The Mir106a, Mir18b, Mir20b, Mir19b-2, Mir92-2, and Mir363 genes were replaced by an Frt-flanked neomycin cassette. The targeting vector was introduced to V6.5 (C57BL/6 x 129S4/SvJae)F1-derived embryonic stem (ES) cells. The neomycin cassette was removed through Flp-mediated excision. (J:134861)