mom identifies a receptor for the Drosophila JAK/STAT signal transduction pathway and encodes a protein distantly related to the mammalian cytokine receptor family

The JAK/STAT signal transduction pathway controls numerous events inDrosophila melanogaster development. Receptors for the pathway have yet to be identified. Here we have identified a Drosophilagene that shows embryonic mutant phenotypes identical to those in the hopscotch (hop)/JAK kinase and marelle(mrl)/Stat92e mutations. We named this genemaster of marelle (mom). Genetic analyses placemom's function between upd (the ligand) andhop. We further show that cultured cells transfected with themom gene bind UPD and activate the HOP/STAT92E signal transduction pathway. mom encodes a protein distantly related to the mammalian cytokine receptor family. These data show thatmom functions as a receptor of the Drosophila JAK/STAT signal transduction pathway.