The GAL4 system as a tool for unravelling the mysteries of the Drosophila nervous system.

The GAL4 system is a method for directed gene expression that allows genes to be expressed ectopically in numerous cell- or tissue-specific patterns. The technique is being exploited to study the Drosophila melanogaster nervous system at all stages of development, from the embryo to the adult. The GAL4 system is being used to target the expression of novel marker genes in living animals to label cells, or subcellular structures. Directed expression of toxin genes can be used as a method for targeted cell ablation to study the role of cell-cell interactions in development. Ectopic expression helps to elucidate the function of different genes in cell fate determination and differentiation, and is helping to define the regions of the brain involved in sexual behaviour.