scholarly journals Defective X-gating caused by de novo gain-of-function mutations in KCNK3 underlies a developmental disorder with sleep apnea

2021 ◽  
Author(s):  
Janina Soermann ◽  
Marcus Schewe ◽  
Peter Proks ◽  
Thibault Jouen-Tachoire ◽  
Shanlin Rao ◽  
...  
Keyword(s):  
Sleep Apnea ◽  
Developmental Disorder ◽  
De Novo ◽  
Therapeutic Strategies ◽  
K Channel ◽  
Global Public Health ◽  
Gain Of Function ◽  
Public Health Burden ◽  
Channel Opening ◽  
G Protein Coupled

Sleep apnea is a common disorder that represents a global public health burden. KCNK3 encodes TASK-1, a K+ channel implicated in the control of breathing, but its reported link with sleep apnea remains poorly understood. Here we describe a novel developmental disorder with sleep apnea caused by rare de novo gain-of-function mutations in KCNK3. The mutations cluster around the X-gate, a gating motif which controls channel opening, and produce overactive channels that no longer respond to inhibition by G-protein coupled receptor pathways but which can be inhibited by several clinically relevant drugs. These findings demonstrate a clear role for TASK-1 in sleep apnea and identify possible therapeutic strategies.

scholarly journals Biophysical classification of a CACNA1D de novo mutation as a high-risk mutation for a severe neurodevelopmental disorder

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Nadja T. Hofer ◽  
Petronel Tuluc ◽  
Nadine J. Ortner ◽  
Yuliia V. Nikonishyna ◽  
Monica L. Fernándes-Quintero ◽  
...  
Keyword(s):  
High Risk ◽  
Neurodevelopmental Disorders ◽  
Developmental Disorder ◽  
De Novo ◽  
Disease Risk ◽  
Neurodevelopmental Disorder ◽  
Autism Spectrum ◽  
De Novo Mutation ◽  
Loss Of Function ◽  
Gain Of Function

Abstract Background There is increasing evidence that de novo CACNA1D missense mutations inducing increased Cav1.3 L-type Ca2+-channel-function confer a high risk for neurodevelopmental disorders (autism spectrum disorder with and without neurological and endocrine symptoms). Electrophysiological studies demonstrating the presence or absence of typical gain-of-function gating changes could therefore serve as a tool to distinguish likely disease-causing from non-pathogenic de novo CACNA1D variants in affected individuals. We tested this hypothesis for mutation S652L, which has previously been reported in twins with a severe neurodevelopmental disorder in the Deciphering Developmental Disorder Study, but has not been classified as a novel disease mutation. Methods For functional characterization, wild-type and mutant Cav1.3 channel complexes were expressed in tsA-201 cells and tested for typical gain-of-function gating changes using the whole-cell patch-clamp technique. Results Mutation S652L significantly shifted the voltage-dependence of activation and steady-state inactivation to more negative potentials (~ 13–17 mV) and increased window currents at subthreshold voltages. Moreover, it slowed tail currents and increased Ca2+-levels during action potential-like stimulations, characteristic for gain-of-function changes. To provide evidence that only gain-of-function variants confer high disease risk, we also studied missense variant S652W reported in apparently healthy individuals. S652W shifted activation and inactivation to more positive voltages, compatible with a loss-of-function phenotype. Mutation S652L increased the sensitivity of Cav1.3 for inhibition by the dihydropyridine L-type Ca2+-channel blocker isradipine by 3–4-fold. Conclusions and limitations Our data provide evidence that gain-of-function CACNA1D mutations, such as S652L, but not loss-of-function mutations, such as S652W, cause high risk for neurodevelopmental disorders including autism. This adds CACNA1D to the list of novel disease genes identified in the Deciphering Developmental Disorder Study. Although our study does not provide insight into the cellular mechanisms of pathological Cav1.3 signaling in neurons, we provide a unifying mechanism of gain-of-function CACNA1D mutations as a predictor for disease risk, which may allow the establishment of a more reliable diagnosis of affected individuals. Moreover, the increased sensitivity of S652L to isradipine encourages a therapeutic trial in the two affected individuals. This can address the important question to which extent symptoms are responsive to therapy with Ca2+-channel blockers.

scholarly journals Influenza classification from short reads with VAPOR facilitates robust mapping pipelines and zoonotic strain detection for routine surveillance applications

2019 ◽  
Vol 36 (6) ◽  
pp. 1681-1688
Author(s):  
Joel A Southgate ◽  
Matthew J Bull ◽  
Clare M Brown ◽  
Joanne Watkins ◽  
Sally Corden ◽  
...  
Keyword(s):  
De Novo ◽  
Influenza Viruses ◽  
Supplementary Information ◽  
Global Public Health ◽  
Human Origin ◽  
Short Read ◽  
Public Health Burden ◽  
Routine Surveillance ◽  
Surveillance Applications ◽  
Strain Detection

Abstract Motivation Influenza viruses represent a global public health burden due to annual epidemics and pandemic potential. Due to a rapidly evolving RNA genome, inter-species transmission, intra-host variation, and noise in short-read data, reads can be lost during mapping, and de novo assembly can be time consuming and result in misassembly. We assessed read loss during mapping and designed a graph-based classifier, VAPOR, for selecting mapping references, assembly validation and detection of strains of non-human origin. Results Standard human reference viruses were insufficient for mapping diverse influenza samples in simulation. VAPOR retrieved references for 257 real whole-genome sequencing samples with a mean of >99.8% identity to assemblies, and increased the proportion of mapped reads by up to 13.3% compared to standard references. VAPOR has the potential to improve the robustness of bioinformatics pipelines for surveillance and could be adapted to other RNA viruses. Availability and implementation VAPOR is available at https://github.com/connor-lab/vapor. Supplementary information Supplementary data are available at Bioinformatics online.

scholarly journals Influenza Classification from Short Reads with VAPOR Facilitates Robust Mapping Pipelines and Zoonotic Strain Detection for Routine Surveillance Applications

2019 ◽  
Author(s):  
J. A. Southgate ◽  
M. J. Bull ◽  
C. M. Brown ◽  
J. Watkins ◽  
S. Corden ◽  
...  
Keyword(s):  
Influenza A ◽  
De Novo ◽  
Real Data ◽  
Single Step ◽  
Influenza Viruses ◽  
Global Public Health ◽  
Human Origin ◽  
Short Read ◽  
Public Health Burden ◽  
Conventional Mapping

BackgroundInfluenza viruses are associated with a significant global public health burden. The segmented RNA genome of influenza changes continually due to mutation, and the accumulation of these changes within the antigenic recognition sites of haemagglutinin (HA) and neuraminidase (NA) in turn leads to annual epidemics. Influenza A is also zoonotic, allowing for exchange of segments between human and non-human viruses, resulting in new strains with pandemic potential. These processes necessitate a global surveillance system for influenza monitoring. To this end, whole-genome sequencing (WGS) has begun to emerge as a useful tool. However, due to the diversity and mutability of the influenza genome, and noise in short-read data, bioinformatics processing can present challenges.ResultsConventional mapping approaches can be insufficient when a sub-optimal reference strain is chosen. For short-read datasets simulated from influenza H1N1 HA sequences, read recovery after single-reference mapping was routinely as low as 90% for human-origin influenza sequences, and often lower than 10% for those from avian hosts. To this end, we developed a de Bruijn Graph (DBG)-based classifier of influenza WGS datasets: VAPOR. In real data benchmarking using 257 WGS read sets with corresponding de novo assemblies, VAPOR provided classifications for all samples with a mean of >99.8% identity to assembled contigs. This resulted in an increase in the number of mapped reads by 6.8% on average, up to a maximum of 13.3%. Additionally, using simulations, we demonstrate that classification from reads may be applied to detection of reassorted strains.ConclusionsVAPOR has potential to simplify bioinformatics pipelines for surveillance, providing a novel method for detection of influenza strains of human and non-human origin directly from reads, minimization of potential data loss and bias associated with conventional mapping, and allowing visualization of alignments that would otherwise require slow de novo assembly. Whilst with expertise and time these pitfalls can largely be avoided, with pre-classification they are remedied in a single step. Furthermore, our algorithm could be adapted in future to surveillance of other RNA viruses. VAPOR is available at https://github.com/connor-lab/vapor.

Analysis of a Ca2+-activated K+channel that mediates hyperpolarization via the thrombin receptor pathway

1998 ◽  
Vol 275 (5) ◽  
pp. C1342-C1348 ◽  
Author(s):  
Richard Sullivan ◽  
Suneil K. Koliwad ◽  
Diana L. Kunze
Keyword(s):  
K Channel ◽  
Thrombin Receptor ◽  
Human Leukemia ◽  
Cellular Activation ◽  
Thrombin Receptors ◽  
Channel Opening ◽  
Transitory Phase ◽  
Inwardly Rectifying ◽  
G Protein Coupled ◽  
Inside Out

Dami human leukemia cells express G protein-coupled thrombin receptors that operate through the phospholipase C pathway. When these receptors are activated by α-thrombin or by thrombin receptor-activating peptide, an elevation in cytosolic Ca2+concentration develops that is accompanied by hyperpolarization of the plasma membrane. This transitory phase of hyperpolarization is primarily mediated by inwardly rectifying, Ca2+-activated K+channels that have an inward conductance of ∼24 pS. In cell-attached patches the channels open within seconds after superfusion of the cell with thrombin receptor-activating peptide. In inside-out patches, perfusion of submicromolar Ca2+onto the cytosolic surface of the membrane is sufficient to activate the channels. In outside-out patches, channel opening can be blocked by nanomolar concentrations of charybdotoxin. The function of these intermediate-sized inwardly rectifying, Ca2+-activated K+channels has not been established; however, by analogy with other cell systems, they may serve to regulate cell volume during cellular activation or to increase the electromotive drive that sustains Na+and/or Ca2+influx through ligand-gated cation channels.

scholarly journals Deacetylation as a receptor-regulated direct activation switch for pannexin channels

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yu-Hsin Chiu ◽  
Christopher B. Medina ◽  
Catherine A. Doyle ◽  
Ming Zhou ◽  
Adishesh K. Narahari ◽  
...  
Keyword(s):  
G Protein Coupled Receptors ◽  
Activation Mechanism ◽  
Lysine Acetylation ◽  
Intercellular Signaling ◽  
Histone Deacetylase 6 ◽  
Pannexin 1 ◽  
Lysine Deacetylase ◽  
Channel Opening ◽  
Lysine Residues ◽  
G Protein Coupled

AbstractActivation of Pannexin 1 (PANX1) ion channels causes release of intercellular signaling molecules in a variety of (patho)physiological contexts. PANX1 can be activated by G protein-coupled receptors (GPCRs), including α1-adrenergic receptors (α1-ARs), but how receptor engagement leads to channel opening remains unclear. Here, we show that GPCR-mediated PANX1 activation can occur via channel deacetylation. We find that α1-AR-mediated activation of PANX1 channels requires Gαq but is independent of phospholipase C or intracellular calcium. Instead, α1-AR-mediated PANX1 activation involves RhoA, mammalian diaphanous (mDia)-related formin, and a cytosolic lysine deacetylase activated by mDia – histone deacetylase 6. HDAC6 associates with PANX1 and activates PANX1 channels, even in excised membrane patches, suggesting direct deacetylation of PANX1. Substitution of basally-acetylated intracellular lysine residues identified on PANX1 by mass spectrometry either prevents HDAC6-mediated activation (K140/409Q) or renders the channels constitutively active (K140R). These data define a non-canonical RhoA-mDia-HDAC6 signaling pathway for GαqPCR activation of PANX1 channels and uncover lysine acetylation-deacetylation as an ion channel silencing-activation mechanism.

scholarly journals Gain-of-function GABRB3 variants identified in vigabatrin-hypersensitive epileptic encephalopathies

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Nathan L Absalom ◽  
Vivian W Y Liao ◽  
Kavitha Kothur ◽  
Dinesh C Indurthi ◽  
Bruce Bennetts ◽  
...  
Keyword(s):  
De Novo ◽  
Drug Effects ◽  
Receptor Expression ◽  
Aminobutyric Acid ◽  
Loss Of Function ◽  
Molecular Phenotype ◽  
Gain Of Function ◽  
Gene Encoding ◽  
Epileptic Encephalopathies ◽  
Receptor Phenotype

Abstract Variants in the GABRB3 gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with GABRB3 variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A GABRB3 variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of de novo variants in GABRB3 (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the GABRB3 p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the GABRB3 variant. The mRNA of these constructs was injected into Xenopus oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the GABRB3 p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of GABRB3 variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function GABRB3 variants.

scholarly journals De novo TRPV4 Leu619Pro variant causes a new channelopathy characterised by giant cell lesions of the jaws and skull, skeletal abnormalities and polyneuropathy

2021 ◽  
pp. jmedgenet-2020-107427
Author(s):  
Aviel Ragamin ◽  
Carolina C Gomes ◽  
Karen Bindels-de Heus ◽  
Renata Sandoval ◽  
Angelia V Bassenden ◽  
...  
Keyword(s):  
Giant Cell ◽  
De Novo ◽  
Neuromuscular Disorders ◽  
Somatic Mosaicism ◽  
Ion Leakage ◽  
Gain Of Function ◽  
Therapeutic Modalities ◽  
Organ Systems ◽  
Heterozygous Variant ◽  
Systemic Disorder

BackgroundPathogenic germline variants in Transient Receptor Potential Vanilloid 4 Cation Channel (TRPV4) lead to channelopathies, which are phenotypically diverse and heterogeneous disorders grossly divided in neuromuscular disorders and skeletal dysplasia. We recently reported in sporadic giant cell lesions of the jaws (GCLJs) novel, somatic, heterozygous, gain-of-function mutations in TRPV4, at Met713.MethodsHere we report two unrelated women with a de novo germline p.Leu619Pro TRPV4 variant and an overlapping systemic disorder affecting all organs individually described in TRPV4 channelopathies.ResultsFrom an early age, both patients had several lesions of the nervous system including progressive polyneuropathy, and multiple aggressive giant cell-rich lesions of the jaws and craniofacial/skull bones, and other skeletal lesions. One patient had a relatively milder disease phenotype possibly due to postzygotic somatic mosaicism. Indeed, the TRPV4 p.Leu619Pro variant was present at a lower frequency (variant allele frequency (VAF)=21.6%) than expected for a heterozygous variant as seen in the other proband, and showed variable regional frequency in the GCLJ (VAF ranging from 42% to 10%). In silico structural analysis suggests that the gain-of-function p.Leu619Pro alters the ion channel activity leading to constitutive ion leakage.ConclusionOur findings define a novel polysystemic syndrome due to germline TRPV4 p.Leu619Pro and further extend the spectrum of TRPV4 channelopathies. They further highlight the convergence of TRPV4 mutations on different organ systems leading to complex phenotypes which are further mitigated by possible post-zygotic mosaicism. Treatment of this disorder is challenging, and surgical intervention of the GCLJ worsens the lesions, suggesting the future use of MEK inhibitors and TRPV4 antagonists as therapeutic modalities for unmet clinical needs.

scholarly journals Neutralizing Antibody Therapeutics for COVID-19

Viruses ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 628
Author(s):  
Aeron C. Hurt ◽  
Adam K. Wheatley
Keyword(s):  
High Risk ◽  
Neutralizing Antibodies ◽  
Controlled Trial ◽  
Antiviral Treatment ◽  
Severe Disease ◽  
Neutralizing Antibody ◽  
Supplemental Oxygen ◽  
European Medicines Agency ◽  
Global Public Health ◽  
Public Health Burden

The emergence of SARS-CoV-2 and subsequent COVID-19 pandemic has resulted in a significant global public health burden, leading to an urgent need for effective therapeutic strategies. In this article, we review the role of SARS-CoV-2 neutralizing antibodies (nAbs) in the clinical management of COVID-19 and provide an overview of recent randomized controlled trial data evaluating nAbs in the ambulatory, hospitalized and prophylaxis settings. Two nAb cocktails (casirivimab/imdevimab and bamlanivimab/etesevimab) and one nAb monotherapy (bamlanivimab) have been granted Emergency Use Authorization by the US Food and Drug Administration for the treatment of ambulatory patients who have a high risk of progressing to severe disease, and the European Medicines Agency has similarly recommended both cocktails and bamlanivimab monotherapy for use in COVID-19 patients who do not require supplemental oxygen and who are at high risk of progressing to severe COVID-19. Efficacy of nAbs in hospitalized patients with COVID-19 has been varied, potentially highlighting the challenges of antiviral treatment in patients who have already progressed to severe disease. However, early data suggest a promising prophylactic role for nAbs in providing effective COVID-19 protection. We also review the risk of treatment-emergent antiviral resistant “escape” mutants and strategies to minimize their occurrence, discuss the susceptibility of newly emerging SARS-COV-2 variants to nAbs, as well as explore administration challenges and ways to improve patient access.

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