Karsenti E, Newport J, Hubble R, Kirschner M
J Cell Biol. 1984 May;98(5):1730-45. doi: 10.1083/jcb.98.5.1730.
We have designed experiments that distinguish centrosomal , nuclear, and cytoplasmic contributions to the assembly of the mitotic spindle. Mammalian centrosomes acting as microtubule-organizing centers were assayed by injection into Xenopus eggs either in a metaphase or an interphase state. Injection of partially purified centrosomes into interphase eggs induced the formation of extensive asters. Although centrosomes injected into unactivated eggs (metaphase) did not form asters, inhibition of centrosomes is not irreversible in metaphase cytoplasm: subsequent activation caused aster formation. When cytoskeletons containing nuclei and centrosomes were injected into the metaphase cytoplasm, they produced spindle-like structures with clearly defined poles. Electron microscopy revealed centrioles with nucleated microtubules. However, injection of nuclei prepared from karyoplasts that were devoid of centrosomes produced anastral microtubule arrays around condensing chromatin. Co-injection of karyoplast nuclei with centrosomes reconstituted the formation of spindle-like structures with well-defined poles. We conclude from these experiments that in mitosis, the centrosome acts as a microtubule-organizing center only in the proximity of the nucleus or chromatin, whereas in interphase it functions independently. The general implications of these results for the interconversion of metaphase and interphase microtubule arrays in all cells are discussed.
我们设计了一些实验，以区分中心体、细胞核和细胞质对有丝分裂纺锤体组装的贡献。通过将处于中期或间期状态的哺乳动物中心体注射到非洲爪蟾卵中，对作为微管组织中心的哺乳动物中心体进行了测定。将部分纯化的中心体注射到间期卵中会诱导形成广泛的星体。虽然注射到未激活卵（中期）中的中心体不会形成星体，但在中期细胞质中对中心体的抑制并非不可逆转：随后的激活会导致星体形成。当将含有细胞核和中心体的细胞骨架注射到中期细胞质中时，它们会产生具有明确界定极的纺锤体样结构。电子显微镜显示有带核微管的中心粒。然而，注射从不含中心体的核体制备的细胞核会在浓缩染色质周围产生无星微管阵列。将核体细胞核与中心体共同注射可重建具有明确界定极的纺锤体样结构的形成。我们从这些实验中得出结论，在有丝分裂中，中心体仅在细胞核或染色质附近作为微管组织中心起作用，而在间期它独立发挥功能。讨论了这些结果对所有细胞中中期和间期微管阵列相互转化的一般意义。
