在立体脑电图深度电极的微量脑组织中检测到体细胞镶嵌性致病性变异梯度。

Somatic Mosaic Pathogenic Variant Gradient Detected in Trace Brain Tissue From Stereo-EEG Depth Electrodes.

机构信息

From the Department of Medicine (Austin Health) (Z.Y., M.F.B., S.K.P., I.E.S., S.F.B., P.P., M.S.H.), University of Melbourne, Heidelberg; Population Health and Immunity Division (M.F.B., M.B.), The Walter and Eliza Hall Institute of Medical Research, Parkville; Department of Medical Biology (M.F.B., M.B.), The University of Melbourne, Parkville; Department of Neurology (A.N., P.K., T.J.O.B., P.P.), Royal Melbourne Hospital, Parkville; Department of Neurology (A.N., J.A.L., T.W., M.T., P.K., T.J.O.B., P.P.), Alfred Hospital, Melbourne; Department of Medicine (A.N., P.K., T.J.O.B.), Royal Melbourne Hospital, University of Melbourne, Parkville; Department of Neurosciences (A.N., J.A.L., T.W., M.T., P.K., T.J.O.B., P.P.), The Central Clinical School, Monash University, Melbourne; Department of Neurology (A.N.), St Vincent's Hospital, Fitzroy; Department of Neurosurgery (M.K.H.), The Alfred Hospital, Melbourne; Florey Institute of Neuroscience and Mental Health (S.K.P., I.E.S.), Heidelberg; Murdoch Children's Research Institute (I.E.S., M.S.H.), Parkville; Department of Paediatrics (I.E.S.), University of Melbourne, Royal Children's Hospital, Parkville; and Bladin-Berkovic Comprehensive Epilepsy Program (S.F.B., P.P.), Department of Neurology, Austin Health, Heidelberg, Australia.

出版信息

Neurology. 2022 Dec 5;99(23):1036-1041. doi: 10.1212/WNL.0000000000201469.

DOI:10.1212/WNL.0000000000201469

PMID:36192176

Abstract

BACKGROUND AND OBJECTIVES

Mosaic pathogenic variants restricted to the brain are increasingly recognized as a cause of focal epilepsies. We aimed to identify a mosaic pathogenic variant and its anatomical gradient in brain DNA derived from trace tissue on explanted stereoelectroencephalography (SEEG) electrodes.

METHODS

We studied a patient with nonlesional multifocal epilepsy undergoing presurgical evaluation with SEEG. After explantation, the electrodes were divided into 3 pools based on their brain location (right posterior quadrant, left posterior quadrant, hippocampus/temporal neocortex). Tissue from each pool was processed for trace DNA that was whole genome amplified prior to high-depth exome sequencing. Droplet digital PCR was performed to quantify mosaicism. A brain-specific glial fibrillary acidic protein (GFAP) assay enabled cell-of-origin analysis.

RESULTS

We demonstrated a mosaic gradient for a novel pathogenic loss-of-function variant (c.530G>A, p.W177X) predicted to lead to nonsense-mediated decay. Strikingly, the mosaic gradient correlated strongly with the SEEG findings because the highest variant allele frequency was in the right posterior quadrant, reflecting the most epileptogenic region on EEG studies. An elevated GFAP level indicated enrichment of brain-derived cells in SEEG cell suspension.

DISCUSSION

This study demonstrates a proof of concept that mosaic gradients of pathogenic variants can be established using trace tissue from explanted SEEG electrodes.

摘要

背景与目的

局限于大脑的嵌合致病性变异体越来越被认为是局灶性癫痫的病因。我们旨在从立体定向脑电图（SEEG）电极取出的痕量组织中鉴定出嵌合致病性变异体及其在脑 DNA 中的解剖梯度。

方法

我们研究了一位接受术前评估的非病变性多灶性癫痫患者。SEEG 取出后，根据电极在大脑中的位置（右后象限、左后象限、海马/颞叶新皮质）将其分为 3 个池。从每个池的组织中提取痕量 DNA，然后进行全基因组扩增，再进行高通量外显子测序。通过微滴数字 PCR 进行嵌合性定量分析。一种脑特异性胶质纤维酸性蛋白（GFAP）检测方法可进行细胞起源分析。

结果

我们展示了一种新型致病性失活变异体（c.530G>A，p.W177X）的嵌合梯度，该变异体预测会导致无义介导的衰变。引人注目的是，嵌合梯度与 SEEG 发现具有很强的相关性，因为最高的变异等位基因频率出现在右后象限，反映了 EEG 研究中最具致痫性的区域。GFAP 水平升高表明在 SEEG 细胞悬液中富集了源自大脑的细胞。