Molecular characterization of anterior-like cells in Dictyostelium discoideum.

Prestalk cells are found in the anterior 15% of slugs of Dictyostelium discoideum and prespore cells are found in the remaining posterior portions. Neutral red staining as well as immunostaining with antisera prepared against spores or a spore-coat protein has indicated that there are cells in the posterior region which have properties similar to prestalk cells. This cell population, called anterior-like cells, has been isolated by density separation of posterior slug fractions. This anterior-like cell preparation contained approximately 80% neutral red-stained cells, none of which carried a surface antigen specific to prespore cells (MUD-1 antigen). These cells also lacked antigens recognized by antisera to the spore-coat proteins or by a prespore-specific monoclonal antibody isolated for this study (mLJ1). Anterior-like cells were found to modify the lysosomal enzymes acid phosphatase and alpha-mannosidase in a manner found specifically in prestalk cells. They also synthesized two prestalk-specific proteins and contain two prestalk-specific mRNA transcripts. Anterior-like cells also failed to express a large number of prespore-specific characteristics. Although very similar to prestalk cells, anterior-like cells differ from them in that they express a prespore-specific protein PSP59 and the levels of the prestalk-specific mRNA transcripts and one of the prestalk-specific proteins ST430 appear to be lower.