The basement membrane (BM) represents a barrier to cell migration and,consequently, needs to be broken down before normal and tumourigenic cells can migrate during development and metastasis, respectively. On , Medioni and Noselli report that during Drosophila oogenesis, the anterior polar cells of the egg chamber are transiently and asymmetrically capped with BM proteins before they migrate into the developing egg chamber with outer border cells. This apical capping of polar cells involves the Drab5-dependent basal-to-apical transcytosis of BM proteins; subsequent cap shedding, which precedes migration, requires the presence of the outer border cells. Thus, as in tumours, BM degradation at the leading edge of the border cell cluster is required before migration can start. Further studies in this genetically amenable model should provide insights into this novel behaviour of the BM in invasive cell clusters.
