O'Connor L T, Goetz B D, Couve E, Song J, Duncan I D
Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin at Madison 53706, USA.
Mol Cell Neurosci. 2000 Oct;16(4):396-407. doi: 10.1006/mcne.2000.0889.
Hypomyelination and subsequent demyelination of the taiep rat CNS are thought to result from the abnormal accumulation of microtubules (MTs) in oligodendrocytes that disrupts intracellular transport of components needed to form and maintain the myelin sheath. In this study, myelin gene expression was evaluated in mutant and age-matched controls to determine if MT abnormalities affect the distribution of myelin proteins and their mRNAs. Immunohistochemical analysis of taiep brains and spinal cords revealed a gradual decrease in levels of several myelin proteins including myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG), and 2',3'-cyclic nucleotide 3'-phosphodiesterase. Accompanying early declines in MAG and PLP, accumulations of immunoreactive products were detected within oligodendrocytes, consistent with a defect in protein trafficking. Northern blot analysis indicated that diminishing protein levels could not be attributed to changes in transcriptional activity, except for MBP of which mRNA levels decreased with age. Cellular localization of MBP mRNA by in situ hybridization further revealed that transcripts were concentrated within oligodendrocyte cell bodies instead of uniformly distributed throughout processes. These results demonstrate that changes in expression and intracellular localization of myelin gene products are concurrent with increases in MT mass in taiep oligodendrocytes and support our hypothesis that cytoskeletal defects prevent the normal transport of elements required for the formation and maintenance of the myelin sheath.
人们认为，泰耶普大鼠中枢神经系统的髓鞘形成不足及随后的脱髓鞘是由少突胶质细胞中微管（MTs）异常积聚所致，这种积聚扰乱了形成和维持髓鞘所需成分的细胞内运输。在本研究中，对突变体和年龄匹配的对照动物的髓鞘基因表达进行了评估，以确定MT异常是否会影响髓鞘蛋白及其mRNA的分布。对泰耶普大鼠的脑和脊髓进行免疫组织化学分析发现，包括髓鞘碱性蛋白（MBP）、蛋白脂蛋白（PLP）、髓鞘相关糖蛋白（MAG）和2',3'-环核苷酸3'-磷酸二酯酶在内的几种髓鞘蛋白水平逐渐下降。随着MAG和PLP的早期下降，在少突胶质细胞内检测到免疫反应产物的积聚，这与蛋白质运输缺陷一致。Northern印迹分析表明，除了MBP（其mRNA水平随年龄下降）外，蛋白质水平的降低不能归因于转录活性的变化。通过原位杂交对MBP mRNA进行细胞定位进一步显示，转录本集中在少突胶质细胞的细胞体内，而不是均匀分布在整个细胞突起中。这些结果表明，髓鞘基因产物的表达和细胞内定位变化与泰耶普大鼠少突胶质细胞中MT质量的增加同时发生，并支持我们的假设，即细胞骨架缺陷会阻止形成和维持髓鞘所需元素的正常运输。
