The ROSA:LNL:tTA targeting vector was designed to insert a
loxP-flanked STOP cassette (containing a neomycin resistance cassette and transcriptional STOP element) just upstream of a optimized form of the tetracycline controlled transactivator ("mtTA") into the
Gt(ROSA)26Sor locus. The donating investigator reports that the construct was electroporated into 129P2/OlaHsd-derived HM-1 embryonic stem (ES) cells, correctly targeted ES cells were injected into recipient blastocysts and the resultant chimeric mice were bred to C57BL/6J mice to establish the colony. Mutant mice on a mixed genetic background (mostly C57BL/6 with some 129 or FVB/N) were sent to The Jackson Laboratory (as Stock No.
008600). Upon arrival, some mice were bred with C57BL/6J using a marker-assisted, speed congenic approach to generate this congenic strain (Stock No. 011008).