Rag1/Rag2^tm1Mnz

A targeting vector was designed to remove a 7.6 kb genomic segment encoding the antisilencing element (ASE) between the Rag1 and Rag2 genes and replace it with a loxP-flanked neomycin-Cre self excision cassette. Cre was driven by the angiotensin converting enzyme promoter, specific for testis expression. The vector was introduced to E14 129P2/OlaHsd-derived embryonic stem (ES) cells. Excision left a single loxP site in place of the deleted element. Rag1 and Rag2 transcript levels decrease to almost below the detection limit, as measured by RT-PCR. Expression is decreased to a lesser extent in CD4-CD8- thymocytes. Small decreases in mRNA abundance in pro-B and pre-B cells are within the margin of error for the experiments. Rag1 and Rag2 transcript levels decrease to almost below the detection limit, as measured by RT-PCR. Expression is decreased to a lesser extent in CD4-CD8- thymocytes. Small decreases in mRNA abundance in pro-B and pre-B cells are within the margin of error for the experiments. (J:90487)