Ca signaling regulates ecmB expression,cell differentiation and slug regeneration in Dictyostelium

Ca²⁺ regulates cell differentiation and morphogenesis in a diversity of organisms and dysregulation of Ca²⁺ signal transduction pathways leads to many cellular pathologies. In Dictyostelium Ca²⁺ induces ecmB expression and stalk cell differentiation in vitro. Here we have analyzed the pattern of ecmB expression in intact and bisected slugs and the effect of agents that affect Ca²⁺ levels or antagonize calmodulin (CaM) on this expression pattern. We have shown that Ca²⁺ and CaM regulate ecmB expression and pstAB/pstB cell differentiation in vivo. Agents that increase intracellular Ca²⁺ levels increased ecmB expression and/or pstAB and pstB cell differentiation, while agents that decrease intracellular Ca²⁺ or antagonize CaM decreased it. In isolated slug tips agents that affect Ca²⁺ levels and antagonize CaM had differential effect on ecmB expression and cell differentiation in the anterior versus posterior zones. Agents that increase intracellular Ca²⁺ levels increased the number of ecmB expressing cells in the anterior region of slugs, while agents that decrease intracellular Ca²⁺ levels or antagonize CaM activity increased the number of ecmB expressing cells in the posterior. We have also demonstrated that agents that affect Ca²⁺ levels or antagonize CaM affect cells motility and regeneration of shape in isolated slug tips and backs and regeneration of tips in isolated slug backs. To our knowledge, this is the first study detailing the pattern of ecmB expression in regenerating slugs as well as the role of Ca²⁺ and CaM in the regeneration process and ecmB expression.