Jitterbug/Filamin and Myosin-II form a complex in tendon cells required to maintain epithelial shape and polarity during musculoskeletal system development.

During musculoskeletal system development, mechanical tension is generated between muscles and tendon-cells. This tension is required for muscle differentiation and is counterbalanced by tendon-cells avoiding tissue deformation. Both, Jbug/Filamin, an actin-meshwork organizing protein, and non-muscle Myosin-II (Myo-II) are required to maintain the shape and cell orientation of the Drosophila notum epithelium during flight muscle attachment to tendon cells. Here we show that halving the genetic dose of Rho kinase (Drok), the main activator of Myosin-II, enhances the epithelial deformation and bristle orientation defects associated with jbug/Filamin knockdown. Drok and activated Myo-II localize at the apical cell junctions, tendon processes and are associated to the myotendinous junction. Further, we found that Jbug/Filamin co-distribute at tendon cells with activated Myo-II. Finally, we found that Jbug/Filamin and Myo-II are in the same molecular complex and that the actin-binding domain of Jbug/Filamin is necessary for this interaction. These data together suggest that Jbug/Filamin and Myo-II proteins may act together in tendon cells to balance the tension generated during development of muscles-tendon interaction, maintaining the shape and polarity of the Drosophila notum epithelium.