Elucidating Differences between Meiotic and Mitotic Spindles

描述（由申请人提供）：正确的染色体分离对于正常的细胞分裂和发育至关重要。在多细胞生物中，基于微管的双极纺锤体是一种大型复杂的细胞机器，负责在细胞分裂期间正确分离和分配染色体。在高等真核生物中，纺锤体的结构和功能必须不断调整，以满足单一生物体内独特细胞分裂的要求。例如，在减数分裂期间，纺锤体具有圆形的极，并且是无中心体的，缺乏突出的星形微管，而有丝分裂纺锤体通常具有集中的极，中心体发出星形微管阵列。研究表明，在减数分裂和有丝分裂提取物中组装的纺锤体在形态上类似于它们在体内的对应物，这表明存在决定纺锤体结构的内在因素。在单一遗传背景下，纺锤体如何在各种条件下被修饰以满足特定的功能性要求还不清楚。这里提出的实验将调查不同细胞起源但相同遗传背景的纺锤体之间的明显结构差异，特别是减数分裂与有丝分裂。核心假设是减数分裂和有丝分裂纺锤体在分子组成和调控上不同。为了了解纺锤体的差异，我们将重点研究纺锤体的结构和分子差异， 两极和中心体通过三个特定的目标。通过所提出的目标，我们将确定是否细胞质因素指定纺锤杆结构，研究如何和哪些纺锤杆和中心体因素差异调节减数分裂与有丝分裂，以及如何改变纺锤杆结构和分子组成改变整体纺锤功能和动力学。我们将采用独特的模型系统非洲爪蟾的优势，通过使用体外和体内的方法和操作，将补充与计算机建模的组合。拟议的研究将阐明导致功能和结构纺锤体差异的潜在分子机制，这将促进我们对染色体分离和细胞分裂的理解，这是许多人类疾病和癌症的关键过程。因此，这项研究的结果将提高我们对基本细胞生物学和人类疾病进展的理解。

DESCRIPTION (provided by applicant): Proper chromosome segregation is essential for normal cell division and development. In multi-cellular organisms, the microtubule-based bipolar spindle is a large complex cellular machine responsible for correctly separating and partitioning chromosomes during cell division. In higher eukaryotes, spindle structure and function must constantly tailor to meet the requirements imposed by unique cell divisions within a single organism. For example, during meiotic divisions spindles have rounded poles and are acentrosomal lacking prominent astral microtubules whereas mitotic spindles generally have focused poles with centrosomes that emanate astral microtubule arrays. It has been shown that spindles assembled in meiotic and mitotic extracts morphologically resemble their in vivo counterparts, which suggests that there are intrinsic factors determining spindle structure. How spindles within a single genetic background become modified under various conditions in order to meet specific functional requisites is not well understood. The experiments proposed here will investigate distinct structural differences between spindles of different cellular origins but identical genetic backgrounds, specifically meiotic versus mitotic. The central hypothesis is that meiotic and mitotic spindles differ in molecular composition and regulation. To understand spindle differences, we will focus on investigating structural and molecular differences of spindle poles and centrosomes through three specific aims. Through the proposed aims we will determine whether cytoplasmic factors specify spindle pole structure, examine how and which spindle pole and centrosome factors are differentially regulated in meiosis versus mitosis, and how changing spindle pole structure and molecular composition alters overall spindle function and dynamics. We will employ the advantages of the unique model system Xenopus laevis, by using a combination of in vitro and in vivo approaches and manipulations that will be complemented with in silico modeling. The proposed research will elucidate the underlying molecular mechanisms contributing to functional and structural spindle differences that will advance our understanding of chromosome segregation and cell division, which is a crucial process involved in many human diseases and cancer. Therefore, the proposed work is significant, as the results from this study will improve our understanding of basic cell biology an the progression of human disease.