Starter Grant: Spatial Control of Mitosis by Septins

格拉德费尔特博士将研究具有多个细胞核的细胞是如何通过分隔素在空间上调控细胞分裂的。在这些研究中，使用了一种多核丝状真菌——棉丝Ashbya gossypii，它的细胞核是异步分裂的。非同步核分裂使细胞能够以空间方式限制对外部环境信号的反应。setin蛋白是一种保守的丝形成蛋白，组装成皮质环，似乎通过在细胞中建立有丝分裂促进区在棉蚜核分裂中起作用。初步研究表明，棉蚜核在隔素环附近分裂，缺少隔素的细胞核分裂的空间格局受到干扰。因此，间隔似乎给原子核提供了空间方向，从而决定了分裂的位置。棉蚜的隔素组合成多种形态不同的组织，细胞中是否所有的隔素结构都能促进有丝分裂，以及隔素在核周期的哪个阶段起作用，目前尚不清楚。Gladfelter博士假设，间隔蛋白加速了分裂周期G2的进程，只有一部分间隔蛋白结构具有指导有丝分裂的能力。为了验证这些假设，核分裂的动力学和septin组织的变化将在活细胞中使用延时显微镜同时观察。将septin环、纺锤体极体（SPB，真菌中心体）和细胞核的组成部分用不同的荧光标记蛋白标记，以检测单个细胞中的septin和核分裂进程，从而产生菌株。这些实验将定义形态上不同的间隔蛋白结构如何产生和成熟，以及核进展的动力学如何取决于不同间隔蛋白组织的存在。这些实验结果将为研究多核细胞中septin环的组装机制以及septin如何与细胞周期机制沟通提供基础。更广泛的影响：这项工作将在达特茅斯学院参加女性参与科学计划（WISP）的本科生的帮助下进行。

Dr. Gladfelter will investigate how cell division is regulated spatially by septins in cells with several nuclei. For these studies, a multinucleated, filamentous fungus called Ashbya gossypii in which nuclei divide asynchronously is used. Asynchronous nuclear division enables cells to restrict responses to external environmental signals in a spatial manner. Septins, which are conserved, filament-forming proteins that assemble into cortical rings, appear to function in A. gossypii nuclear division by establishing mitosis promoting zones in the cell. Preliminary data demonstrates that nuclei divide near septin rings in A. gossypii and that the spatial pattern of nuclear division is disturbed in cells lacking septins. Thus, the septins appear to give spatial directions to nuclei that determine the position of division. A. gossypii septins assemble into a variety of morphologically distinct organizations and it is unclear whether all septin structures in the cell can promote mitosis and in which phase of the nuclear cycle septins act. Dr. Gladfelter hypothesizes that septins accelerate progression through G2 of the division cycle and that only a subset of septin structures have the power to direct mitosis. To test these hypotheses, the dynamics of nuclear division and changes in septin organization will be observed simultaneously in living cells using time-lapse microscopy. Strains will be generated in which components of the septin ring, the spindle pole body (SPB, fungal centrosome) and the nucleus are labeled with different fluorescently tagged proteins to detect septins and nuclear division progression in individual cells. These experiments will define how morphologically distinct septin structures arise and mature and how the kinetics of nuclear progression depends upon the presence of different septin organizations. The results of these experiments will provide a foundation for studying both the mechanisms of septin ring assembly in multinucleated cells and the basis for how the septins communicate with the cell cycle machinery. Broader Impacts: This work will be performed with the assistance of undergraduate woman at Dartmouth College who participate in the Woman In Science Program (WISP).