Migration and transcriptional profiling of sacral neural crest derivatives in the lower urinary tract

Examining calcium events during neural crest (NC) migration has the potential to shed light on cell communication duringmigration and patterningevents.However, typical analysis of calciumtransients during embryogenesis has been limited to cultured cells using fluorescent indicators added to the culture media which make the cells easy to visualize but not necessarily representative of their in vivo behavior. Here we studied the spontaneous calcium transients during NC migration in vivo using a genetically encoded calcium sensor (GECI), GCaMP3 which is not toxic to the embryo like synthetic indicators but is still easily imaged. The GCaMP3 vector was electroporated into pre-migratory NC cells and calcium transients were visualized in vivo in whole chick embryos and in sagittal slice trunk explants using confocal time-lapse imaging. First we conclude trunk NC cells displayed significantly more calcium transients than cranial NC cells, especially once trunkNC cells reached thedorsal aorta and during aggregation into sympathetic ganglia (SG). Second, blocking of N-cadherin activity in trunkNC cells near the presumptive SG led to a dramatic decrease in the frequency of calcium transients. Finally, we found that calcium transients were predictive of trunk NC cells aggregating into a cluster to form an SG anlagen. Our data suggest a model in which calcium transients are correlatedwith trunkNCcellmigrationandaggregationof cells into discrete sympathetic ganglia and highlight the power of using GECI's during an embryogenic event.