<i>Drosophila</i> genotypes used in this work.

Mitosis and meiosis have two mechanisms for regulating the accuracy of chromosome segregation: error correction and the spindle assembly checkpoint (SAC). We have investigated the function of several checkpoint proteins in meiosis I of Drosophila oocytes. Increased localization of several SAC proteins was found upon depolymerization of microtubules by colchicine. However, unattached kinetochores or errors in biorientation of homologous chromosomes do not induce increased SAC protein localization. Furthermore, the metaphase I arrest does not depend on SAC genes, suggesting the APC is inhibited even if the SAC is not functional. Two SAC proteins, ROD of the ROD-ZW10-Zwilch (RZZ) complex and MPS1, are also required for the biorientation of homologous chromosomes during meiosis I, suggesting an error correction function. Both proteins aid in preventing or correcting erroneous attachments and depend on SPC105R for localization to the kinetochore. We have defined a region of SPC105R, amino acids 123–473, that is required for ROD localization and biorientation of homologous chromosomes at meiosis I. Surprisingly, ROD removal from kinetochores and movement towards spindle poles, termed “streaming,” is independent of the dynein adaptor Spindly and is not linked to the stabilization of end-on attachments. Instead, meiotic RZZ streaming appears to depend on cell cycle stage and may be regulated independently of kinetochore attachment or biorientation status. We also show that Spindly is required for biorientation at meiosis I, and surprisingly, the direction of RZZ streaming.有丝分裂与减数分裂存在两种调控染色体分离准确性的核心机制：错误校正与纺锤体组装检验点（spindle assembly checkpoint, SAC）。本研究针对果蝇卵母细胞减数分裂I期的多种检验点蛋白功能展开了系统性探究。经秋水仙素处理诱导微管解聚后，我们观测到多种SAC蛋白的定位水平显著上调。然而，未附着的动粒或同源染色体双向定向错误并不会触发SAC蛋白定位的上调。进一步研究发现，中期I阻滞并不依赖于SAC基因，这提示即便SAC通路功能丧失，后期促进复合物（APC）仍可被有效抑制。两种SAC蛋白——ROD-ZW10-Zwilch（RZZ）复合物中的ROD与MPS1，同时也是减数分裂I期同源染色体双向定向所必需的蛋白，这表明二者具备错误校正功能。这两种蛋白均可辅助阻止或纠正错误的微管-动粒附着，且它们向动粒的定位依赖于SPC105R。我们明确了SPC105R中一段由123至473位氨基酸组成的区域，该区域是ROD动粒定位以及减数分裂I期同源染色体双向定向所必需的。令人意外的是，ROD从动粒移除并向纺锤体极移动的过程（被称为“流式转运”）既不依赖于动力蛋白适配体Spindly，也与末端附着的稳定化无关。相反，减数分裂过程中的RZZ流式转运似乎依赖于细胞周期阶段，且可能独立于动粒附着状态或同源染色体双向定向状态受到调控。此外，我们还证实Spindly是减数分裂I期同源染色体双向定向所必需的，同时该蛋白也会影响RZZ流式转运的方向，这一发现同样出人意料。