Genetic Modifiers of Childhood Epilepsy

儿童癫痫的基因修饰

• 批准号: 8759567
• 负责人: Jennifer A Kearney
• 金额: $ 33.8万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8759567
• 关键词: Address; Age-Months; Backcrossings; Candidate Disease Gene; Childhood; Chromosomes, Human, Pair 5; Clinical; Code; Cognitive; Complex; Congenic Strain; DNA; Data Set; Development; Developmental Delay Disorders; Disease Progression; Encephalopathies; Epilepsy; Etiology; Event; Exhibits; Failure; Febrile Convulsions; Functional disorder; Gene Expression Profile; Genes; Genetic; Genetic Identity; Goals; Hippocampus (Brain); Human; Individual; Infant; Interneurons; Life; Longevity; Maps; Modeling; Molecular; Mus; Mutation; Neurons; Outcome; Pathway interactions; Patients; Penetrance; Phase; Phenotype; Predisposition; Quantitative Trait Loci; Reporting; Resistance; Resolution; Risk; SCN1A protein; Seizures; Severities; Severity of illness; Sodium; Sodium Channel; Syndrome; Testing; Transgenes; Transgenic Organisms; base; clinical phenotype; congenic; density; improved; insight; loss of function mutation; mortality; neurophysiology; new therapeutic target; novel therapeutics; premature; public health relevance; resistant strain; response; simple febrile seizure; transcriptome sequencing; voltage

DESCRIPTION (provided by applicant): Mutations in voltage-gated sodium channels are responsible for several human epilepsies with varying degrees of clinical severity. Over 800 mutations in SCN1A, encoding the neuronal voltage-gated sodium channel Nav1.1, have been reported patients. SCN1A mutations are associated with epilepsy phenotypes on the genetic epilepsy with febrile seizures plus (GEFS+) spectrum. The GEFS+ spectrum ranges from simple febrile seizures on the mild end of the spectrum to Dravet syndrome on the severe end. Heterozygous loss-of-function mutations in SCN1A result in Dravet syndrome, an infant-onset epileptic encephalopathy characterized by a variety of seizure types, developmental delay and elevated mortality risk. A common feature of monogenic epilepsies is variable expressivity in individuals carrying the same mutation, suggesting that clinical severity is influenced by genetic modifiers. Mice with heterozygous deletion of Scn1a (Scn1a+/-) model a number of features of Dravet syndrome, including spontaneous seizures and increased mortality risk. Loss of Scn1a results in reduced sodium current in hippocampal GABAergic interneurons, which is predicted to increase excitability due to failure of inhibition. Phenotype severity in Scn1a+/- mice is strongly dependent on strain background. Scn1a+/- mice on the resistant 129 strain background (129.Scn1a+/-) have no overt phenotype and live a normal lifespan. In contrast, Scn1a+/- mice on a (129xB6)F1 strain background (F1.Scn1a+/-) exhibit spontaneous seizures and premature lethality, with 50% dying by 1 month of age. Based on the strain- dependent difference in phenotype, we hypothesize that genetic modifiers influence Scn1a+/- phenotype severity. We recently mapped several modifier loci that influence premature lethality of Scn1a+/- mice. In the current proposal, we will perform fine mapping and candidate gene analysis with the goal of identifying the responsible modifier genes. In addition to the strain-dependent differences in clinical severity, we also observed strain-dependent differences in hippocampal neuron sodium currents (INa). GABAergic interneurons isolated from the F1.Scn1a+/- mice exhibit decreased INa density compared to wildtype littermate controls. In contrast, INa density is preserved in GABAergic interneurons isolated from 129.Scn1a+/- and is no different from wildtype littermates. This suggests that interneurons from strain 129 compensate for the loss of Nav1.1, while F1 interneurons do not. Based on this observation, we hypothesize that there are strain differences in compensatory capacity in the context of Scn1a heterozygous deletion. We propose to perform RNA-seq analysis to characterize hippocampal transcriptome differences during the critical phase of phenotype onset in susceptible F1.Scn1a+/- and resistant 129.Scn1a+/- mice. The results of this analysis will suggest candidate modifier genes and pathways that influence phenotype severity in Scn1a+/- mice. Identification of Dravet syndrome modifier genes will provide insight into the pathophysiology of epilepsy and will suggest novel therapeutic strategies for the improved treatment of human patients.

描述(由申请人提供)：电压门控钠通道的突变是几种临床严重程度不同的人类癫痫的原因。据报道，编码神经元电压门控钠通道Nav1.1的SCN1A基因有800多个突变。在遗传性癫痫伴热性惊厥加(GEFS+)谱上，SCN1A突变与癫痫表型相关。GEFS+谱范围从轻度的单纯发热性惊厥到重度的Drave氏综合征。SCN1A杂合性功能丧失突变导致Drave氏综合征，这是一种婴儿发作性癫痫脑病，其特征是各种癫痫类型、发育延迟和死亡风险增加。单基因癫痫的一个共同特征是携带相同突变的个体的表达能力不同，这表明临床严重程度受到遗传修饰物的影响。携带Scn1a杂合缺失(Scn1a+/-)的小鼠可建立一系列Drave氏综合征的模型，包括自发性癫痫发作和死亡风险增加。Scn1a的缺失导致了海马GABA能中间神经元钠电流的减少，这被认为是由于抑制失败而增加了兴奋性。Scn1a+/-小鼠的表型严重性很强 依赖于菌株背景。耐药129株背景(129)的SCN1a+/-小鼠没有明显的表型，并能正常存活。相比之下，(129xB6)F1品系背景(F1.Scn1a+/-)的Scn1a+/-小鼠表现出自发性癫痫发作和过早死亡，50%的小鼠在1个月大前死亡。根据菌株在表型上的差异，我们假设遗传修饰物影响Scn1a+/-表型严重程度。我们最近定位了几个影响Scn1a+/-小鼠过早死亡的修饰基因座。在目前的提案中，我们将进行精细定位和候选基因分析，以确定负责的修饰基因。除了临床严重程度上的应变依赖性差异外，我们还观察到海马神经元钠电流(INA)的应变依赖性差异。从F1Scn1a+/-小鼠分离的GABA能中间神经元与野生型小鼠相比，表现出较低的INa密度。相反，从129个Scn1a+/-分离的GABA能中间神经元中，INa密度保持不变，与野生型斜生动物没有什么不同。这表明129菌株的中间神经元弥补了Nav1.1的丢失，而F1中间神经元不补偿。基于这一观察，我们假设在Scn1a杂合缺失的背景下，在补偿能力方面存在菌株差异。我们建议进行RNA-seq分析，以表征在表型开始的关键阶段，敏感的F1 Scn1a+/-和抗性的129 Scn1a+/-小鼠的海马区转录组的差异。这项分析的结果将提示影响Scn1a+/-小鼠表型严重性的候选修饰基因和途径。Dravet综合征修饰基因的识别将为癫痫的病理生理学提供深入的认识，并将为改进人类患者的治疗提出新的治疗策略。