A 32kb genomic BAC fragment that encompasses brk. A multi-tag cassette composed of 2xTag:FLAG, 3xTag:HA and Tag:StrepII has been inserted at the C-terminal end of the brk coding sequence. An FRT cassette that encodes the EGFP coding sequence followed by stop sequences has been inserted in the brk 5'UTR. In the absence of FLP recombinase, the EGFP sequence is expressed under the control of endogenous brk regulatory sequences, and the brk coding sequence is not expressed.