The function of the IRM protein Kirre in sensory pathway formation

本基金申请旨在阐明果蝇视觉和嗅觉系统中突触发生中的α蛋白功能。免疫球蛋白超家族的细胞粘附蛋白的一个小的保守家族。在果蝇中，该蛋白质家族包括不规则交叉C/Roughest（IrreC/Rst）、Kin-of-irre/Dumbfounded（Kirre/Duf）以及它们的相互作用蛋白质伴侣Sticks-and-Stones（SNS）和Hibris（Hbs）。它们与C.在哺乳动物中与Neph 1、Neph 2、Neph 3和Nephrin相关。我们将分析果蝇和小鼠的这些蛋白质在建立神经元连接中的作用，重点是果蝇中的单个神经元细胞类型。L4神经元是唯一的单极细胞在苍蝇板入侵相邻的墨盒。在近端板层，它们与三个L2神经元和六个其他L4神经元形成突触。Kirre在这些侧枝之间的相互接触部位特异性表达，其缺失导致突触数量减少。在嗅觉系统中，果蝇的Kirre和Rst以及它们在小鼠中的直系同源物也在嗅觉受体神经元的轴突终末上表达。使用突变体分析和基于二进制基因表达和flipase系统的各种方法，我们将操纵Kirre表达神经元及其相互作用的细胞伙伴，例如，G.通过过表达反义寡核苷酸转基因或通过敲低使用UAS-RNAi表达的基因。细胞自主和非自主的影响将区分使用遗传镶嵌分析和有丝分裂重组的Gal 4抑制剂Gal 80的诱导损失。将通过使用突触标记物和电子显微镜直接检查来测试对突触发生的影响。突变体和转化体中改变的连接性的行为后果将被用作敏感的传感器，例如，通过在kirre-遗传背景上重新引入细胞类型特异性kirre+来拯救对特定气味剂的敏感性。

This grant application aims at the elucidation of IRM protein function in synaptogenesis, in both the visual and olfactory system of Drosophila. IRM proteins are a small conserved family of cell adhesion proteins of the immunoglobulin superfamily. In Drosophila this protein family comprises Irregular Chiasm C/Roughest (IrreC/Rst), Kin-of-irre/Dumbfounded (Kirre/Duf), and their interacting protein partners Sticks-and-Stones (SNS) and Hibris (Hbs). They are related to Syg-1 and Syg-2 in C. elegans and to Neph1, Neph2, Neph3 and Nephrin in mammals. We will analyze the role of these proteins from Drosophila and mouse in the establishment of neuronal connectivity by focusing on single neuronal cell types in the fly. L4 neurons are the only monopolar cells in the fly lamina that invade neighbouring cartridges. In the proximal lamina layer they form synapses with three L2 neurons and with six other L4 neurons. Kirre is specifically expressed at sites of mutual contact between these collaterals and its absence leads to reduced synapse numbers. In the olfactory system, Kirre and Rst in Drosophila and their orthologs in mouse are also expressed on axon terminals of olfactory receptor neurons. Using mutant analysis and various methods based on binary gene expression and flipase systems we will manipulate the genetic constitution of the Kirre expressing neurons and their interacting cellular partners, e. g. by overexpressing IRM transgenes or by knocking down genes expressed using UAS-RNAi. Cell autonomous and non-autonomous effects will be distinguished by the use of genetic mosaic analysis and the induced loss of Gal4 inhibitor Gal80 by mitotic recombination. Effects on synaptogenesis will be tested by use of synaptic markers and by direct inspection in the electron microscope. Behavioural consequences of altered connectivity in mutants and transformants will be used as sensitive sensors, e.g. rescue of sensitivity to specific odorants will be done by reintroducing cell type specifically kirre+ on kirre- genetic background.