Neural specificity of elav expression: defining a Drosophila promoter for directing expression to the nervous system.

The Drosophila melanogaster vital gene, embryonic lethal abnormal visual system (elav), is required for the postdeterminative development of the nervous system. Its gene product encodes an RNA binding protein that was found to be expressed in all neurons right after their birth. This specific, ubiquitous, and continuous pattern of neural expression has led to the increasingly popular use of ELAV protein as a neural-specific marker. To understand the molecular basis of this neural-specific expression, we have defined and analyzed the structure of the elav promoter. Cis-acting sequences important for conferring the neural specificity of elav expression were identified by analyzing the reporter gene expression in transformants carrying different elav-beta-galactosidase fusion genes. This analysis delimits a 333-bp region (-92 to +241) that is necessary for specifying the elav pattern of nervous system expression. A 3.5-kb promoter fragment encompassing this region was designed for targeting gene expression specifically to the nervous system and would be a useful tool for the analysis of nervous system function.