Starter Grant: Spatial Control of Mitosis by Septins

Gladfelter博士将研究细胞分裂如何在空间上由具有多个核的细胞中的分隔蛋白调节。在这些研究中，使用了一种称为棉阿舒囊菌的多核丝状真菌，其中细胞核不同步分裂。异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。Septins是一种保守的、能形成皮层环的蛋白质，在A.通过在细胞中建立促进有丝分裂的区域来促进棉花核分裂。初步资料表明，在A. gossypii的细胞核分裂的空间格局受到干扰，缺乏隔蛋白的细胞。因此，分隔蛋白似乎为决定分裂位置的细胞核提供了空间方向。A.棉隔蛋白组装成各种形态上不同的组织，并且尚不清楚细胞中的所有隔蛋白结构是否都能促进有丝分裂以及隔蛋白在核周期的哪个阶段起作用。Gladfelter博士假设，septins加速了分裂周期的G2期进展，并且只有一部分septin结构具有指导有丝分裂的能力。为了验证这些假设，将使用延时显微镜在活细胞中同时观察细胞核分裂的动态和septin组织的变化。将产生菌株，其中用不同的荧光标记蛋白标记隔膜环、纺锤体极体（SPB，真菌中心体）和细胞核的组分，以检测单个细胞中的隔膜和核分裂进程。这些实验将定义形态上不同的septin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septin组织的存在。这些实验的结果将为研究多核细胞中septin环组装的机制以及septins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妇女参与科学计划（WISP）的女本科生的协助下进行。

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).