不同类型KCNQ2基因突变所致癫痫五例临床分析

目的探讨KCNQ2基因突变不同基因型与癫痫患儿临床表型之间的关系。方法分析2017年10月-2018年10月河北省儿童医院神经内科收治的5例KCNQ2基因突变相关性癫痫患儿,并查阅万方、中国知网(CNKI)、PubMed、Uptodate等数据库,结合相关文献进行总结。结果本研究共收集5例KCNQ2基因突变阳性患儿,其中自发突变3例:含错义突变2例,截短突变1例;家系遗传2例;错义突变、无义突变各1例。3例自发突变临床表型均为癫痫性脑病,家系遗传中1例为良性家族性新生儿癫痫。家系1同一位点突变呈现3种不同表型。结论①KCNQ2基因突变不仅可以引起良性家族性新生儿癫痫(BFNE),还可引起多种癫痫性脑病;②自发突变更可能导致癫痫性脑病;③同一家系携带同一基因突变位点成员也可能有不同表型。     

钾离子通道KCNQ2、KCNQ3与良性家族性新生儿惊厥

钾离子通道与中枢神经元的电活动密切相关,其结构和功能异常将改变神经元兴奋性,引起癫痫发作,其中,KC-NQ2、KCNQ3通道异常即导致良性家族性新生儿惊厥(BFNS)。深入探讨BFNS的KCNQ2、KCNQ3通道突变分子致病机制,将有助于引导BFNS今后的基因治疗研究,并为遗传咨询提供理论基础。     

良性家族性新生儿惊厥三家系的基因诊断研究

目的 探讨中国人良性家族性新生儿惊厥(BFNS)的基因特点，为该病的基因诊断提供依据。方法 应用聚合酶链反应(PCR)-变性聚丙烯酰胺凝胶电泳技术，对3个中国BFNS家系的KCNQ2及KCNQ3基因位点进行连锁分析；采用PCR-DNA直接测序法对此3家系进行KCNQ2基因突变分析。结果 连锁分析排除3家系致病基因与KCNQ3基因连锁，提示家系3与KCNQ2基因连锁，不能除外家系1、2与。KCNQ2基因连锁；KCNQ2基因突变分析在3个家系中发现1种移码突变1931delG及3种同义突变G543A、C912T和T2154A。结论 中国人BFNS患者中存在KCNQ2基因突变；中国人BFNS具有遗传异质性，在KCNQ2、KCNQ3之外可能还有另外的致病基因；BFNS的表型和基因型可能有一定的相关性。     

良性家族性婴儿癫痫的临床特征及遗传学研究

目的探讨我国良性家族性婴儿癫痫(BFIE)的临床特征及致病基因谱。方法收集10例BFIE患儿的临床资料,通过靶向捕获二代测序发现可疑致病性突变基因,并经Sanger测序验证基因突变来源。结果 10例患儿起病年龄2～14月龄(中位年龄为5月龄),表现为部分性发作或部分继发全面性发作。6例患儿起病初期呈丛集性发作。9例予抗癫痫药物治疗,服药后发作易控制,1例未用抗癫痫药未再发作。随访8～18个月,均于2岁以内停止。10例患儿均有基因突变,9例为家族遗传性突变,1例为新生突变。6例PRRT2基因突变、2例SCN2A基因突变和2例KCNQ2基因突变。除1例PRRT2基因突变位点(c.439GC)已报道,余9例为未报道的新突变。结论婴儿起病的BFIE多表现为部分性发作或部分继发全面性发作,抗癫痫药物治疗多可短期控制;PRRT2、SCN2A、KCNQ2基因为致病基因,突变位点和方式多样。     

良性家族性婴儿惊厥一家系的临床、脑电图及致病基因分析

目的 报告一个新的良性家族性婴儿惊厥(benign familial infantile convulsions or seizures,BFIC或BFIS)家系,并探讨其临床、脑电图及疾病基因特点.方法 对该家系进行详细的调查,并对其临床资料、脑电图进行分析.采集该家系11名成员的静脉血并抽提其基因组DNA,采用PCR-DNA直接测序及PCR-单链构象多态性分析的方法对先证者进行KCNQ2、KCNQ3和SCN2A基因突变分析.结果 该家系3代共有患者6例,均于出生后6个月左右出现无热性癫痫发作,1岁之内完全消失,智能及体格发育正常,血生化、染色体核型分析及头部影像学检查未见异常.先证者于15岁时出现了发作性运动障碍,24h动态脑电图可见癫痫波发放,KCNQ2、KCNQ3和SCN2A基因突变分析未在该家系发现致病突变.结论 BFIC具有临床和遗传异质性,可伴发作性运动障碍,且脑电图可有癫痫波发放;KCNQ2、KCNQ3和SCN2A不是该家系的致病基因,可能存在新的致病基因.     

家族性中枢神经系统血管母细胞瘤VHL基因突变与临床预后分析

目的 探讨汉族人家族性中枢神经系统血管母细胞瘤（HB）的临床特点及家系表现和VHL基因突变的关系.方法 回顾性分析9个家族15例经手术和病理证实的HB患者进行临床分析.对长期随访的7个家族中的12例患者和15例相关家族成员抽取外周血进行VHL基因测序.对于测序阴性的患者,对其DNA进行三个外显子实时定量PCR测定.结果 本组15例HBs中,多发性肿瘤10例,共34个肿瘤.进行开颅和脊髓手术17次,共切除HB22个.基因测序发现在4种点突变.通过实时定量PCR发现2个家族外显子1大片段缺失.在未发病家族成员中检出携带者3例.随访期间发现2例复发和3例新生的HB,主要集中在移码突变和拼接错误的家族中.通过再次手术和对脑干HB进行γ刀治疗,效果较好.结论 VHL相关的HB易复发,并不断有新生HB出现.基因测序和实时定量PCR联合应用可以提高VHL基因突变的检出率.基因突变分析可有助于未发病基因突变携带者确诊,基因突变的分型有助于对患者的预后进行判断.     

结蛋白病的临床进展

结蛋白病(desminopathy),又称骨骼肌心肌病或结蛋白相关性肌肉病,是由于结蛋白基因突变导致的一种遗传性肌肉病,属于肌原纤维肌病的一种亚型,约占肌原纤维肌病患者的1/3[1].1998年Goldfarb等[2]发现结蛋白基因存在致病突变,到目前已经在大约90个家族性或散发病例中发现了40多种结蛋白基因突变.     

PRRT2基因突变致病机制与相关疾病的研究进展

正富含脯氨酸的跨膜蛋白2 (Proline-rich transmembrane protein 2,PRRT2)是位于16号染色体的一个小基因,内部包含4个外显子,2～4号外显子编码包含340个氨基酸的多域蛋白,是由国内学者鉴定出的第一个发作性运动诱发性运动障碍的致病基因~([1])。越来越多的研究发现,PRRT2基因突变与多种发作性疾病相关。PRRT2存在多样突变类型,包括移码突变、错义突变、无义突变,多数突变可导致PRRT2截短蛋白的出现,这种短截蛋白极易被细胞中的蛋白酶体降解,造成功能缺失,从而致病~([2])。无论是在散发性还是家族性病例中,对发作性运动诱发性运动障碍(paroxysmal kinesigenic dyskinesia,PKD)、良性家族性婴儿癫痫(be-     

家族性低钾型周期性麻痹的基因突变与临床特征

目的筛查家族性低钾型周期性麻痹相关基因突变位点,总结该病基因型和临床表型的相关性.方法应用聚合酶链反应（PCR）和DNA测序技术,对14个家族性低钾型周期性麻痹家系中的14例先证者进行候选基因CACNA1S、SCN4A、KCNE3的筛查,阳性者再对其家系中其他患者和健康亲属进行测序分析.结果14个家系中有3个家系其先证者存在已知的低钾型周期性麻痹相关突变（1个家系发生CACNA1S基因R1239H突变,2个家系发生SCN4A基因的R672H突变）.进一步对3个突变家系中4例其他患者和34名健康亲属测序分析发现,R1239H突变为完全外显率,R672H突变为不全外显率.同时还发现2种突变在发病年龄和乙酰唑胺的疗效等方面存在差异.结论中国低钾型周期性麻痹患者存在CACNA1S基因R1239H和SCN4A基因的R672H突变,2种突变的临床表型存在差异.     

结节性硬化症伴癫痫发作患者基因突变类型与临床表型相关性研究

目的探讨结节性硬化症伴癫痫发作患者的基因突变类型与临床表型的关系。方法对2013年10月至2019年10月在广东三九脑科医院确诊的结节性硬化症伴癫痫发作患者进行TSC基因检测,对基因阳性者进行基因突变类型分型,并收集其临床资料,从而探讨不同基因突变类型与临床表型的关系。结果共85例患者TSC基因检测阳性,其中TSC1基因突变34例(40.0%)分别为:剪切突变4例(11.8%)、移码突变10例(29.4%)、无义突变4例(11.8%)及错义突变16例(47.0%)。TSC2基因突变51例(60.0%)分别为:剪切突变3例(5.9%)、移码突变19例(37.3%)、无义突变1例(1.9%)、错义突变25例(49.0%)及大片段缺失3例(5.9%)。突变类型均以移码突变及错义突变的突变率较高。对起病年龄进行分层,分为≤1岁、～3岁、～6岁、～18岁、18岁,发现不同起病年龄在TSC1及TSC2基因中有统计学差异(P 0.05)。同时发现肾脏病变及智力低下的发生率在TSC1及TSC2基因中有统计学意义(分别P 0.05)。此外,根据基因突变类型进行分组,分为移码突变组、错义突变组及其他突变(包括剪切突变、无义突变及大片段缺失)组,发现心脏病变的发生率在不同基因突变类型中有统计学差异(分别P 0.05)。结论 TSC1及TSC2基因突变类型及临床表型多样,TSC2起病年龄更小,更容易出现肾脏病变及智力低下。错义突变更易发生心脏病变。基因类型-临床表型的研究可对TSC患者的疾病发展及预后做出初步评估。     

Functional analysis of novel KCNQ2 and KCNQ3 gene variants found in a large pedigree with benign familial neonatal convulsions (BFNC)

Benign familial neonatal convulsion (BFNC) is a rare autosomal dominant disorder caused by mutations in KCNQ2 and KCNQ3, two genes encoding for potassium channel subunits. A large family with nine members affected by BFNC is described in the present study. All affected members of this family carry a novel deletion/insertion mutation in the KCNQ2 gene (c.761_770del10insA), which determines a premature truncation of the protein. In addition, in the family of the proposita's father, a novel sequence variant (c.2687A>G) in KCNQ3 leading to the p.N821S amino acid change was detected. When heterologously expressed in Chinese hamster ovary cells, KCNQ2 subunits carrying the mutation failed to form functional potassium channels in homomeric configuration and did not affect channels formed by KCNQ2 and/or KCNQ3 subunits. On the other hand, homomeric and heteromeric potassium channels formed by KCNQ3 subunits carrying the p.N821S variant were indistinguishable from those formed by wild-type KCNQ3 subunits. Finally, the current density of the cells mimicking the double heterozygotic condition for both KCNQ2 and KCNQ3 alleles of the proband was decreased by approximately 25% when compared to cells expressing only wild-type alleles. Collectively, these results suggest that, in the family investigated, the KCNQ2 mutation is responsible for the BFNC phenotype, possibly because of haplo-insufficiency, whereas the KCNQ3 variant is functionally silent, a result compatible with its lack of segregation with the BFNC phenotype.     

Developmental changes in KCNQ2 and KCNQ3 expression in human brain: possible contribution to the age-dependent etiology of benign familial neonatal convulsions

Several mutations of KCNQ2 and KCNQ3 are considered to be associated with benign familial neonatal convulsions (BFNC). BFNC is characterized by seizures starting within several days of life and spontaneous remission within weeks to months. KCNQ channel is a heteromeric voltage-dependent potassium channel consisting of KCNQ2 and KCNQ3 subunits. To clarify the age-dependent etiology of BFNC, we examined the developmental changes in KCNQ2 and KCNQ3 expression in human hippocampus, temporal lobe, cerebellum and medulla oblongata obtained from 23 subjects who died at 22 gestation weeks to adulthood. Formalin-fixed and paraffin-embedded specimens were used for immunohistochemistry. Unique developmental changes in KCNQ2 and KCNQ3 were found in each region. A high expression of KCNQ2 was identified in the hippocampus, temporal cortex, cerebellar cortex and medulla oblongata in fetal life, but such expression decreased after birth. The expression of KCNQ3 increased in late fetal life to infancy. Simultaneous and high expressions of KCNQ2 and KCNQ3 were observed in each region from late fetal life to early infancy, coinciding with the time when BFNC occurs. Such coexpression may contribute to the pathogenesis of BFNC.     

Sodium and potassium channel dysfunctions in rare and common idiopathic epilepsy syndromes

Mutations in the SCN1A gene are found in up to 80% of individuals with severe myoclonic epilepsy of infancy (SMEI), and mutations in KCNQ2 and KCNQ3 were identified in benign familial neonatal convulsions (BFNC) as well as in single families with Rolandic epilepsy (RE) and idiopathic generalized epilepsies (IGE). This paper summarizes recent findings concerning sodium (SCN1A) and potassium channel (KCNQ2 and KCNQ3) dysfunctions in the pathogenesis of rare and common idiopathic epilepsies (IE). SMEI, severe idiopathic generalized epilepsy of infancy (SIGEI), and myoclonic–astatic epilepsy (MAE) are rare IE. Because of some semeiologic overlap, a comparative analysis of the SCN1A gene performed in 20 patients with MAE and in 18 with SIGEI. This revealed mutations in three subjects with SIGEI only. Since BFNC are over-represented in families with RE, a mutational analysis was performed in 58 families with RE with and without BNFC. This revealed functionally relevant mutations in two index cases with BNFC, and three missense mutations (one resulting in a significantly reduced potassium current amplitude) in three patients with RE, but without BNFC. One KCNQ3 missense variant was also detected in eight out of 455 IGE patients but not in 454 controls, and a silent KCNQ2-SNP was found over-represented in both epilepsy samples. These findings confirm that mutations in the SCN1A gene are mainly involved in the pathogenesis of SMEI, rarely in that of SIGEI, and are commonly not found in patients with MAE. They also demonstrate that sequence variations of the KCNQ2 and KCNQ3 genes may contribute to the etiology of common IE syndromes.     

A novel mutation of KCNQ3 gene in a Chinese family with benign familial neonatal convulsions

Benign familial neonatal convulsions (BFNC, also named benign familial neonatal seizures, BFNS) is a rare autosomal dominant inherited epilepsy syndrome with clinical and genetic heterogeneity. Two voltage-gated potassium channel subunit genes, KCNQ2 and KCNQ3, have been identified to cause BFNC1 and BFNC2, respectively. To date, only three mutations of KCNQ3, all located within exon 5, have been reported. By limited linkage analysis and mutation analysis of KCNQ3 in a Chinese family with BFNC, we identified a novel missense mutation of KCNQ3, c.988C>T located within exon 6. c.988C>T led to the substitution Cys for Arg in amino acid position 330 (p.R330C) in KCNQ3 potassium channel, which possibly impaired the neuronal M-current and altered neuronal excitability. Seizures of all BFNC patients started from day 2 to 3 after birth and remitted during 1 month, and no recurrence was found. One family member who displayed fever-associated seizures for two times at age 5 years and was diagnosed as febrile seizures, however, did not carry this mutation, which suggests that febrile seizures and BFNC have different pathogenesis. To our knowledge, this is the first report of KCNQ3 mutation in Chinese family with BFNC.     

The new voltage gated potassium channel KCNQ5 and neonatal convulsions

In 1998, mutations in the voltage gated potassium channel gene KCNQ2 were found to be the main cause underlying the autosomal dominant inherited syndrome of benign familial neonatal convulsions (BFNC). In one BFNC family a mutation was found in an homologous gene, KCNQ3. We have now identified another brain-expressed member of this ion channel subfamily, KCNQ5, which maps to chromosome 6q14. On the genomic level KCNQ5 is composed of 14 exons, which are coding for 897 amino acid residues. Mutation analysis made KCNQ5 unlikely as a candidate gene for benign neonatal convulsions in patients with a positive family history for neonatal or early infantile seizures, but without mutations in the KCNQ2 or KCNQ3 genes.     

Neonatal Epilepsy Syndromes and GEFS+: Mechanistic Considerations

Summary:  Genetic analyses of familial epilepsies over the past decade have identified mutations in several different ion channel genes that result in neonatal or early-onset seizure disorders, including benign familial neonatal convulsions (BFNC), generalized epilepsy with febrile seizures plus (GEFS+), and severe myoclonic epilepsy of infancy (SMEI). These genes encode voltage-gated Na⁺ channel subunits ( SCN1A , SCN2A , SCN1B ), voltage-gated K⁺ channel subunits ( KCNQ2 , KCNQ3 ), and a ligand-gated neurotransmitter receptor subunit ( GABRG2 ). While the opportunity to genotype patients for mutations in these genes can have an immediate and significant impact on our ability to diagnose and provide genetic counseling to patients, the ultimate goal is to use this molecular knowledge to develop effective treatments and cures for each disorder. This will necessitate elucidation of the molecular, cellular, and network mechanisms that translate ion channel defects into specific epilepsy phenotypes. The functional analysis of epileptogenic channel mutations in vitro and in vivo has already provided a vast amount of raw biophysical data, but attempts to interpret these data to explain clinical phenotypes so far appear to raise as many questions as they answer. Nevertheless, patterns are beginning to emerge from these early studies that will help define the full scope of the challenges ahead while simultaneously providing the foundation of future efforts to overcome them. Here, I discuss some of the potential mechanisms that have been uncovered recently linking mutant ion channel genes to neonatal epilepsy syndromes and GEFS+.     

De novo KCNQ2 mutations in patients with benign neonatal seizures

Benign familial neonatal convulsions (BFNC) are characterized by unprovoked seizures during the first weeks of life with spontaneous remission after a few months. Mutations have been identified in the voltage-gated potassium ion channels KCNQ2 and KCNQ3. The authors performed a mutation analysis of KCNQ2 and KCNQ3 in six patients of whom four had no family history of neonatal seizures. The authors identified three KCNQ2 mutations in four patients that all arose de novo.     

Potassium Channels: How Genetic Studies of Epileptic Syndromes Open Paths to New Therapeutic Targets and Drugs

Summary: How can epilepsy gene hunting lead to better care for patients with epilepsy? Lessons may be learned from the progress made by identifying the mutated genes that cause Benign Familial Neonatal Convulsions (BFNC). In 1998, a decade of clinical and laboratory-based genetics work resulted in the cloning of the KCNQ2 potassium channel gene at the BFNC locus on chromosome 20. Subsequently, computer "mining" of public DNA databases allowed the rapid identification of three more brain KCNQ genes. Mutations in each of these additional genes were implicated as causes of human hereditary diseases: epilepsy (KCNQ3), deafness (KCNQ4), and, possibily, retinal degeneration (KCNQ5). Physiologists discovered that the KCNQ genes encoded subunits of the "M-channel," a type of potassium channel known to control repetitive neuronal discharges. Finally, pharmacologists discovered that retigabine, a novel anticonvulsant with a broad but distinctive efficacy profile in animal studies, was a potent KCNQ channel opener. These studies suggest that KCNQ channels may be an important new class of targets for anticonvulsant therapies. The efficacy of retigabine is currently being tested in multicenter clinical trials; identification of its molecular targets will allow it to be more efficiently exploited as a "lead compound." Cloned human KCNQ channels can now be expressed in cultured cells for "high-throughput" screening of drug candidates. Ongoing studies of the KCNQ channels in humans and animal models will refine our understanding of how M-channels control excitability at the cellular, network, and behavioral levels, and may reveal additional targets for therapeutic manipulation.