DEVELOPMENTAL GENE EXPRESSION IN C ELEGANS

我们感兴趣的是转录因子在细胞发育过程中决定细胞命运的调节作用。我们的模型系统是线虫线虫(一种非寄生蠕虫)，它因其体积小、易于实验室培养、解剖简单、快速繁殖和遗传学而被广泛用于发育研究。我们目前对几个转录因子(MyoD、E、Twist和MEF-2)感兴趣，这些转录因子在其他系统中已被确定为对肌肉形成重要。与华盛顿卡内基研究所的安迪·菲尔斯博士合作，我们已经证明线虫MyoD和Twist因子对包括肌肉在内的胚胎后中胚层细胞的形成和模式具有重要作用。通过研究这些基因突变导致的表型，我们开始确定它们在调节线虫特定肌肉细胞亚群发育中的确切作用。这些突变体还为基因筛选提供了一个起点，以确定在调控体系中起作用的其他因素。我们工作的第二个方面集中在细胞分化和细胞周期之间的联系。通常，细胞必须退出细胞周期(停止增殖)才能分化。在其他生物和组织培养中的研究已经证明，分化因子，如肌肉细胞中的MyoD，在拮抗G1细胞周期因子导致细胞周期退出的作用。利用正向和反向遗传方法，我们证明了细胞周期蛋白D和CDK-4/6因子调节线虫细胞周期的G1期。令人惊讶的是，这些G1调节器只在胚胎后发育期间发挥作用，因此它们在胚胎发生期间对肌肉分化不是重要的。这些研究进一步表明，胚胎发育过程中细胞的快速增殖没有细胞周期的G1期。我们目前正在探索在胚胎后发育过程中解决这些细胞周期调节因子和肌源性因子之间可能相互作用的方法。-MyoD，肌肉，肌肉发生，线虫，bHLH，细胞周期，扭转

We are interested in transcription factors that function in the regulation of cell fate determination during development. Our model system is the nematode C. elegans (a non-parasitic worm) that is widely used for developmental studies because of its small size, ease of culture in the laboratory, simple anatomy, rapid proliferation, and genetics. We are currently interested in several transcription factors (MyoD, E, Twist, and Mef-2) that have been identified in other systems as important for muscle formation. In collaboration with Dr. Andy Fires group at the Carnegie Institution of Washington we have shown that the C. elegans MyoD and Twist factors are important for the formation and patterning of post-embryonic mesodermal cells including muscle. By studying the phenotypes that result from mutations in these genes we are beginning to define their exact roles in regulating the development of specific subsets of muscle cells in C. elegans. The mutants also provide a starting point for genetic screens to identify other factors operating in the regulatory hierarchy. A second aspect of our work focuses on the connection between cellular differentiation and the cell cycle. Usually, cells must exit the cell cycle (stop proliferating) in order to differentiate. Studies in other organisms and tissue culture have demonstrated a role for differentiation factors, such as MyoD in muscle cells, in antagonizing the action of G1 cell cycle factors leading to cell cycle exit. Using forward and reverse genetic approaches we have demonstrated that cyclin D and CDK-4/6 factors regulate the G1 phase of the cell cycle in C. elegans. Surprisingly, these G1 regulators only function during postembryonic development so they can not be important for muscle differentiation during embryogenesis. These studies further suggest that the rapid proliferation of cells during embryogenesis occurs without a G1 phase of the cell cycle. We are currently exploring ways to address possible interactions between these cell cycle regulators and myogenic factors during post-embryonic development. - MyoD, muscle, myogenesis, C. elegans, bHLH, cell cycle, twist