Tg(Il9-cre)#Stck

A targeting construct containing a cre-IRES-mCherry sequence was inserted upstream of the ATG translation initiation site of Il9 via homologous recombination into a BAC clone (RP24-282A18). The recombined BAC was injected into fertilized (CBA x B10)F1 oocytes. Analyses of T cells isolated from crosses to ROSA26-EYFP mice identified only 10% of Il9-producing cells were marked by EYFP. It was discovered that the IRES and mCherry in the construct was disabled because of a premature translational start site in the IRES sequence which possibly diminished activity from the ATG of mCherry sequence. (J:177640)