Identification of a Stat Gene That Functions in Drosophila Development

Abstract A Drosophila Stat gene ( D-Stat ) with a zygotic segmental expression pattern was identified. This protein becomes phosphorylated on Tyr-704 when coexpressed in Schneider cells with a Drosophila janus kinase (JAK), Hopscotch (HOP). The phosphorylated protein binds specifically to the consensus sequence TTCCCGGAA. Suppressor mutations of hop Tum-l , a dominant hyperactive allele of hop whose phenotype is hematocyte overproduction and tumor formation, were selected. One of these mutants stat HJ , mapped to the same chromosomal region (92E) as does D-Stat , had an incompletely penetrant pair rule phenotype, and exhibited aberrant expression of the pair rule gene even skipped ( eve ) at the cellular blastoderm stage. Two D-STAT-binding sites were identified within the eve stripe 3 enhancer region. Mutations in either of the STAT-binding sites greatly decreased the stripe 3 expression in transgenic flies. Clearly, the JAK–STAT pathway is connected to Drosophila early development.