THE DROSOPHILA ABRUPT GENE ENCODES A BTB-ZINC FINGER REGULATORY PROTEIN THAT CONTROLS THE SPECIFICITY OF NEUROMUSCULAR CONNECTIONS

Motor axons make synaptic connections with specific muscles, and this specificity unfolds during development as motoneuron growth cones make specific pathway choices and ultimately recognize and synapse on thei r specific muscle targets. The Drosophila clueless mutation was identi fied previously in a genetic screen for mutations that disrupt motoneu ron guidance and connectivity. We show here that clueless is allelic t o abrupt. The abrupt gene is required for the embryonic formation of s pecific synaptic connections between a subset of motoneurons and a sub set of muscles. Mutations in abrupt also reveal its role in establishi ng and maintaining muscle attachments, adult sensory cell formation, a nd morphogenesis of adult appendages. The abrupt gene encodes a zinc f inger protein with a conserved BTB domain. abrupt is expressed in musc le nuclei but not motoneurons, suggesting that abrupt controls the mus cle expression of molecules required for correct motoneuron targeting, as well as molecules required for correct muscle attachments.