Tramtrack co-operates to prevent inappropriate neural development in Drosophila

Abstract

Each sensory organ of the Drosophila peripheral nervous system is derived from a single sensory organ precursor cell (SOP). These originate in territories defined by expression of the proneural genes of the Achaete–Scute complex (AS–C). Formation of ectopic sensilla outside these regions is prevented by transcriptional repression of proneural genes. We demonstrate that the BTB/POZ-domain transcriptional repressor Tramtrack (Ttk) co-operates in this repression. Ttk is expressed ubiquitously, except in proneural clusters and SOPs. Ttk over-expression represses proneural genes and sensilla formation. Loss of Ttk enhances bristle-promoting mutants. Using neural repression as an assay, we dissected functional domains of Ttk, confirming the importance of the bric-à-brac–tramtrack–broad complex (BTB) motif. We show that the Ttk BTB domain is a protein–protein interaction motif mediating tetramer formation.