Border-cell migration requires integration of spatial and temporal signals by the BTB protein Abrupt

Abstract

During development, elaborate patterns of cell differentiation and movement must occur in the correct locations and at the proper times. Developmental timing has been studied less than spatial pattern formation and the mechanisms integrating the two are poorly understood. Border cell migration in the Drosophila ovary occurs specifically at stage 9. Timing of the migration is regulated by the steroid hormone ecdysone, whereas spatial patterning of the migratory population requires localized activity of the JAK/STAT pathway. Ecdysone signaling is patterned spatially as well as temporally, although the mechanisms are not well understood. In stage 9 egg chambers, ecdysone signaling is highest in anterior follicle cells including the border cells. We identify the gene abrupt as a repressor of ecdysone signaling and border cell migration. Abrupt protein is normally lost from border cell nuclei during stage 9, in response to JAK/STAT activity. This contributes to the spatial pattern of the ecdysone response. Abrupt attenuates ecdysone signaling via a direct interaction with the bHLH domain of the P160 ecdysone receptor coactivator Taiman (Tai). Together these findings provide a molecular mechanism by which spatial and temporal cues are integrated.