Linking motorneuron fate and connectivity in Drosophila

描述（由申请人提供）：我们的长期目标是利用果蝇的遗传方法来了解运动神经元命运规范和分化的分子机制。在本提案中，我们关注运动神经元命运与轴突引导的联系机制。在影响运动神经元发育的突变体的大规模筛选中，我们已经确定了foxO和Mmp2，两者都在运动神经元亚群中表达，并且对于适当的运动轴突引导是必要的。我们关注这两种进化上保守的蛋白质，因为它们为阐明运动神经元的不同行为如何受到发育调节提供了新的切入点。我们的目标是完成这些基因的分子、遗传和表型分析，以了解观察到的突变表型。FoxO是一种转录因子，以其在胰岛素信号通路中的作用而闻名，它受细胞外信号的调节。我们的初步数据表明FoxO在运动神经元簇中特异性表达，以响应靶源信号。详细的表达和表型分析将阐明FoxO在运动神经元发育中的作用。此外，我们将通过分子和遗传上位实验确定运动神经元中调节FoxO表达的信号通路。基质金属蛋白酶（Mmps）包括一个大家族。跨膜和分泌蛋白酶，这些蛋白酶可以一起切割ECM的几乎所有成分。Mmp2在运动神经元的刻板群体中表达，是运动轴突正确引导所必需的。我们将描述Mmp2在有丝分裂后神经元中的表达模式，并通过分析Mmp2突变胚胎中运动轴突的生长来阐明其在运动轴突引导中的作用。此外，我们将通过分析Mmp2与已知调节这一关键寻路步骤的引导分子之间的遗传相互作用，确定Mmp2是否对运动轴突去血循环是必要的。这些研究将促进我们对分子如何在不同的运动神经元群体中发挥作用以协调建立适当的神经肌肉连接模式的理解。运动神经元分化是神经元发育过程中的重要事件，在人类发育和疾病中可能受到干扰。此外，由于foxO和Mmp2都是进化上保守的蛋白，在具有强烈临床意义的途径中起作用，因此这些研究应该具有广泛的生物学和医学意义。

DESCRIPTION (provided by applicant): Our long term aim is to use a genetic approach in Drosophila to understand molecular mechanisms of motorneuron fate specification and differentiation. In this proposal, we focus on mechanisms linking motorneuron fate to axon guidance. In a large-scale screen for mutants affecting motorneuron development, we have identified foxO and Mmp2, both of which are expressed in motorneuron subsets and necessary for proper motor axon guidance. We focus on these two evolutionarily-conserved proteins as they provide us with novel entry points for elucidating how distinct behaviors of motorneurons are developmentally regulated. Our goals here are to complete molecular, genetic, and phenotypic analyses of these genes in order to understand the observed mutant phenotypes. FoxO is a transcription factor best known for its role in the insulin signaling pathway where it is regulated by extracellular signals. Our preliminary data suggest that FoxO is expressed specifically in clusters of motorneurons in response to a target-derived signal. Detailed expression and phenotypic analyses will elucidate the role of FoxO in motorneuron development. Furthermore, we will identify the signaling pathway(s) regulating FoxO expression in motorneurons through molecular and genetic epistasis experiments. Matrix metalloproteinases (Mmps) comprise a large family of. transmembrane and secreted proteases that together cleave nearly every component of the ECM. Mmp2 is expressed in stereotyped populations of motorneurons and is necessary for proper motor axon guidance. We will characterize the expression pattern of Mmp2 in post-mitotic neurons and elucidate its role in motor axon guidance by analyzing motor axon outgrowth in Mmp2 mutant embryos. Additionally, we will establish whether Mmp2 is necessary for motor axon defasciculation by analyzing genetic interactions between Mmp2 and guidance molecules known to regulate this key pathfinding step. These studies will advance our understanding of how molecules acting in distinct motorneuron populations coordinate to establish proper patterns of neuromuscular connectivity. Motorneuron differentiation is an essential event in neuronal development and can be disrupted in human development and disease. Furthermore, since both foxO and Mmp2 are evolutionarily-conserved proteins acting in pathways of intense clinical interest, these studies should have broad biological and medical significance.