For adipocyte differentiation assays, confluent cultures of 3T3-L1 and Swiss 3T3 subclones were exposed to induction medium containing dexamethasone (1 μM), insulin (5 μg/ml), and isobutylmethylxanthine (0.5 mM) (DMI) and 10% FBS. 48 hours after induction, cells were maintained in DMEM containing insulin (5 μg/ml) and 10% FBS until ready for harvest. For NIH 3T3 cells, differentiation medium contained DMI, 6% FBS, and 1 μM rosiglitazone. After induction, cells were maintained in medium containing 6% FBS, insulin, and 1 μM rosiglitazone until ready for harvest. For BMP-induced adipogenesis of NIH 3T3 cell lines, cells were grown to confluence, and maintained at post-confluence, in medium containing 6 ng/mL BMP4 or 25 ng/mL BMP2 along with insulin and rosiglitazone. The derivation and genotyping of Zfp423 knockout mice has been previously described 14 (link), 23 (link). All animal experiments were performed according to procedures approved by the Dana-Farber Cancer Institute’s and Beth Isreal Deconess Medical Center’s Institutional Animal Care and Use Committee.