Mechanisms of actin regulation in synaptogenesis versus axon guidance

描述(申请人提供)：轴突引导和突触发生代表了神经元发育中不同的生物学过程，但它们是由一组重叠的外部线索调节的，包括netrin、WNT和信号素。在轴突引导中，这些信号调节肌动蛋白细丝(F-肌动蛋白)的形成进入生长锥的细丝延伸，而在突触发生中，它们指示F-肌动蛋白在新生的突触前区域组装，以支撑突触前组装程序的招募。为了确定相同的外部线索如何在指定轴突引导与突触发生时指导不同的肌动蛋白动力学，我们将研究秀丽线虫这两个过程中肌动蛋白的调控机制。由于线虫是半透明的，其刻板的轴突形态和突触图案很容易使用细胞和突触特异的荧光标记观察到。此外，易于进行正向遗传筛选，再加上丰富的可用特征突变体，使线虫成为研究神经元发育的强大遗传模型。我们将首先调查已知的相对贡献 肌动蛋白调节蛋白对轴突的引导和特定神经元中的突触发生。我们假设肌动蛋白调节蛋白的亚类在轴突引导或突触发生中具有排他性的作用，并且这些肌动蛋白调节蛋白的不同调控和功能是这两个过程中涉及的不同肌动蛋白动力学的基础。同时，我们将使用正向遗传学方法来识别将突触模式线索与突触前F-肌动蛋白组装联系起来的新基因。最后，通过研究肌动蛋白调节因子和多个外部线索之间的遗传相互作用，我们将揭示这些线索是如何收敛到调节肌动蛋白动力学的。神经元中异常的肌动蛋白调控与许多神经疾病有关，包括帕金森氏症和自闭症。更全面地了解神经元中肌动蛋白的调节机制是设计有效治疗这些疾病的重要一步。

DESCRIPTION (provided by applicant): Axon guidance and synaptogenesis represent distinct biological processes in the development of a neuron, yet they are mediated by an overlapping set of extrinsic cues, including netrin, wnt, and semaphorin. In axon guidance, these cues modulate the formation of actin filaments (F- actin) into the filopodial extensions of the growth cone, whereas in synaptogenesis, they direct F-actin assembly at nascent presynaptic regions to scaffold the recruitment of the presynaptic assembly program. To ascertain how the same extrinsic cues instruct dissimilar actin dynamics when specifying axon guidance versus synaptogenesis, we will examine the mechanisms of actin regulation during these two processes in Caenorhabditis elegans. As C. elegans is translucent, its stereotyped axon morphology and synapse patterning are easily observed using cell- and synapse-specific fluorescent markers. Furthermore, the ease of conducting forward genetic screens, combined with the wealth of available characterized mutants, makes C. elegans a powerful genetic model for the study of neuronal development. We will first investigate the relative contribution of known actin regulators to axon guidance and synaptogenesis in a specific neuron. We hypothesize that subsets of actin regulators have an exclusive role in either axon guidance or synaptogenesis, and that the differential regulation and function of these actin regulators underlies the distinct actin dynamics involved in these two processes. In parallel, we will use a forward genetic approach to identify novel genes which link synapse-patterning cues to presynaptic F-actin assembly. Finally, by examining genetic interactions between actin regulators and the multiple extrinsic cues which mediate axon guidance and synaptogenesis in a single cell, we will uncover how these cues converge to modulate actin dynamics. Aberrant actin regulation in neurons has been linked to a number of neurological disorders, including Parkinson's disease and autism. A more complete understanding of the mechanisms of actin regulation in neurons is an important step in designing effective therapies for these conditions.