Lineage-associated wiring properties of Drosphila brain neurons

 描述(申请人提供)：大脑功能建立在大量神经元的精确连接基础上。连通性又在很大程度上取决于神经元的遗传连接特性，包括它们的轴突投射、分支和与特定伙伴的突触接触的位置。为了理解和操纵大脑回路，我们需要详细了解在发育中的神经元中表达的基因如何控制这个细胞的连接特性。对于遗传学研究，果蝇提供了许多优势，因为几乎每一个基因都可以作为敲除或激活一种细胞类型的靶点 有选择性的方式。在研究神经元电路的背景下，更重要的是，果蝇的大脑由一些可管理的刻板印象的神经元谱系组成，这些神经元是从胚胎中出生的单个干细胞(神经母细胞)下来的。在其增殖过程中，每个神经母细胞表达一组特定的基因(转录因子)，这些基因被认为指定了特定神经母细胞在特定时间间隔内出生的神经元的连接特性。这些神经元形成了一个所谓的亚系。为了了解大脑回路的遗传控制，我们和其他人采取了一种方法，记录了谱系和亚系的结构属性，并将它们与神经母细胞中基因表达的动态模式相关联。在之前的资助期间，我们已经生成了组成成虫和幼虫大脑的所有谱系的详细地图和3D模型。我们在此提出继续和扩展这项工作的三个目标。首先，我们将重建幼虫大脑谱系及其亚系的子集的连接性，这些亚系形成了一个特定的， 很好地描述了电路。这种重建将以迄今为止无与伦比的分辨率完成，使用一系列数千个连续的电子显微镜切片，并结合一个专门开发的软件包，允许我们将所有突触分配给特定的神经元及其谱系。其次，我们将使用一种系统地标记在神经母细胞中表达的所有转录因子的技术，将绘制在幼虫大脑中的结构定义的谱系与胚胎的神经母细胞联系起来，然后跟踪这些基因从神经母细胞到谱系的表达。第三，我们将筛选和确定基因的特征，这些基因起到引导血统在回路中的适当位置的作用。

 DESCRIPTION (provided by applicant): Brain function is based upon the precise connectivity of a large number of neurons. Connectivity in turn depends in large part on the genetically determined wiring properties of neurons, including their neurite projection, branching, and placement of synaptic contacts with specific partners. To understand and manipulate brain circuits one needs a detailed knowledge of how the genes expressed in a developing neuron control the wiring properties of this cell. For genetic studies, Drosophila offers many advantages, in that virtually every gene can be targeted for knock-out or activation in a cell type selective manner. More importantly in the context of studying neuronal circuitry, the Drosophila brain is composed of a manageable number of stereotyped neuronal lineages, groups of neurons descended from individual stem cells (neuroblasts) born in the embryo. During the course of its proliferation, each neuroblast expresses characteristic sets of genes (transcription factors) which are thought to specify the wiring properties of the neurons born from that particular neuroblast during a particular time interval. These neurons form a so called sublineage. To learn about the genetic control of brain circuitry we and others have taken the approach to document the structural properties of lineages and sublineages, and correlate them to the dynamic pattern of gene expression in the neuroblast. During the previous funding period we have generated detailed maps and 3D models of all lineages constituting the adult and larval brain. We here propose three aims that continue and extend this work. First, we will reconstruct the connectivity of a subset of larval brain lineages and their sublineages that form a particular, well characterized circuit. This reconstruction will be done at a so far unparalleled level of resolution, using a series of several thousand contiguous electron microscopic sections in conjunction with a specially developed software package that allows us to assign all synapses to specific neurons and their lineages. Secondly, we will link the structurally defined lineages mapped in the larval brain with the neuroblasts of the embryo, using a technique that systematically labels all transcription factors expressed in neuroblasts and then follows the expression of these genes from neuroblast to lineage. Thirdly, we will screen for and genetically characterize genes that play a role in directing lineages to their proper place in a circuit.