Chromosome micromanipulation. 3. Spindle fiber tension and the reorientation of mal-oriented chromosomes.
Chromosome micromanipulation. 3. Spindle fiber tension and the reorientation of mal-oriented chromosomes.
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DOI：
10.1083/jcb.43.1.40
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发表时间：
1969-10
期刊：
影响因子：
--
通讯作者：
Koch CA
中科院分区：
文献类型：
--
作者：
Nicklas RB;Koch CA
着丝粒重定位是保证染色体正常分布的关键过程。在活着的蝗虫精母细胞中，发生了两条染色体取向相同(单极取向)但不稳定的二价体：迟早会有一条染色体重新定位，结果是稳定的两极取向，随后正常的后期分离到相反的两极。两极取向稳定的一个可能来源是指向相反两极的法向纺锤体力，这会略微拉伸二价轴。这种张力在单极方向上是缺乏的，因为所有的染色体纺锤体纤维和纺锤力都指向一个极点。张力的可能作用已经通过对单极取向的二价体的微操作来直接测试，以人为地产生缺失的张力。无一例外，在张力释放之前，这样的二价体永远不会重新定向；在对八个电池中的八个二价体进行的实验中，累积了超过5小时的总时间。在对照实验中，在没有张力的情况下，这些相同的二价体平均在16分钟内从单极取向重新定向。受控重定向和染色体分离可以从这些和相关实验的结果中得到解释。
Kinetochore reorientation is the critical process ensuring normal chromosome distribution. Reorientation has been studied in living grasshopper spermatocytes, in which bivalents with both chromosomes oriented to the same pole (unipolar orientation) occur but are unstable: sooner or later one chromosome reorients, the stable, bipolar orientation results, and normal anaphase segregation to opposite poles follows. One possible source of stability in bipolar orientations is the normal spindle forces toward opposite poles, which slightly stretch the bivalent. This tension is lacking in unipolar orientations because all the chromosomal spindle fibers and spindle forces are directed toward one pole. The possible role of tension has been tested directly by micromanipulation of bivalents in unipolar orientation to artificially create the missing tension. Without exception, such bivalents never reorient before the tension is released; a total time "under tension" of over 5 hr has been accumulated in experiments on eight bivalents in eight cells. In control experiments these same bivalents reoriented from a unipolar orientation within 16 min, on the average, in the absence of tension. Controlled reorientation and chromosome segregation can be explained from the results of these and related experiments.