A targeting vector was designed to insert a floxed nuclear lacZ followed by H2BGFP fusion protein, and frt-flanked neomycin resistance selection cassette, immediately before the endogenous start codon. The H2BGFP fusion protein consists of the coding sequence for the human HIST1H2BB gene [histone 1 H2bb] followed C-terminally by Enhanced Green Fluorescent Protein (EGFP) gene. (J:204126)