JAKs and STATs in invertebrate model organisms

Invertebrate organisms provide systems to elucidate the developmental roles of Janus kinase (JAK)/signal transducers and activators of transcription ( STAT) signaling pathways, thereby complementing research conducted with mam malian cells and animals. Components of the JAK/STAT protein pathway have b een identified and characterized in the fruit fly Drosophila melanogaster a nd the cellular slime mold Dictyostelium discoideum. This review summa rite s the molecular and genetic data obtained from these model organisms. In pa rticular, a Drosophila JAK/STAT pathway regulates normal segmentation, cell proliferation, and differentiation, and hyperactivation of the pathway lea ds to tumor formation and leukemia-like defects. A Dictyostelium STAT regul ates the development of stalk cells during the multicellular part of the li fe cycle. Future research utilizing these organisms should continue to prov ide insights into the roles and regulation of these proteins and their sign aling pathways.