Identification and characterization of genes encoding proteins with polar expression in different Drosophila cells

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In all organisms cell polarity crucially depends on the interplay of often-polar localized determinants and a polarized organization of the cytoskeleton. In the past, genetic approaches have identified several key players organizing polar cells such as Inscuteable, Crumbs, Bazooka and Stardust. Subsequently, the use of antibodies generated against the encoded proteins revealed their polar localization in fixed material. These tools turned out to be extremely valuable in analyzing cell behaviour in the context of a developing organism. Howver, to fully understand the generation and maintenance of polarized cells it will be necessary to use GFP-tagged proteins which will allow in vivo analyses of the dynamic regulation of cell polarity. In addition, we have to seek additional genes that encode proteins with a polar distribution. One way to identify such proteins is to use a random GFPtagging approach (Morin et al., 2001). Here, A GFP containing exon, which is inserted in a transposon based vector, is introduced by chance into an intron of an endogenous fly gene. Following splicing a fusion protein is generated (depending on the fusion frame) that is generally transported to its normal subcellular localization. Once a specific subcellular expression pattern is defined, mutations in the gene can be easily generated by imprecise excision of the transposon. This powerful combination of genetics and cell biology will provide new insights into the mechanisms that regulate cell polarity in a broad range of tissues.