Letourneau P C, Shattuck T A, Ressler A H
J Neurosci. 1986 Jul;6(7):1912-7. doi: 10.1523/JNEUROSCI.06-07-01912.1986.
Branching of elongating neurites in vitro occurs by the division of a growth cone into 2 or more daughter neurites. An important initial step is a broadening of the growth cone with establishment of a quiescent central growth cone margin. Within the spreading growth cone, microtubules and associated neuritic components diverge and become oriented toward the lateral protrusive margins of the leading edge (Letourneau, 1983). We have found that a low concentration of the microtubule-stabilizing agent taxol severely reduces the incidence of growth cone branching by cultured sensory and sympathetic neurons from chick embryos. In the presence of taxol, neurites are broader and have more microtubules than normally. Divergence of microtubules entering the growth cone from the proximal neurite is reduced in the presence of taxol, and quiescence of the central growth cone margin is less frequent. We propose that a critical step in branching is the separation and spreading of the neurite cytoskeleton by tensions generated at the lateral margins of the edge of the growth cone. Because taxol increases neurite size and microtubule content without increasing protrusive activity to the same extent, tensions produced in the motile leading edge are insufficient to spread the microtubules and associated neuritic materials into separate arrays for nascent branches.
体外伸长神经突的分支是通过生长锥分裂为两个或更多子神经突而发生的。一个重要的初始步骤是生长锥变宽，并建立静止的中央生长锥边缘。在扩展的生长锥内，微管和相关的神经突成分发散并朝着前缘的侧向突出边缘定向（勒图尔诺，1983年）。我们发现，低浓度的微管稳定剂紫杉醇会严重降低鸡胚培养的感觉神经元和交感神经元生长锥分支的发生率。在紫杉醇存在的情况下，神经突比正常情况下更宽，微管更多。在紫杉醇存在的情况下，从近端神经突进入生长锥的微管发散减少，中央生长锥边缘的静止情况也不那么频繁。我们提出，分支的一个关键步骤是通过在生长锥边缘的侧向边缘产生的张力使神经突细胞骨架分离和扩展。因为紫杉醇增加了神经突大小和微管含量，但没有在相同程度上增加突出活动，所以在活动的前缘产生的张力不足以将微管和相关的神经突物质扩展成新生分支的单独阵列。
