A cassette containing Hoxd11-IRES2-nlslacZ was inserted into the Gt(ROSA)26Sor locus via homologous recombination in YFP3.1 ES cells. The inserted cassette has a floxed PGK-neo STOP sequence preceding it, preventing Hoxd11 or lacZ transcription unless cre-mediated excision of the STOP has taken place. Targeted ES cells were injected into C57BL/6J blastocysts. This line was maintained on a C57BL/6J background. (J:137524)