Fig. 3. De novo generation of left-right (LR) asymmetry via three sources of positional information. Node pit cells of E8.0 mouse embryo are illustrated. Each cilium (red bar) protrudes from a node pit cell (light blue) towards the ventral side of the mouse embryo. The cilium is also posteriorly tilted, most probably because the position of the basal body (green) is posteriorly shifted within each cell. Each cilium rotates in a clockwise direction when viewed from the ventral side. The posterior tilt of the ciliary rotation axis generates a leftwards flow instead of a vortex. LR asymmetry is thus formed de novo through a combination of dorsoventral information, anteroposterior information and the unidirectionality of ciliary rotation.