A systems-level approach to parental genomic imprinting: the imprinted gene network includes extracellular matrix genes and regulates cell cycle exit and differentiation. Mus musculus

We used the 3T3-L1 preadipocyte cell line (Green and Kehinde. Cell 5:19-25, 1974; ATCC CL-173), in which adipogenic differentiation is experimentally induced when quiescent 3T3-L1 cells are incubated with serum and IDX (insulin, dexamethasone, isobutylmethylxanthine). Following IDX addition, the cells retract and re-enter the cell cycle in the so-called clonal expansion phase. Two to three days later the cells definitively exit the cell cycle, express adipocyte-specific genes, and accumulate lipids to form lipid droplets. Overall design: 3T3-L1 cells were grown in DMEM/FBS 10% until they reached confluence and entred quiescence following contact inhibition. The cells were kept confluent in the same medium for 2 days. The medium was renewed and supplemented with IDX for 48 hours. The medium was supplemented with insulin and renewed every 2 days until the adipogenic differentiation was completed.