Dictyostelium discoideum (countin3 -) Forms Small Fruiting Bodies

In the cellular slime mold Dictyostelium discoideum, Countin and Countin2 proteins are thought to control the size of the multicellular structure since the countin strain forms a huge fruiting body and countin2 strain forms a small fruiting body. Recently, the countin3 gene encoding a polypeptide homologous to Countin and Countin2 was identified in the D. discoideum genome. The countin3 strain formed a 1.8-fold larger number of aggregates, resulting in smaller fruiting bodies compared to those formed by the wild-type. The extent of cell-cell adhesion was reduced in the mutant, indicating that Countin3 protein regulates size by controlling the amounts of proteins responsible for the adhesion.