Genes controlling asymmetric cell divisions during C. elegans development

描述（由申请人提供）：开发中的一个基本问题是如何指定细胞。阐明细胞类型特异性的机制对于理解和最终治疗人类疾病（如癌症）至关重要，因为这一过程发生了改变。一种指定细胞类型的机制是不对称细胞分裂，其中一个细胞分裂产生两个采用不同命运的子细胞。细胞内不对称分子和细胞信号似乎都使神经母细胞极化，但两者之间的联系一直缺乏。我们已经发现，信号对于某些产生凋亡细胞和神经前体的不对称分裂是必不可少的，并且已经确定了在这些分裂中不对称分布的分子。我们研究的总体目标是了解细胞内在机制和信号如何调节这些分裂过程中产生的神经元的命运。这项提议有三个目的。1)我们拟确定细胞聚合素GRP-1调控不对称细胞分裂的机制。我们的模型提出，GRP-1在V5中发挥作用，调节V5和不对称分裂的神经母细胞之间的信号传导，我们将在几个需要GRP-1功能的分裂中严格测试这一想法。我们将检验PI3K调控GRP-1并通过ARF-1和ARF-6介导其作用的模型。GRP-1在细胞核中的惊人定位提出了一个有趣的可能性，即细胞分裂素可能在细胞核中起作用，我们将询问GRP-1是否在细胞核中发挥作用。最后，我们将研究RNG-1和CNT-2这两个可能在GRP-1通路中起作用的分子。2)我们打算确定wnt如何调节Q神经母细胞的不对称分裂，这也需要PIG-1和GRP-1的功能。我们的初步实验表明，三个wnt和两个卷曲受体参与了这些分裂。我们将测试剩余的Wnt和Wnt受体的作用，更详细地描述这些突变对分裂的影响，并测试Wnt信号是否在GRP-1或PIG-1途径中起作用。3)我们对GRP-1和Wnt信号的分析表明，细胞信号调节不对称细胞分裂。我们将继续EMS筛选，并开始RNAi筛选，以确定在这些信号事件中起作用的分子，以及与HAM-1和PIG-1起作用的分子。

DESCRIPTION (provided by applicant): A fundamental question in development is how cells are specified. Elucidating mechanisms of cell-type specification is essential to the understanding and eventually treating human diseases, such as cancer, where this process is altered. One mechanism that specifies cell type is Asymmetric Cell Division, where a cell divides to produce two daughter cells that adopt distinct fates. Both intracellular asymmetric molecules and cell signaling appear to polarize neuroblasts, but a connection between the two mechanisms has been lacking. We have found that signaling is essential for certain asymmetric divisions that produce apoptotic cells and neural precursors and have identified molecules that are asymmetrically distributed in these divisions. The overall goal of our research is to understand how both cell intrinsic mechanisms and signaling regulate the fates of the neurons that are generated during these divisions. The proposal has three aims. 1) We propose to determine how the cytohesin GRP-1 regulates asymmetric cell divisions. Our model proposes that GRP-1 functions in V5 to regulate signaling between V5 and asymmetrically dividing neuroblasts, and we will test this idea rigorously for several divisions that require GRP-1 function. We will test the model that PI3K regulates GRP-1 and mediates its effects though ARF-1 and ARF-6. GRP-1's surprising localization to the nucleus raises the interesting possibility that cytohesins may function there, and we will ask whether GRP-1 carries out its functions in the nucleus. Finally, we will pursue RNG-1 and CNT-2, two molecules that may function in the GRP-1 pathway. 2) We propose to determine how Wnts regulate asymmetric divisions of the Q neuroblast, which also require both PIG-1 and GRP-1 function. Our preliminary experiments indicate that three Wnts and two Frizzled receptors are involved in these divisions. We will test the roles of the remaining Wnts and Wnt receptors, characterize the effects of these mutations on the divisions in more detail and test whether Wnt signaling acts in the GRP-1 or PIG-1 pathways. 3) Our analysis of GRP-1 and Wnt signaling indicates that cell signaling regulates asymmetric cell divisions. We will continue our EMS screens and begin RNAi screens to identify molecules that function in these signaling events, as well as molecules that act with HAM-1 and PIG-1.