MSN and neoplasm: We recently carried out an in vivo large-scale screen for genes that affect tumour behaviour by (i) generating positively marked clones on the dorsal thorax of the fly that are homozygous mutant for the neoplastic tumour suppressor gene lethal (2) giant larvae (lgl4); (ii) specifically labelling the mutant tissue with GFP:Moe (the actin-binding domain of moesin fused to GFP), thereby labelling the actin cytoskeleton of these cells; (iii) overexpressing an RNAi transgene to deplete expression of a gene of interest specifically within the mutant, labelled tissue.