To find novel factors required for gene regulation in the Drosophila embryo, we have analyzed mutants isolated in a screen for maternal factors required for embryo patterning performed in the Nüsslein-Volhard laboratory in Tübingen (Luschnig et al. 2004). In my laboratory, we studied 15 mutants that cause segmentation defects and examined gene expression patterns in mutant embryos. We selected two mutants that produce specific gene expression phenotypes. These genes have been mapped, isolated and characterized molecularly. One mutant disrupts the brakeless gene. Brakeless is a nuclear protein of unknown function. In brakeless mutant embryos, we observed expanded expression domains of the gap genes Krüppel (Kr) and knirps (kni). We found that Tailless-mediated repression of kni expression is impaired in brakeless mutants. Tailless and Brakeless bind each other in vitro and interact genetically.
