A Developmental Surprise

Release Date:
7/16/1998
Contact:
Doris Brody, NIGMS

The molecules that direct development and cellular differentiation are of obvious interest to scientists seeking to learn about birth defects, genetic disorders, cancer, and many other diseases. And for equally obvious reasons, these molecules are easiest to study in relatively simple organisms--but not too simple, because the organisms must be capable of differentiating. Dictyostelium discoideum, the common slime mold, has long been a favorite organism for the study of development. It is certainly simple enough--usually it takes the form of a single-celled, soil-dwelling amoeba. But it has another form. When food runs out, the amoebae come together to form a multicelled, slug-like creature that can crawl and disperse by producing stalk and spore structures. It is this differentiated behavior that makes Dictyostelium so interesting to developmental biologists.

For many years, researchers believed that a molecule called cAMP was required for slug development in Dictyostelium. This molecule is of special interest because, in mammals and humans, cAMP is a vital chemical messenger involved in memory, the action of hormones, and development. However, studies by NIGMS grantee Dr. Adam Kuspa and his colleagues at Baylor College of Medicine threaten to throw cAMP out of its starring role in slime mold development.

Dr. Kuspa's group has shown that a different molecule, called PKA (for protein kinase A), not cAMP, can power all steps of Dictyostelium development, from slug to spore. They did this by engineering mutant slime mold cells that lack cAMP, but that can produce PKA. Surprisingly, in these mutant cells, PKA performed all of the steps previously attributed to cAMP and the cells developed normally. Knowing the role of PKA and cAMP in Dictyostelium will now permit studies of how the specific pathways by which these molecules function may operate in higher organisms.

REFERENCE

Wand B, Kuspa A. Dictyostelium development in the absence of cAMP. Science 1997;277:251-4.

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