencing in 18 families with at least two affected narcolepsy with cataplexy subjects revealed non-synonymous mutations in the second exon of P2RY11 in two families, and P2RY11 re-sequencing in 250 non-familial cases and 135 healthy control subjects revealed further six different non-synonymous mutations in the second exon of P2RY11 in seven patients. No mutations were found in healthy controls. Six of the eight narcolepsy-associated P2Y11 mutations resulted in significant functional deficits in P2Y11 signalling through both Ca2+ and cAMP signalling pathways. In conclusion, our data show that decreased P2Y11 signalling plays an important role in the development of narcolepsy with cataplexy.

Clinical heterogeneity associated with KCNA1 mutations include cataplexy and nonataxic presentations.

Mutations in the KCNA1 gene are known to cause episodic ataxia/myokymia syndrome type 1 (EA1). Here, we describe two families with unique presentations who were enrolled in an IRB-approved study, extensively phenotyped, and whole exome sequencing (WES) performed. Family 1 had a diagnosis of isolated cataplexy triggered by sudden physical exertion in multiple affected individuals with heterogeneous neurological findings. All enrolled affected members carried a KCNA1 c.941T>C (p.I314T) mutation. Family 2 had an 8-year-old patient with muscle spasms with rigidity for whom WES revealed a previously reported heterozygous missense mutation in KCNA1 c.677C>G (p.T226R), confirming the diagnosis of EA1 without ataxia. WES identified variants in KCNA1 that explain both phenotypes expanding the phenotypic spectrum of diseases associated with mutations of this gene. KCNA1 mutations should be considered in patients of all ages with episodic neurological phenotypes, even when ataxia is not present. This is an example of the power of genomic approaches to identify pathogenic mutations in unsuspected genes responsible for heterogeneous diseases.

High-amplitude theta wave bursts characterizing narcoleptic mice and patients are also produced by histamine deficiency in mice.

Histamine and orexins are wake promoters released by hypothalamic neurons. The activity of histamine neurons is increased by orexin neurons. Recently, it has been shown that orexin deficiency entails high-amplitude theta wave bursts during rapid eye movement sleep and cataplexy in narcoleptic mice. The primary aim of this study was to assess whether histamine system is involved in high-amplitude theta wave burst generation during rapid eye movement sleep. The secondary aim was to assess the effects of combined histamine and orexin deficiency on high-amplitude theta wave bursts during rapid eye movement sleep in mice. Twelve histidine-decarboxylase knockout mice with congenital histamine deficiency, seven double mutant mice with combined deficiency of orexin neurons and histamine, and 11 wild-type control mice were studied with electrodes for sleep recordings and a telemetric blood pressure transducer. High-amplitude theta wave bursts during rapid eye movement sleep were detected in each of the histidine-decarboxylase knockout and double mutant mice, whereas only one burst was found in a wild-type control mouse. High-amplitude theta wave bursts occurred significantly more often and were significantly longer in double mutant than in histidine-decarboxylase knockout mice. In conclusion, it was demonstrated that, similarly to orexin, the chronic impairment of histamine entailed high-amplitude theta wave bursts during rapid eye movement sleep. The current data also suggested a synergistic role of orexin and histamine signalling on high-amplitude theta wave bursts during rapid eye movement sleep in mice.

A novel DNMT1 mutation associated with early onset hereditary sensory and autonomic neuropathy, cataplexy, cerebellar atrophy, scleroderma, endocrinopathy, and common variable immune deficiency.

DNA methyltransferase 1 (DNMT1) is an enzyme which has a role in methylation of DNA, gene regulation, and chromatin stability. Missense mutations in the DNMT1 gene have been previously associated with two neurological syndromes: hereditary sensory and autonomic neuropathy type 1 with dementia and deafness (HSAN1E) and autosomal dominant cerebellar ataxia, deafness, and narcolepsy (ADCA-DN). We report a case showing overlap of both of these syndromes plus associated clinical features of common variable immune deficiency, scleroderma, and endocrinopathy that could also be mutation associated. Our patient was found to be heterozygous for a previously unreported frameshift mutation, c.1635_1637delCAA p.(Asn545del) in the DNMT1 gene exon 20. This case displays both the first frameshift mutation described in the literature which is associated with a phenotype with a high degree of overlap between HSAN1E and ADCA-DN and early age of onset (c. 8 years). Our case is also of interest as the patient displays a number of new non-neurological features, which could also be DNMT1 mutation related.

Highlights from the 15th International Congress of Twin Studies/Twin Research: Differentiating MZ Co-twins Via SNPs; Mistaken Infant Twin-Singleton Hospital Registration; Narcolepsy With Cataplexy; Hearing Loss and Language Learning/Media Mentions: Broadway Musical Recalls Conjoined Hilton Twins; High Fashion Pair; Twins Turn 102; Insights From a Conjoined Twin Survivor.

Highlights from the 15th International Congress of Twin Studies are presented. The congress was held November 16-19, 2014 in Budapest, Hungary. This report is followed by summaries of research addressing the differentiation of MZ co-twins by single nucleotide polymorphisms (SNPs), an unusual error in infant twin-singleton hospital registration, twins with childhood-onset narcolepsy with cataplexy, and the parenting effects of hearing loss in one co-twin. Media interest in twins covers a new Broadway musical based on the conjoined twins Violet and Daisy Hilton, male twins becoming famous in fashion, twins who turned 102 and unique insights from a conjoined twin survivor. This article is dedicated to the memory of Elizabeth (Liz) Hamel, DZA twin who met her co-twin for the first time at age seventy-eight years. Liz and her co-twin, Ann Hunt, are listed in the 2015 Guinness Book of Records as the longest separated twins in the world.

High amplitude theta wave bursts: a novel electroencephalographic feature of rem sleep and cataplexy.

High amplitude theta wave bursts (HATs) were originally described during REMS and cataplexy in ORX-deficient mice as a novel neurophysiological correlate of narcolepsy (Bastianini et al., 2012). This finding was replicated the following year by Vassalli et al. in both ORX-deficient narcoleptic mice and narcoleptic children during cataplexy episodes (Vassalli et al., 2013). The relationship between HATs and narcolepsy-cataplexy in mice and patients indicates that the lack of ORX peptides is responsible for this abnormal EEG activity, the physiological meaning of which is still unknown. This review aimed to explore different phasic EEG events previously described in the published literature in order to find analogies and differences with HATs observed in narcoleptic mice and patients. We found similarities in terms of morphology, frequency and duration between HATs and several physiological (mu and wicket rhythms, sleep spindles, saw-tooth waves) or pathological (SWDs, HVSs, bursts of polyphasic complexes EEG complexes reported in a mouse model of CJD, and BSEs) EEG events. However, each of these events also shows significant differences from HATs, and thus cannot be equaled to them. The available evidence thus suggests that HATs are a novel neurophysiological phenomenon. Further investigations on HATs are required in order to investigate their physiological meaning, to individuate their brain structure(s) of origin, and to clarify the neural circuits involved in their manifestation.

Role of the medial prefrontal cortex in cataplexy.

Narcolepsy is characterized by chronic sleepiness and cataplexy, episodes of profound muscle weakness that are often triggered by strong, positive emotions. Narcolepsy with cataplexy is caused by a loss of orexin (also known as hypocretin) signaling, but almost nothing is known about the neural mechanisms through which positive emotions trigger cataplexy. Using orexin knock-out mice as a model of narcolepsy, we found that palatable foods, especially chocolate, markedly increased cataplexy and activated neurons in the medial prefrontal cortex (mPFC). Reversible suppression of mPFC activity using an engineered chloride channel substantially reduced cataplexy induced by chocolate but did not affect spontaneous cataplexy. In addition, neurons in the mPFC innervated parts of the amygdala and lateral hypothalamus that contain neurons active during cataplexy and that innervate brainstem regions known to regulate motor tone. These observations indicate that the mPFC is a critical site through which positive emotions trigger cataplexy.

Electroencephalogram paroxysmal θ characterizes cataplexy in mice and children.

Astute control of brain activity states is critical for adaptive behaviours and survival. In mammals and birds, electroencephalographic recordings reveal alternating states of wakefulness, slow wave sleep and paradoxical sleep (or rapid eye movement sleep). This control is profoundly impaired in narcolepsy with cataplexy, a disease resulting from the loss of orexin/hypocretin neurotransmitter signalling in the brain. Narcolepsy with cataplexy is characterized by irresistible bouts of sleep during the day, sleep fragmentation during the night and episodes of cataplexy, a sudden loss of muscle tone while awake and experiencing emotions. The neural mechanisms underlying cataplexy are unknown, but commonly thought to involve those of rapid eye movement-sleep atonia, and cataplexy typically is considered as a rapid eye movement sleep disorder. Here we reassess cataplexy in hypocretin (Hcrt, also known as orexin) gene knockout mice. Using a novel video/electroencephalogram double-blind scoring method, we show that cataplexy is not a state per se, as believed previously, but a dynamic, multi-phased process involving a reproducible progression of states. A knockout-specific state and a stereotypical paroxysmal event were introduced to account for signals and electroencephalogram spectral characteristics not seen in wild-type littermates. Cataplexy almost invariably started with a brief phase of wake-like electroencephalogram, followed by a phase featuring high-amplitude irregular theta oscillations, defining an activity profile distinct from paradoxical sleep, referred to as cataplexy-associated state and in the course of which 1.5-2 s high-amplitude, highly regular, hypersynchronous paroxysmal theta bursts (∼7 Hz) occurred. In contrast to cataplexy onset, exit from cataplexy did not show a predictable sequence of activities. Altogether, these data contradict the hypothesis that cataplexy is a state similar to paradoxical sleep, even if long cataplexies may evolve into paradoxical sleep. Although not exclusive to overt cataplexy, cataplexy-associated state and hypersynchronous paroxysmal theta activities are highly enriched during cataplexy in hypocretin/orexin knockout mice. Their occurrence in an independent narcolepsy mouse model, the orexin/ataxin 3 transgenic mouse, undergoing loss of orexin neurons, was confirmed. Importantly, we document for the first time similar paroxysmal theta hypersynchronies (∼4 Hz) during cataplexy in narcoleptic children. Lastly, we show by deep recordings in mice that the cataplexy-associated state and hypersynchronous paroxysmal theta activities are independent of hippocampal theta and involve the frontal cortex. Cataplexy hypersynchronous paroxysmal theta bursts may represent medial prefrontal activity, associated in humans and rodents with reward-driven motor impulse, planning and conflict monitoring.

Narcolepsy: an interface among neurology, immunology, sleep, and genetics.

Narcolepsy is a primary disorder of the central nervous system resulting from genetic, environmental, and immunological interactions defined as excessive daytime sleepiness plus cataplexy, hallucinations, sleep paralysis, and sleep fragmentation. The pathophysiology is not entirely known, but the interaction among genetic predisposition, environmental exposition, and immune component with consequent hypocretin-1 deficiency is the model to explain narcolepsy type I. The mechanism of narcolepsy type II is less understood. There is a delay of over ten years for the diagnosis of narcolepsy around the world. Patients with narcolepsy have many comorbidities with a negative impact on quality of life. The treatment of narcolepsy must contain an educational approach for the family, coworkers, and patients. Scheduled naps and sleep hygiene are essential to minimize the dose of medications. Much progress has been seen in the pharmacological treatment of narcolepsy with new stimulants, different presentations of oxybate, and recent studies with orexin agonists. Narcolepsy is a rare disease that needs to be more understood and highlighted to avoid delayed diagnosis and severe disabilities in patients.

A narcolepsia é um distúrbio primário do sistema nervoso central resultante das interações genéticas, ambientais e imunológicas definidas como sonolência diurna excessiva mais cataplexia, alucinações, paralisia do sono e fragmentação do sono. A fisiopatologia não é completamente conhecida, mas a interação entre predisposição genética, exposição ambiental e componente imunológico com consequente deficiência de hipocretina-1 é o modelo para explicar a narcolepsia tipo I. O mecanismo da narcolepsia tipo II é menos compreendido. Há um atraso de mais de dez anos para o diagnóstico da narcolepsia em todo o mundo. Pacientes com narcolepsia apresentam muitas comorbidades com impacto negativo na qualidade de vida. O tratamento da narcolepsia deve conter uma abordagem educativa para a família, colegas de trabalho e pacientes. Cochilos programados e higiene do sono são importantes para minimizar a dose dos medicamentos. Muito progresso foi observado no tratamento farmacológico da narcolepsia com novos estimulantes, diferentes apresentações de oxibato e estudos recentes com agonistas de orexina. A narcolepsia é uma doença rara que precisa ser mais compreendida e destacada para evitar atrasos no diagnóstico e incapacidades graves nos pacientes.

Clinical, polysomnographic and genome-wide association analyses of narcolepsy with cataplexy: a European Narcolepsy Network study.

The aim of this study was to describe the clinical and PSG characteristics of narcolepsy with cataplexy and their genetic predisposition by using the retrospective patient database of the European Narcolepsy Network (EU-NN). We have analysed retrospective data of 1099 patients with narcolepsy diagnosed according to International Classification of Sleep Disorders-2. Demographic and clinical characteristics, polysomnography and multiple sleep latency test data, hypocretin-1 levels, and genome-wide genotypes were available. We found a significantly lower age at sleepiness onset (men versus women: 23.74 ± 12.43 versus 21.49 ± 11.83, P = 0.003) and longer diagnostic delay in women (men versus women: 13.82 ± 13.79 versus 15.62 ± 14.94, P = 0.044). The mean diagnostic delay was 14.63 ± 14.31 years, and longer delay was associated with higher body mass index. The best predictors of short diagnostic delay were young age at diagnosis, cataplexy as the first symptom and higher frequency of cataplexy attacks. The mean multiple sleep latency negatively correlated with Epworth Sleepiness Scale (ESS) and with the number of sleep-onset rapid eye movement periods (SOREMPs), but none of the polysomnographic variables was associated with subjective or objective measures of sleepiness. Variant rs2859998 in UBXN2B gene showed a strong association (P = 1.28E-07) with the age at onset of excessive daytime sleepiness, and rs12425451 near the transcription factor TEAD4 (P = 1.97E-07) with the age at onset of cataplexy. Altogether, our results indicate that the diagnostic delay remains extremely long, age and gender substantially affect symptoms, and that a genetic predisposition affects the age at onset of symptoms.

Role of pontine sub-laterodorsal tegmental nucleus (SLD) in rapid eye movement (REM) sleep, cataplexy, and emotion.

Pontine sub-laterodorsal tegmental nucleus (SLD) is crucial for REM sleep. However, the necessary role of SLD for REM sleep, cataplexy that resembles REM sleep, and emotion memory by REM sleep has remained unclear. To address these questions, we focally ablated SLD neurons using adenoviral diphtheria-toxin (DTA) approach and found that SLD lesions completely eliminated REM sleep accompanied by wake increase, significantly reduced baseline cataplexy amounts by 40% and reward (sucrose) induced cataplexy amounts by 70% and altered cataplexy EEG Fast Fourier Transform (FFT) from REM sleep-like to wake-like in orexin null (OXKO) mice. We then used OXKO animals with absence of REM sleep and OXKO controls and examined elimination of REM sleep in anxiety and fear extinction. Our resulted showed that REM sleep elimination significantly increased anxiety-like behaviors in open field test (OFT), elevated plus maze test (EPM) and defensive aggression and impaired fear extinction. The data indicate that in OXKO mice the SLD is the sole generator for REM sleep; (2) the SLD selectively mediates REM sleep cataplexy (R-cataplexy) that merges with wake cataplexy (W-cataplexy); (3) REM sleep enhances positive emotion (sucrose induced cataplexy) response, reduces negative emotion state (anxiety), and promotes fear extinction.

A series of 7 cases of patients with narcolepsy with hypocretin deficiency without the HLA DQB1*06:02 allele.

STUDY OBJECTIVES: We report data collected from 2 reference European sleep centers on a series of patients with narcolepsy with hypocretin-1 deficiency and absence of the human leukocyte antigens (HLA) DQB1*06:02 allele. METHODS: Clinical data, HLA DQ markers, and cerebrospinal fluid assessments were collected retrospectively from Caucasian patients with a diagnosis of narcolepsy type 1 with cerebrospinal fluid hypocretin-1 deficiency (< 110 pg/ml) and absence of the HLA DQB1*06:02 allele, with follow-up with at least 1 visit within the last 4 years, consecutively admitted to 2 European sleep centers (Lugano, Switzerland and Montpellier, France). RESULTS: Seven patients (3 of 29 patients in Lugano and 4 of 328 in Montpellier) were diagnosed with narcolepsy with hypocretin-1 deficiency and absence of HLA DQB1*06:02 (ie, 2% of patients with narcolepsy type 1). Regarding the HLA-DQB1 genotyping, 4 cases were positive for HLA DQB1*03:01, 1 for DQB1*03:02, and 3 for DQB1*02:01. Three patients had atypical cataplexy and 1 had no cataplexy. Only 2 patients had both a mean sleep latency of less than 8 minutes and more than 2 sleep onset rapid eye movement periods on the Multiple Sleep Latency Test, indicative of a less severe condition. CONCLUSIONS: Although rare, this series of 7 cases confirms that hypocretin-deficient narcolepsy should not be excluded in the absence of HLA DQB1*06:02, especially if patients are carriers of other high-risk HLA-DQB1 alleles (DQB1*03:01, *03:02, *02:01). These data support the hypothesis that narcolepsy type 1 is a wider disease spectrum linked to the loss of hypocretin peptide. CITATION: Miano S, Barateau L, De Pieri M, et al. A series of 7 cases of patients with narcolepsy with hypocretin deficiency without the HLA DQB1*06:02 allele. J Clin Sleep Med. 2023;19(12):2053-2057.

A unique association? A narcolepsy type 1 case comorbid with Primary Biliary Cholangitis.

The aim of the study was to present a woman affected of a narcolepsy with cataplexy (narcolepsy type 1) comorbid with an asymptomatic Primary Biliary Cholangitis (PBC). The HLA haplotype was DRB1*15:01, DQA1*01:02, DQB1*06:02. The allele DQB1*06:02 has been considered until now protective for PBC and dual pathology has not been published. We think the important clinical message of the Case would be of continuing to monitor adults with narcolepsy type 1 for late complications that may be associated with other autoimmune conditions. Clinicians should be aware of the relationship between Narcolepsy and PBC. This highlights the need for screening and management in these individuals.

Pharmacological options for narcolepsy: are they the way forward?

INTRODUCTION: Narcolepsy is an under-recognized, rare neurologic disorder of hypersomnolence that is associated with increased mortality and medical and psychiatric co-morbidities. Narcolepsy exerts a substantial economic burden on patients and society. There is currently no cure, and life-long symptomatic therapy is needed. Available drugs do not modify the disease course. AREAS COVERED: This manuscript provides an overview of narcolepsy symptoms, diagnosis, pathophysiology, current pharmacotherapies, and emerging treatments. Gaps and unresolved issues in diagnosis and management of narcolepsy are discussed to answer whether pharmacological options are the way forward. EXPERT OPINION: Diagnostic criteria for narcolepsy (ICSD-3) need revision and greater clarity. Improved recognition of cataplexy and other symptoms through educational outreach, new biomarkers, improved test scoring through artificial intelligence algorithms, and use of machine learning may facilitate earlier diagnosis and treatment. Pharmacological options need improved symptomatic therapy in addition to targeted therapies that address the loss of hypocretin signaling. Optimal narcolepsy care also needs a better understanding of the pathophysiology, recognition of the different phenotypes in narcolepsy, identification of at-risk individuals and early recognition of symptoms, better diagnostic tools, and a database for research and disease monitoring of treatment, side-effects, and comorbidities.

Orexin gene transfer into zona incerta neurons suppresses muscle paralysis in narcoleptic mice.

Cataplexy, a sudden unexpected muscle paralysis, is a debilitating symptom of the neurodegenerative sleep disorder, narcolepsy. During these attacks, the person is paralyzed, but fully conscious and aware of their surroundings. To identify potential neurons that might serve as surrogate orexin neurons to suppress such attacks, the gene for orexin (hypocretin), a peptide lost in most human narcoleptics, was delivered into the brains of the orexin-ataxin-3 transgenic mouse model of human narcolepsy. Three weeks after the recombinant adenoassociated virus (rAAV)-mediated orexin gene transfer, sleep-wake behavior was assessed. rAAV-orexin gene delivery into neurons of the zona incerta (ZI), or the lateral hypothalamus (LH) blocked cataplexy. Orexin gene transfer into the striatum or in the melanin-concentrating hormone neurons in the ZI or LH had no such effect, indicating site specificity. In transgenic mice lacking orexin neurons but given rAAV-orexin, detectable levels of orexin-A were evident in the CSF, indicating release of the peptide from the surrogate neurons. Retrograde tracer studies showed that the amygdala innervates the ZI consistent with evidence that strong emotions trigger cataplexy. In turn, the ZI projects to the locus ceruleus, indicating that the ZI is part of a circuit that stabilizes motor tone. Our results indicate that these neurons might also be recruited to block the muscle paralysis in narcolepsy.