A model explaining the control of Ablim1 expression in the node and the left LPM. (a) Nodal flow and Pkd2 activate both the Nodal, Pitx2 pathway and a second pathway "X". Both pathways in turn activate Ablim1 in the left LPM. (b) In the node, the initial change of Ablim1 expression, from low level pan-nodal to a perinodal ring, require nodal flow and Pkd2 activity. Subsequent L-R asymmetry of perinodal ring expression may be controlled by nodal flow and its interaction with the remodelling of the node during development.