ntrol as was shown when leptin and the sympathetic nervous system axis were shown to negatively regulate bone mass [8]. To confirm a role for Sam68 in the regulation of adipocyte differentiation, we isolated primary MEFs from 14.5-day-old Sam68+/+ and Sam68−/− embryos. The primary Sam68−/− MEFs were differentiated into adipocytes in vitro in culture medium containing 5 μM pioglitazone to induce adipogenesis. Cells at days 0, 4, 6, and 12 were stained with Oil red O to monitor adipogenesis. Adipogenesis was more pronounced in the wild-type MEFs cultures than in the Sam68−/− MEFs, consistent with the positive role of endogenous Sam68 in adipocyte differentiation (Figure 7). The expression of key transcription factors including the PPARγ and KLF5 was impaired in Sam68−/− differentiated MEFs compared with Sam68+/+ MEFs, consistent with impaired adipogenesis in the absence of Sam68 (Figure 7). These data, together with data confirming a lean phenotype in Sam68−/− mice (N. Torabi and S. Richard, unpublished data), support the hypothesis that Sam68 modulates the differentiation of mesenchymal cells.
Figure 7  Ex Vivo Adipo