Somatic variants in new candidate genes identified in focal cortical dysplasia type II
Somatic variants in new candidate genes identified in focal cortical dysplasia type II
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DOI：
10.1111/epi.16481
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发表时间：
2020-03-26
期刊：
影响因子：
5.6
通讯作者：
Wu, Ye
中科院分区：
文献类型：
--
作者：
Zhang, Zhongbin;Gao, Kai;Wu, Ye
目的II型局灶性皮质发育不良（FCDII）是儿童耐药性癫痫常见的皮质发育畸形。FCDII与哺乳动物雷帕霉素靶蛋白（mTOR）相关通路基因的体细胞突变和mTOR上调相关。在10%~ 63%的FCDII样本中发现了体细胞突变，突变等位基因的频率为0.93%~ 33.5%。方法收集17例经手术病理证实的FCDII患儿的FCD病灶、病灶周围脑组织和外周血标本，分析FCDII的致病基因。我们进行了全外显子组测序，并遵循一套筛选和分析策略，以确定脑表达基因中潜在的有害体细胞变异（PDSV）。我们进行了位点特异性扩增子测序以验证结果。结果在17个样本中的6个样本中，我们在7个基因中鉴定出7个PDSV，包括2个移码变异和5个错义变异。变异等位基因频率为1.29%~ 5.50%。这些基因是MTOR、TSC 2、IRS 1、RAB 6 B、RALA、HTR 6和ZNF 337。IRS 1、RAB 6 B、ZNF 337、RALA和HTR 6中的PDSV先前与FCD无关。在一个病变中，在两个基因中发现了两个PDSV。在转染的细胞系中，我们证明了与携带野生型IRS 1的细胞相比，c.1791dupG（在来自患者1的FCDII中鉴定）导致截短的IRS 1和显著的mTOR超活化。mTOR在患者1的FCDII组织中也被激活。意义在17名儿童中的6名中的FCDII病变中鉴定出7个PDSV。五个变异基因以前与皮质畸形无关。我们证明了IRS 1变体在体外导致mTOR超活化。虽然功能实验是必要的，结果提供了新的候选基因的FCDII的发病机制的证据。
Objective Focal cortical dysplasia type II (FCDII) is a malformation of cortex development commonly found in children with drug-resistant epilepsy. FCDII has been associated with somatic mutations in mammalian target of rapamycin (mTOR)-related pathway genes and an upregulation of mTOR. Somatic mutations were found in 10%-63% of FCDII samples; the frequency of the mutant allele was 0.93%-33.5%. This study aimed to find new candidate genes involved in FCDII.Methods We collected resected FCD lesions, perilesional brain tissues, and peripheral blood from 17 children with pathologically confirmed FCDII. We performed whole exome sequencing and followed a set of screening and analysis strategies to identify potentially deleterious somatic variants (PDSVs) in brain-expressed genes. We performed site-specific amplicon sequencing to validate the results. We also performed an in vitro functional study on an IRS1 variant.Results In six of 17 samples, we identified seven PDSVs in seven genes, including two frameshift variants and five missense variants. The frequencies of the variant allele were 1.29%-5.50%. The genes were MTOR, TSC2, IRS1, RAB6B, RALA, HTR6, and ZNF337. PDSVs in IRS1, RAB6B, ZNF337, RALA, and HTR6 had not been previously associated with FCD. In one lesion, two PDSVs were found in two genes. In a transfected cell line, we demonstrated that the c.1791dupG (identified in FCDII from Patient 1) led to a truncated IRS1 and significant mTOR hyperactivation compared to cells that carried wild-type IRS1. mTOR was also activated in FCDII tissue from Patient 1.Significance Seven PDSVs were identified in FCDII lesions in six of 17 children. Five variant genes had not been previously associated with cortical malformations. We demonstrated that the IRS1 variant led to mTOR hyperactivation in vitro. Although functional experiments are needed, the results provide evidence for novel candidate genes in the pathogenesis of FCDII.