Fig. 1.

c-Abl is required for adipocyte differentiation. (A) c-Abl activity increases during adipogenesis. 3T3-L1 adipoblasts were induced to differentiate with medium containing 5 μg/mL insulin, 1 μM dexamethasone, and 0.5 mM 3-isobutyl-1-methylxanthine (IBMX). Cells were lysed at the indicated times, and protein levels were analyzed by Western blotting. The proteasomal subunit PSMA4 served as a loading control. (B) STI-571 inhibits adipocyte differentiation. 3T3-L1 cells were induced to differentiate with addition of STI-571 at the indicated concentrations or DMSO on days 0–5. Cells were stained with oil red O and photographed at day 8. Relative intracellular lipid content was obtained by dissolving oil red O and measuring optical density (OD) at 520 nm (***P < 0.005). (C) c-Abl is required in adipocyte differentiation. 3T3-L1 expressing shRNA against either GFP or c-Abl were induced to differentiate and stained with oil red O at day 10. Intracellular lipid content was measured as in B (***P < 0.005). (D) c-Abl is required for expression of PPARγ and its target genes during adipogenesis. 3T3-L1 cells expressing shRNA against either GFP or c-Abl were induced to differentiate and lysed at the indicated times. Protein levels were analyzed by Western blotting. (E) c-Abl is required for transcription of PPARγ proadipogenic target genes but not for transcription of PPARγ itself. At day 4 of differentiation, 3T3-L1 cells were analyzed for mRNA expression of the indicated genes by quantitative PCR (***P < 0.005). Sequences of the oligos used are listed in Table S1.