Establishment of germ-line-competent embryonic stem (ES) cells using differentiation inhibiting activity.

The regulatory factor Differentiation Inhibiting Activity/Leukaemia Inhibitory Factor (DIA/LIF) suppresses the differentiation of cultured embryonic stem (ES) cells. In the present study, it is shown that ES cell lines can be derived and maintained in the absence of feeder layers using medium supplemented with purified DIA/LIF. These cells can differentiate normally in vitro and in vivo and they retain the capacity for germ-line transmission. DIA/LIF therefore fulfils the essential function of feeders in the isolation of pluripotential stem cells.