Analysis of the Distruption Mutant of the Oscillin Homolog Gene of Dictyostelium discoideum

A homolog of oscillin, the Ca 2+ oscillation-inducing factor of the hamster, was identified from the cellular slime mold Dictyostelium discoideum and designated Dd-oscillin. In the developmental stages of D. discoideum, the gene is expressed at the prestalk region which contains a higher concentration of cytosolic Ca 2+ than the pre-spore region. The Dd-oscillin null strain aggregated but did not develop further when the cells were plated on non-nutrient agar at a density of 1.5×1 0 6 cells/cm 2 , showing that the Dd-oscillin gene is important for development. Since the null cells carrying the hamster oscillin gene formed fruiting body, the hamster oscillin was the homolog of Dd-oscillin as far as function is concerned. In addition, the null cells formed fruiting body in the presence of 2,5-di(tert-butyl)-1,4-hydroquinone (BHQ: a specific inhibitor of Ca 2+ -ATPase activity in the endoplasmic reticulum). These results suggest that Dd-oscillin will increase cytosolic Ca 2+ in the cells and promote further development.