Holt Ian, Nguyen Thi Man, Wehnert Manfred, Morris Glenn E
Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK.
Neuromuscul Disord. 2006 Jun;16(6):368-73. doi: 10.1016/j.nmd.2006.03.014. Epub 2006 May 11.
Emery-Dreifuss muscular dystrophy results from mutations in either emerin or lamin A/C and is caused by loss of some unknown function of emerin-lamin A/C complexes. This function must be of special importance in the skeletal and cardiac muscles that are affected by the disease. Some lamin A/C mutant proteins form 'nuclear foci' in the nucleoplasm when overexpressed by transient transfection and similar aggregates have been seen in cultured skin fibroblasts from patients with Emery-Dreifuss muscular dystrophy, suggesting that mis-assembly of the A-type lamina may be involved in the pathogenesis. Whereas an earlier study of cultured skin fibroblasts compared several different missense mutations in lamin A/C, we have chosen to study one particular Emery-Dreifuss mutation (R249Q) in greater detail. We found that the proportion of fibroblast nuclei containing abnormal lamin A/C aggregates can vary from 0.5 to 23.6% depending on the culture conditions. In particular, switching from a 'slow growth' medium to 'rapid growth' media increased both the number and size of nuclear aggregates. Similar results were obtained with fibroblasts from a second unrelated patient with the same mutation. In contrast to these aggregates of endogenous lamin A/C, 'nuclear foci' formed after transfection of mouse embryo fibroblasts by mutant lamin A/C were not affected by culture conditions. Faulty assembly of the nuclear lamina by mutated lamin A/C molecules could be partly responsible for the disease phenotype, though this has not been proven. The present study suggests that inappropriate lamin A/C assembly may be preventable by manipulation of cell growth conditions.
埃默里 - 德赖富斯肌营养不良症是由emerin或核纤层蛋白A/C的突变引起的，是由于emerin - 核纤层蛋白A/C复合物某些未知功能的丧失所致。该功能在受该疾病影响的骨骼肌和心肌中必定具有特殊重要性。一些核纤层蛋白A/C突变蛋白在通过瞬时转染过度表达时会在核质中形成“核灶”，并且在埃默里 - 德赖富斯肌营养不良症患者的培养皮肤成纤维细胞中也观察到了类似的聚集体，这表明A型核纤层的错误组装可能参与了发病机制。虽然早期对培养皮肤成纤维细胞的研究比较了核纤层蛋白A/C中的几种不同错义突变，但我们选择更详细地研究一种特定的埃默里 - 德赖富斯突变（R249Q）。我们发现，含有异常核纤层蛋白A/C聚集体的成纤维细胞核的比例可根据培养条件在0.5%至23.6%之间变化。特别是，从“缓慢生长”培养基切换到“快速生长”培养基会增加核聚集体的数量和大小。来自另一位具有相同突变的无关患者的成纤维细胞也获得了类似结果。与内源性核纤层蛋白A/C的这些聚集体不同，突变型核纤层蛋白A/C转染小鼠胚胎成纤维细胞后形成的“核灶”不受培养条件影响。突变的核纤层蛋白A/C分子对核纤层的错误组装可能部分导致了疾病表型，尽管这尚未得到证实。本研究表明，通过控制细胞生长条件，可能预防不适当的核纤层蛋白A/C组装。
