THE RESPONSIVENESS OF EMBRYONIC STEM-CELLS TO ALPHA AND BETA INTERFERONS PROVIDES THE BASIS OF AN INDUCIBLE EXPRESSION SYSTEM FOR ANALYSIS OF DEVELOPMENTAL CONTROL GENES

Embryonic stem (ES) cells, derived from the inner cell mass of the pre implantation mouse embryo, are used increasingly as an experimental to ol for the investigation of early mammalian development. The different iation of these cells in vitro can be used as an assay for factors tha t regulate early developmental decisions in the embryo, while the effe cts of altered gene expression during early embryogenesis can be analy zed in chimeric mice generated from modified ES cells. The experimenta l versatility of ES cells would be significantly increased by the deve lopment of systems which allow precise control of heterologous gene ex pression. In this paper, we report that ES cells are responsive to alp ha and beta interferons (IFNs). This property has been exploited for t he development of inducible ES cell expression vectors, using the prom oter of the human IFN-inducible gene, 6-16. The properties of these ve ctors have been analyzed in both transiently and stably transfected ES cells. Expression was minimal or absent in unstimulated ES cells, cou ld be stimulated up to 100-fold by treatment of the cells with IFN, an d increased in linear fashion with increasing levels of IFN. High leve ls of induced expression were maintained for extended periods of time in the continuous presence of the inducing signal or following a 12-h pulse with IFN. Treatment of ES cells with IFN did not affect their gr owth or differentiation in vitro or compromise their developmental pot ential. This combination of features makes the 6-16-based expression v ectors suitable for the functional analysis of developmental control g enes in ES cells.