Eph/ephrins and N-cadherin coordinate to control the pattern of sympathetic ganglia.

Previous studies have suggested that the segmental pattern of neural-crest-derived sympathetic ganglia arises as a direct result of signals that restrict neural crest cell migratory streams through rostral somite halves. We recently showed that the spatiotemporal pattern of chick sympathetic ganglia formation is a two-phase process. Neural crest cells migrate laterally to the dorsal aorta, then surprisingly spread out in the longitudinal direction, before sorting into discrete ganglia. Here, we investigate the function of two families of molecules that are thought to regulate cell sorting and aggregation. By blocking Eph/ephrins or N-cadherin function, we measure changes in neural crest cell migratory behaviors that lead to alterations in sympathetic ganglia formation using a recently developed sagittal slice explant culture and 3D confocal time-lapse imaging. Our results demonstrate that local inhibitory interactions within inter-ganglionic regions, mediated by Eph/ephrins, and adhesive cell-cell contacts at ganglia sites, mediated by N-cadherin, coordinate to sculpt discrete sympathetic ganglia.