Growing and starving Dictyostelium cells produce distinct density-sensing factors.

Prestarvation factor (PSF) and conditioned medium factor (CMF) are two autocrine factors produced by Dictyostelium cells. Although secreted at different times in the Dictyostelium life cycle (PSF by growing cells and CMF by starving cells), both factors are glycoproteins that are used by cells to measure their own density, and both are important in cell aggregation. To examine the relationship between PSF and CMF, a CMF antisense transformant was tested for the production of PSF during growth. Although this transformant produced extremely low levels of CMF, its production of PSF was essentially normal. We conclude that these two factors are not products of the same gene.