Project description:Preadipocytes initiate differentiation into adipocytes through a cascade of events. Mitotic clonal expansion, as one of the earliest event, is essential for adipogenesis. However, the underlying mechanisms that regulate mitotic clonal expansion remain elusive. SIRT6 is a member of the evolutionarily conserved sirtuin family of NAD+ dependent protein deacetylases and plays roles in genomic stability, aging, glucose metabolism and inflammatory response. Here, we show that SIRT6 deficiency in preadipocytes blocked their adipogenesis. Analysis of gene expression during adipogenesis reveals that KIF5C, which belongs to kinesin family, is negatively regulated by SIRT6. Furthermore, we show that KIF5C is a negative factor for adipogenesis through interacting with CK2α’, a catalytic subunit of CK2. This interaction blocks CK2α’ nuclear translocation and CK2 kinase activity, and inhibits mitotic clonal expansion during adipogenesis. Thus, SIRT6 acts as an important factor of adipogenesis through inhibiting KIF5C expression and enhancing CK2 kinase activity.
Project description:We attempted to analyze the effect of PRMT1 knockdown in adipogenesis.3T3-L1 preadipocytes were used to investigate aipogenesis in vitro. Analysis of the transcriptomics from siNC and siPRMT1 3T3-L1 cells at MDI induction for 24 h and 72 h provides new insight into the collective roles of PRMT1 in mitotic clonal expansion and adipocyte differentiation.
Project description:Differentiation of 3T3-L1 cells into adipocytes involves a highly orchestrated series of events including clonal expansion, growth arrest and terminal differentiation. The mechanisms coordinating these different steps are not yet fully understood. Here we investigated whether micro (mi)RNAs play a role in this process. Microarray analysis was performed to detect miRNA expression during 3T3-L1 preadipocyte differentiation. Several miRNAs, including let-7, were up-regulated during 3T3-L1 adipogenesis. Ectopic introduction of let-7 into 3T3-L1 cells inhibited clonal expansion as well as terminal differentiation. The mRNA encoding high mobility group AT-hook 2 (HMGA2), a transcription factor that regulates growth and proliferation in other contexts, was inversely correlated with let-7 levels during 3T3-L1 cell adipogenesis, and let-7 markedly reduced HMGA2 concentrations. Knockdown of HMGA2 inhibited 3T3-L1 differentiation. These results suggest that let-7 plays an important role in adipocyte differentiation and that it does so in part by targeting HMGA2, thereby regulating the transition from clonal expansion to terminal differentiation. 3T3-L1 cells were induced to differentiation into mature adipocytes using a canonical DMI cocktail. The time point at two days after confluency of 3T3-L1 was defined as day 0. Samples were collected at day 0, day 1, day 4, and day 7. The expression of microRNAs at day 1, day 4, and day 7 was compared to that of day 0.
Project description:Pericentric heterochromatin silencing at mammalian centromeres is essential for mitotic fidelity and genomic stability. Defective pericentric silencing is observed in senescent cells, aging tissues, and mammalian tumors, but the underlying mechanisms and functional consequences of these defects are unclear. Here, we uncover a pivotal role of the human SIRT6 enzyme in pericentric transcriptional silencing, and this function protects against mitotic defects, genomic instability, and cellular senescence. At pericentric heterochromatin, SIRT6 promotes deacetylation of a new substrate, histone H3 lysine K18 (H3K18), and inactivation of SIRT6 in cells leads to H3K18 hyperacetylation and aberrant accumulation of pericentric transcripts. Strikingly, RNAi-depletion of these transcripts rescues the mitotic and senescence phenotypes of SIRT6-deficient cells. Together, our findings reveal a new function for SIRT6 and H3K18Ac regulation at heterochromatin, and demonstrate the pathogenic role of de-regulated pericentric transcription in aging- and cancer- related cellular dysfunction. H3K18ac, H3K9ac, H3K9me3, H3K56ac and Input ChIP-seq for U2OS cell
Project description:Differentiation of 3T3-L1 cells into adipocytes involves a highly orchestrated series of events including clonal expansion, growth arrest and terminal differentiation. The mechanisms coordinating these different steps are not yet fully understood. Here we investigated whether micro (mi)RNAs play a role in this process. Microarray analysis was performed to detect miRNA expression during 3T3-L1 preadipocyte differentiation. Several miRNAs, including let-7, were up-regulated during 3T3-L1 adipogenesis. Ectopic introduction of let-7 into 3T3-L1 cells inhibited clonal expansion as well as terminal differentiation. The mRNA encoding high mobility group AT-hook 2 (HMGA2), a transcription factor that regulates growth and proliferation in other contexts, was inversely correlated with let-7 levels during 3T3-L1 cell adipogenesis, and let-7 markedly reduced HMGA2 concentrations. Knockdown of HMGA2 inhibited 3T3-L1 differentiation. These results suggest that let-7 plays an important role in adipocyte differentiation and that it does so in part by targeting HMGA2, thereby regulating the transition from clonal expansion to terminal differentiation.
Project description:PPARγ is a master transcriptional regulator of adipogenesis. Hence, the identification of PPARγ coactivators should help reveal mechanisms controlling gene expression in adipose tissue development and physiology. We show that the non-coding RNA Steroid receptor RNA Activator, SRA, associates with PPARγ and coactivates PPARγ-dependent reporter gene expression. Overexpression of SRA in ST2 adipocyte precursor cells promotes their differentiation into adipocytes. Conversely, knockdown of endogenous SRA inhibits 3T3-L1 preadipocyte differentiation. Microarray analysis reveals hundreds of SRA-responsive genes in adipocytes, including genes in cell cycle, insulin and TNFα signaling pathways. Some functions of SRA may involve mechanisms other than coactivation of PPARγ. SRA increases insulin-stimulated glucose uptake in adipocytes. SRA promotes S-phase entry during mitotic clonal expansion, decreases expression of cyclin-dependent kinase inhibiters p21Cip1 and p27Kip1, and increases phosphorylation of Cdk1/Cdc2. SRA also inhibits the TNFα-induced phosphorylation of c-Jun NH2-terminal kinase. In conclusion, SRA enhances adipogenesis and adipocyte function through multiple pathways.
Project description:PPARM-NM-3 is a master transcriptional regulator of adipogenesis. Hence, the identification of PPARM-NM-3 coactivators should help reveal mechanisms controlling gene expression in adipose tissue development and physiology. We show that the non-coding RNA Steroid receptor RNA Activator, SRA, associates with PPARM-NM-3 and coactivates PPARM-NM-3-dependent reporter gene expression. Overexpression of SRA in ST2 adipocyte precursor cells promotes their differentiation into adipocytes. Conversely, knockdown of endogenous SRA inhibits 3T3-L1 preadipocyte differentiation. Microarray analysis reveals hundreds of SRA-responsive genes in adipocytes, including genes in cell cycle, insulin and TNFM-NM-1 signaling pathways. Some functions of SRA may involve mechanisms other than coactivation of PPARM-NM-3. SRA increases insulin-stimulated glucose uptake in adipocytes. SRA promotes S-phase entry during mitotic clonal expansion, decreases expression of cyclin-dependent kinase inhibiters p21Cip1 and p27Kip1, and increases phosphorylation of Cdk1/Cdc2. SRA also inhibits the TNFM-NM-1-induced phosphorylation of c-Jun NH2-terminal kinase. In conclusion, SRA enhances adipogenesis and adipocyte function through multiple pathways. Total RNA was isolated from fully differentiated (MDIT day 4) SRA overexpressing (pMSCV-SRA) and control (pMSCV empty vector) ST2 adipocytes, or fully differentiated (MDIT day 8) shSRA knockdown (pSuperior-shSRA) or shControl (pSuperior-shcontrol) 3T3-L1 adipocytes. Genome wide gene expression analysis was performed using Affymetrix mouse genome 430 2.0 arrays. Triplicate samples were analyzed.
Project description:Changes of gene expression in primary cell cultures of salmon adipose-derived stromal-vascular fraction were studied at six time-points that covered the key differentiation events: confluence, clonal expansion, determination and establishment of the mature adipocyte phenotype.
Project description:Pericentric heterochromatin silencing at mammalian centromeres is essential for mitotic fidelity and genomic stability. Defective pericentric silencing is observed in senescent cells, aging tissues, and mammalian tumors, but the underlying mechanisms and functional consequences of these defects are unclear. Here, we uncover a pivotal role of the human SIRT6 enzyme in pericentric transcriptional silencing, and this function protects against mitotic defects, genomic instability, and cellular senescence. At pericentric heterochromatin, SIRT6 promotes deacetylation of a new substrate, histone H3 lysine K18 (H3K18), and inactivation of SIRT6 in cells leads to H3K18 hyperacetylation and aberrant accumulation of pericentric transcripts. Strikingly, RNAi-depletion of these transcripts rescues the mitotic and senescence phenotypes of SIRT6-deficient cells. Together, our findings reveal a new function for SIRT6 and H3K18Ac regulation at heterochromatin, and demonstrate the pathogenic role of de-regulated pericentric transcription in aging- and cancer- related cellular dysfunction.
Project description:The temporal order of DNA replication along chromosomes is reorganized in the context of cell differentiation and disease states and is thought to reflect transcriptional competence of the genome. During differentiation of mouse 3T3-L1 cells into adipocytes, cells undergo one or two rounds of cell division called mitotic clonal expansion (MCE). MCE is an essential step for adipogenesis; however, little is known about the regulation of DNA replication during this period. Here, we performed genome-wide mapping of replication timing (RT) in mouse 3T3-L1 cells before and during MCE and identified a number of chromosomal regions shifting toward either earlier or later replication through two rounds of replication. These RT changes were confirmed in individual cells by single-cell DNA replication sequencing. Coordinate changes between a shift toward earlier replication and transcriptional activation of adipogenesis-associated genes were observed. RT changes occur before full expression of these genes, indicating that RT reorganization may contribute to the mature adipocyte phenotype. To support this, cells undergoing two rounds of DNA replication during MCE have higher potential to differentiate into lipid droplet-accumulating adipocytes, compared with cells undergoing a single round of DNA replication and non-replicating cells.