Assembly pathway of the anastral Drosophila oocyte meiosis I spindle
Assembly pathway of the anastral Drosophila oocyte meiosis I spindle
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DOI：
10.1242/jcs.02304
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发表时间：
2005-04-15
影响因子：
4
通讯作者：
Endow, SA
中科院分区：
文献类型：
--
作者：
Sköld, HN;Komma, DJ;Endow, SA
许多物种的卵母细胞减数分裂纺锤体是无星状的，缺乏中心体来形成微管。体侧纺锤体的组装途径不同于大多数有丝分裂纺锤体。在这里，我们分析了果蝇卵母细胞减数分裂I纺锤体的组装和Nonclaret disjunctional （Ncd）马达在纺锤体组装中的作用，使用温和型和突变型Ncd与GFP融合。出乎意料的是，我们在生发囊泡破裂时观察到运动相关的紫菀向凝聚的染色体迁移，在那里它们在染色体上形成微管。新成核的微管随机排列，然后围绕二价染色体排列。我们发现减数分裂纺锤体是通过微管包裹的染色体的横向结合形成双极纺锤体的。根据对固定卵母细胞的分析，微管相关二价染色体之间的横向相互作用可能是由Ncd马达介导的微管交联介导的。我们在这里报道纺锤体组装发生在微管运动缺陷的ncd突变体中，但微管包被染色体之间的横向相互作用是不稳定的，这表明ncd沿着微管运动需要稳定染色体之间的相互作用。更严重的ncd突变体可能缺乏atp酶活性，阻止染色体间横向相互作用的形成，并导致微管伸长缺陷。因此，在装配过程中，果蝇卵母细胞减数分裂I纺锤体组装涉及运动相关的母细胞成核微管和Ncd运动活动，以形成和稳定微管相关染色体之间的相互作用。这是第一个完整的说明装配一个astral主轴和具体步骤，需要Ncd运动活动，揭示新的和意想不到的特点的过程。
Oocyte meiotic spindles of many species are anastral and lack centrosomes to nucleate microtubules. Assembly of anastral spindles occurs by a pathway that differs from that of most mitotic spindles. Here we analyze assembly of the Drosophila oocyte meiosis I spindle and the role of the Nonclaret disjunctional (Ncd) motor in spindle assembly using mild-type and mutant Ncd fused to GFP. Unexpectedly, we observe motor-associated asters at germinal vesicle breakdown that migrate towards the condensed chromosomes, where they nucleate microtubules at the chromosomes. Newly nucleated microtubules are randomly oriented, then become organized around the bivalent chromosomes. We show that the meiotic spindle forms by lateral associations of microtubule-coated chromosomes into a bipolar spindle. Lateral interactions between microtubule-associated bivalent chromosomes may be mediated by microtubule crosslinking by the Ncd motor, based on analysis of fixed oocytes. We report here that spindle assembly occurs in an ncd mutant defective for microtubule motility, but lateral interactions between microtubule-coated chromosomes are unstable, indicating that Ncd movement along microtubules is needed to stabilize interactions between chromosomes. A more severe ncd mutant that probably lacks ATPase activity prevents formation of lateral interactions between chromosomes and causes defective microtubule elongation. Anastral Drosophila oocyte meiosis I spindle assembly thus involves motor-associated asters to nucleate microtubules and Ncd motor activity to form and stabilize interactions between microtubule-associated chromosomes during the assembly process. This is the first complete account of assembly of an anastral spindle and the specific steps that require Ncd motor activity, revealing new and unexpected features of the process.