Henderson C G, Tucker J B, Mogensen M M, Mackie J B, Chaplin M A, Slepecky N B, Leckie L M
School of Biological and Medical Sciences, University of St Andrews, Fife, Scotland.
J Cell Sci. 1995 Jan;108 ( Pt 1):37-50. doi: 10.1242/jcs.108.1.37.
Large cell surface-associated microtubule bundles that include about 3,000 microtubules assemble in certain epithelial cells called inner pillar cells in the mouse organ of Corti. Microtubule-organizing centres (MTOCs) at both ends and near the middle of each cell act in concert during control of microtubule positioning. In addition, the three cell surface-associated microtubule-organizing centres are involved in coordinating the connection of bundle microtubules to cytoskeletal components in neighbouring cells and to a basement membrane. The precisely defined locations of the three MTOCs specify the cell surface regions where microtubule ends will finally be anchored. The MTOCs are modified as anchorage proceeds. Substantial fibrous meshworks assemble at the surface sites occupied by the MTOCs and link microtubule ends to cell junctions. This procedure also connects the microtubule bundle to cytoskeletal arrays in neighbouring cells at two of the MTOC sites, and to the basilar membrane (a substantial basement membrane) in the case of the third site. A fourth meshwork that is not positioned at a major MTOC site is involved in connecting one side of the microtubule bundle to the cytoskeletons of two other cell neighbours. The term surfoskelosome is suggested for such concentrations of specialized cytoskeletal materials and junctions at cell surface anchorages for cytoskeletal arrays. The large microtubule bundle in each cell is composed of two closely aligned microtubule arrays. Bundle assembly begins with nucleation of microtubules by a centrosomal MTOC that is attached to the apical cell surface. These microtubules elongate downwards and the plus ends of many of them are apparently captured by a basal MTOC that is attached to the plasma membrane at the bottom of the cell. In the lower portion of the cell, the microtubule bundle also includes a basal array of microtubules but these elongate in the opposite direction. This investigation provides evidence that they extend upwards from the basal MTOC to be captured by a medial MTOC which is attached to the plasma membrane and situated near the mid-level of the cell. However, there are substantial indications that the basal array's microtubules are also nucleated by the apically situated centrosomal MTOC, but escape from it, and are translocated downwards for capture of their plus ends by the basal MTOC. If this is the case, then these microtubules continue to elongate after translocation and extend back up to the medial MTOC, which captures their minus ends.
在小鼠柯蒂氏器中，一种包含约3000根微管的大型细胞表面相关微管束，会在某些被称为内柱细胞的上皮细胞中组装。每个细胞两端及中部附近的微管组织中心（MTOC）在控制微管定位过程中协同作用。此外，三个细胞表面相关微管组织中心参与协调束状微管与相邻细胞的细胞骨架成分以及基底膜的连接。三个MTOC的精确定位确定了微管末端最终将锚定的细胞表面区域。随着锚定过程的进行，MTOC会发生改变。大量纤维网络在MTOC占据的表面位点组装，并将微管末端连接到细胞连接点。这一过程还在两个MTOC位点将微管束与相邻细胞的细胞骨架阵列相连，在第三个位点则与基底膜（一种重要的基底膜）相连。位于一个主要MTOC位点之外的第四个网络，参与将微管束的一侧与另外两个相邻细胞的细胞骨架相连。对于细胞表面细胞骨架阵列锚定处这种特殊细胞骨架材料和连接的聚集，建议使用“表面骨架体”这一术语。每个细胞中的大型微管束由两个紧密排列的微管阵列组成。束状组装始于附着在细胞顶端表面的中心体MTOC对微管的成核作用。这些微管向下延伸，其中许多微管的正端显然被附着在细胞底部质膜上的基底MTOC捕获。在细胞的下部，微管束还包括一组基底微管阵列，但这些微管向相反方向延伸。这项研究提供的证据表明，它们从基底MTOC向上延伸，被附着在质膜上且位于细胞中层附近的中间MTOC捕获。然而，有大量迹象表明，基底阵列的微管也是由位于顶端的中心体MTOC成核的，但它们从中逃脱，并向下移位，以便其正端被基底MTOC捕获。如果是这种情况，那么这些微管在移位后继续延伸，并向上延伸回到中间MTOC，中间MTOC捕获它们的负端。
