Rediscovery of the Nucleolinus

描述（由申请人提供）：核仁是存在于许多（如果不是所有）细胞中的细胞器。它在有丝分裂和肿瘤转化过程中的行为使早期研究者提出了它在细胞分裂中的作用。然而，自核仁核被发现以来的100多年里，人们对核仁核的组成和功能几乎一无所知。因为它紧靠核仁，在大多数细胞中不容易看见，所以常被误认为是核仁的一部分。幸运的是，有一些细胞，如蛤（Spisula solidissima）卵母细胞，其中核仁明显。这些例外为研究核仁核在细胞生理学中的作用提供了线索，并为研究其功能提供了机会。利用Spisula卵母细胞作为模型系统，我们已经做了三个观察，可能将核仁与中心体联系起来，中心体是动物细胞的主要微管组织中心。首先，中心体rna在中心体形成之前特异性定位于核核仁。其次，在减数分裂过程中，核仁核的最后可见位置与减数分裂纺锤极的位置一致，在那里中心体组织星状微管和纺锤体微管，为细胞分裂做准备。第三，在中心体形成前核仁核被切除的初步实验导致减数分裂受阻。这些观察结果使我们假设核仁是新生中心体形成所必需的。Spisula卵母细胞模型将通过两种互补的方法来验证这一假设：1)原位核核核激光消融，然后检查其对中心体组装和细胞分裂装置其他组件的影响；2)在无细胞系统中分离核核仁形成中心体的分析。我们预计，这些实验将描绘一个模型，其中核仁被激活暴露于卵母细胞细胞质，然后在形成第一个卵母细胞中心体(s)的功能。这一发现将代表着我们对中心体生物发生的理解的根本进步，并对细胞和生物医学科学具有广泛的影响。

DESCRIPTION (provided by applicant): The nucleolinus is an organelle present in many, if not all cells. Its behavior during mitosis and neoplastic transformation led early investigators to propose a role in cell division. Yet, more than 100 years since its discovery, virtually nothing is known about the composition or function of the nucleolinus. Because it is closely apposed to the nucleolus and not easily visible in most cells, it is often mistaken as a part of the nucleolus. Fortunately, there are some cells, such as surf clam (Spisula solidissima) oocytes, in which the nucleolinus is prominent. Such exceptions provide clues to a role for the nucleolinus in cell physiology and opportunities to study function. Using Spisula oocytes as a model system, we have made three observations that potentially link the nucleolinus to the centrosome, the principle microtubule organizing center of animal cells. First is that centrosomal RNAs are specifically localized to the nucleolinus before centrosome formation. Second, the last visible position of the nucleolinus during meiosis coincides with the site of the meiotic spindle pole, where the centrosome organizes astral and spindle microtubules in preparation for cell division. Third, preliminary experiments in which the nucleolinus was ablated before centrosome formation resulted in a blockage of meiosis. These observations lead us to hypothesize that the nucleolinus is required for de novo centrosome formation. The Spisula oocyte model will be used to test this hypothesis in two complementary approaches: 1) laser ablation of the nucleolinus in situ followed by examination of its effects on assembly of centrosomes and other components of the cell division apparatus; 2) analysis of centrosome formation from isolated nucleolini in a cell-free system. We anticipate that these experiments will delineate a model in which the nucleolinus is activated by exposure to oocyte cytoplasm, and then functions in forming the first oocyte centrosome(s). Such a finding would represent a fundamental advance in our understanding of centrosome biogenesis and have broad implications for cell and biomedical sciences.