A key question in developmental biology is how different tissues maintain proportional growth during development. A striking example of this is the tiling of sensory dendrites across the body wall of the Drosophila larva: during early larval life, the neuronal dendrites extend to cover the entire body wall, without overlapping. As the larva grows further, tiling is maintained – meaning that the dendrites and the overlying epithelium grow proportionally (dendrite-substrate coupling). On p. Jay Parrish and colleagues investigate the mechanistic basis of this coupling, finding that the microRNA bantam (which they previously showed to be required in the epithelial body wall for proper scaling) regulates endoreplication of these epithelial cells. Inhibiting endoreplication by multiple means disrupts dendrite-substrate coupling such that dendrites overgrow. Moreover, they show that integrin expression in the epithelium is controlled by bantam and other regulators of endoreplication, and is in turn important for appropriate dendrite-epithelial contacts to be made and maintained for proportional growth. Thus, by coordinating cell growth (endoreplication) with epithelial cell-dendrite adhesion, coupled tissue growth can efficiently be achieved.
