Department of Pediatrics, Wayne State University School of Medicine, Detroit, MI, USA.
Department of Neurosurgery, Wayne State University School of Medicine, Detroit, MI, USA.
Neurobiol Dis. 2018 Jan;109(Pt A):76-87. doi: 10.1016/j.nbd.2017.10.004. Epub 2017 Oct 7.
Tuberous sclerosis complex (TSC) is characterized by hamartomatous lesions in various organs and arises due to mutations in the TSC1 or TSC2 genes. TSC mutations lead to a range of neurological manifestations including epilepsy, cognitive impairment, autism spectrum disorders (ASD), and brain lesions that include cortical tubers. There is evidence that seizures arise at or near cortical tubers, but it is unknown why some tubers are epileptogenic while others are not. We have previously reported increased tryptophan metabolism measured with α[C]-methyl-l-tryptophan (AMT) positron emission tomography (PET) in epileptogenic tubers in approximately two-thirds of patients with tuberous sclerosis and intractable epilepsy. However, the underlying mechanisms leading to seizure onset in TSC remain poorly characterized. MicroRNAs are enriched in the brain and play important roles in neurodevelopment and brain function. Recent reports have shown aberrant microRNA expression in epilepsy and TSC. In this study, we performed microRNA expression profiling in brain specimens obtained from TSC patients undergoing epilepsy surgery for intractable epilepsy. Typically, in these resections several non-seizure onset tubers are resected together with the seizure-onset tubers because of their proximity. We directly compared seizure onset tubers, with and without increased tryptophan metabolism measured with PET, and non-onset tubers to assess the role of microRNAs in epileptogenesis associated with these lesions. Whether a particular tuber was epileptogenic or non-epileptogenic was determined with intracranial electrocorticography, and tryptophan metabolism was measured with AMT PET. We identified a set of five microRNAs (miR-142-3p, 142-5p, 223-3p, 200b-3p and 32-5p) that collectively distinguish among the three primary groups of tubers: non-onset/AMT-cold (NC), onset/AMT-cold (OC), and onset/AMT-hot (OH). These microRNAs were significantly upregulated in OH tubers compared to the other two groups, and microRNA expression was most significantly associated with AMT-PET uptake. The microRNAs target a group of genes enriched for synaptic signaling and epilepsy risk, including SLC12A5, SYT1, GRIN2A, GRIN2B, KCNB1, SCN2A, TSC1, and MEF2C. We confirmed the interaction between miR-32-5p and SLC12A5 using a luciferase reporter assay. Our findings provide a new avenue for subsequent mechanistic studies of tuber epileptogenesis in TSC.
结节性硬化症（TSC）的特征是各种器官出现错构瘤病变，由 TSC1 或 TSC2 基因突变引起。TSC 突变导致一系列神经系统表现，包括癫痫、认知障碍、自闭症谱系障碍（ASD）和包括皮质结节在内的脑部病变。有证据表明癫痫发作发生在皮质结节处或其附近，但尚不清楚为什么有些结节具有致痫性，而有些则没有。我们之前曾报道，在大约三分之二的患有结节性硬化症和耐药性癫痫的患者中，使用 [C]-α-甲基-l-色氨酸（AMT）正电子发射断层扫描（PET）测量到致痫性结节中的色氨酸代谢增加。然而，导致 TSC 中癫痫发作的潜在机制仍未得到充分描述。微 RNA 在大脑中含量丰富，在神经发育和大脑功能中发挥重要作用。最近的报告显示，微 RNA 在癫痫和 TSC 中表达异常。在这项研究中，我们对接受耐药性癫痫手术的 TSC 患者的脑标本进行了微 RNA 表达谱分析。通常情况下，在这些切除术中，由于其位置接近，会同时切除多个非癫痫发作起始的结节和起始的结节。我们直接比较了致痫性结节（伴有或不伴有 PET 测量的色氨酸代谢增加）与非起始性结节，以评估这些病变相关的微 RNA 在致痫形成中的作用。颅内脑电图确定了一个特定的结节是否具有致痫性或非致痫性，并用 AMT PET 测量色氨酸代谢。我们确定了一组五个微 RNA（miR-142-3p、142-5p、223-3p、200b-3p 和 32-5p），它们可以区分三种主要类型的结节：非起始/AMT-冷（NC）、起始/AMT-冷（OC）和起始/AMT-热（OH）。与其他两组相比，OH 结节中这些微 RNA 的表达显著上调，并且微 RNA 表达与 AMT-PET 摄取最显著相关。这些微 RNA 靶向一组富含突触信号和癫痫风险的基因，包括 SLC12A5、SYT1、GRIN2A、GRIN2B、KCNB1、SCN2A、TSC1 和 MEF2C。我们使用荧光素酶报告基因检测证实了 miR-32-5p 与 SLC12A5 之间的相互作用。我们的研究结果为随后研究 TSC 结节性癫痫形成的机制提供了新的途径。
