Identification of downstream targets of Mirror, a transcription factor in Drosophila melanogaster

Mirror, a member of the Iroquois family in Drosophila, is involved in embryonic development and in planar polarity in the eye. mirror encodes a homeodomain containing protein, which is believed to act as a transcription factor. Mirror is expressed in the dorsal half of the Drosophila eye, where it plays a key role in forming the equator. This dorsal-ventral midline is established by an interplay of different signalling molecules and complex pathways. Mirror restricts expression of the protein Fringe to the ventral half of the eye and mediates Notch activation at the fringe- expressing boundary, which leads to formation of the equator. In the developing embryo Mirror is expressed most strikingly in stripes at the anterior side of the segmental border and in the central nervous system (CNS), however its function there is unknown. Furthermore it is not known if Mirror acts as an activator or repressor in the embryo. The absence of Mirror leads to segmentation and dorsal closure defects in the embryo and results in embryonic lethality. The formation of the CNS is also disrupted. The aim of this work was to identify genes that are controlled by Mirror during embryonic development. To detect downstream targets of Mirror I have over-expressed Mirror in fly embryos and compared their modified gene expression with control embryos. Mirror loss-of-function embryos have also been analysed. Changes in gene expression were assessed using Drosophila Genome Arrays. To evaluate the microarray data I analysed the expression of potential target genes in Mirror over-expressing and mirror loss-of-function embryos with in situ hybridization and antibody staining techniques. The analysis of potential Mirror targets is presented in my thesis.