The JAK/STAT pathway is required for border cell migration during Drosophila oogenesis.

During Drosophila oogenesis, border cells perform a stereotypic migration. Slbo, a C/EBP transcription factor, is required for this migration. Here we identify Drosophila Stat92E (signal transducer and activator of transcription) in a screen for gain-of-function suppressors of the slbo mutant phenotype. By clonal analysis for Stat92E and hop (Drosophila JAK) mutants we find that the JAK/STAT pathway is required in border cells for their migration. The activating ligand for the pathway, Unpaired, is expressed in polar cells. Polar cells are specialized cells which can induce border cell fate in anterior follicle cells. On its own, ectopic expression of Unpaired can induce ectopic expression of border cell markers including Slbo. However, Stat92E mutant cells still express normal levels of Slbo protein, thus Stat92E must regulate other targets critical for border cell migration.