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。阐明细胞类型指定的机制对于理解和最终治疗这一过程发生变化的人类疾病(如癌症)至关重要。一种指定细胞类型的机制是不对称细胞分裂，即一个细胞分裂产生两个采用不同命运的子细胞。细胞内的不对称分子和细胞信号似乎都能使神经母细胞极化，但这两种机制之间缺乏联系。我们已经发现，信号对于某些不对称分裂是必不可少的，这些不对称分裂产生了凋亡细胞和神经前体，并识别了不对称分布在这些分裂中的分子。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在这些分裂过程中产生的神经元的命运。该提案有三个目标。1)我们建议确定细胞粘附素GRP-1如何调节细胞的不对称分裂。我们的模型提出了GRP-1在V5中的作用，以调节V5和不对称分裂的神经母细胞之间的信号传递，我们将对需要GRP-1功能的几个部门进行严格的测试。我们将验证PI3K调节GRP-1的模型，并通过ARF-1和ARF-6介导其作用。S对GRP-1在细胞核的意外定位提出了一个有趣的可能性，即细胞粘附素可能在那里发挥作用，我们将询问GRP-1是否在细胞核中发挥其功能。最后，我们将继续研究RNG-1和CNT-2，这两个分子可能在GRP-1途径中发挥作用。2)我们建议确定WNTS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功能。我们的初步实验表明，三个WNTT和两个Frizzled型受体参与了这些分裂。我们将测试剩余的Wnts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途径中发挥作用。3)我们对GRP-1和Wnt信号的分析表明，细胞信号调节细胞的不对称分裂。我们将继续我们的EMS筛选，并开始RNAi筛选，以确定在这些信号事件中发挥作用的分子，以及与HAM-1和PIG-1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.