Does tension keep you in shape? Relevance of Drosophila melanogaster peripodial epithelium on final organ size

Abstract

How animal organs sense and control that they have reached their species specific target size is a longstanding biological question that hasn¿t been fully addressed yet. Possible mechanisms have been proposed in which molecular concentrations vary throughout organ development and regulate the termination of the process. But during growth, organs not only experience chemical variations but also undergo mechanical stress. We are currently exploring the role tension may play regulating organ growth. Most of what is currently known about growth control mechanisms has been deciphered using the primordia of the adult organs in Drosophila, called imaginal discs. Drosophila imaginal discs are flat sacs of monolayered epithelium. Of the two epithelial sheets, the Peripodial epithelium (PE) plays an ancillary role, not giving rise to adult structures, but participating in the final eversion of the discs during metamorphosis. Therefore, the PE has a mechanical role. We have shown that PE cells accumulate thick acto-myosin bundles with an anterior-posterior orientation, indicative of a strong polarized tension. Therefore, the PE could exert some mechanical influence during disc growth. We will present data on the quantitative characterization of cell and tissue parameters (size, polarity, acto-myosin accumulation, neighbors distribution, cell connectivity, etc) of the PE during disc development, with the aim to infer global properties of the tissue. To relate cell/tissue properties with tension sensing, we will analyze how the subcellular localization of Yki, the co-transcriptional activator of the Hippo pathway and tension sensor, correlates with those properties.