Sox9-Meis1 inactivation is required for adipogenesis, advancing Pref-1+ to PDGFRa+ cells [microrarray]

Adipocytes arise from commitment and differentiation of adipose precursors in white adipose tissue (WAT). In studying adipogenesis, precursor markers, including Pref-1 and PDGFRα, are used to isolate precursors from stromal vascular fraction of WAT, but the relationship among the markers is not known. Here, we used Pref-1 promoter-rtTA system in mice for labeling Pref-1+ cells and for inducible inactivation of Pref-1 target, Sox9. We show requirement of Sox9 for maintenance of Pref-1+ proliferative, early precursors. Upon Sox9 inactivation, these Pref-1+ cells become PDGFRa+ cells that express early adipogenic markers. Thus, we show for the first time that Pref-1+ cells precede PDGFRa+ cells in the adipogenic pathway and that Sox9 inactivation is required for WAT growth and expansion. Furthermore, we show that, in maintaining early adipose precursors, Sox9 activates Meis1 which prevents adipogenic differentiation. Our study also demonstrates the Pref-1 promoter-rtTA system for inducible gene inactivation in early adipose precursor population. Sox9 ablation increases PDGFRα+ cells, inhibiting cell cycle, muscle and osteoblast/osteoclast differentiation, while inducing genes of hematopoietic cell lineage and inflammatory response. Microarray heatmap of differentially expressed genes (more than 1.5-fold) between floxed and PreASKO PDGFRα+ ingWAT SVF of 6 wk-old female mice fed dox at P1 (n=3 pooled).