We developed a new model system, Drosophila nurse cell differentiation, to study these questions. Our system allows us to precisely manipulate Polycomb Group proteins and study their function during silencing initiation and maintenance using microscopy, molecular biology, and genomics. Using our nurse cell differentiation system, we discovered how two Polycomb proteins, Scm and Pcl, regulate the initiation of two types of gene silencing. Read more about it here