Calcium signaling during convergent extension in Xenopus

Background: During Xenopus gastrulation, cell intercalation drives converge nt extension of dorsal tissues. This process requires the coordination of m otility throughout a large population of cells. The signaling mechanisms th at regulate these movements in space and time remain poorly understood. Results: To investigate the potential contribution of calcium signaling to the control of morphogenetic movements, we visualized calcium dynamics duri ng convergent extension using a calcium-sensitive fluorescent dye and a nov el confocal microscopy system. We found that dramatic intercellular waves o f calcium mobilization occurred in cells undergoing convergent extension in explants of gastrulating Xenopus embryos. These waves arose stochastically with respect to timing and position within the dorsal tissues. Waves propa gated quickly and were often accompanied by a wave of contraction within th e tissue. Calcium waves were not observed in explants of the ventral margin al zone or prospective epidermis. Pharmacological depletion of intracellula r calcium stores abolished the calcium dynamics and also inhibited converge nt extension without affecting cell fate. These data indicate that calcium signaling plays a direct role in the coordination of convergent extension c ell movements. Conclusions: The data presented here indicate that intercellular calcium Si gnaling plays an important role in vertebrate convergent extension. We sugg est that calcium waves may represent a widely used mechanism by which large groups of cells can coordinate complex cell movements.