An oligosaccharide-containing factor that induces cell differentiation in Dictyostelium discoideum

When Dictyostelium discoideum amoebae (strain V12 M2) are spread at high density on agar containing 1 mM cyclic AMP, essentially all the cells differentiate into stalk cells after 2-3 days. We showed previously that isolated amoebae plated at low density on agar containing cyclic AMP do not differentiate, but can be induced to do so by a layer of high density helper cells from which they are separated by a thin cellophane membrane. We now show that the high density cell population releases a dialyzable factor that, in the presence of cyclic AMP, is capable of inducing isolated amoebae to differentiate into stalk cells. Sugar inhibition, sensitivity to glycosidases, and lectin affinity suggest that the differentiation-inducing activity requires the integrity of an oligosaccharide group containing sialic acid, L-fucose, and N-acetylgalactosamine. In addition, a phosphate group appears to be necessary for biological activity.