The experimental strategy. A1) Western blot analyses showing STAT3 and P-STAT3 and A2) band shift analyses of specific LIF-dependent complexes in ES cells depleted of LIF for 24 h and reinduced with LIF for 10 to 120 min. or in pluripotent cells (+ LIF) as indicated. LIF specific complexe containing STAT3 (arrow) and non specific complexe (asterisk) are indicated. B) Diagram summarising the cell growth conditions used for microarray experiments: Mouse ES cells, in the pluripotent state (grown with LIF for 48 h, Pluri.) or induced to differentiate by LIF withdrawal for 24 h [reversible commitment (Rev.)] or 48 h [irreversible commitment (Irrev.)], have been treated for 25 min. with 10% FBS or 10% FBS and 500 pM LIF (+), as indicated, before harvesting. Sample numbers correspond to the conditions compared in Tables 1 to 7 (see Additional file 1). C) Quality controls of LIF response: Protein RIPA cell extracts from ES cells grown with LIF for 48 h or without LIF for 24 or 48 h and not treated (-) or treated for 25 min with FBS or FBS and LIF as in B). Western blot analysis were performed with antibodies reacting against all forms of STAT3 (STAT3), the activated STAT3 (P-STAT3 Tyr705) or with OCT4 and ERK2. D) Semi-quantitative RT-PCR performed with total RNAs from ES cells grown as indicated in B), have been performed with primers corresponding to the indicated genes.