A homolog of oscillin, the Ca2+ oscillation-inducing factor of the hamster,
was identified from the cellular slime mold Dictyostelium discoideum and d
esignated Dd-oscillin. In the developmental stages of D. discoideum, the ge
ne is expressed at the prestalk region which contains a higher concentratio
n of cytosolic Ca2+ than the prespore region. The Dd-oscillin null strain a
ggregated but did not develop further when the cells were plated on non-nut
rient agar at a density of 1.5x10(6) cells/cm(2), showing that the Dd-oscil
lin gene is important for development. Since the null cells carrying the ha
mster oscillin gene formed fruiting body, the hamster oscillin was the homo
log of Dd-oscillin as far as function is concerned. In addition, the null c
ells formed fruiting body in the presence of 2,5-di(tert-butyl)-1,4-hydroqu
inone (BHQ: a specific inhibitor of Ca2+-ATPase activity in the endoplasmic
reticulum). These results suggest that Dd-oscillin will increase cytosolic
Ca2+ in the cells and promote further development.