Kinetochore-Independent Chromosome Poleward Movement during Anaphase of Meiosis II in Mouse Eggs
Kinetochore-Independent Chromosome Poleward Movement during Anaphase of Meiosis II in Mouse Eggs
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DOI：
10.1371/journal.pone.0005249
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发表时间：
2009-04-13
期刊：
影响因子：
3.7
通讯作者：
Li, Rong
中科院分区：
文献类型：
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作者：
Deng, Manqi;Gao, Juntao;Li, Rong
着丝点被认为是连接纺锤体微管与染色体的关键结构，在有丝分裂过程中对染色体分离起重要作用。由于含有着丝体的有丝分裂细胞和无丝体减数分裂卵母细胞之间纺锤体组装的机制不同，减数分裂纺锤体如何产生极性力来驱动两轮减数分裂染色体分离以实现基因组单倍体化尚不清楚。我们利用DNA珠粒能够在没有着丝点的情况下诱导双极纺锤体形成的事实，研究了小鼠卵减数分裂II期间DNA珠粒在诱导纺锤体中的行为。有趣的是，DNA小珠向两极移动的时间和速度与减数分裂染色体相似，尽管所有的小珠都向同一个纺锤极移动。动力蛋白功能的破坏破坏了DNA小珠的极向运动，但减数分裂染色体却没有，这表明染色体极向运动存在不同的动力蛋白依赖和动力蛋白独立的力产生机制，后者可能依赖于着丝点的存在。与观察到的DNA珠向两极运动一致，精子单倍体染色质（注射到中期卵子后也诱导双极纺锤体形成，但未形成可检测到的着丝点结构）在后期也经历了与DNA珠相似的向两极运动。结果表明，在染色质诱导的减数分裂纺锤体中，着丝点附着在纺锤体微管上并不是后期染色质向两极运动所必需的。
Kinetochores are considered to be the key structures that physically connect spindle microtubules to the chromosomes and play an important role in chromosome segregation during mitosis. Due to different mechanisms of spindle assembly between centrosome-containing mitotic cells and acentrosomal meiotic oocytes, it is unclear how a meiotic spindle generates the poleward forces to drive two rounds of meiotic chromosome segregation to achieve genome haploidization. We took advantage of the fact that DNA beads are able to induce bipolar spindle formation without kinetochores and studied the behavior of DNA beads in the induced spindle in mouse eggs during meiosis II. Interestingly, DNA beads underwent poleward movements that were similar in timing and speed to the meiotic chromosomes, although all the beads moved together to the same spindle pole. Disruption of dynein function abolished the poleward movements of DNA beads but not of the meiotic chromosomes, suggesting the existence of different dynein-dependent and dynein-independent force generation mechanisms for the chromosome poleward movement, and the latter may be dependent on the presence of kinetochores. Consistent with the observed DNA bead poleward movement, sperm haploid chromatin (which also induced bipolar spindle formation after injection to a metaphase egg without forming detectable kinetochore structures) also underwent similar poleward movement at anaphase as DNA beads. The results suggest that in the chromatin-induced meiotic spindles, kinetochore attachments to spindle microtubules are not absolutely required for chromatin poleward movements at anaphase.