title: Modulator recognition factor-2 is required for adipogenesis in mouse embryo fibroblasts and 3T3-L1 cells.
abstract: Previous study showed that mice lacking modulator recognition factor-2 (Mrf-2) were lean, with significant decreases in white adipose tissue. One postulated mechanism for the lean phenotype in Mrf-2 knockout mice is a defect in adipogenesis. In order to investigate this further, we examined the effects of Mrf-2 deficiency on adipogenesis in vitro. In mouse fibroblasts (MEFs) derived from Mrf-2(-/-) embryos, and in 3T3-L1 cells after knockdown of Mrf-2 by small interference RNA (siRNA) there was a potent inhibition of hormone-induced lipid accumulation, and significant decreases in the expression of the adipogenic transcription factors CCAAT/enhancer-binding protein (C/EBP) alpha and peroxisome proliferator-activated receptor-gamma and the mature adipocyte genes they control. Transduction of Mrf-2(-/-) MEFs with a retroviral vector expressing the longer Mrf-2 splice variant (Mrf-2B) stimulated both gene expression and lipid accumulation. Because 3T3-L1 cells are committed to the adipocyte lineage, we used this simpler model system to examine the effects of Mrf-2 deficiency on adipocyte maturation. Analyses of both mRNA and protein revealed that knockdown of Mrf-2 in 3T3-L1 cells prolonged the expression of C/EBP homologous protein-10, a dominant-negative form of C/EBP. Consistent with these findings, suppression of Mrf-2 also inhibited the DNA-binding activity of C/EBPbeta. These data suggest that Mrf-2 facilitates the induction of the two key adipogenic transcription factors C/EBPalpha and peroxisome proliferator-activated receptor-gamma indirectly by permitting hormone-mediated repression of the adipogenic repressor C/EBP homologous protein-10.
authors.affiliation: Department of Molecular Biology, City of Hope Beckman Research Institute, 1500 East Duarte Road, Duarte, CA 91010, USA.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamakawa
authors.forename: Robert H
authors.initials: RH
authors.lastname: Whitson
authors.forename: Shu-Lian
authors.initials: SL
authors.lastname: Li
authors.forename: Keiichi
authors.initials: K
authors.lastname: Itakura
mesh_terms: D041721:3T3-L1 Cells; D050156:Adipogenesis / Q000235:genetics*; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D015151:Immunoblotting; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: C503806:Arid5b protein, mouse; D022763:CCAAT-Enhancer-Binding Protein-alpha; D004268:DNA-Binding Proteins; D047495:PPAR gamma; D034741:RNA, Small Interfering; D014157:Transcription Factors