The function of the IRM protein Kirre in sensory pathway formation
Final Report Abstract
In our project we contributed to the elucidation of the role of the IRM protein Kirre in the visual and olfactory system of Drosophila. We previously showed that 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 analyzed the role of these proteins from Drosophila in the establishment of neuronal connectivity by focusing on single neuronal cell types in the fly visual and olfactory systems. 1. In the lamina of the fly visual system L4 neurons are the only monopolar cells 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 a near to complete absence of reciprocal synapses between L4 neurons. Also input synapses from L2 were not detected any more. 2. In the olfactory system, Kirre in Drosophila and its orthologs in mouse are also expressed on axon terminals of olfactory receptor neurons. Using mutant analysis and methods based on two binary gene expression systems we manipulated the genetic constitution of the neurons pre- and postsynaptically independently. We present evidence that in the olfactory system synapses of olfactorial receptor neurons (ORNs) onto projection neurons depend on presynaptic Kirre expression. Presynaptic Kirre modifies postsynaptic distribution of a GFP coupled Da7-subunit of the nicotinic acetylcholin receptor. Knocking down kirre in specific ORNs affects behavioural responses towards specific odors.
Publications
- (2014). The irre cell recognition module (IRM) protein Kirre is required to form the reciprocal synaptic network of L4 neurons in the Drosophila lamina. J. Neurogenet. 28, 291–301
Lüthy, K., Ahrens, B., Rawal, S., Lu, Z., Tarnogorska, D., Meinertzhagen, I. A., and Fischbach, K. F.
(See online at https://doi.org/10.3109/01677063.2014.883390) - (2015). The Role of IRM Protein Kirre in the Olfactory System of Drosophila melanogaster. Dissertation. Albert-Ludwigs-Universität Freiburg. Fakultät für Biologie
Shilpa Rawal
(See online at https://dx.doi.org/10.6094/UNIFR/11361)
