The transgene contains a ~120 kb B1 repeat deletion subfragment of ~485 kb C3H YAC ICRFy903F1113. The YAC contains the entire Gata3 gene plus upstream and downstream regulatory regions and was modified by inserting loxP sites into introns 1 and 2. Diagnostic SacII and XhoI were engineered in introns 1 and 2, respectively. Three mouse lines were established. (J:51930)