Fig. 8. A model for the coordination of visceral and diencephalic LR asymmetry. LR cues from the dorsal organizer/node (zebrafish shield) are transmitted to the tailbud, possibly by the migration of forerunner cells or YSL nuclei, and these cues activate spaw in the left lateral plate (purple). Spaw ligand expressed near the developing heart (red) diffuses to the dorsal diencephalon (unbroken arrow, direct signaling) or initiates an Spaw-dependent relay (broken arrow) that involves other signaling molecules, in order to allow stable cyclops, pitx2c and lefty1 expression in the left part of the epiphyseal/habenular region of the diencephalon (green). The blunted line indicates the presence of a midline barrier and/or repression to the right of the zebrafish midline, as implied by several lines of evidence (Chen et al., 1997; Chin et al., 2000; Concha et al., 2000; Danos and Yost, 1996; Liang et al., 2000) (Table 1).