GAGA Regulates Border Cell Migration in .

Collective cell migration is a complex process that happens during normal development of many multicellular organisms, as well as during oncological transformations. In oogenesis, a small set of follicle cells originally located at the anterior tip of each egg chamber become motile and migrate as a cluster through nurse cells toward the oocyte. These specialized cells are referred to as border cells (BCs) and provide a simple and convenient model system to study collective cell migration. The process is known to be complexly regulated at different levels and the product of the () gene, the C/EBP transcription factor, is one of the key elements in this process. However, little is known about the regulation of expression. On the other hand, the ubiquitously expressed transcription factor GAGA, which is encoded by the () gene was previously demonstrated to be important for oogenesis. Here, we found that mutations cause substantial defects in BC migration. Partially, these defects are explained by the reduced level of expression in BCs. Additionally, a strong genetic interaction between and mutants, along with the presence of putative GAGA binding sites within the promoter and enhancer, suggests the direct regulation of this gene by GAGA. This idea is supported by the reduction in the -Gal4-driven GFP expression within BC clusters in mutant background. However, the inability of overexpression to compensate defects in BC migration caused by mutations suggests that there are other GAGA target genes contributing to this process. Taken together, the results define GAGA as another important regulator of BC migration in oogenesis.