Linking motorneuron fate and connectivity in Drosophila

描述（由申请人提供）：我们的长期目标是在果蝇中使用遗传方法来理解运动神经元命运特化和分化的分子机制。在这个建议中，我们专注于连接运动神经元的命运轴突指导的机制。在一个大规模的筛选影响运动神经元发育的突变体，我们已经确定了foxO和Mmp2，这两个都是在运动神经元亚群和必要的适当的运动轴突的指导。我们专注于这两个进化上保守的蛋白质，因为它们为我们提供了新的切入点，阐明不同的运动神经元的行为是如何发育调节。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，最为人所知的是其在胰岛素信号传导途径中的作用，其中其受细胞外信号调节。我们的初步数据表明，FoxO是专门表达在集群的运动神经元在响应目标源性信号。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性实验来鉴定调节运动神经元中FoxO表达的信号通路。基质金属蛋白酶（Mmps）是一个大家族。跨膜蛋白酶和分泌蛋白酶一起切割ECM的几乎每种组分。mmp 2在运动神经元的定型群体中表达，并且对于适当的运动轴突引导是必要的。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突变胚胎中的运动轴突生长来阐明其在运动轴突指导中的作用。此外，我们将通过分析Mmp2和已知调节这一关键寻路步骤的指导分子之间的遗传相互作用，确定Mmp2是否是运动轴突去束所必需的。这些研究将促进我们对不同运动神经元群体中分子如何协调以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中的重要事件，并且在人类发育和疾病中可能被破坏。此外，由于foxO和Mmp2都是进化上保守的蛋白质，作用于具有强烈临床意义的途径，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.