A Tag:V5 epitope has been inserted at the N-terminal end of the E(spl)m8-HLH coding sequence, at the endogenous locus. In addition, a FRT site has been inserted 210bp 3' to the E(spl)m8-HLH stop codon, and another FRT site has been inserted 172bp 5' of the start codon of the upstream E(spl)m7-HLH gene. A loxP cassette containing a Disc\RFP3xP3.cUa marker is present downstream of the FRT site that is 3' to the E(spl)m8-HLH stop codon.