Function and specificity of LIM domains in Drosophila nervous system and wing development

LIM domains are found in a variety of proteins, including cytoplasmic and nuclear LIM-only proteins, LIM-homeodomain (LIM-HD) transcription factors and LIM-kinases. Although the ability of LIM domains to interact with other proteins has been clearly established in vitro and in cultured cells, their in vivo function is unknown. Here we use Drosophila to test the roles of the LIM domains of the LIM-HD family member Apterous (Ap) in wing and nervous system development. Using a rescuing assay of the ap mutant phenotype, we have found that the LIM domains are essential for Ap function. Furthermore, expression of LIM domains alone can act in a dominant-negative fashion to disrupt Ap function. The Ap LIM domains can be replaced by those of another family member to generate normal wing structure, but LIM domains are not interchangeable during axon pathfinding of the Ap neurons. This suggests that the Ap LIM domains mediate different protein interactions in different developmental processes, and that LIM domains can participate in conferring specificity of target gene selection.