Drosophila fat and dachsous genes are members of the FAT family. The dachsous gene encodes a huge transmem­brane protein similar to the fat gene. Dachsous and Fat proteins contain large tandem arrays of cadherin domains (27 and 34, respectively). Both proteins have a cytoplas­mic domain with a sequence similar to the cytoplasmic β-catenin-binding domain of the classical cadherins. The dachsous gene is necessary for correct thorax, leg and wing development in Drosophila. They are tumor suppres­sor genes and their disruption causes imaginal disc hyper­plasia [14].

      Several mammalian FAT homologues have been iden­tified in rats, mice and humans. All these proteins have large extracellular domains, containing many cadherin repeats, EGF repeats and laminin-A G repeats. The FAT family proteins are highly expressed in proliferating tis­sues during development and are usually less prevalent in adult tissues [1]. The probable role of these proteins is in cell repulsion that allows cells to migrate for proper mor­phogenesis. Another possible role is as a brake on cell proliferation [3,1,15].