A targeting vector was designed to contain a CAG promoter, followed by a loxP-STOP-LoxP (LSL) sequence and an H2B-mCherry fusion protein (coding sequence for the human HIST1H2BB gene [histone 1 H2bb] followed C-terminally by Enhanced Red Fluorescent Protein gene) An AttB-PGKNeo-AttP cassette was placed downstream of the H2B-mCherry fusion protein. This entire construct was inserted into the Gt(ROSA)26Sor locus. PhiC31-mediated recombination removed the neomycin resistance cassette. (J:221246)