Quantitative Oct4 overproduction in mouse embryonic stem cells results in prolonged mesoderm commitment during hematopoietic differentiation in vitro

¹ Institut Gustave Roussy, IFR54, U790 INSERM, Villejuif, France

^* To whom correspondence should be addressed. E-mail: vclayet{at}igr.fr.

	Abstract

The Oct4 transcription factor is essential for the self-renewal and pluripotency of embryonic stem (ES) cells. Oct4 level also control the fate of ES cells. We analyzed the effects of Oct4 overproduction on the hematopoietic differentiation of ES cells. Oct4 was introduced into ES cells via a bicistronic retroviral vector, and cells were selected on the basis of Oct4 production, with Oct4⁺ and Oct4⁺⁺ displaying two-fold and three- to four-fold overproduction, respectively. Oct4 overproduction inhibited hematopoietic differentiation in a dose-dependent manner, following the induction of such differentiation by the formation of day 6 embryoid bodies (EB6). This effect resulted from defective EB6 formation rather defective hematopoietic differentiation. In contrast, when hematopoiesis was induced by the formation of blast colonies, the effects of Oct4 depended on the level of overproduction: two-fold overproduction increased hematopoietic differentiation whereas higher levels of overproduction markedly inhibited hematopoietic development. This increase or maintenance of Oct4 levels appears to alter the kinetics and pattern of mesoderm commitment, thereby modifying hemangioblast generation. These results demonstrate that Oct4 acts as a master regulator of ES differentiation.

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