ACTIN-FILAMENTS, STEREOCILIA, AND HAIR-CELLS OF THE BIRD COCHLEA .4. HOW THE ACTIN-FILAMENTS BECOME ORGANIZED IN DEVELOPING STEREOCILIA AND IN THE CUTICULAR PLATE
ACTIN-FILAMENTS, STEREOCILIA, AND HAIR-CELLS OF THE BIRD COCHLEA .4. HOW THE ACTIN-FILAMENTS BECOME ORGANIZED IN DEVELOPING STEREOCILIA AND IN THE CUTICULAR PLATE
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DOI：
10.1016/0012-1606(86)90048-5
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发表时间：
1986-07-01
影响因子：
2.7
通讯作者：
DEROSIER, DJ
中科院分区：
文献类型：
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作者：
TILNEY, LG;DEROSIER, DJ
在8日龄的胚胎中，可以在雏鸡耳蜗毛细胞上发现立体纤毛；每个毛细胞内都有一小群肌动蛋白细丝，它们从立体纤毛的顶端延伸到细胞的顶端细胞质。然而，这些细丝并不是以规则的方式排列的，而且往往发现在立体纤毛的侧缘附近，相邻细丝之间有很大的空间。到第9天时，相邻肌丝之间的间隙变小，即使在横截面上肌动蛋白螺旋的交叉点不在规则晶格上，也存在相邻肌动蛋白螺旋交叉点的区域。到10-11天时，肌动蛋白细丝逐渐变得更多地交叉连接在一起，我们可以在纵切面上看到由于交叉桥的周期性而产生的水平条纹。在横截面上，细丝开始在六角形晶格上生活。然而，每个立体纤毛含有不到100根肌动蛋白细丝。有证据表明，一旦最大的交叉桥和六角形的细丝堆积(11-12天)，通过将肌动蛋白细丝有序地添加到现有的细丝束的侧边，立体纤毛的宽度增加，到第26天，我们发现多达400根细丝都堆积在六角形的晶格上。因此，维管束的形成有两个阶段。在第一种情况下，少量的细丝凝聚成六角形的交联束。在第二种情况下，在类似于晶体生长的过程中，通过在束的外围添加细丝来增加束的直径。根据对根状纤毛和体纤毛细丝伸长的观察，我们得出结论：根状纤毛是通过在非优先端添加亚单位而生长的，而体纤毛则是通过在首选端添加亚单位来伸长的。有趣的是，这两种相加模式发生在不同的发育时期。
In 8-day-old embryos stereocilia can be identified on the hair cells of the chick cochlea; within each is a small population of actin filaments which extend from the tip of the stereocilium to the apical cytoplasm of the cell. These filaments are not ordered in a regular way, however, and tend to be found near the lateral margins of the stereocilia with large spaces between adjacent filaments. By 9 days the spaces between adjacent filaments are reduced and there are regions where the crossover points of adjacent actin helices are in register even though in cross section filaments do not lie on a regular lattice. By 10-11 days the actin filaments become progressively more crossbridged together and we can recognize in longitudinal section horizontal stripes caused by the periodicity of the crossbridges. In transverse section the filaments begin to life on a hexagonal lattice. Each stereocilium, however, contains less than 100 actin filaments. Evidence is presented that once crossbridging is maximal and the filaments hexagonally packed (Days 11-12), the stereocilia increase in width by the orderly addition of actin filaments to the lateral margins of the existing filament bundle so that by Day 26 we find up to 400 filaments all packed on a hexagonal lattice. Thus there are two stages in bundle formation. In the first a small number of filaments condense into a hexagonally packed, crosslinked bundle. In the second, the bundle increases in diameter by addition of filaments to the periphery of the bundle in a process akin to crystal growth. From observations on the elongation of filaments in the rootlets and stereocilia, we conclude that rootlets grow by addition of subunits at the nonpreferred end while stereocilia elongate by addition to the preferred end. What makes this interesting is that these two modes of addition occur at different developmental times.