MOLECULAR GENETIC ANALYSIS OF INSECT NEUROPEPTIDES AND THEIR RECEPTORS IN DROSOPHILA MELANOGASTER

Neuropeptides/neurohormones are short peptidic fragments secreted by specific neurons in the CNS. They are widespread in the animal kingdom from the worms up to the mammals. They exert hormonal effects and regulate many developmental and physiological functions e.g. development of the central and peripheral nervous system, production of the major hormones, fertility, water balance, cardiac rhythm, behaviour etc.

The genetic “dissection”, i.e. isolation of mutants and their analysis is the strategy which gives the highest “resolution” in the analysis of gene function and interaction. Drosophila with its well-known genetics, molecular biology and fully annotated genome sequence offers unique advantages for such studies. As a holometabolous insect, it is especially suitable for studying the genetic regulation of insect development and physiology. The availability of complete insect (fruitfly, honey bee, Anopheles mosquito) genome sequences greatly accelerated the identification of neuropeptide genes and their receptors. Based on the Genome Project, the genes coding for these proteins are all known in Drosophila. Most of the peptides have diverse effects depending on the availability of the different receptors in the various tissues, their connections to the different signalling pathways, etc. These issues are largely unknown even in the case of the biochemically well-known peptides. It is the elucidation of these diverse functions where the genetic approach in the fly can be very fruitful.

Up to now, no systematic genetic analysis of neurohormone mechanism of action has been made in any system. We have started with the genetic analysis of a group of Drosophila genes producing the so-called FMRFamide-related (FaRP) neuropeptides (FMRFamides, myosuppressins and sulfakinin peptides) and their G-protein-coupled receptors (GPCRs). RNAi (specific decay of mRNA induced by double-stranded RNA) mutants are available for all these genes and we have started with their analysis. The isolation of specific peptide and receptor mutants by targeted mutagenesis as well as transgenic constructs overexpressing the gene products are also in progress. By analysing the mutant phenotypes and their interactions with representative signal transduction mutants, we establish the genetic network regulating the production, functions and interactions of these genes in neuropeptide signalling. Such studies in the Drosophila model can make important contributions to the knowledge of the human and insect neurohormone systems, which is important with respect to their application in human pharmacology and insect control, respectively. This new project is based on international cooperation with Czech and Belgian laboratories (Dr. K. Slama, Prague and Prof. Dr. A. De Loof, Leuven, respectively)