NEJM：GNAQ体细胞突变引发Sturge–Weber综合征

斯德奇-韦伯综合征是一种散发性先天性神经皮肤疾病，其特征为累及三叉神经眼支分布区域内皮肤的葡萄酒色斑、脑软脑膜和脉络膜的毛细血管静脉血管畸形、青光眼、癫痫发作、卒中和智力障碍等。目前的假说认为，斯德奇-韦伯综合征和葡萄酒色斑均由体细胞嵌合突变扰乱血管发育引起，病变所表现出的严重程度和累及范围取决于突变发生时的发育阶段。迄今为止，尚未有相关突变得到鉴定。美国巴尔的摩市约翰斯霍普金斯医学院生物化学、细胞和分子生物学研究组的Matthew D. Shirley博士等人进行了相关研究，他们发现，斯德奇-韦伯综合征和葡萄酒色斑是由GNAQ中一种体细胞激活突变引起的，这一发现证实了一项早已存在的假说。研究成果发表于国际权威杂志NEJM 2013年5月13日在线版上。

研究人员对3例斯德奇-韦伯综合征患者明显受累组织和正常组织的匹配样本进行了全基因组DNA测序。研究者对来自50例斯德奇-韦伯综合征患者、葡萄酒色斑患者和无此两种疾病对照参与者的97份样本采用扩增子测序法和SNaPshot检测法检验其是否存在体细胞嵌合突变，并采用相关效应子的磷酸化特异性抗体和一种荧光素酶报告探针，检验了相关突变对下游细胞信号转导的作用。

结果显示，在88%的斯德奇-韦伯综合征受试者（26例中的23例）和92%的明显非综合征性葡萄酒色斑患者（13例中的12例）的受累组织样本中，成功鉴定出了GNAQ的一种非同义单核苷酸变异体（c.548G→A，精氨酸183谷氨酰氨），但与上述两种疾病无关的4例脑血管畸形患者受累组织样本或6例对照者的全部样本均未鉴定出这一变异体。研究发现，受累组织中突变体等位基因发生率介于1.0%～18.1%之间。细胞外信号调节激酶活性在突变体Gαq转基因表达期间有适度增加。

研究人员由此得出结论，斯德奇-韦伯综合征和葡萄酒色斑是由GNAQ中一种体细胞激活突变引起的，这一发现证实了一项早已存在的假说。

Sturge–Weber Syndrome and Port-Wine Stains Caused by Somatic Mutation in GNAQ
Background
The Sturge–Weber syndrome is a sporadic congenital neurocutaneous disorder characterized by a port-wine stain affecting the skin in the distribution of the ophthalmic branch of the trigeminal nerve, abnormal capillary venous vessels in the leptomeninges of the brain and choroid, glaucoma, seizures, stroke, and intellectual disability. It has been hypothesized that somatic mosaic mutations disrupting vascular development cause both the Sturge–Weber syndrome and port-wine stains, and the severity and extent of presentation are determined by the developmental time point at which the mutations occurred. To date, no such mutation has been identified.
Methods
We performed whole-genome sequencing of DNA from paired samples of visibly affected and normal tissue from 3 persons with the Sturge–Weber syndrome. We tested for the presence of a somatic mosaic mutation in 97 samples from 50 persons with the Sturge–Weber syndrome, a port-wine stain, or neither (controls), using amplicon sequencing and SNaPshot assays, and investigated the effects of the mutation on downstream signaling, using phosphorylation-specific antibodies for relevant effectors and a luciferase reporter assay.
Results
We identified a nonsynonymous single-nucleotide variant (c.548G→A, p.Arg183Gln) in GNAQ in samples of affected tissue from 88% of the participants (23 of 26) with the Sturge–Weber syndrome and from 92% of the participants (12 of 13) with apparently nonsyndromic port-wine stains, but not in any of the samples of affected tissue from 4 participants with an unrelated cerebrovascular malformation or in any of the samples from the 6 controls. The prevalence of the mutant allele in affected tissues ranged from 1.0 to 18.1%. Extracellular signal-regulated kinase activity was modestly increased during transgenic expression of mutant Gαq.
Conclusions
The Sturge–Weber syndrome and port-wine stains are caused by a somatic activating mutation in GNAQ. This finding confirms a long-standing hypothesis. (Funded by the National Institutes of Health and Hunter's Dream for a Cure Foundation.)