Endow S A, Komma D J
Department of Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
J Cell Sci. 1998 Sep;111 ( Pt 17):2487-95. doi: 10.1242/jcs.111.17.2487.
The meiosis II spindle of Drosophila oocytes is distinctive in structure, consisting of two tandem spindles with anastral distal poles and an aster-associated spindle pole body between the central poles. Assembly of the anastral:astral meiosis II spindle occurs by reorganization of the meiosis I spindle, without breakdown of the meiosis I spindle. The unusual disk- or ring-shaped central spindle pole body forms de novo in the center of the elongated meiosis I spindle, followed by formation of the central spindle poles. gamma-Tubulin transiently localizes to the central spindle pole body, implying that the body acts as a microtubule nucleating center for assembly of the central poles. Localization of gamma-tubulin to the meiosis II spindle is dependent on the microtubule motor protein, Nonclaret disjunctional (Ncd). Absence of Ncd results in loss of gamma-tubulin localization to the spindle and destabilization of microtubules in the central region of the spindle. Assembly of the anastral:astral meiosis II spindle probably involves rapid reassortment of microtubule plus and minus ends in the center of the meiosis I spindle - this can be accounted for by a model that also accounts for the loss of gamma-tubulin localization to the spindle and destabilization of microtubules in the absence of Ncd.
果蝇卵母细胞的减数分裂II纺锤体在结构上独具特色，由两个串联的纺锤体组成，其远端极无星状体，且在中央极之间有一个与星体相关的纺锤体极体。无星状体：有星体的减数分裂II纺锤体通过减数分裂I纺锤体的重组而形成，减数分裂I纺锤体不会解体。不同寻常的盘状或环状中央纺锤体极体在拉长的减数分裂I纺锤体中央重新形成，随后中央纺锤体极形成。γ-微管蛋白短暂定位于中央纺锤体极体，这意味着该极体作为微管成核中心参与中央极的组装。γ-微管蛋白在减数分裂II纺锤体上的定位依赖于微管运动蛋白——非红非分离蛋白（Ncd）。缺乏Ncd会导致γ-微管蛋白无法定位于纺锤体，纺锤体中央区域的微管稳定性降低。无星状体：有星体的减数分裂II纺锤体的组装可能涉及减数分裂I纺锤体中央微管正负端的快速重新排列——这可以用一个模型来解释，该模型也能解释在缺乏Ncd时γ-微管蛋白无法定位于纺锤体以及微管稳定性降低的现象。
