Ljungberg M Cecilia, Bhattacharjee Meenakshi B, Lu Yaojuan, Armstrong Dawna L, Yoshor Daniel, Swann John W, Sheldon Michael, D'Arcangelo Gabriella
Cain Foundation Laboratories, Texas Children's Hospital, Houston, TX, USA.
Ann Neurol. 2006 Oct;60(4):420-9. doi: 10.1002/ana.20949.
The cortex of patients with cortical dysplasia contains several abnormal cell types. Among the dysplastic cells, cytomegalic neurons are known to be electrically hyperactive and may contribute to epileptic activity. In this study, we sought to identify molecular markers of cytomegalic neurons in focal or hemispheric cortical dysplasia and to determine whether the activity of the mammalian target of rapamycin (mTOR) kinase is abnormally high in these cells.
Microarray analysis of gene expression in large dysplastic cells microdissected from cortical dysplasia surgical specimens was used to identify markers of cytomegalic neurons. Immunohistochemistry and immunofluorescence analysis of cortical sections was used to validate the microarray results and to probe the activity of mTOR in cytomegalic neurons using phospho-specific antibodies directed against known mTOR targets.
We demonstrate that the neurofilament heavy chain is a reliable marker of cytomegalic neurons and that targets of the mTOR kinase, such as the ribosomal protein S6, eIF4G, and Akt, are hyperphosphorylated in these dysplastic neurons.
We conclude that mTOR kinase hyperactivation is a molecular mechanism underlying the development of cytomegalic neurons. This finding may lead to the development of novel therapeutic approaches for childhood epilepsy associated with cortical dysplasia.
皮质发育异常患者的皮质包含几种异常细胞类型。在发育异常的细胞中，巨细胞神经元已知电活动亢进，可能促成癫痫活动。在本研究中，我们试图鉴定局灶性或半球性皮质发育异常中巨细胞神经元的分子标志物，并确定雷帕霉素哺乳动物靶点（mTOR）激酶在这些细胞中的活性是否异常升高。
对从皮质发育异常手术标本中显微切割得到的大型发育异常细胞进行基因表达微阵列分析，以鉴定巨细胞神经元的标志物。对皮质切片进行免疫组织化学和免疫荧光分析，以验证微阵列结果，并使用针对已知mTOR靶点的磷酸化特异性抗体探测巨细胞神经元中mTOR的活性。
我们证明神经丝重链是巨细胞神经元的可靠标志物，并且mTOR激酶的靶点，如核糖体蛋白S6、eIF4G和Akt，在这些发育异常的神经元中发生了过度磷酸化。
我们得出结论，mTOR激酶过度激活是巨细胞神经元发育的分子机制。这一发现可能会促成针对与皮质发育异常相关的儿童癫痫的新型治疗方法的开发。
