Fig. 1

HP1β is essential to maintain pluripotency and cell proliferation in ESCs. a Premature differentiation of HP1β^−/− ESCs. Shown are WT (left), HP1α^−/− (middle), and HP1β^−/− (right) ESCs grown in the presence (top) or absence (bottom) of LIF. WT and HP1α^−/− ESCs maintain normal growth and colony morphology whereas the HP1β^−/− ESCs tend to spontaneously differentiate and form flat colonies (red outline). Scale bar = 200 μm. b Cell proliferation assay. Proliferation rate is reduced in HP1β^−/− ESCs, but unaltered in HP1α^−/− ESCs. c Histological analyses of teratomas formed by WT, HP1α^−/− and HP1β^−/−ESCs. The three germ layers were observed in all teratomas but neuroectodermal differentiation (dark blue) appeared particularly enriched in the HP1β^−/− cells. Scale bar = 200 μm. d Accelerated neuronal differentiation in directed differentiation of HP1β^−/− ESCs. Neuronal progenitor cells (NPCs) from WT and HP1β^−/− ESCs were immunostained with Tuj1. Scale bar = 25 μm