Abstract
BackgroundAlthough many molecular regulators of adipogenesis have been identified a comprehensive catalogue of components is still missing. Recent studies showed that the retinoblastoma protein (pRb) was expressed in the cell cycle and late cellular differentiation phase during adipogenesis. To investigate this dual role of pRb in the early and late stages of adipogenesis we used microarrays to perform a comprehensive systems-level analysis of the common transcriptional program of the classic 3T3-L1 preadipocyte cell line, wild-type mouse embryonic fibroblasts (MEFs), and retinoblastoma gene-deficient MEFs (Rb-/- MEFs).FindingsComparative analysis of the expression profiles of 3T3-L1 cells and wild-type MEFs revealed genes involved specifically in early regulation of the adipocyte differentiation as well as secreted factors and signaling molecules regulating the later phase of differentiation. In an attempt to identify transcription factors regulating adipogenesis, bioinformatics analysis of the promoters of coordinately and highly expressed genes was performed. We were able to identify a number of high-confidence target genes for follow-up experimental studies. Additionally, combination of experimental data and computational analyses pinpointed a feedback-loop between Pparg and Foxo1.To analyze the effects of the retinoblastoma protein at the transcriptional level we chose a perturbated system (Rb-/- MEFs) for comparison to the transcriptional program of wild-type MEFs. Gene ontology analysis of 64 deregulated genes showed that the Rb-/- MEF model exhibits a brown(-like) adipocyte phenotype. Additionally, the analysis results indicate a different or additional role for pRb family member involvement in the lineage commitment.ConclusionIn this study a number of commonly modulated genes during adipogenesis in 3T3-L1 cells and MEFs, potential transcriptional regulation mechanisms, and differentially regulated targets during adipocyte differentiation of Rb-/- MEFs could be identified. These data and the analysis provide a starting point for further experimental studies to identify target genes for pharmacological intervention and ultimately remodeling of white adipose tissue into brown adipose tissue.
Highlights
Evidence accumulating during the past decades has convincingly revealed that adipocytes and adipose tissue are acting as a storage depot for fat, but are actively involved in regulating whole body energy balance, and much attention has been dedicated to decipher molecular events and to identify factors involved in fat cell development
In this study a number of commonly modulated genes during adipogenesis in 3T3-L1 cells and mouse embryonic fibroblasts (MEFs), potential transcriptional regulation mechanisms, and differentially regulated targets during adipocyte differentiation of Rb-/- MEFs could be identified. These data and the analysis provide a starting point for further experimental studies to identify target genes for pharmacological intervention and remodeling of white adipose tissue into brown adipose tissue
Common transcriptional program of adipocyte differentiation in MEFs and 3T3-L1 cells To compare transcriptional regulation during adipocyte differentiation of the established 3T3-L1 cell line and mouse embryonic fibroblasts (MEFs), gene expression in MEFs was studied in three independent experiments with whole genome cDNA microarrays (>27k elements) using seven time points (d0, d1, d2, d3, d4, d6, d10) after hormonal induction in relation to expression levels at the preconfluent stage (Additional file 1)
Summary
Evidence accumulating during the past decades has convincingly revealed that adipocytes and adipose tissue are acting as a storage depot for fat, but are actively involved in regulating whole body energy balance, and much attention has been dedicated to decipher molecular events and to identify factors involved in fat cell development. One group of proteins - the pocket proteins including the retinoblastoma protein (pRb) and other members (p130, p107) - was expressed during both, the cell cycle phase and late cellular differentiation This dual role of pRb in the early and late stages of adipogenesis was described in other studies [3,4,5,6]. Recent studies showed that the retinoblastoma protein (pRb) was expressed in the cell cycle and late cellular differentiation phase during adipogenesis To investigate this dual role of pRb in the early and late stages of adipogenesis we used microarrays to perform a comprehensive systems-level analysis of the common transcriptional program of the classic 3T3-L1 preadipocyte cell line, wild-type mouse embryonic fibroblasts (MEFs), and retinoblastoma gene-deficient MEFs (Rb-/- MEFs)
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