UASt sequences regulate expression of Delta in which the extracellular domain has been replaced in its entirety by Tag:LIG(FSHb) and the intracellular domain has been replaced by six copies of a mutated Tag:MYC epitope (the K residue in all six copies of the epitope has been mutated to R and the LI dipeptide that comprises a clathrin internalization signal that bypasses the requirement for Epsin has been mutated in all but the last copy). The coding sequence is tagged with HRP immediately upstream of the Delta transmembrane domain. A single FRT site is present in between the UASt and coding sequences.