TC10-Like/TC10βLong Regulates Adipogenesis by Controlling Mitotic Clonal Expansion

To elucidate molecular Mechanisms of adipocyte differentiation, we previously isolated TC10-like/TC10 beta L), regulates of G protein signaling 2 (RGS2), factor for adipocyte differentiation (fad) 104 and fad158, which were transiently expressed in the early phase of adipogenesis. These four genes seen to be positive regulators of adipogenesis, since their knockdown resulted in the inhibition of adipocyte differentiation. When growth-arrested 3T3-L1 cells were induced to differentiate, they first reentered the cell cycle and underwent several rounds of cell division, a process known as mitotic clonal expansion (MCE). Although MCE is required for completion of the differentiation program, its molecular mechanisms are not fully understood. We examined the roles of these four genes during MCE. Knockdown of the expression of TCL/TC10 beta L impaired MCE, while that of RGS2 or fad104 had a rather weak effect and that of fad158 had no effect. The suppression of TCL/TC10 beta L inhibited the incorporation of bromodeoxyuridine (BrdU), indicating that DNA synthesis was prevented by the knockdown. Interestingly, the knockdown of TCL/TC10 beta L inhibited the expression of the CCAAT/enhancer-binding protein (C/EBP) family, C/EBP beta and C/EBP delta, during MCE. The results strongly suggest that TCL/TC10 beta L regulates adipocyte differentiation by controlling MCE and this regulatory effect is closely linked to C/EBP beta and C/EBP delta expression.