Sequence encoding a FRT-stop-FRT cassette followed by a 6xTag:HA tag has been inserted into the endogenous Nrx-1 locus, at the C-terminal end of the coding sequence. This results in a conditionally tagged allele; in the absence of FLP, the expressed Nrx-1 protein is not tagged with Tag:HA due to the stop cassette. If the FRT cassette is excised using FLP, the expressed Nrx-1 protein is tagged with 6xTag:HA.