H2BC21 and osteosarcoma: Imaging of live human osteosarcoma (U2OS) cells and human embryonic kidney cells (HEK293) transiently expressing RHINO and a fluorescent histone H2B protein (mCherry-H2B) revealed exclusively nuclear staining with a strong nucleolar definition and discrete foci of heterogeneous dimensions over a low diffuse background (inset) (Figure 1B, C and Supplementary Movie 1).