SLC6A1基因突变致癫痫表型谱及其基因型-临床表型关系研究

Epileptic phenotype spectrum of SLC6A1 gene mutations and their genotype-phenotype correlation

目的探讨SLC6A1基因突变致癫痫表型谱及其基因型-临床表型关系。方法选择自2019年1月至2024年1月于广州医科大学附属第二医院神经内科癫痫中心就诊的400例病因不明癫痫患者进行SLC6A1基因突变筛查,分析SLC6A1基因突变患者的临床特征、突变致病性以及其中错义突变导致的SLC6A1基因编码蛋白的氨基酸间氢键改变、蛋白稳定性及氨基酸疏水性改变情况;同时在PubMed、HGMD及中国知网数据库中进行全面检索,收集截至2024年8月30日发表的SLC6A1基因突变致癫痫的文献报道,分析其最常见且最具特征性癫痫表型间错义突变占比差异以及错义突变在SLC6A1基因编码蛋白loop区占比差异情况。结果(1)400例病因不明癫痫患者中5例发生SLC6A1基因突变,其中2例发生新生杂合剪切位点突变(c.850-1G>A、c.1324-1G>A),对应的癫痫表型为部分性癫痫伴重度发育迟缓、儿童失神癫痫伴轻度发育迟缓;2例发生新生杂合错义突变(c.187G>A/p.Gly63Ser、c.1081C>A/p.Pro361Thr),对应的癫痫表型为部分性癫痫伴轻度发育迟缓、全面性癫痫伴重度发育迟缓;1例发生未知来源杂合错义突变(c.700G>A/p.Gly234Ser),对应的癫痫表型为Lennox-Gastaut综合征。4个新生突变评估为致病或可能致病,1个来源未知突变评估为不确定意义。另外,3个错义突变致编码蛋白氨基酸间氢键数量或结合方式发生明显改变,编码蛋白的稳定性显著下降及氨基酸疏水性明显降低。(2)目前已报道的与癫痫相关的SLC6A1基因突变共84个,结合本研究基因筛查结果,共计89个,包括53个错义突变、33个截短突变、3个框内插入/缺失突变,涉及7种癫痫表型,其中38个涉及肌阵挛失张力癫痫,16个涉及癫痫,12个涉及癫痫性脑病,8个涉及儿童失神癫痫,6个涉及儿童期起病癫痫,6个涉及全面性癫痫,3个涉及局灶性癫痫。肌阵挛失张力癫痫组与癫痫性脑病组间错义突变占比的差异无统计学意义(P>0.05),但与肌阵挛失张力癫痫组相比,癫痫性脑病组的错义突变在loop区占比明显更高,差异有统计学意义(P<0.05)。结论SLC6A1基因突变可致复杂多样的癫痫表型谱且多数伴发育迟缓,编码蛋白分子亚区效应可能是SLC6A1基因突变致肌阵挛失张力癫痫与癫痫性脑病临床表型差异的一个潜在机制。

ObjectiveTo explore the epileptic phenotype spectrum of SLC6A1 gene mutations and their genotype-phenotype correlation.MethodsFour hundred patients with epilepsy of unknown etiology admitted to Epilepsy Center,Department of Neurology,Second Affiliated Hospital of Guangzhou Medical University from July 2019 to July 2024 were enrolled to screen the SLC6A1 gene mutations;the clinical characteristics,mutation pathogenicity,and changes of hydrogen bond between amino acids,stability and amino acid hydrophobicity of SLC6A1 gene encoded proteins caused by missense mutations in patients with SLC6A1 gene mutations were analyzed.At the same time,a comprehensive search was conducted in PubMed,HGMD and CNKI databases to collect the publicly reported SLC6A1 gene mutations related to epilepsy up to September 8,2024;differences in proportion of missense mutations between the two most common and featured epileptic phenotypes and proportion of missense mutations in loops of SLC6A1 gene coding proteins were analyzed.ResultsFive patients carried SLC6A1 gene mutations in 400 patients with epilepsy of unknown etiology:2 had de novo heterozygous canonical splice site mutations(c.850-1G>A and c.1324-1G>A),with phenotypes as partial epilepsy combined with severe development delay and childhood absence epilepsy combined with mild developmental delay;2 had de novo heterozygous missense mutations(c.187G>A/p.Gly63Ser and c.1081C>A/p.Pro361Thr),with phenotypes as partial epilepsy combined with mild development delay and generalized epilepsy combined with severe development delay;and one had heterozygous missense mutation of unknown origin(c.700G>A/p.Gly234Ser),with phenotype as Lennox-Gastaut syndrome.Four de novo mutations were evaluated as having pathogenic or likely pathogenic features,and one mutation of unknown origin was evaluated as of uncertain significance.In addition,3 missense mutations caused significant changes in number or bonding form of hydrogen bonds between amino acids of the encoded proteins,with obviously decreased stability and hydrophobicity of the encoded proteins.(2)Results of literature analysis showed that 84 SLC6A1 mutations have been reported to be associated with epilepsy;combined with the genetic results in this study,a total of 89 SLC6A1 mutations were identified,including 53 missense mutations,33 nonsense mutations,and 3 in-frame/in-del mutations;7 epilepsy phenotypes were involved,including 38 patients with myoclonic atonic epilepsy(MAE),16 with epilepsy,12 with epileptic encephalopathy,8 with childhood absence epilepsy,6 with childhood-onset epilepsy,6 with generalized epilepsy,and 3 with focal epilepsy.No significant difference in proportion of missense mutations was noted between MAE and epileptic encephalopathy patients(P>0.05);however,the proportion of missense mutations in loops of the epileptic encephalopathy patients was significantly higher than that of the MAE patients(P<0.05).Conclusion SLC6A1 gene mutations can cause complex and diverse epilepsy phenotype spectrum,and most patients are accompanied by developmental delay;subregional effect of the encoded protein molecules may be a potential mechanism for different clinical phenotypes between MAE and epileptic encephalopathy caused by SLC6A1 gene mutations.