Malatesta Manuela, Scassellati Catia, Meister Gunter, Plöttner Oliver, Bühler Dirk, Sowa Gabriele, Martin Terence E, Keidel Eva, Fischer Utz, Fakan Stanislav
Centre of Electron Microscopy, University of Lausanne, 1005 Lausanne, Switzerland.
Exp Cell Res. 2004 Jan 15;292(2):312-21. doi: 10.1016/j.yexcr.2003.08.022.
Mutations in the survival of motor neuron (SMN) gene are the major cause of spinal muscular atrophy (SMA). The SMN gene encodes a 38-kDa protein that localises in the cytoplasm and in nuclear bodies termed Gemini of coiled bodies (gems). When visualised by immunofluorescence microscopy, gems often appeared either in close proximity to, or entirely overlapping with coiled (Cajal) bodies (CBs) implying a possible functional relationship between these nuclear domains. With the aim of identifying subnuclear compartments corresponding to gems, we have investigated the intranuclear localisation of SMN and of its interacting protein Gemin2 by immunoelectron microscopy in cultured cells and in liver cells of hibernating dormouse. These antigens are highly enriched in round-shaped electron-dense fibro-granular clusters (EFGCs), which also display a biochemical composition similar to gems visualised by immunofluorescence microscopy. Our data reveal a novel SMN/Gemin2 containing nuclear domain and support the idea that it represents the structural counterpart of gems seen in the light microscope.
运动神经元存活（SMN）基因突变是脊髓性肌萎缩症（SMA）的主要病因。SMN基因编码一种38 kDa的蛋白质，该蛋白质定位于细胞质和称为螺旋体Gemini（gems）的核小体中。当通过免疫荧光显微镜观察时，gems常常出现在紧邻卷曲（卡哈尔）体（CBs）处或与卷曲体完全重叠，这意味着这些核结构域之间可能存在功能关系。为了鉴定与gems相对应的核内区室，我们通过免疫电子显微镜研究了培养细胞和冬眠睡鼠肝细胞中SMN及其相互作用蛋白Gemin2的核内定位。这些抗原高度富集于圆形电子致密的纤维颗粒簇（EFGCs）中，这些簇还显示出与通过免疫荧光显微镜观察到的gems相似的生化组成。我们的数据揭示了一个包含新型SMN/Gemin2的核结构域，并支持这样一种观点，即它代表了在光学显微镜下看到的gems的结构对应物。
