A 2A-GAL4 cassette followed by a Disc\RFP3xP3.cUa marker has been inserted into the endogenous Octβ1R locus, at the 3' end of the open reading frame of the RC isoform. This results in the GAL4 driver being expressed as a separate protein under the control of endogenous Octβ1R regulatory sequences (the expression of only the RC isoform is expected to be trapped by GAL4).