A 2A-lexA::GAD cassette followed by a Disc\RFP3xP3.cUa marker has been inserted into the endogenous Oamb locus, at the 3' end of the open reading frame of the RB isoform. This results in the lexA::GAD driver being expressed as a separate protein under the control of endogenous Oamb regulatory sequences (the expression of only the RB isoform is expected to be trapped by lexA::GAD).