H2BC21 and osteosarcoma: To determine the spatial distribution of euchromatin and heterochromatin, the distribution of H2B-mCherry (H2B) and H3.3-EGFP (H3.3) was captured by confocal fluorescence microscopy in optical z-sections in live human osteosarcoma cells (U2OS) transfected with pTandemH (Figure 1B).