Cilia take charge in L–R asymmetry

Left–right asymmetry is determined by the distinct activities of two populations of cilia in the node of the mouse embryo, according to results from James McGrath, Martina Brueckner (Yale Univesity, New Haven, CT), and colleagues.Previous experiments suggested that ciliary movement at the node generates movement of the extracellular fluid surrounding the node, called nodal flow. Nodal flow is critical for establishing L–R asymmetry and requires the motor protein left–right dynein (lrd). But just what kind of signal could be at work in such a situation was unclear. To find out, Brueckner and her team engineered a mouse expressing GFP-tagged lrd under the control of the wild-type lrd promoter. GFP-lrd is expressed in the central cilia in the node, but is absent from a second population of cilia surrounding those expressing lrd. With...