Figure 1.

Preparation of murine ESC and Mb expressing (β-Gal and validation of cardiogenic commitment. β-Gal activity was revealed by incubation with X-Gal reagent and visualized by light microscopy in CGR8 ESC (a) maintained in a pluripotent state by LIF or (b) differentiated in vitro in embryonic bodies (EBs), and (c) in proliferating D7LNB1 Mb. The commitment of ESC was assessed by flow cytofluorimetry using anti-SSEA-1 staining (d). Pretreatment with BMP-2 turned down the expression of SSEA-1 in approximately 65% of the cells (red area), as compared with the level expressed by non-pretreated cells (blue area). (e) The numbers of beating EB were compared with or without BMP-2 pretreatment. EBs were scored positively when at least three separate areas of the mesodermal layer were contracting. Data are means ± SEM of four experiments. Upon commitment, (f) the expression of cardiac genes was quantified and presented relatively to that of non-pretreated cells. ESC, embryonic stem cells; Mb, myoblasts; LIF, leukemia inhibitory factor.