Two types of cellular movement underlie proper gonad formation in animals:individual cell migration, where primordial germ cells migrate from their site of origin to contact the cells of the somatic gonad; and coordinated tissue morphogenesis, where germ cells and somatic cells coalesce to form the embryonic gonad. Now Ruth Lehman and colleagues shed light on these little understood events with their phenotypic and molecular characterization of the fear of intimacy (foi) gene in Drosophila (see ). foi is required for gonad coalescence, but not for somatic gonad or germ cell identity. Its protein, which is predicted to belong to a novel family of conserved transmembrane proteins and is required in gonadal mesoderm for coalescence to occur, localises to the cell surface, where the authors propose that it might cooperate with E-cadherin in this morphogenetic process.
