Developmental and epileptic encephalopathies are a heterogeneous group of disorders characterized by early-onset, often severe epileptic seizures, EEG abnormalities, on a background of developmental impairment that tends to worsen as a consequence of epilepsy. DEEs may result from both non-genetic and genetic etiologies. Genetic DEEs have been associated with mutations in many genes involved in different functions including cell migration, proliferation, and organization, neuronal excitability, and synapse transmission and plasticity. Functional studies performed in different animal models and clinical trials on patients have contributed to elucidate pathophysiological mechanisms underlying many DEEs and explored the efficacy of different treatments. Here, we provide an extensive review of the phenotypic spectrum included in the DEEs, of the genetic determinants and pathophysiological mechanisms underlying these conditions. We also provide a brief overview of the most effective treatment now available and of the emerging therapeutic approaches.

/pdf/developmental-and-epileptic-encephalopathies-from-genetic-2jhnzus5.pdf

Developmental and epileptic encephalopathies: from genetic heterogeneity to phenotypic continuum.

Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.

Clinical and Genetic Overview of Paroxysmal Movement Disorders and Episodic Ataxias.

Persistently depolarizing sodium (Na+) leak currents enhance electrical excitability1,2. The ion channel responsible for the major background Na+ conductance in neurons is the Na+ leak channel, non-selective (NALCN)3,4. NALCN-mediated currents regulate neuronal excitability linked to respiration, locomotion and circadian rhythm4–10. NALCN activity is under tight regulation11–14 and mutations in NALCN cause severe neurological disorders and early death15,16. NALCN is an orphan channel in humans, and fundamental aspects of channel assembly, gating, ion selectivity and pharmacology remain obscure. Here we investigate this essential leak channel and determined the structure of NALCN in complex with a distinct auxiliary subunit, family with sequence similarity 155 member A (FAM155A). FAM155A forms an extracellular dome that shields the ion-selectivity filter from neurotoxin attack. The pharmacology of NALCN is further delineated by a walled-off central cavity with occluded lateral pore fenestrations. Unusual voltage-sensor domains with asymmetric linkages to the pore suggest mechanisms by which NALCN activity is modulated. We found a tightly closed pore gate in NALCN where the majority of missense patient mutations cause gain-of-function phenotypes that cluster around the S6 gate and distinctive π-bulges. Our findings provide a framework to further study the physiology of NALCN and a foundation for discovery of treatments for NALCN channelopathies and other electrical disorders. Structural and functional studies of the sodium leak channel, non-selective (NALCN) in complex with a distinct auxiliary subunit reveal the structural basis of the channel function and pharmacology and the functional impact of mutations that cause NALCN channelopathies.

Structure of the human sodium leak channel NALCN

NALCN, a sodium leak channel expressed mainly in the central nervous system, is responsible for the resting Na+ permeability that controls neuronal excitability. Dysfunctions of the NALCN channelosome, NALCN with several auxiliary subunits, are associated with a variety of human diseases. Here, we report the cryo-EM structure of human NALCN in complex with FAM155A at an overall resolution of 3.1 angstroms. FAM155A forms extensive interactions with the extracellular loops of NALCN that may help stabilize NALCN in the membrane. A Na+ ion-binding site, reminiscent of a Ca2+ binding site in Cav channels, is identified in the unique EEKE selectivity filter. Despite its ‘leaky’ nature, the channel is closed and the intracellular gate is sealed by S6I, II-III linker and III-IV linker. Our study establishes the molecular basis of Na+ permeation and voltage sensitivity, and provides important clues to the mechanistic understanding of NALCN regulation and NALCN channelosome-related diseases. NALCN, a sodium leak channel, plays a key role in regulating the resting membrane potential and controlling neuronal excitability. Here the authors report a cryo-EM structure of human NALCN in complex with FAM155A, that with complementary functional analyses provide insights on its ion selectivity, voltage sensing and specific interactions with auxiliary subunits.

/pdf/structure-of-the-human-sodium-leak-channel-nalcn-in-complex-1pk20hcwla.pdf

Structure of the human sodium leak channel NALCN in complex with FAM155A.

Low cardiorespiratory fitness (VO2peak) is highly associated with chronic disease and mortality from all causes. Whilst exercise training is recommended in health guidelines to improve VO2peak, there is considerable inter-individual variability in the VO2peak response to the same dose of exercise. Understanding how genetic factors contribute to VO2peak training response may improve personalisation of exercise programs. The aim of this study was to identify genetic variants that are associated with the magnitude of VO2peak response following exercise training. Participant change in objectively measured VO2peak from 18 different interventions was obtained from a multi-centre study (Predict-HIIT). A genome-wide association study was completed (n = 507), and a polygenic predictor score (PPS) was developed using alleles from single nucleotide polymorphisms (SNPs) significantly associated (P   0.1). Significant correlations were found for beta coefficients of variants in the Predict-HIIT (P < 1 × 10–4) and the validation study (P <  × 10–6), indicating that general effects of the loci exist, and that with a higher statistical power, more significant genetic associations may become apparent. Ongoing research and validation of current and previous findings is needed to determine if genetics does play a large role in VO2peak response variance, and whether genomic predictors for VO2peak response trainability can inform evidence-based clinical practice. Trial registration Australian New Zealand Clinical Trials Registry (ANZCTR), Trial Id: ACTRN12618000501246, Date Registered: 06/04/2018, http://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374601&isReview=true
 .

/pdf/genome-wide-association-study-of-response-to-interval-and-4k47zfschb.pdf

Genome wide association study of response to interval and continuous exercise training: the Predict-HIIT study.

NALCN is a conserved cation channel, which conducts a permanent sodium leak current and regulates resting membrane potential and neuronal excitability. It is part of a large ion channel complex, the “NALCN channelosome”, consisting of multiple proteins including UNC80 and UNC79. The predominant neuronal expression pattern and its function suggest an important role in neuronal function and disease. So far, biallelic NALCN and UNC80 variants have been described in a small number of individuals leading to infantile hypotonia, psychomotor retardation, and characteristic facies 1 (IHPRF1, OMIM 615419) and 2 (IHPRF2, OMIM 616801), respectively. Heterozygous de novo NALCN missense variants in the S5/S6 pore-forming segments lead to congenital contractures of the limbs and face, hypotonia, and developmental delay (CLIFAHDD, OMIM 616266) with some clinical overlap. In this study, we present detailed clinical information of 16 novel individuals with biallelic NALCN variants, 1 individual with a heterozygous de novo NALCN missense variant and an interesting clinical phenotype without contractures, and 12 individuals with biallelic UNC80 variants. We report for the first time a missense NALCN variant located in the predicted S6 pore-forming unit inherited in an autosomal-recessive manner leading to mild IHPRF1. We show evidence of clinical variability, especially among IHPRF1-affected individuals, and discuss differences between the IHPRF1- and IHPRF2 phenotypes. In summary, we provide a comprehensive overview of IHPRF1 and IHPRF2 phenotypes based on the largest cohort of individuals reported so far and provide additional insights into the clinical phenotypes of these neurodevelopmental diseases to help improve counseling of affected families.

/pdf/genetic-variants-in-components-of-the-nalcn-unc80-unc79-ion-4dnvj3805w.pdf

Genetic variants in components of the NALCN-UNC80-UNC79 ion channel complex cause a broad clinical phenotype (NALCN channelopathies).

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Genetic variants in components of the NALCN-UNC80-UNC79 ion channel complex cause a broad clinical phenotype (NALCN channelopathies).