Characterisation of genes that regulate centriole stability and ciliogenesis

在大多数有丝分裂过程中发生的染色体分离主要是由微管产生的力完成的。在大多数情况下，这些微管来自基于中心体的微管组织中心。中心体是一个复杂的结构，它包括一对中心粒，周围环绕着一种被称为中心周围物质的蛋白质营养物质。在每个有丝分裂细胞分裂时，中心粒对必须分裂、复制并分离到纺锤体的相对两极，这就是所谓的中心体周期。然而，当细胞停止分裂以执行其末端分化程序时，中心粒也必须认识到这种情况，并相应地阻止中心体周期。随着哺乳动物上皮细胞的最终分裂，子代细胞中未复制的中心粒经历特定的变化并迁移到细胞膜，在那里它们将产生初级纤毛。这些细胞器是细胞膜的延伸，可以促进细胞的运动、机械转导，同时也在细胞信号转导中发挥核心作用。在线虫中，纤毛仅限于感觉神经元；分化的上皮细胞没有初级纤毛，也没有中心粒/中心体的证据。我们已经证明，在特定的发育背景下，中心粒与细胞周期解偶联，而在肠道、外阴和皮下组织的上皮细胞中，中心粒在最终细胞分裂后被积极消除。因此，线虫的上皮细胞可能不具有初生纤毛，因为它们的中心粒在末端分化时被主动消除。*为了研究最终分裂后中心粒消除的过程，我们进行了遗传分析，以确定在分化时不消除中心粒的突变体。使用中心粒特异的标记，我们试图分离破坏分化的上皮细胞，即肠道中的中心粒及时消除的突变体。从这个初步筛选中，我们确定了一个突变体，它允许中心粒持续存在于线虫的肠道上皮细胞中。然而，这些中心粒没有形成纤毛，这表明有丝分裂后中心粒的存在不足以形成纤毛。我们将使用经典的遗传分析和新的转基因方法来识别可能阻止这种转换的基因或将有丝分裂的中心粒转换为纤毛所需的基因。

The chromosome segregation that occurs during most mitotic divisions is accomplished largely by forces generated by microtubules. In most cases these microtubules emanate from the centrosome-based microtubule organising centre. The centrosome is a complex structure that comprises a centriole pair surrounded by a proteinaceous nuage referred to as the pericentriolar material. At each mitotic cell division the centriole pair must split, duplicate and separate to opposing poles of the spindle in what is referred to as the centrosome cycle. However when cells cease their divisions to execute their terminal differentiation program the centrioles too must recognize this condition and accordingly arrest the centrosome cycle. Following the final division in mammalian epithelial cells the unduplicated centrioles present in the daughter cells undergo specific changes and migrate to the cell membrane where they will generate the primary cilium. These organelles are extensions of the cell membrane and can contribute to cell motility, mechanotransduction, while also playing a central role in cell signalling. ***In C. elegans, cilia are restricted to the sensory neurons; differentiated epithelial cells do not possess primary cilia nor do they show evidence of a centriole/centrosome. We have shown that in specific developmental contexts the centrioles uncouple from the cell cycle, while in the epithelial cells of the gut, the vulva, and the hypodermis, the centrioles are actively eliminated following the final cell division. The epithelial cells of C. elegans therefore do not possess primary cilia potentially because their centrioles are actively eliminated upon terminal differentiation. ***To investigate the process involved in centriole elimination following the final division we genetic analysis to identify mutants that do not eliminate their centrioles upon differentiation. Using a centriole-specific marker we sought to isolate mutants that disrupted the timely elimination of the centrioles in differentiated epithelia, namely in the intestine. From this pilot screen we identified one mutant that allows the centrioles to persist in the gut epithelial cells in C. elegans. These centrioles however do not become cilia suggesting that the presence of a post-mitotic centriole is not sufficient for the formation of a cilium. We will use by classic genetic analysis and novel transgenic approaches to identify genes that may block this conversion or are required to convert a mitotic centriole into a cilium.