scholarly journals Gabra2 is a genetic modifier of Dravet syndrome in mice

2020 ◽  
Author(s):  
Nicole A. Hawkins ◽  
Toshihiro Nomura ◽  
Samantha Duarte ◽  
Robert W. Williams ◽  
Gregg E. Homanics ◽  
...  
Keyword(s):  
Protein Expression ◽  
De Novo ◽  
Genetic Modifier ◽  
Clinical Severity ◽  
Dravet Syndrome ◽  
Unexpected Death ◽  
Increased Risk ◽  
Hippocampal Synapses ◽  
Severe Epilepsy ◽  
Strain Dependent

AbstractPathogenic variants in epilepsy genes result in a spectrum of clinical presentation, ranging from benign phenotypes to intractable epilepsies with significant co-morbidities and increased risk of sudden unexpected death in epilepsy (SUDEP). One source of this phenotypic heterogeneity is modifier genes that affect penetrance, dominance or expressivity of a primary pathogenic variant. Mouse models of epilepsy also display varying degrees of clinical severity on different genetic backgrounds. Mice with heterozygous deletion of Scn1a (Scn1a+/−) model Dravet syndrome, a severe epilepsy most often caused by SCN1A haploinsufficiency. Scn1a+/− heterozygous mice recapitulate key features of Dravet syndrome, including febrile and afebrile spontaneous seizures, SUDEP, and cognitive and behavioral deficits. The Scn1a+/− mouse model also exhibits strain-dependent phenotype severity. Scn1a+/− mice maintained on the 129S6/SvEvTac (129) strain have normal lifespan and no overt seizures. In contrast, admixture with C57BL/6J (B6) results in severe epilepsy and premature lethality in [B6×129]F1.Scn1a+/− mice. In previous work, we identified Dravet Survival Modifier loci (Dsm1-Dsm5) responsible for strain-dependent differences in survival. Gabra2, encoding the GABAA α2 subunit, was nominated as the top candidate modifier at the Dsm1 locus on chromosome 5. Direct measurement of GABAA receptors found lower abundance of α2-containing receptors in hippocampal synapses of B6 mice relative to 129. We also identified a B6-specific single nucleotide intronic deletion within Gabra2 that lowers mRNA and protein by nearly 50%. Repair of this de novo deletion reestablished normal levels of Gabra2 transcript and protein expression. In the current study, we used B6 mice with the repaired Gabra2 allele to validate it as a modifier of phenotype severity in Scn1a+/− mice. Repair of Gabra2 restored transcript and protein expression, increased abundance of α2-containing GABAA receptors in hippocampal synapses, and improved seizure and survival phenotypes of Scn1a+/− mice. These findings validate Gabra2 as a genetic modifier of Dravet syndrome.

scholarly journals Gabra2 is a genetic modifier of Dravet syndrome in mice

2021 ◽  
Author(s):  
Nicole A. Hawkins ◽  
Toshihiro Nomura ◽  
Samantha Duarte ◽  
Levi Barse ◽  
Robert W. Williams ◽  
...  
Keyword(s):  
Genetic Modifier ◽  
Clinical Severity ◽  
Dravet Syndrome ◽  
Behavioral Deficits ◽  
Single Nucleotide ◽  
Pathogenic Variants ◽  
Spontaneous Seizures ◽  
Hippocampal Synapses ◽  
Epilepsy Models ◽  
Severe Epilepsy

AbstractPathogenic variants in epilepsy genes result in a spectrum of clinical severity. One source of phenotypic heterogeneity is modifier genes that affect expressivity of a primary pathogenic variant. Mouse epilepsy models also display varying degrees of clinical severity on different genetic backgrounds. Mice with heterozygous deletion of Scn1a (Scn1a+/−) model Dravet syndrome, a severe epilepsy most often caused by SCN1A haploinsufficiency. Scn1a+/− mice recapitulate features of Dravet syndrome, including spontaneous seizures, sudden death, and cognitive/behavioral deficits. Scn1a+/− mice maintained on the 129S6/SvEvTac (129) strain have normal lifespan and no spontaneous seizures. In contrast, admixture with C57BL/6J (B6) results in epilepsy and premature lethality. We previously mapped Dravet Survival Modifier loci (Dsm1-Dsm5) responsible for strain-dependent differences in survival. Gabra2, encoding the GABAA α2 subunit, was nominated as a candidate modifier at Dsm1. Direct measurement of GABAA receptors found lower abundance of α2-containing receptors in hippocampal synapses of B6 mice relative to 129. We also identified a B6-specific single nucleotide deletion within Gabra2 that lowers mRNA and protein by nearly 50%. Repair of this deletion reestablished normal levels of Gabra2 expression. In this study, we used B6 mice with a repaired Gabra2 allele to evaluate Gabra2 as a genetic modifier of severity in Scn1a+/− mice. Gabra2 repair restored transcript and protein expression, increased abundance of α2-containing GABAA receptors in hippocampal synapses, and rescued epilepsy phenotypes of Scn1a+/− mice. These findings validate Gabra2 as a genetic modifier of Dravet syndrome, and support enhancing function of α2-containing GABAA receptors as treatment strategy for Dravet syndrome.

scholarly journals Sudden unexpected death in genetic epileptic encephalopathies: a role of neurocardiac genes

2018 ◽  
Vol 10 (3) ◽  
pp. 63-70
Author(s):  
E. D. Belousova ◽  
M. A. Shkolnikova
Keyword(s):  
High Risk ◽  
Sudden Unexpected Death ◽  
Dravet Syndrome ◽  
Unexpected Death ◽  
Sodium Potassium ◽  
Epileptic Encephalopathies ◽  
Increased Risk ◽  
Clinical Conditions ◽  
Cultured Cardiomyocytes

It is well known that sudden unexpected death in epilepsy (SUDEP) is one of the most significant factors of mortality in epileptic patients. There is an increased risk of SUDEP in genetic epileptic encephalopathies (EE), partly because those syndromes are associated with mutations in the “neurocardiac” genes, which have been implicated in both epilepsy and cardiac arrhythmias. In these clinical conditions, functions of ion selective channels (sodium, potassium and etc.) are affected; for example, in children with Dravet syndrome, the risk of SUDEP is 40 times higher than that in children with common epilepsy syndromes. In a murine model of SCN1A epilepsy, a prolongation of QT interval coincided with a seizure; in addition, an excessive excitability of cultured cardiomyocytes was demonstrated. A high risk of SUDEP is characteristic for EE caused by mutation in the SCN8A gene. Other prognostic biomarkers of SUDEP may include mutations in sodium channel genes, such as SCN4A, SCN10A, and SCN11A. Our knowledge about SUDEP associated with potassium channel dysfunctions is still very limited. There are likely some mutations in other genes, that can modify (increase or decrease) the risk of SUDEP in EE. If patients with genetic EE are indeed at a high risk for SUDEP, they must be followed up by cardiologists alongside with neurologists. Provided this hypothesis is proved, any newly diagnosed arrhythmia should be carefully monitored and treated (with medications and/or interventions), in order to improve the survival rate in genetic EE.

scholarly journals Activation of JAK2/STAT5 Pathway Reduces Expression Level of DNMT3a in MPN Cell Line

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 5394-5394
Author(s):  
Jie Zhou ◽  
Aibin Liang ◽  
Shaoguang Li ◽  
Wenjun Zhang ◽  
Jianfei FU
Keyword(s):  
Protein Expression ◽  
Cell Line ◽  
Dna Methyltransferase ◽  
De Novo ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasms ◽  
Expression Level ◽  
Hematopoietic Stem ◽  
Expression Levels ◽  
Increased Risk

Introduction: Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell (HSC) disorders characterized by overproduction of mature blood cells and increased risk of transformation to acute myeloid leukemia (AML), and JAK2V167F is the most frequent MPN driving mutation detected in >95% of PV and 50-60% ET and PMF. DNMT3A is a de novo DNA methyltransferase that catalyzes the addition of methyl groups into active chromatin in CpG-rich regions leading to gene inactivation. Dnmt3a-/- HSC have enhanced self-renewal and a block in differentiation in vivo. Previous study showed that JAK2V617F and Dnmt3a loss cooperate to induce myelofibrosis through activated enhancer-driven inflammation, while whether JAK2V617F regulates DNMT3a still remains unclear. AZ960 is a potent and selective ATP competitive inhibitor of the JAK2 kinase, and previous studies reported that AZ960 possessed the activity selectively against JAK2. LY2784544 has been identified as a selective inhibitor of JAK2V617F and has undergone clinical trials for the treatment of several myeloproliferative disorders. Methods: Empty vector (control) and mutant JAK2V617F were transduced into BaF3 cells using a lentivirus system. JAK2V617F-expressing BaF3 cells grow IL-3 independent and were selected by fluorescence-activated cell sorting (FACS) for GFP expression. The protein expression levels of p-STAT5 and DNMT3a were detected by western blotting. JAK2V617F-expressing and control BaF3 cells were incubated with gradient concentration of LY2784544 or AZ960 to inhibit JAK2/STAT5 pathway. Results: The expression levels of p-STAT5 were obviously up-regulated in the JAK2V617F-expressing BaF3 cells, and DNMT3a was down-regulated. After 1-hour incubation in the serial diluted LY2784544, p-STAT5 were reduced in JAK2V617F-expressing BaF3 cells, with expression of DNMT3a elevated. To further confirm the correlation between JAK2/STAT5 pathway and expression of DNMT3a, another JAK2 inhibitor AZ960 was tested similar to LY2784544. With p-STAT5 expression suppressed, protein level of DNMT3a showed significantly promotion. Conclusion: We observed that JAK2V167F mutation suppresses protein expression levels of DNMT3a in MPN cell lines. JAK2 inhibition by AZ960 and LY2784544 significantly improved expression levels of DNMT3a. The activation of JAK2/STAT5 pathway reduces expression level of DNMT3a in MPN cell line, and the specific mechanism still needs to be explored. Figure Disclosures No relevant conflicts of interest to declare.

Antisense oligonucleotides increase Scn1a expression and reduce seizures and SUDEP incidence in a mouse model of Dravet syndrome

2020 ◽  
Vol 12 (558) ◽  
pp. eaaz6100 ◽  
Author(s):  
Zhou Han ◽  
Chunling Chen ◽  
Anne Christiansen ◽  
Sophina Ji ◽  
Qian Lin ◽  
...  
Keyword(s):  
Mouse Model ◽  
Antisense Oligonucleotides ◽  
De Novo ◽  
Nuclear Gene ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Unexpected Death ◽  
Α Subunit ◽  
Gene And Protein Expression ◽  
Electrographic Seizures

Dravet syndrome (DS) is an intractable developmental and epileptic encephalopathy caused largely by de novo variants in the SCN1A gene, resulting in haploinsufficiency of the voltage-gated sodium channel α subunit NaV1.1. Here, we used Targeted Augmentation of Nuclear Gene Output (TANGO) technology, which modulates naturally occurring, nonproductive splicing events to increase target gene and protein expression and ameliorate disease phenotype in a mouse model. We identified antisense oligonucleotides (ASOs) that specifically increase the expression of productive Scn1a transcript in human cell lines, as well as in mouse brain. We show that a single intracerebroventricular dose of a lead ASO at postnatal day 2 or 14 reduced the incidence of electrographic seizures and sudden unexpected death in epilepsy (SUDEP) in the F1:129S-Scn1a+/− × C57BL/6J mouse model of DS. Increased expression of productive Scn1a transcript and NaV1.1 protein was confirmed in brains of treated mice. Our results suggest that TANGO may provide a unique, gene-specific approach for the treatment of DS.

Two autopsy cases of sudden unexpected death from Dravet syndrome with novel de novo SCN1A variants

2020 ◽  
Vol 42 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Yukiko Hata ◽  
Yuko Oku ◽  
Hiromichi Taneichi ◽  
Tomomi Tanaka ◽  
Noboru Igarashi ◽  
...  
Keyword(s):  
De Novo ◽  
Sudden Unexpected Death ◽  
Dravet Syndrome ◽  
Unexpected Death

scholarly journals Risk Factors, and Clinical and Etiological Characteristics of Ischemic Strokes in COVID-19-Infected Patients: A Systematic Review of Literature

2021 ◽  
pp. 1-4
Author(s):  
Simone Vidale
Keyword(s):  
Risk Factors ◽  
Systematic Review ◽  
Clinical Features ◽  
Case Reports ◽  
Clinical Severity ◽  
Large Artery ◽  
Causal Association ◽  
Review Of Literature ◽  
Increased Risk ◽  
Long Time

<b><i>Background and Purpose:</i></b> Coronavirus disease 2019 (CO­VID-19) infection is an ongoing pandemic and worldwide health emergency that has caused important changes in healthcare systems. Previous studies reported an increased risk of thromboembolic events, including stroke. This systematic review aims to describe the clinical features and etiological characteristics of ischemic stroke patients with CO­VID-19 infection. <b><i>Method:</i></b> A literature search was performed in principal databases for studies and case reports containing data concerning risk factors, clinical features, and etiological characteristics of patients infected with COVID-19 and suffering from stroke. Descriptive and analytical statistics were applied. <b><i>Results:</i></b> Overall, 14 articles were included for a total of 93 patients. Median age was 65 (IQR: 55–75) years with prevalence in males. Stroke occurred after a median of 6 days from COVID-19 infection diagnosis. Median National of Institute of Health Stroke Scale (NIHSS) score was 19. Cryptogenic (Cry) strokes were more frequent (51.8%), followed by cardioembolic etiology, and they occurred a long time after COVID-19 diagnosis compared with large-artery atherosclerosis strokes (<i>p</i><sub>trend</sub>: 0.03). The clinical severity of stroke was significantly associated with the severity grade of COVID-19 infection (<i>p</i><sub>trend</sub>: 0.03). <b><i>Conclusions:</i></b> Ischemic strokes in COVID-19-infected patients were clinically severe, affecting younger patients mainly with Cry and cardioembolic etiologies. Further multicenter prospective registries are needed to better describe the causal association and the effect of COVID-19 infection on stroke.

scholarly journals The study of sodium and potassium channel gene single-nucleotide variation significance in non-mechanical forms of epilepsy

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Ozada Khamdiyeva ◽  
Zhanerke Tileules ◽  
Gulminyam Baratzhanova ◽  
Anastassiya Perfilyeva ◽  
Leyla Djansugurova
Keyword(s):  
Ion Channel ◽  
Potassium Channel ◽  
De Novo ◽  
Potassium Ion ◽  
Dravet Syndrome ◽  
De Novo Mutations ◽  
Single Nucleotide ◽  
Channel Gene ◽  
Sodium And Potassium ◽  
Potassium Channel Gene

Abstract Background Epilepsy is one of the most common and heterogeneous neurological diseases. The main clinical signs of the disease are repeated symptomatic or idiopathic epileptic seizures of both convulsive and non-convulsive nature that develop against a background of lost or preserved consciousness. The genetic component plays a large role in the etiology of idiopathic forms of epilepsy. The study of the molecular genetic basis of neurological disorders has led to a rapidly growing number of gene mutations known to be involved in hereditary ion channel dysfunction. The aim of this research was to evaluate the involvement of single-nucleotide variants that modify the function of genes (SCN1A, KCNT1, KCNTС1, and KCNQ2) encoding sodium and potassium ion channel polypeptides in the development of epilepsy. Results De novo mutations in the sodium channel gene SCN1A c.5347G>A (p. Ala1783Thr) were detected in two patients with Dravet syndrome, with a deletion in exon 26 found in one. Three de novo mutations in the potassium channel gene KCNT1 c.2800G>A (p. Ala934Thr), were observed in two patients with temporal lobe epilepsy (TLE) and one patient with residual encephalopathy. Moreover, a control cohort matched to the case cohort did not reveal any SNVs among conditionally healthy individuals, supporting the pathogenic significance of the studied SNVs. Conclusion Our results are supported by literature data showing that the sodium ion channel gene SCN1A c.5347G>A mutation may be involved in the pathogenesis of Dravet syndrome. We also note that the c.2800G>A mutation in the potassium channel gene KCNT1 can cause not only autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) but also other forms of epilepsy. To treat pathogenetic mutations that accelerate the function of sodium and potassium ion channels, we recommend ion channel blockade drug therapy.

scholarly journals Dravet syndrome associated mutations in GABRA1, GABRB2 and GABRG2 define the genetic landscape of defects of GABAA receptors

2021 ◽  
Author(s):  
Ciria C Hernandez ◽  
XiaoJuan Tian ◽  
Ningning Hu ◽  
Wangzhen Shen ◽  
Mackenzie A Catron ◽  
...  
Keyword(s):  
Gabaa Receptor ◽  
De Novo ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
First Year ◽  
Genes Encoding ◽  
Genetic Landscape ◽  
Clonic Seizures ◽  
Trafficking Defects ◽  
First Year Of Life

Abstract Dravet syndrome is a rare, catastrophic epileptic encephalopathy that begins in the first year of life, usually with febrile or afebrile hemiclonic or generalized tonic-clonic seizures followed by status epilepticus. De novo variants in genes that mediate synaptic transmission such as SCN1A and PCDH19 are often associated with Dravet syndrome. Recently, GABAA receptor subunit genes (GABRs) encoding α1 (GABRA1), β3 (GABRB3) and γ2 (GABRG2), but not β2 (GABRB2) or β1 (GABRB1), subunits are frequently associated with Dravet syndrome or Dravet syndrome-like phenotype. We performed next generation sequencing on 870 patients with Dravet syndrome and identified nine variants in three different GABRs. Interestingly, the variants were all in genes encoding the most common GABAA receptor, the α1β2γ2 receptor. Mutations in GABRA1 (c.644T&gt;C, p.L215P; c.640C&gt;T, p.R214C; c.859G&gt;A; V287I; c.641G&gt;A, p.R214H) and GABRG2 (c.269C&gt;G, p.T90R; c.1025C&gt;T, p.P342L) presented as de novo cases, while in GABRB2 two variants were de novo (c.992T&gt;C, p.F331S; c.542A&gt;T, p.Y181F) and one was autosomal dominant and inherited from the maternal side (c.990_992del, p.330_331del). We characterized the effects of these GABR variants on GABAA receptor biogenesis and channel function. We found that defects in receptor gating were the common deficiency of GABRA1 and GABRB2 Dravet syndrome variants, while mainly trafficking defects were found with the GABRG2 (c.269C&gt;G, p.T90R) variant. It seems that variants in α1 and β2 subunits are less tolerated than in γ2 subunits, since variant α1 and β2 subunits express well but were functionally deficient. This suggests that all of these GABR variants are all targeting GABR genes that encode the assembled α1β2γ2 receptor, and regardless of which of the three subunits are mutated, variants in genes coding for α1, β2 and γ2 receptor subunits make them candidate causative genes in the pathogenesis of Dravet syndrome.

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