Movements of the Schwann cell nucleus implicate progression of the inner (axon-related) Schwann cell process during myelination.
Movements of the Schwann cell nucleus implicate progression of the inner (axon-related) Schwann cell process during myelination.
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DOI：
10.1083/jcb.109.1.273
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发表时间：
1989-07
期刊：
影响因子：
--
通讯作者：
Bates M
中科院分区：
文献类型：
--
作者：
Bunge RP;Bunge MB;Bates M
虽然几十年来人们已经知道外周髓鞘是由一个延伸的，螺旋形的，和压实的许旺细胞（SC）质膜片形成的，这种独特的螺旋完成的机制仍然未知。我们研究了髓鞘形成之前、期间和之后（24-72小时）SC核的运动，以确定这种核运动（在早期报告中指出）是否会为髓鞘形成机制提供有用的见解。我们使用啮齿动物感觉神经元和SC培养物，其中髓鞘形成的起始相对同步，并且亮视野条件允许轴突、致密髓鞘和SC核的位置的分辨率。随后通过电子显微镜（EM）检查观察到的区域;对8个具有已知核运动史的髓鞘形成SC进行详细的EM分析。我们观察到，在髓鞘形成前，SC沿着沿着较大轴突的长度延伸，显然与相邻的SC竞争轴突表面接触。这种延长先于致密髓鞘的沉积。SC核环绕轴突被发现参加早期髓鞘形成。这种运动很少大于每3小时0.25转;平均而言，观察期间形成的节间（0.8 +/- 0.1转/24小时）比观察前开始形成的节间（0.3 +/- 0.1转/24小时）的核运动更多。细胞核的环行运动一般是单向的，同一轴突上相邻的髓鞘形成干细胞的环行运动方向可能相同或相反，且环行运动与髓鞘内主要致密线的数目不成正比。一个关键的发现是，在所有八个案例中，核运动的总体方向与螺旋SC过程的内端相同，因此与螺旋外端的方向相反。我们的结论是，对应的方向的核旋转和内端的螺旋细胞质唇牵连积极的进展，内唇的轴突表面形成膜螺旋的髓鞘，核运动所产生的牵引的推进近轴唇。这种解释与发现与SC细胞质的外部唇相关的基底层和黄斑粘附连接相吻合;这些属性意味着SC的该区域的锚定而不是移动。
Although it has been known for several decades that peripheral myelin is formed from an extended, spiraled, and compacted sheet of Schwann cell (SC) plasma membrane, the mechanism by which this unique spiraling is accomplished remains unknown. We have studied the movements of SC nuclei before, during, and subsequent to myelin formation (over periods of 24-72 h) to determine if this nuclear motion (noted in earlier reports) would provide useful insights into the mechanism of myelinogenesis. We used rodent sensory neuron and SC cultures in which initiation of myelinogenesis is relatively synchronized and bright field conditions that allowed resolution of the axon, compact myelin, and position of the SC nucleus. Observed areas were subsequently examined by electron microscopy (EM); eight myelinating SCs with known nuclear movement history were subjected to detailed EM analysis. We observed that, prefatory to myelination, SCs extended along the length of larger axons, apparently competing with adjacent SCs for axonal surface contact. This lengthening preceded the deposition of compact myelin. SC nuclear circumnavigation of the axon was found to attend early myelin sheath formation. This movement was rarely greater than 0.25 turns per 3 h; on the average, more nuclear motion was seen in relation to internodes that formed during observation (0.8 +/- 0.1 turns/24 h) than in relation to those that had begun to form before observation (0.3 +/- 0.1 turns/24 h). Nuclear circumnavigation generally proceeded in one direction, could be in similar or opposite direction in neighboring myelinating SCs on the same axon, and was not proportional to the number of major dense lines within the myelin sheath. A critical finding was that, in all eight cases examined, the overall direction of nuclear movement was the same as that of the inner end of the spiraling SC process, and thus opposite the direction of the outer end of the spiral. We conclude that the correspondence of the direction of nuclear rotation and inner end of the spiraling cytoplasmic lip implicates active progression of the inner lip over the axonal surface to form the membranous spiral of myelin, the nuclear motion resulting from towing by the advancing adaxonal lip. This interpretation fits with finding basal lamina and macular adhering junctions associated with the external lip of SC cytoplasm; these attributes would imply anchorage rather than movement of this region of the SC.