The Phenotypic Continuum of ATP1A3-Related Disorders

Subjective cognitive decline in conjunction with cerebrospinal fluid anti-ATP1A3 autoantibodies and a low amyloid β 1-42/1-40 ratio: Report and literature review

BACKGROUND

Animal studies reveal the role of the sodium/potassium transporting ATPase α-3 subunit (ATP1A3) in maintaining the resting membrane potential and thus in synaptic information processing and potentially cognitive disorders. However, autoantibodies against AT1A3 have not previously been reported in patients with subjective cognitive decline.

CASE PRESENTATION

We report the case of a 57-year-old female who underwent neuropsychological testing, magnetic resonance imaging (MRI) and 18 F fluorodesoxyglucose positron emission tomography (FDG-PET) imaging, and cerebrospinal fluid (CSF) analysis. Neural autoantibodies were assessed in serum and CSF. We found a normal cognitive profile together with a self-reported cognitive decline, and such consistent with subjective cognitive decline (SCD). Analysis of the cerebrospinal fluid revealed anti-ATP1A3 autoantibodies. ATP1A3 autoantibodies were also detected in serum. Analysis of amyloid pathology markers in the CSF showed a slightly reduced amyloid β1-42/ amyloid β1-40 ratio. In view of the possible paraneoplastic autoantibodies, whole-body FDG-PET was performed, which did not reveal a malignancy-specific lesion. FDG-PET of the brain also showed no hypometabolism. We diagnosed SCD based on CSF-affirmed possible Alzheimer´s pathologic change with ATP1A3 autoantibodies in CSF and serum.

CONCLUSIONS

To our knowledge, this is the first report of CSF and serum ATP1A3 autoantibodies associated with SCD although an incidental finding cannot be fully excluded. In addition, amyloid pathology was detected via CSF biomarkers, suggesting that ATP1A3 autoantibodies are a potentially promising biomarker in SCD with an Alzheimer´s pathologic change if confirmed in large-scale studies.

Unusual Phenotypic Variability in Paroxysmal Dystonia Associated with Rare ATP1A3 Mutation: A Case Report and Review

Paroxysmal dyskinesias, marked by sudden involuntary movements, poses diagnostic challenges because of its heterogeneous nature and overlap with other movement disorders. Genetic factors, especially variants in the ATP1A3 gene, have been linked to various neurologic conditions, including paroxysmal dystonia. We report a 5-year-old patient with a rare ATP1A3 gene variant (c.2309T>G, p.(Leu770Arg)), previously documented in only 1 other patient. Unlike the earlier report, the patient presented distinct clinical features, with a focus on dystonia rather than hemiplegia and no intellectual impairment. This phenotypic variability highlights the challenges in diagnosis and treatment. We discuss differential diagnoses, including Alternating Hemiplegia of Childhood, and emphasize the need for comprehensive genetic testing and multidisciplinary care. Our study advocates for further research to better understand the spectrum of ATP1A3-related disorders and enhance diagnostic accuracy and patient management in paroxysmal dystonia.

ATP1A3 Variants, Variably Penetrant Short QT Intervals, and Lethal Ventricular Arrhythmias

Importance

Alternating hemiplegia of childhood (AHC) is a disorder that can result from pathogenic variants in ATP1A3-encoded sodium-potassium adenosine triphosphatase alpha 3 (ATP1A3). While AHC is primarily a neurologic disease, some individuals experience sudden unexplained death (SUD) potentially associated with cardiac arrhythmias.

Objective

To determine the impact of ATP1A3 variants on cardiac electrophysiology and whether lethal ventricular arrhythmias are associated with SUD in patients with AHC.

Design, Setting, and Participants

In this international, multicenter case-control study from 12 centers across 10 countries, patients with AHC were grouped by ATP1A3 variant status (positive vs negative) and into subgroups with the most common AHC variants (D801N, E815K, G947R, and other). A healthy control cohort was established for comparison. Blinded, manual measurements of QT intervals and corrected QT interval (QTc) were performed independently by 2 pediatric cardiac electrophysiologists. Induced pluripotent stem cell cardiomyocytes were derived from patients with AHC who were positive for the D801N variant of ATP1A3 (iPSC-CMD801N cells). Data analysis was performed from April to June 2022.

Exposure

Presence of ATP1A3 variant.

Main Outcomes and Measures

The primary outcome was QTc. Outcomes, including survival, were abstracted and variants were mapped on cryogenic electron microscopy structure maps. iPSC-CMD801N cells were used to validate ventricular repolarization and arrhythmic susceptibility in vitro.

Results

Among the 222 individuals included (148 with AHC and 74 control), the mean (SD) age at diagnostic electrocardiography was 11.0 (9.4) years and 119 (54%) were female. The cohort with AHC consisted of 148 largely unrelated probands (mean [SD] age at diagnostic electrocardiography, 11.5 [10.5] years). Of these, 123 individuals were ATP1A3 genotype positive, including 35 (28%) with the D801N variant, 21 (17%) with the E815K variant, 8 (7%) with the G947R variant, and 8 (7%) with a loss-of-function variant. Probands with the D801N variant had shorter mean (SD) QTcs (381.8 [36.6] milliseconds; 24 [69%] with QTc <370 milliseconds) compared with those who had the E815K variant (393.6 [43.1] milliseconds; P = .001; 4 [19%] with QTC <370 milliseconds), the G947R variant (388.4 [26.5] milliseconds; P = .02; 1 [13%] with QTc <370 milliseconds), a loss-of-function variant (403.0 [33.5] milliseconds; P < .001; 1 [13%] with QTc <370 milliseconds), all other variants (387.8 [37.1] milliseconds; P < .001; 44 [86%] with QTc <370 milliseconds), and healthy controls (415.4 [21.0] milliseconds; P < .001; 0 with QTc <370 milliseconds). Three D801N-positive individuals had a major cardiac event, compared with 0 major cardiac events in all other individuals (P = .02). The D801N variant and 4 rare variants (D805N, P323S, S772R, and C333F) found in individuals with the shortest QTcs localized to the potassium-binding domain of ATP1A3. IPSC-CMD801N lines demonstrated shortened action potential duration, higher mean diastolic potential, and delayed afterdepolarizations compared with controls.

Conclusions and Relevance

Nearly 70% of individuals with D801N variants of ATP1A3 had short QTcs (<370 milliseconds), with an association between ventricular arrhythmias and cardiac arrest. This may underlie the SUD etiology in AHC.

Neurological and psychiatric characterization of rapid-onset dystonia-parkinsonism over time

INTRODUCTION

The onset of symptoms in Rapid-onset dystonia-parkinsonism (RDP) is typically over days to weeks and is often triggered by stressors like fever or childbirth. Limited information is available on how the motor and nonmotor symptoms evolve over the course of the disease. Our longitudinal study analyzed data from a cohort of RDP patients, documenting their symptoms across multiple visits.

METHODS

We characterized the phenotypic evolution of 14 individuals positive for ATP1A3 mutations (7 females, 7 males; mean examination age = 37 years, mean age of onset = 20 years). We focused on neurologic, cognitive, and neuropsychological data collected during in-person visits (mean interval between testing = 5½ years).

RESULTS

Initially, all participants exhibited bulbar symptoms. Headaches were noted in 50 %, seizures in 31 %, and tremors in 36 %. At follow-up, 29 % of those initially without headaches developed them, 22 % without prior seizures experienced them, and 56 % previously without tremors developed them. No improvements were seen in those with headaches; however, seizures and tremors improved in 25 % and 80 % of cases, respectively. For Burke-Fahn-Marsden Dystonia Rating Scale, Unified Parkinson's Disease Rating Scale, and International Cooperative Ataxia Rating Scale scores, improvement consisted of the reduction of the symptom. Cognitive functions improved from mildly impaired to low-average, and psychiatric evaluations indicated mild anxiety levels, slight increases in obsessive-compulsive behaviors, and decreased depression scores over time.

CONCLUSIONS

This longitudinal analysis highlights the complex evolution of RDP, demonstrating significant variability in motor function and other symptoms such as headaches, seizures, and tremors.

Genetic Diversity and Expanded Phenotypes in Dystonia: Insights from Large-Scale Exome Sequencing

Dystonia is one of the most prevalent movement disorders, characterized by significant clinical and etiological heterogeneity. Despite considerable heritability (~25%) and the identification of several disease-linked genes, the etiology in most patients remains elusive. Moreover, understanding the correlations between clinical manifestation and genetic variants has become increasingly complex. To comprehensively unravel dystonia's genetic spectrum, we performed exome sequencing on 1,924 dystonia patients [40.3% male, 92.9% White, 93.2% isolated dystonia, median age at onset (AAO) 33 years], including 1,895 index patients, who were previously genetically unsolved. The sample was mainly based on two dystonia registries (DysTract and the Dystonia Coalition). Further, 72 additional patients of Asian ethnicity, mainly from Malaysia, were also included. We prioritized patients with negative genetic prescreening, early AAO, positive family history, and multisite involvement of dystonia. Rare variants in genes previously linked to dystonia (n=405) were examined. Variants were confirmed via Sanger sequencing, and segregation analysis was performed when possible. We identified 137 distinct likely pathogenic or pathogenic variants (according to ACMG criteria) across 51 genes in 163/1,924 patients [42.9% male, 85.9% White, 68.7% isolated dystonia, median AAO 19 years]. This included 153/1,895 index patients, resulting in a diagnostic yield of 8.1%. Notably, 77/137 (56.2%) of these variants were novel, with recurrent variants in EIF2AK2, VPS16, KCNMA1, and SLC2A1, and novel variant types such as two splice site variants in KMT2B, supported by functional evidence. Additionally, 321 index patients (16.9%) harbored variants of uncertain significance in 102 genes. The most frequently implicated genes included VPS16, THAP1, GCH1, SGCE, GNAL, and KMT2B. Presumably pathogenic variants in less well-established dystonia genes were also found, including KCNMA1, KIF1A, and ZMYND11. At least six variants (in ADCY5, GNB1, IR2BPL, KCNN2, KMT2B, and VPS16) occurred de novo, supporting pathogenicity. ROC curve analysis indicated that AAO and the presence of generalized dystonia were the strongest predictors of a genetic diagnosis, with diagnostic yields of 28.6% in patients with generalized dystonia and 20.4% in those with AAO < 30 years. This study provides a comprehensive examination of the genetic landscape of dystonia, revealing valuable insights into the frequency of dystonia-linked genes and their associated phenotypes. It underscores the utility of exome sequencing in establishing diagnoses within this heterogeneous condition. Despite prescreening, presumably pathogenic variants were identified in almost 10% of patients. Our findings reaffirm several dystonia candidate genes and expand the phenotypic spectrum of some of these genes to include prominent, sometimes isolated dystonia.

Epilepsy with eyelid myoclonia in a patient with ATP1A3-related neurologic disorder

We report on an 11 year old Polish girl who experienced paroxysmal episodes with decreased consciousness, (hemi)plegia, movement disorders, slurred speech, dysphagia, and abnormal eye movements. An extensive etiological work-up (brain MRI, EEG, EMG, NCS, toxic, metabolic, infectious, and auto-immune screening) was not conclusive. A genetic analysis with whole-exome sequencing demonstrated a de novo heterozygous mutation in the ATP1A3 gene (c.2232C>G, p.Asn744Lys). A 48 h video-EEG monitoring that was conducted in our unit later confirmed the absence of ictal discharge during an episode of hemidystonia, demonstrating its non-epileptic etiology. However, several discharges of generalized spike waves, which were facilitated by intermittent photic stimulation and eyelid closure were recorded, of which a few were associated with eyelid myoclonia. Taken together, these findings are characteristic of epilepsy with eyelid myoclonia. The clinical picture of this patient partially fulfills the diagnostic criteria of relapsing encephalopathy with cerebellar ataxia as well as alternating hemiplegia of childhood. It is increasingly recognized that the distinct syndromes described with ATP1A3 mutations are overlapping and could be identified in the same patients. Certain variations in ATP1A3 have been linked to an increased risk of developing generalized epilepsy syndromes. We hereby present the second case in the literature of a patient with epilepsy with eyelid myoclonia with an ATP1A3-related neurological disorder.

Spinocerebellar Ataxias: Phenotypic Spectrum of PolyQ versus Non-Repeat Expansion Forms

Spinocerebellar ataxias (SCA) are most frequently due to (CAG)n (coding for polyglutamine, polyQ) expansions and, less so, to expansion of other oligonucleotide repeats (non-polyQ) or other type of variants (non-repeat expansion SCA). In this study we compared polyQ and non-repeat expansion SCA, in a cohort of patients with hereditary ataxia followed at a tertiary hospital. From a prospective study, 88 patients (51 families) with SCA were selected, 74 (40 families) of whom genetically diagnosed. Thirty-eight patients (51.4%, 19 families) were confirmed as having a polyQ (no other repeat-expansions were identified) and 36 (48.6%, 21 families) a non-repeat expansion SCA. Median age-at-onset was 39.5 [30.0-45.5] for polyQ and 7.0 years [1.00-21.50] for non-repeat expansion SCA. PolyQ SCA were associated with cerebellar onset, and non-repeat expansion forms with non-cerebellar onset. Time to diagnosis was longer for non-repeat expansion SCA. The most common polyQ SCA were Machado-Joseph disease (MJD/SCA3) (73.7%) and SCA2 (15.8%); whereas in non-repeat expansion SCA ATX-CACNA1A (14.3%), ATP1A3-related ataxia, ATX-ITPR1, ATX/HSP-KCNA2, and ATX-PRKCG (9.5% each) predominated. Disease duration (up to inclusion) was significantly higher in non-repeat expansion SCA, but the difference in SARA score was not statistically significant. Cerebellar peduncles and pons atrophy were more common in polyQ ataxias, as was axonal neuropathy. SCA had a wide range of genetic etiology, age-at-onset and presentation. Proportion of polyQ and non-repeat expansion SCA was similar; the latter had a higher genetic heterogeneity. While polyQ ataxias were typically linked to cerebellar onset in adulthood, non-repeat expansion forms associated with early onset and non-cerebellar presentations.

Novel mouse model of alternating hemiplegia of childhood exhibits prominent motor and seizure phenotypes

Pathogenic variants in ATP1A3 encoding the neuronal Na/K-ATPase cause a spectrum of neurodevelopmental disorders including alternating hemiplegia of childhood (AHC). Three recurrent ATP1A3 variants are associated with approximately half of known AHC cases and mouse models of two of these variants (p.D801N, p.E815K) replicated key features of the human disorder, which include paroxysmal hemiplegia, dystonia and seizures. Epilepsy occurs in 40-50 % of individuals affected with AHC, but detailed investigations of seizure phenotypes were limited in the previously reported mouse models. Using gene editing, we generated a novel AHC mouse expressing the third most recurrent ATP1A3 variant (p.G947R) to model neurological phenotypes of the disorder. Heterozygous Atp1a3-G947R (Atp1a3G947R) mice on a pure C57BL/6J background were born at a significantly lower frequency than wildtype (WT) littermates, but in vitro fertilization or outcrossing to a different strain (C3HeB/FeJ) generated offspring at near-Mendelian genotype ratios, suggesting a defect in reproductive fitness rather than embryonic lethality. Heterozygous mutant mice were noticeably smaller and exhibited premature lethality, hyperactivity, anxiety-like behaviors, severe motor dysfunction including low grip strength, impaired coordination with abnormal gait and balance, reduced REM sleep, and cooling-induced hemiplegia and dystonia. We also observed a prominent seizure phenotype with lower thresholds to chemically (flurothyl, kainic acid) and electrically induced seizures, post-handling seizures, sudden death following seizures, and abnormal EEG activity. Together, our findings support face validity of a novel AHC mouse model with quantifiable traits including co-morbid epilepsy that will be useful as an in vivo platform for investigating pathophysiology and testing new therapeutic strategies for this rare neurodevelopmental disorder.

A case of alternating hemiplegia in 2-month-old children with nystagmus as the first symptom: A case report

RATIONALE

This case report delves into the rare neurological condition known as alternating hemiplegia of childhood (AHC), focusing on its clinical manifestations, diagnostic approaches, and treatment options. AHC typically presents in infants under the age of 18 months with intermittent episodes of hemiplegia, often triggered by stressors such as environmental changes, bathing, or emotional stress. Recognizing the clinical features of AHC is crucial for early identification and intervention.

PATIENT CONCERNS

The paper presents a case of a 2-month-old child with nystagmus as the initial symptom, followed by limb movement disorder in the left upper limb and weakness in the right limbs. The child's condition did not improve with treatment at an external hospital, highlighting the complexity of the disease and the need for specialized care.

DIAGNOSES

After a comprehensive review of the patient's medical history, physical examination, and imaging studies, the child was diagnosed with AHC. The diagnosis was confirmed through video electroencephalogram and whole-exome gene detection, which revealed a de novo mutation in the ATP1A3 gene, identified as pathogenic according to the American College of Medical Genetics and Genomics guidelines.

INTERVENTIONS

The child was admitted to Peking University First Hospital and treated with levetiracetam and flunarizine oral administration. These medications were chosen for their efficacy in managing the symptoms of AHC, particularly the hemiplegic episodes.

OUTCOMES

Post-treatment, the child experienced a reduction in the frequency and intensity of hemiplegic attacks compared to the initial stage. However, the child still exhibited paroxysmal symptoms and abnormal eye movements, and developmental milestones were delayed, indicating the need for ongoing care and monitoring.

LESSONS

This case underscores the importance of early recognition and prompt intervention in managing children with AHC. The varied clinical presentations of AHC necessitate vigilance for early differential diagnosis. Although AHC is currently incurable, appropriate treatment can mitigate the impact of complications and improve the long-term quality of life for affected children, facilitating better societal integration.

Epigenetic patterns, accelerated biological aging, and enhanced epigenetic drift detected 6 months following COVID-19 infection: insights from a genome-wide DNA methylation study

BACKGROUND

The epigenetic status of patients 6-month post-COVID-19 infection remains largely unexplored. The existence of long-COVID, or post-acute sequelae of SARS-CoV-2 infection (PASC), suggests potential long-term changes. Long-COVID includes symptoms like fatigue, neurological issues, and organ-related problems, regardless of initial infection severity. The mechanisms behind long-COVID are unclear, but virus-induced epigenetic changes could play a role.

METHODS AND RESULTS

Our study explores the lasting epigenetic impacts of SARS-CoV-2 infection. We analyzed genome-wide DNA methylation patterns in an Italian cohort of 96 patients 6 months after COVID-19 exposure, comparing them to 191 healthy controls. We identified 42 CpG sites with significant methylation differences (FDR < 0.05), primarily within CpG islands and gene promoters. Dysregulated genes highlighted potential links to glutamate/glutamine metabolism, which may be relevant to PASC symptoms. Key genes with potential significance to COVID-19 infection and long-term effects include GLUD1, ATP1A3, and ARRB2. Furthermore, Horvath's epigenetic clock showed a slight but significant age acceleration in post-COVID-19 patients. We also observed a substantial increase in stochastic epigenetic mutations (SEMs) in the post-COVID-19 group, implying potential epigenetic drift. SEM analysis identified 790 affected genes, indicating dysregulation in pathways related to insulin resistance, VEGF signaling, apoptosis, hypoxia response, T-cell activation, and endothelin signaling.

CONCLUSIONS

Our study provides valuable insights into the epigenetic consequences of COVID-19. Results suggest possible associations with accelerated aging, epigenetic drift, and the disruption of critical biological pathways linked to insulin resistance, immune response, and vascular health. Understanding these epigenetic changes could be crucial for elucidating the complex mechanisms behind long-COVID and developing targeted therapeutic interventions.

Phenotype Distinctions in Mice Deficient in the Neuron-Specific α3 Subunit of Na,K-ATPase: Atp1a3tm1Ling/+ and Atp1a3 +/D801Y

ATP1A3 is a Na,K-ATPase gene expressed specifically in neurons in the brain. Human mutations are dominant and produce an unusually wide spectrum of neurological phenotypes, most notably rapid-onset dystonia parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). Here we compared heterozygotes of two mouse lines, a line with little or no expression (Atp1a3tm1Ling/+) and a knock-in expressing p.Asp801Tyr (D801Y, Atp1a3 +/D801Y). Both mouse lines had normal lifespans, but Atp1a3 +/D801Y had mild perinatal mortality contrasting with D801N mice (Atp1a3 +/D801N), which had high mortality. The phenotypes of Atp1a3tm1Ling/+ and Atp1a3 +/D801Y were different, and testing of each strain was tailored to its symptom range. Atp1a3tm1Ling/+ mice displayed little at baseline, but repeated ethanol intoxication produced hyperkinetic motor abnormalities not seen in littermate controls. Atp1a3 +/D801Y mice displayed robust phenotypes: hyperactivity, diminished posture consistent with hypotonia, and deficiencies in beam walk and wire hang tests. Symptoms also included qualitative motor abnormalities that are not well quantified by conventional tests. Paradoxically, Atp1a3 +/D801Y showed sustained better performance than wild type on the accelerating rotarod. Atp1a3 +/D801Y mice were overactive in forced swimming and afterward had intense shivering, transient dystonic postures, and delayed recovery. Remarkably, Atp1a3 +/D801Y mice were refractory to ketamine anesthesia, which elicited hyperactivity and dyskinesia even at higher dose. Neither mouse line exhibited fixed dystonia (typical of RDP patients), spontaneous paroxysmal weakness (typical of AHC patients), or seizures but had consistent, measurable neurological abnormalities. A gradient of variation supports the importance of studying multiple Atp1a3 mutations in animal models to understand the roles of this gene in human disease.

In vitro study of ATP1A3 p.Ala275Pro mutant causing alternating hemiplegia of childhood and rapid-onset dystonia-parkinsonism

Introduction

We previously reported that ATP1A3 c.823G>C (p.Ala275Pro) mutant causes varying phenotypes of alternative hemiplegia of childhood and rapid-onset dystonia-parkinsonism in the same family. This study aims to investigate the function of ATP1A3 c.823G>C (p.Ala275Pro) mutant at the cellular and zebrafish models.

Methods

ATP1A3 wild-type and mutant Hela cell lines were constructed, and ATP1A3 mRNA expression, ATP1A3 protein expression and localization, and Na+-K+-ATPase activity in each group of cells were detected. Additionally, we also constructed zebrafish models with ATP1A3 wild-type overexpression (WT) and p.Ala275Pro mutant overexpression (MUT). Subsequently, we detected the mRNA expression of dopamine signaling pathway-associated genes, Parkinson's disease-associated genes, and apoptosisassociated genes in each group of zebrafish, and observed the growth, development, and movement behavior of zebrafish.

Results

Cells carrying the p.Ala275Pro mutation exhibited lower levels of ATP1A3 mRNA, reduced ATP1A3 protein expression, and decreased Na+-K+-ATPase activity compared to wild-type cells. Immunofluorescence analysis revealed that ATP1A3 was primarily localized in the cytoplasm, but there was no significant difference in ATP1A3 protein localization before and after the mutation. In the zebrafish model, both WT and MUT groups showed lower brain and body length, dopamine neuron fluorescence intensity, escape ability, swimming distance, and average swimming speed compared to the control group. Moreover, overexpression of both wild-type and mutant ATP1A3 led to abnormal mRNA expression of genes associated with the dopamine signaling pathway and Parkinson's disease in zebrafish, and significantly upregulated transcription levels of bad and caspase-3 in the apoptosis signaling pathway, while reducing the transcriptional level of bcl-2 and the bcl-2/bax ratio.

Conclusion

This study reveals that the p.Ala275Pro mutant decreases ATP1A3 protein expression and Na+/K+-ATPase activity. Abnormal expression of either wild-type or mutant ATP1A3 genes impairs growth, development, and movement behavior in zebrafish.

Dopa-responsive dystonia and paroxysmal dystonic attacks associated with ATP1A3 gene variant

An 18-year-old man had episodes of severe generalised dystonia, from aged 7 months and becoming progressively more frequent. He also had gradually developed interictal limb dystonia. He was initially diagnosed with paroxysmal kinesigenic dyskinesia but he did not improve with several medications. A levodopa trial led to levodopa-induced dyskinetic movements. However, a lower titration of 25 mg of levodopa two times per day substantially improved his motor features and quality of life. Laboratory investigations and MR scans of the brain were unremarkable. Whole-exome sequencing identified a pathogenic variant in the ATP1A3 gene. The ATP1A3-spectrum disorders include non-classical phenotypes such as paroxysmal dystonic attacks. A response to dopamine response is unusual in these disorders. This case highlights the importance of levodopa trials in early-onset dystonia cases.

Exploring the Genetic Landscape of Chorea in Infancy and Early Childhood: Implications for Diagnosis and Treatment

Chorea is a hyperkinetic movement disorder frequently observed in the pediatric population, and, due to advancements in genetic techniques, an increasing number of genes have been associated with this disorder. In genetic conditions, chorea may be the primary feature of the disorder, or be part of a more complex phenotype characterized by epileptic encephalopathy or a multisystemic syndrome. Moreover, it can appear as a persistent disorder (chronic chorea) or have an episodic course (paroxysmal chorea). Managing chorea in childhood presents challenges due to its varied clinical presentation, often involving a spectrum of hyperkinetic movement disorders alongside neuropsychiatric and multisystemic manifestations. Furthermore, during infancy and early childhood, transient motor phenomena resembling chorea occurring due to the rapid nervous system development during this period can complicate the diagnosis. This review aims to provide an overview of the main genetic causes of pediatric chorea that may manifest during infancy and early childhood, focusing on peculiarities that can aid in differential diagnosis among different phenotypes and discussing possible treatment options.

Channelopathies in epilepsy: an overview of clinical presentations, pathogenic mechanisms, and therapeutic insights

Pathogenic variants in genes encoding ion channels are causal for various pediatric and adult neurological conditions. In particular, several epilepsy syndromes have been identified to be caused by specific channelopathies. These encompass a spectrum from self-limited epilepsies to developmental and epileptic encephalopathies spanning genetic and acquired causes. Several of these channelopathies have exquisite responses to specific antiseizure medications (ASMs), while others ASMs may prove ineffective or even worsen seizures. Some channelopathies demonstrate phenotypic pleiotropy and can cause other neurological conditions outside of epilepsy. This review aims to provide a comprehensive exploration of the pathophysiology of seizure generation, ion channels implicated in epilepsy, and several genetic epilepsies due to ion channel dysfunction. We outline the clinical presentation, pathogenesis, and the current state of basic science and clinical research for these channelopathies. In addition, we briefly look at potential precision therapy approaches emerging for these disorders.

Emerging therapies for childhood-onset movement disorders

PURPOSE OF REVIEW

We highlight novel and emerging therapies in the treatment of childhood-onset movement disorders. We structured this review by therapeutic entity (small molecule drugs, RNA-targeted therapeutics, gene replacement therapy, and neuromodulation), recognizing that there are two main approaches to treatment: symptomatic (based on phenomenology) and molecular mechanism-based therapy or 'precision medicine' (which is disease-modifying).

RECENT FINDINGS

We highlight reports of new small molecule drugs for Tourette syndrome, Friedreich's ataxia and Rett syndrome. We also discuss developments in gene therapy for aromatic l-amino acid decarboxylase deficiency and hereditary spastic paraplegia, as well as current work exploring optimization of deep brain stimulation and lesioning with focused ultrasound.

SUMMARY

Childhood-onset movement disorders have traditionally been treated symptomatically based on phenomenology, but focus has recently shifted toward targeted molecular mechanism-based therapeutics. The development of precision therapies is driven by increasing capabilities for genetic testing and a better delineation of the underlying disease mechanisms. We highlight novel and exciting approaches to the treatment of genetic childhood-onset movement disorders while also discussing general challenges in therapy development for rare diseases. We provide a framework for molecular mechanism-based treatment approaches, a summary of specific treatments for various movement disorders, and a clinical trial readiness framework.

Sensational site: the sodium pump ouabain-binding site and its ligands

Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.

Genetic Update and Treatment for Dystonia

A neurological condition called dystonia results in abnormal, uncontrollable postures or movements because of sporadic or continuous muscular spasms. Several varieties of dystonia can impact people of all ages, leading to severe impairment and a decreased standard of living. The discovery of genes causing variations of single or mixed dystonia has improved our understanding of the disease's etiology. Genetic dystonias are linked to several genes, including pathogenic variations of VPS16, TOR1A, THAP1, GNAL, and ANO3. Diagnosis of dystonia is primarily based on clinical symptoms, which can be challenging due to overlapping symptoms with other neurological conditions, such as Parkinson's disease. This review aims to summarize recent advances in the genetic origins and management of focal dystonia.

Alternating hemiplegia of childhood misdiagnosed as hysteria: a case report

BACKGROUND

Alternating hemiplegia of childhood (AHC) is a rare pediatric syndrome characterized by recurring episodes of hemiplegia or quadriplegia, and frequently accompanied by dystonic posturing, choreoathetosis movements, anomalous ocular motions, and a gradual deterioration in cognitive function. The principal etiology of this disorder is traced back to mutations in the ATP1A3 gene.

CASE PRESENTATION

Here, we report a 16-year-old girl with recurrent hemiplegia since her infancy. This patient has experienced paroxysmal limb weakness and aphasia for over 15 years, and has kept seeking medical attention but without receiving effective treatment. A misdiagnosis of hysteria persisted for over 4 years until the patient's admission to our hospital. Whole-exome sequencing identified a known pathogenic heterozygous c.2270T>C (p.Leu757Pro) mutation in her ATP1A3 gene. Notably, her clinical manifestations, including pathological emotional responses and autonomic dysfunction, differed from the established profile associated with the same ATP1A3 mutation, which typically present with intellectual disability, a rostrocaudal symptom gradient, choreoathetosis, and dysarthria. The patient was finally diagnosed with AHC and treated with flunarizine thus significantly ameliorated hemiplegic episodes.

CONCLUSIONS

This case enhances our understanding of the intricate clinical manifestations of AHC, which require careful differentiation from various diseases such as epilepsy, hysteria, and paroxysmal dyskinesias. In the diagnosis of patients presenting with suspected symptoms, adhering to a systematic approach for localizing and diagnosing neurological disorders is crucial to prevent misdiagnosis and inappropriate treatments. Additionally, when AHC is suspected in a patient, genetic testing should be considered as part of the diagnostic approach.

[Developmental and epileptic encephalopathy produced by the ATP1A2 mutation]

A case of DEE98, a rare developmental and epileptic encephalopathy related to previously reported the de novo missense mutation p.Arg908Gln in the ATP1A2 gene, is described. A girl examined first time in 11 months had microcephaly, severe mental and motor delay, strabismus, spastic paraparesis and pachypolymicrogyria on brain MRI that is atypical for DEE98. Epilepsy with polymorphic seizures started at the age of 15 months. There was a remission lasting 9 months, after which seizures renewed. DEE98 was diagnosed at the age of 2 years 9 months by exome sequencing verified by trio Sanger sequencing. Another finding from high-throughput exome sequencing were two previously undescribed heterozygous variants of uncertain pathogenicity in the SPART gene, which causes autosomal recessive spastic paraplegia type 20 (SPG20); Sanger sequencing confirmed the trans position of the variants. The common clinical sign with typical SPG20 was early spastic paraparesis with contractures; other symptoms did not coincide. Considering the phenotypic diversity of SPG20 and the possibility of a combination of two independent diseases, we performed an additional study of the pathogenicity of SPART variants at the mRNA level: pathogenicity was not confirmed, and there were no grounds to diagnose SPG20.

Small molecule regulators of microRNAs identified by high-throughput screen coupled with high-throughput sequencing

MicroRNAs (miRNAs) regulate fundamental biological processes by silencing mRNA targets and are dysregulated in many diseases. Therefore, miRNA replacement or inhibition can be harnessed as potential therapeutics. However, existing strategies for miRNA modulation using oligonucleotides and gene therapies are challenging, especially for neurological diseases, and none have yet gained clinical approval. We explore a different approach by screening a biodiverse library of small molecule compounds for their ability to modulate hundreds of miRNAs in human induced pluripotent stem cell-derived neurons. We demonstrate the utility of the screen by identifying cardiac glycosides as potent inducers of miR-132, a key neuroprotective miRNA downregulated in Alzheimer's disease and other tauopathies. Coordinately, cardiac glycosides downregulate known miR-132 targets, including Tau, and protect rodent and human neurons against various toxic insults. More generally, our dataset of 1370 drug-like compounds and their effects on the miRNome provides a valuable resource for further miRNA-based drug discovery.

Contribution of m5C RNA Modification-Related Genes to Prognosis and Immunotherapy Prediction in Patients with Ovarian Cancer

Background

5-Methylcytosine (m5C) RNA modification is closely implicated in the occurrence of a variety of cancers. Here, we established a novel prognostic signature for ovarian cancer (OC) patients based on m5C RNA modification-related genes and explored the correlation between these genes with the tumor immune microenvironment.

Methods

Methylated-RNA immunoprecipitation sequencing helped us to identify candidate genes related to m5C RNA modification at first. Based on TCGA database, we screened the differentially expressed candidate genes related to the prognosis and constructed a prognostic model using LASSO Cox regression analyses. Notably, the accuracy of the model was evaluated by Kaplan-Meier analysis and receiver operator characteristic curves. Independent prognostic risk factors were investigated by Cox proportional hazard model. Furthermore, we also analyzed the biological functions and pathways involved in the signature. Finally, the immune response of the model was visualized in great detail.

Results

Totally, 2,493 candidate genes proved to be involved in m5C modification of RNA for OC. We developed a signature with prognostic value consisting of six m5C RNA modification-related genes. Specially, samples have been split into two cohorts with low- and high-risk scores according to the model, in which the low-risk OC patients exhibited dramatically better overall survival time than those with high-risk scores. Besides, not only was this model a prognostic factor independent of other clinical characteristics but it predicted the intensity of the immune response in OC. Significantly, the accuracy and availability of the signature were verified by ICGC database.

Conclusions

Our study bridged the gap between m5C RNA modification and the prognosis of OC and was expected to provide an effective breakthrough for immunotherapy in OC patients.

Episodic Ataxias: Primary and Secondary Etiologies, Treatment, and Classification Approaches

Background

Episodic ataxia (EA), characterized by recurrent attacks of cerebellar dysfunction, is the manifestation of a group of rare autosomal dominant inherited disorders. EA1 and EA2 are most frequently encountered, caused by mutations in KCNA1 and CACNA1A. EA3-8 are reported in rare families. Advances in genetic testing have broadened the KCNA1 and CACNA1A phenotypes, and detected EA as an unusual presentation of several other genetic disorders. Additionally, there are various secondary causes of EA and mimicking disorders. Together, these can pose diagnostic challenges for neurologists.

Methods

A systematic literature review was performed in October 2022 for 'episodic ataxia' and 'paroxysmal ataxia', restricted to publications in the last 10 years to focus on recent clinical advances. Clinical, genetic, and treatment characteristics were summarized.

Results

EA1 and EA2 phenotypes have further broadened. In particular, EA2 may be accompanied by other paroxysmal disorders of childhood with chronic neuropsychiatric features. New treatments for EA2 include dalfampridine and fampridine, in addition to 4-aminopyridine and acetazolamide. There are recent proposals for EA9-10. EA may also be caused by gene mutations associated with chronic ataxias (SCA-14, SCA-27, SCA-42, AOA2, CAPOS), epilepsy syndromes (KCNA2, SCN2A, PRRT2), GLUT-1, mitochondrial disorders (PDHA1, PDHX, ACO2), metabolic disorders (Maple syrup urine disease, Hartnup disease, type I citrullinemia, thiamine and biotin metabolism defects), and others. Secondary causes of EA are more commonly encountered than primary EA (vascular, inflammatory, toxic-metabolic). EA can be misdiagnosed as migraine, peripheral vestibular disorders, anxiety, and functional symptoms. Primary and secondary EA are frequently treatable which should prompt a search for the cause.

Discussion

EA may be overlooked or misdiagnosed for a variety of reasons, including phenotype-genotype variability and clinical overlap between primary and secondary causes. EA is highly treatable, so it is important to consider in the differential diagnosis of paroxysmal disorders. Classical EA1 and EA2 phenotypes prompt single gene test and treatment pathways. For atypical phenotypes, next generation genetic testing can aid diagnosis and guide treatment. Updated classification systems for EA are discussed which may assist diagnosis and management.

The role of ATP1A3 gene in epilepsy: We need to know more

The ATP1A3 gene, which encodes the Na⁺/K⁺-ATPase α3 catalytic subunit, plays a crucial role in both physiological and pathological conditions in the brain, and mutations in this gene have been associated with a wide variety of neurological diseases by impacting the whole infant development stages. Cumulative clinical evidence suggests that some severe epileptic syndromes have been linked to mutations in ATP1A3, among which inactivating mutation of ATP1A3 has been intriguingly found to be a candidate pathogenesis for complex partial and generalized seizures, proposing ATP1A3 regulators as putative targets for the rational design of antiepileptic therapies. In this review, we introduced the physiological function of ATP1A3 and summarized the findings about ATP1A3 in epileptic conditions from both clinical and laboratory aspects at first. Then, some possible mechanisms of how ATP1A3 mutations result in epilepsy are provided. We think this review timely introduces the potential contribution of ATP1A3 mutations in both the genesis and progression of epilepsy. Taken that both the detailed mechanisms and therapeutic significance of ATP1A3 for epilepsy are not yet fully illustrated, we think that both in-depth mechanisms investigations and systematic intervention experiments targeting ATP1A3 are needed, and by doing so, perhaps a new light can be shed on treating ATP1A3-associated epilepsy.

ATP1A3-related phenotypes in Chinese children: AHC, CAPOS, and RECA

The aim of this research is to study the phenotype, genotype, treatment strategies, and short-term prognosis of Chinese children with ATP1A3 (Na⁺/K⁺-ATPase alpha 3 gene)-related disorders in Southwest China. Patients with pathogenic ATP1A3 variants identified using next-generation sequencing were registered at the Children's Hospital of Chongqing Medical University from December 2015 to May 2019. We followed them as a cohort and analyzed their clinical data. Eleven patients were identified with de novo pathogenic ATP1A3 heterozygous variants. One (c.2542 + 1G > T, splicing) has not been reported. Eight patients with alternating hemiplegia of childhood (AHC), one with cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS), and two with relapsing encephalopathy with cerebellar ataxia (RECA) were included. The initial manifestations of AHC included hemiplegia, oculomotor abnormalities, and seizures, and the most common trigger was an upper respiratory tract infection without fever. All patients had paroxysmal hemiplegic attacks during their disease course. The brain MRI showed no abnormalities. Six out of eight AHC cases reached a stable disease state after treatment. The initial symptom of the patient with CAPOS was ataxia followed by developmental regression, seizures, deafness, visual impairment, and dysarthria, and the brain MRI indicated mild cerebellar atrophy. No fluctuation was noted after using Acetazolamide. The initial manifestations of the two RECA cases were dystonia and encephalopathy, respectively. One manifested a rapid-onset course of dystonia triggered by a fever followed by dysarthria and action tremors, and independent walking was impossible. The brain MRI image was normal. The other one presented with disturbance of consciousness, seizures, sleep disturbance, tremor, and dyskinesias. The EEG revealed a slow background (δ activity), and the brain MRI result was normal. No response to Flunarizine was noted for them, and it took 61 and 60 months for them to reach a stable disease state, respectively.

CONCLUSION

Pathogenic ATP1A3 variants play an essential role in the pathogenesis of Sodium-Potassium pump disorders, and AHC is the most common phenotype. The treatment strategies and prognosis depend on the phenotype categories caused by different variation sites and types. The correlation between the genotype and phenotype requires further exploration.

WHAT IS KNOWN

• Pathogenic heterozygous ATP1A3 variants cause a spectrum of neurological phenotypes, and ATP1A3-disorders are viewed as a phenotypic continuum presenting with atypical and overlapping features. • The genotype-phenotype correlation of ATP1A3-disorders remains unclear.

WHAT IS NEW

• In this study, the genotypes and phenotypes of ATP1A3-related disorders from Southwest of China were described. The splice-site variation c.2542+1G>T was detected for the first time in ATP1A3-related disorders. • The prognosis of twins with AHC p. Gly947Arg was more serious than AHC cases with other variants, which was inconsistent with previous reports. The phenomenon indicated the diversity of the correlation between the genotype and phenotype.

Genetic Links to Episodic Movement Disorders: Current Insights

Episodic or paroxysmal movement disorders (PxMD) are conditions, which occur episodically, are transient, usually have normal interictal periods, and are characterized by hyperkinetic disorders, including ataxia, chorea, dystonia, and ballism. Broadly, these comprise paroxysmal dyskinesias (paroxysmal kinesigenic and non-kinesigenic dyskinesia [PKD/PNKD], paroxysmal exercise-induced dyskinesias [PED]) and episodic ataxias (EA) types 1-9. Classification of paroxysmal dyskinesias has traditionally been clinical. However, with advancement in genetics and the discovery of the molecular basis of several of these disorders, it is becoming clear that phenotypic pleiotropy exists, that is, the same variant may give rise to a variety of phenotypes, and the classical understanding of these disorders requires a new paradigm. Based on molecular pathogenesis, paroxysmal disorders are now categorized as synaptopathies, transportopathies, channelopathies, second-messenger related disorders, mitochondrial or others. A genetic paradigm also has an advantage of identifying potentially treatable disorders, such as glucose transporter 1 deficiency syndromes, which necessitates a ketogenic diet, and ADCY5-related disorders, which may respond to caffeine. Clues for a primary etiology include age at onset below 18 years, presence of family history and fixed triggers and attack duration. Paroxysmal movement disorder is a network disorder, with both the basal ganglia and the cerebellum implicated in pathogenesis. Abnormalities in the striatal cAMP turnover pathway may also be contributory. Although next-generation sequencing has restructured the approach to paroxysmal movement disorders, the genetic underpinnings of several entities remain undiscovered. As more genes and variants continue to be reported, these will lead to enhanced understanding of pathophysiological mechanisms and precise treatment.