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 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 The Heat Sensing Trpv1 Receptor Is Not a Viable Anticonvulsant Drug Target in the Scn1a+/− Mouse Model of Dravet Syndrome

2021 ◽  
Vol 12 ◽  
Author(s):  
Vaishali Satpute Janve ◽  
Lyndsey L. Anderson ◽  
Dilara Bahceci ◽  
Nicole A. Hawkins ◽  
Jennifer A. Kearney ◽  
...  
Keyword(s):  
Mouse Model ◽  
Drug Target ◽  
Genetic Modifier ◽  
Anticonvulsant Drug ◽  
Dravet Syndrome ◽  
Seizure Threshold ◽  
Drug Resistant ◽  
Spontaneous Seizures ◽  
Temperature Thresholds ◽  
Seizure Models

Cannabidiol has been approved for the treatment of drug-resistant childhood epilepsies including Dravet syndrome (DS). Although the mechanism of anticonvulsant action of cannabidiol is unknown, emerging data suggests involvement of the transient receptor potential cation channel subfamily V member 1 (Trpv1). Pharmacological and genetic studies in conventional seizure models suggest Trpv1 is a novel anticonvulsant target. However, whether targeting Trpv1 is anticonvulsant in animal models of drug-resistant epilepsies is not known. Thus, we examined whether Trpv1 affects the epilepsy phenotype of the F1.Scn1a+/− mouse model of DS. We found that cortical Trpv1 mRNA expression was increased in seizure susceptible F1.Scn1a+/− mice with a hybrid genetic background compared to seizure resistant 129.Scn1a+/− mice isogenic on 129S6/SvEvTac background, suggesting Trpv1 could be a genetic modifier. Previous studies show functional loss of Trpv1 is anticonvulsant. However, Trpv1 selective antagonist SB-705498 did not affect hyperthermia-induced seizure threshold, frequency of spontaneous seizures or survival of F1.Scn1a+/− mice. Surprisingly, Trpv1 deletion had both pro- and anti-seizure effects. Trpv1 deletion did not affect hyperthermia-induced seizure temperature thresholds of F1.Scn1a+/−; Trpv1+/− at P14-16 but was proconvulsant at P18 as it reduced seizure temperature thresholds. Conversely, Trpv1 deletion did not alter the frequency of spontaneous seizures but reduced their severity. These results suggest that Trpv1 is a modest genetic modifier of spontaneous seizure severity in the F1.Scn1a+/− model of DS. However, the opposing pro- and anti-seizure effects of Trpv1 deletion and the lack of effects of Trpv1 inhibition suggest that Trpv1 is unlikely a viable anticonvulsant drug target in DS.

scholarly journals Dravet syndrome and Dravet-like phenotype: a systematic review of the SCN1A and PCDH19 variants

2021 ◽  
Keyword(s):  
Cognitive Deficit ◽  
Significant Proportion ◽  
Dravet Syndrome ◽  
Motor Deficit ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Pathogenic Variants ◽  
Voltage Dependent ◽  
Uncertain Significance ◽  
Similar Disease

Background: Dravet syndrome (DS) is a rare and severe epileptic syndrome of childhood with a prevalence around 1/40,000 people worldwide. Approximately 80% of patients with DS present SCN1A pathogenic variants, which encodes an alpha subunit of a neural voltage- dependent sodium channel. SCN1A variants were also related to DS. There is a correlation between PCDH19 pathogenic variants, encodes the protocadherin 19, and a similar disease to DS known as DS-like phenotype. Objectives: To clarify the differences between DS and DS-like phenotype according to the SCN1A and PCDH19 variants. Methodology: A review from March/2019 to November/2020 was conducted in PubMed and VHL databases, following PRISMA criteria. Results: 19 studies were included and a significant proportion of patients with DS carrying SCN1A was greater than patients with DS-like phenotype harboring PCDH19 variants (76.6% vs. 23.4%). Considering SCN1A and PCDH19, 47 variants were pathogenic and 12 of uncertain significance; 25% were deletions and 75% were single- nucleotide variants. Autism was predominantly observed in patients with DS-like carrying PCDH19 variants compared to SCN1A variants carriers (62.5% vs. 37.5%, p=0.044). In addition, it was noticed a significant predisposition to hyperthermia during seizures in patients with variants in the PCDH19 (p=0.003). There was no significance differences between both groups and cognitive deficit, ataxia, behavior problems, and motor deficit. Conclusions: The study is the first to point out differences between the DS and DS-like phenotype according to the SCN1A and PCDH19 variants.

scholarly journals Case Report: Functional Investigation of an Undescribed Missense Variant Affecting Splicing in a Patient With Dravet Syndrome

2021 ◽  
Vol 12 ◽  
Author(s):  
Peter Sparber ◽  
Svetlana Mikhaylova ◽  
Varvara Galkina ◽  
Yulia Itkis ◽  
Mikhail Skoblov
Keyword(s):  
Missense Variant ◽  
Febrile Seizures ◽  
Dravet Syndrome ◽  
Loss Of Function ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Pathogenic Variants ◽  
Uncertain Significance ◽  
Functional Investigation ◽  
Coding Variants

Pathogenic variants in the SCN1A gene are associated with a spectrum of epileptic disorders ranging in severity from familial febrile seizures to Dravet syndrome. Large proportions of reported pathogenic variants in SCN1A are annotated as missense variants and are often classified as variants of uncertain significance when no functional data are available. Although loss-of-function variants are associated with a more severe phenotype in SCN1A, the molecular mechanism of single nucleotide variants is often not clear, and genotype-phenotype correlations in SCN1A-related epilepsy remain uncertain. Coding variants can affect splicing by creating novel cryptic splicing sites in exons or by disrupting exonic cis-regulation elements crucial for proper pre-mRNA splicing. Here, we report a novel case of Dravet syndrome caused by an undescribed missense variant, c.4852G>A (p.(Gly1618Ser)). By midigene splicing assay, we demonstrated that the identified variant is in fact splice-affecting. To our knowledge, this is the first report on the functional investigation of a missense variant affecting splicing in Dravet syndrome.

scholarly journals Unsuspected somatic mosaicism for FBN1 gene contributes to Marfan syndrome

2021 ◽  
Author(s):  
Pauline Arnaud ◽  
Hélène Morel ◽  
Olivier Milleron ◽  
Laurent Gouya ◽  
Christine Francannet ◽  
...  
Keyword(s):  
Marfan Syndrome ◽  
Somatic Mosaicism ◽  
Variant Calling ◽  
Copy Number Variations ◽  
Pathogenic Variant ◽  
Single Nucleotide Variants ◽  
Bioinformatics Analyses ◽  
Single Nucleotide ◽  
Fbn1 Gene ◽  
Pathogenic Variants

Abstract Purpose Individuals with mosaic pathogenic variants in the FBN1 gene are mainly described in the course of familial screening. In the literature, almost all these mosaic individuals are asymptomatic. In this study, we report the experience of our team on more than 5,000 Marfan syndrome (MFS) probands. Methods Next-generation sequencing (NGS) capture technology allowed us to identify five cases of MFS probands who harbored a mosaic pathogenic variant in the FBN1 gene. Results These five sporadic mosaic probands displayed classical features usually seen in Marfan syndrome. Combined with the results of the literature, these rare findings concerned both single-nucleotide variants and copy-number variations. Conclusion This underestimated finding should not be overlooked in the molecular diagnosis of MFS patients and warrants an adaptation of the parameters used in bioinformatics analyses. The five present cases of symptomatic MFS probands harboring a mosaic FBN1 pathogenic variant reinforce the fact that apparently asymptomatic mosaic parents should have a complete clinical examination and a regular cardiovascular follow-up. We advise that individuals with a typical MFS for whom no single-nucleotide pathogenic variant or exon deletion/duplication was identified should be tested by NGS capture panel with an adapted variant calling analysis.

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 Re-evaluation of single nucleotide variants and identification of structural variants in a cohort of 45 sudden unexplained death cases

2021 ◽  
Author(s):  
Jacqueline Neubauer ◽  
Shouyu Wang ◽  
Giancarlo Russo ◽  
Cordula Haas
Keyword(s):  
Sudden Death ◽  
Cardiac Diseases ◽  
Structural Variants ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Sudden Unexplained Death ◽  
Unexplained Death ◽  
Pathogenic Variants ◽  
The Impact ◽  
Death Cases

AbstractSudden unexplained death (SUD) takes up a considerable part in overall sudden death cases, especially in adolescents and young adults. During the past decade, many channelopathy- and cardiomyopathy-associated single nucleotide variants (SNVs) have been identified in SUD studies by means of postmortem molecular autopsy, yet the number of cases that remain inconclusive is still high. Recent studies had suggested that structural variants (SVs) might play an important role in SUD, but there is no consensus on the impact of SVs on inherited cardiac diseases. In this study, we searched for potentially pathogenic SVs in 244 genes associated with cardiac diseases. Whole-exome sequencing and appropriate data analysis were performed in 45 SUD cases. Re-analysis of the exome data according to the current ACMG guidelines identified 14 pathogenic or likely pathogenic variants in 10 (22.2%) out of the 45 SUD cases, whereof 2 (4.4%) individuals had variants with likely functional effects in the channelopathy-associated genes SCN5A and TRDN and 1 (2.2%) individual in the cardiomyopathy-associated gene DTNA. In addition, 18 structural variants (SVs) were identified in 15 out of the 45 individuals. Two SVs with likely functional impairment were found in the coding regions of PDSS2 and TRPM4 in 2 SUD cases (4.4%). Both were identified as heterozygous deletions, which were confirmed by multiplex ligation-dependent probe amplification. In conclusion, our findings support that SVs could contribute to the pathology of the sudden death event in some of the cases and therefore should be investigated on a routine basis in suspected SUD cases.

Stiripentol: A Novel Antiseizure Medication for the Management of Dravet Syndrome

2019 ◽  
Vol 53 (11) ◽  
pp. 1136-1144 ◽  
Author(s):  
Marcia L. Buck ◽  
Howard P. Goodkin
Keyword(s):  
English Language ◽  
Data Extraction ◽  
Phase 1 ◽  
The United States ◽  
Dravet Syndrome ◽  
Pathogenic Variants ◽  
Search Terms ◽  
Novel Approach ◽  
Study Selection ◽  
Refractory Seizures

Objective: To describe the pharmacology, efficacy, and safety of stiripentol in the treatment of refractory seizures in patients with Dravet syndrome. Data Sources: A search of the English language literature was conducted using PubMed and MEDLINE (1978 to April 2019) with the search terms stiripentol, Dravet syndrome, and refractory epilepsy. Other resources included article bibliographies, prescribing information, and relevant trials at https://clinicaltrials.gov/ . Study Selection and Data Extraction: All phase 1, 2, or 3 trials; observational studies; and retrospective studies were analyzed. Data Synthesis: In controlled studies, stiripentol has been shown to reduce seizure frequency by 50% or more in 40% to 70% of patients with Dravet syndrome. Reductions in seizure duration and episodes of status epilepticus have also been documented. Common adverse effects include somnolence and anorexia. Stiripentol inhibits the metabolism of clobazam and valproate, often requiring dose adjustment. Relevance to Patient Care and Clinical Practice: Stiripentol, a direct allosteric modulator of GABAA receptors, offers a novel approach to treatment in patients with Dravet syndrome, both with and without pathogenic variants of the sodium channel α-1 subunit gene, and potentially other refractory seizures. Although available outside the United States for a decade, it was only recently approved by the Food and Drug Administration for patients 2 years of age and older with Dravet syndrome taking clobazam. Conclusions: Stiripentol is an effective adjunctive therapy for reducing the frequency and duration of refractory seizures in patients with Dravet syndrome. Its role in the treatment of other refractory epilepsies requires further study.

scholarly journals Maple syrup urine disease in Brazilian patients: variants and clinical phenotype heterogeneity

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Ana Vitoria Barban Margutti ◽  
Wilson Araújo Silva ◽  
Daniel Fantozzi Garcia ◽  
Greice Andreotti de Molfetta ◽  
Adriana Aparecida Marques ◽  
...  
Keyword(s):  
Maple Syrup Urine Disease ◽  
In Silico Analysis ◽  
Cross Sectional Study ◽  
Clinical Severity ◽  
Cross Sectional ◽  
Maple Syrup ◽  
Molecular Features ◽  
Pathogenic Variants ◽  
Study Results ◽  
Urine Disease

Abstract Background Maple syrup urine disease (MSUD) is an autosomal recessive inherited metabolic disease caused by deficient activity of the branched-chain α-keto acid dehydrogenase (BCKD) enzymatic complex. BCKD is a mitochondrial complex encoded by BCKDHA, BCKDHB, DBT, and DLD genes. MSUD is predominantly caused by Variants in BCKDHA, BCKDHB, and DBT genes encoding the E1α, E1β, and E2 subunits of BCKD complex, respectively. The aim of this study was to characterize the genetic basis of MSUD by identifying the point variants in BCKDHA, BCKDHB, and DBT genes in a cohort of Brazilian MSUD patients and to describe their phenotypic heterogeneity. It is a descriptive cross-sectional study with 21 MSUD patients involving molecular genotyping by Sanger sequencing. Results Eight new variants predicted as pathogenic were found between 30 variants (damaging and non-damaging) identified in the 21 patients analyzed: one in the BCKDHA gene (p.Tyr120Ter); five in the BCKDHB gene (p.Gly131Val, p.Glu146Glnfs * 13, p.Phe149Cysfs * 9, p.Cys207Phe, and p.Lys211Asn); and two in the DBT gene (p.Glu148Ter and p.Glu417Val). Seventeen pathogenic variants were previously described and five variants showed no pathogenicity according to in silico analysis. Conclusion Given that most of the patients received late diagnoses, the study results do not allow us to state that the molecular features of MSUD variant phenotypes are predictive of clinical severity.

scholarly journals Identification of a likely pathogenic structural variation in the LAMA1 gene by Bionano optical mapping

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Min Chen ◽  
Min Zhang ◽  
Yeqing Qian ◽  
Yanmei Yang ◽  
Yixi Sun ◽  
...  
Keyword(s):  
Optical Mapping ◽  
Pathogenic Variant ◽  
Screening Methods ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Real Time Quantitative Pcr ◽  
Pathogenic Variants ◽  
Whole Exome ◽  
Great Insight

Abstract Recent advances in Bionano optical mapping (BOM) provide a great insight into the determination of structural variants (SVs), but its utility in identification of clinical likely pathogenic variants needs to be further demonstrated and proved. In a family with two consecutive pregnancies affected with ventriculomegaly, a splicing likely pathogenic variant at the LAMA1 locus (NM_005559: c. 4663 + 1 G > C) inherited from the father was identified in the proband by whole-exome sequencing, and no other pathogenic variant associated with the clinical phenotypes was detected. SV analysis by BOM revealed an ~48 kb duplication at the LAMA1 locus in the maternal sample. Real-time quantitative PCR and Sanger sequencing further confirmed the duplication as c.859-153_4806 + 910dup. Based on these variants, we hypothesize that the fetuses have Poretti-Boltshauser syndrome (PBS) presenting with ventriculomegaly. With the ability to determine single nucleotide variants and SVs, the strategy adopted here might be useful to detect cases missed by current routine screening methods. In addition, our study may broaden the phenotypic spectrum of fetuses with PBS.

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