Identification of inducible genes at the early stage of adipocyte differentiation of 3T3-L1 cells.

Adipocyte differentiation takes place via a complex series of steps. While PPARgamma2 and C/EBPalpha are known to be master regulators, the events at the earliest stage of adipocyte differentiation are not yet known. In this study, we cloned the genes which are induced at the beginning of differentiation of 3T3-L1 preadipocyte cells. Of 58 clones obtained, only a few were already reported as the genes that are expressed differentially during adipocyte development. More than 30 clones are known but have been newly identified here as differentially expressed genes. Nineteen clones seemed to be unknown genes. The expression of RGS2, HSP105, Rho (TC10), VDR, and HIF-1alpha genes isolated here rapidly increased after the addition of inducers, and after 3-12 h the levels of expression decreased. The expression patterns of these mRNAs were different among growth-arrested and proliferating 3T3-L1 cells and NIH-3T3 cells, strongly indicating that some of the proteins identified here have crucial roles in the program of adipocyte differentiation.