Molecular and genetic analysis of sanpodo

描述（由申请人提供）：神经系统与其他组织不同的特征是其细胞网络的复杂性。这种复杂性是建立在功能神经系统中神经元的巨大多样性之上的。不对称的细胞分裂，其中前体细胞分裂产生两个不同命运的兄弟细胞，在产生脊椎动物和无脊椎动物神经系统中发现的细胞多样性中发挥核心作用。对果蝇的研究已经开始阐明不对称分裂的遗传和分子基础。这些数据表明，Notch信号通路与膜相关蛋白Numb相反，介导神经（和肌肉）前体的不对称分裂。目前的模型是Numb在前体分裂过程中不对称地分离成一个兄弟，在那里它阻断Notch信号传导并允许该细胞采用CEB1命运。另一个缺乏Numb蛋白的兄弟姐妹接受主动Notch输入并采用CEA1细胞命运。以这种方式，Notch/Numb盒介导大多数（如果不是全部）同胞CNS神经元的二元细胞命运选择。通过遗传筛选，我们确定sanpodo作为一个基因，与Notch途径介导的不对称分裂，sanpodo最初的特点是同源的脊椎动物基因编码的F-肌动蛋白/原肌球蛋白结合蛋白，Tropomodulin。然而，我们的数据提供了令人信服的证据表明，sanpodo不编码Tropomodulin，而是一种新的四次跨膜蛋白。这个提议的目的是阐明sanpodo介导不对称分裂的遗传和分子基础。具体而言，我们建议：（1）确认sanpodo的分子身份;（2）完成sanpodo的系统遗传、表达和分子分析;（3）通过鉴定sanpodo相互作用蛋白阐明sanpodo调节不对称分裂的分子机制。存在Notch途径成员和numb的哺乳动物同源物。最近的遗传、表达和分子研究表明，这些因子也调节哺乳动物的不对称分裂。因此，阐明Sanpodo功能如何与Notch和Numb功能整合以调节不对称细胞分裂，可能为在整个动物发育过程中创造细胞多样性的分子和遗传机制提供一般性见解。

DESCRIPTION (provided by applicant): The feature that sets the nervous system apart from other tissues is the complexity of its cell network. This complexity is founded on the great diversity of neurons that populate a functional nervous system. Asymmetric cell divisions, in which a precursor cell divides to produce two sibling cells of distinct fates, play a central role in generating the cellular diversity found in both vertebrate and invertebrate nervous systems. Research in Drosophila has begun to elucidate the genetic and molecular basis of asymmetric divisions. These data indicate that the Notch signaling pathway acts in opposition to the membrane-associated protein Numb to mediate the asymmetric division of neural (and muscle) precursors. The present model is that Numb is asymmetrically segregated during precursor division into one sibling where it blocks Notch signaling and allows this cell to adopt the CEB1fate. The other sibling, which lacks Numb protein, receives active Notch input and adopts the CEA1cell fate. In this manner, the Notch/Numb cassette mediates the binary cell fate choice of most if not all sibling CNS neurons. Through a genetic screen we identified sanpodo as a gene that acts with the Notch pathway to mediate asymmetric divisions, sanpodo was initially characterized as the homolog of the vertebrate gene encoding the F-actin/tropomyosin binding protein, Tropomodulin. However, our data provide compelling evidence that sanpodo does not encode Tropomodulin but rather a novel four-pass transmembrane protein. The goals of this proposal are to elucidate the genetic and molecular basis through which sanpodo mediates asymmetric divisions. Specifically, we propose: (1) to confirm the molecular identity of sanpodo; (2) to complete a systematic genetic, expression and molecular analysis of sanpodo; and (3) to elucidate the molecular mechanism by which sanpodo regulates asymmetric divisions by identifying Sanpodo-interacting proteins. Mammalian homologs of Notch pathway members and numb exist. Recent genetic, expression and molecular studies suggest these factors also regulate asymmetric divisions in mammals. Thus, the elucidation of how Sanpodo function integrates with that of Notch and Numb to regulate asymmetric cell divisions is likely to provide general insights into the molecular and genetic mechanisms that create cell diversity throughout animal development.