A heat inducible promoter drives expression of sequence encoding the secreted extracellular domain of boss fused to a leucine zipper derived from the Saccharomyces cerevisiae GCN4 gene (GCN4 sequence starts at residue 251, which shortens the α-Helix of the GCN4 coiled-coil domain by two amino acid residues). The presence of the leucine zipper results in the protein produced forming dimers.
Heat induced expression during larval development of boss1 mutants produces adults that exhibit dorsal-ventral stripes of ommatidia lacking R7 cells.
Carried in plasmid "Exboss-GCNa", expressed in S2 cells and oligomerisation of the fusion protein is studied.