Centrosomin and centrosomes in cell division

描述（由申请人提供）：中心粒和中心体是动物中保守的细胞器，对于细胞信号传导、细胞分裂和分化细胞中的专门作用至关重要，影响整个动物的器官功能。在中心粒/基体组装或功能中起作用的蛋白质中的突变，或影响从基体生长的纤毛的蛋白质中的突变，构成了扩展类别的发育和疾病基因的病因学基础。其他中心体蛋白如CDK 5 RAP 2，Pericentrin，sas 4和Aspm的基因突变是影响大脑和/或身体大小的相关综合征的根本原因，但对中心体功能与疾病原因之间联系的理解尚不清楚。要了解疾病或发育过程，我们必须首先了解受影响蛋白质的功能。在这里，我们专注于Centrosomin家族的蛋白质。果蝇中心体蛋白（CNN）的突变研究取得了关键突破，表明它在有丝分裂中心体组装的早期过程中是必需的。中心体是动物细胞中主要的微管组织中心（MTOC），是有丝分裂时微管有效组装成双极纺锤体所必需的。中心体和中心粒蛋白质的分子功能在很大程度上是未知的;事实上，中心体的“零件清单”仍在编制中。我们以果蝇为模型系统，研究中心体蛋白（Cnn）的分子功能及其影响的蛋白质和过程。有了这个模型，我们结合联合收割机经典和分子遗传学方法与细胞生物学和生物化学，利用效率和丰富的工具箱，这个模型提供。估计70%的人类疾病基因在果蝇中具有同源物，验证了其作为脊椎动物生物学模型的用途。然而，通过使用小鼠CNN家族成员CDK 5 RAP 2的小鼠突变体，我们将这些系统连接起来，并更深入地了解导致人类小头畸形的CDK 5 RAP 2突变的病理学。CNN包含两个保守模块。一个结构域，靠近N-末端，调节微管组装在中心体，而在C-末端的第二个结构域调节肌动蛋白组织成裂解沟。第一个结构域的功能是将微管组装因子募集到中心体，而第二个结构域直接结合到Centrocortin（Cen），一种裂解沟组装所需的新因子。在小鼠中，CDK 5 RAP 2突变细胞失去中心粒接合和凝聚，诱导中心粒扩增。在有丝分裂时，这些多余的中心体诱导多极纺锤体组装，暗示CDK 5 RAP 2在有丝分裂时中心体聚集中的作用。多个中心粒还模板化CDK 5 RAP 2突变细胞中的多个初级纤毛。这些发现为更深入地了解中心体调节和控制中心体复制的关键过程铺平了道路。我们的具体目标是：1.通过CNN确定MTOC调节的机制，2.定义Centrocortin的作用及其与CNN在卵裂沟组装中的合作，以及3.定义CDK 5 RAP 2在鼠标中的功能。公共卫生相关性：由于中心粒和中心体在许多发育和生理过程中的重要性，中心粒和中心体基因的突变会导致许多人类疾病。这些疾病包括多囊肾、耳聋、脑积水、肥胖、小头畸形等。该提案的目标是获得对中心粒和中心体的分子和机制理解，这些结构几乎存在于苍蝇和小鼠的每个细胞中，并识别常染色体隐性原发性小头畸形（MCPH）的病理学。

DESCRIPTION (provided by applicant): Centrioles and centrosomes are conserved organelles in animals that are essential for cell signaling, cell division, and for specialized roles in differentiated cells, impacting organ function in whole animals. Mutations in proteins that function in centriole/basal body assembly or function, or which impact the cilia that grow from basal bodies, comprise the etiological basis for an expanding category of developmental and disease genes. Mutations in genes for other centrosomal proteins like CDK5RAP2, Pericentrin, sas4 and Aspm, are the root cause of related syndromes that affect brain and/or body size, yet an understanding of the connection between function at the centrosome and the causes of disease are unclear. To understand the disease or developmental process, we must first understand the functions of the proteins affected. Here we focus on the Centrosomin family of proteins. A key breakthrough came with mutation studies of Drosophila Centrosomin (CNN), showing that it is required in an early process of mitotic centrosome assembly. Centrosomes are the major microtubule-organizing centers (MTOCs) in animal cells and are required for efficient assembly of microtubules into the bipolar spindle apparatus at mitosis. The molecular functions of centrosome and centriole proteins are largely uncharacterized; indeed, the centrosome "parts list" is still being compiled. We employ Drosophila as a model system to investigate the molecular function of Centrosomin (Cnn) and the proteins and processes it impacts. With this model we combine classical and molecular genetic approaches with cell biology and biochemistry, capitalizing on the efficiency and rich tool chest that this model affords. The estimated 70% of human disease genes with homologs in Drosophila validate its use as a model for vertebrate biology. Yet, by employing a mouse mutant for CDK5RAP2, a mouse CNN family member, we bridge these systems and achieve a closer understanding of the pathology that underlies mutations in CDK5RAP2, which cause microcephaly in humans. CNN contains two conserved modules. One domain, near the N-terminus, regulates microtubule assembly at centrosomes, while the second domain at the C-terminus regulates actin organization into cleavage furrows. The first domain functions to recruit a microtubule assembly factor to centrosomes, while the second domain binds directly to Centrocortin (Cen), a novel factor required for cleavage furrow assembly. In mice, CDK5RAP2 mutant cells lose centriole engagement and cohesion, inducing centriole amplification. At mitosis, these excess centrosomes induce multipolar spindle assembly, implicating a role for CDK5RAP2 in centrosome clustering at mitosis. The multiple centrioles also template multiple primary cilia in CDK5RAP2 mutant cells. These findings pave a path toward a deeper understanding of the key processes that centrosomes regulate and that govern the regulation of centrosome replication. Our specific aims are to: 1. Determine the mechanisms of MTOC regulation by CNN, 2. Define the role of Centrocortin and its cooperation with CNN in cleavage furrow assembly, and 3. Define the functions of CDK5RAP2 in the mouse. PUBLIC HEALTH RELEVANCE: Mutations in genes that function at centrioles and centrosomes cause a host of human disorders due to their importance in so many developmental and physiological processes. These ailments include polycystic kidney disease, deafness, hydrocephaly, obesity, microcephaly, and more. The goal of this proposal is to gain molecular and mechanistic understanding of centrioles and centrosomes, structures found in nearly every cell, in flies and mice and discern the pathology of autosomal recessive primary microcephaly (MCPH).