Project description:PPAR? promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is selectively enriched on the entire PPAR? locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPAR?. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of the early adipogenic transcription factor C/EBP? to PPAR? promoter, which promotes PPAR? expression. Interestingly, G9a represses PPAR? expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPAR? expression and facilitating Wnt10a expression, G9a represses adipogenesis.
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis. Examination of gene expression changes in G9a KO brown preadipocytes
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis.
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis.
Project description:PPAR? promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPAR? locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPAR?. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPAR? promoter, which promotes PPAR? expression. Interestingly, G9a represses PPAR? expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPAR? expression and facilitating Wnt10a expression, G9a represses adipogenesis. Examination of 3 different histone modification changes in 3T3-L1 preadipocytes
Project description:G9a is a histone methyltransferase that catalyzes the methylation of histone 3 lysine 9 (H3K9), which is involved in the regulation of gene expression. We had previously reported that G9a is expressed in developing tendons in vivo and in vitro and that G9a-deficient tenocytes show impaired proliferation and differentiation in vitro. In this study, we investigated the functions of G9a in tendon development in vivo by using G9a conditional knockout (G9a cKO) mice. We crossed Sox9Cre/+ mice with G9afl/fl mice to generate G9afl/fl; Sox9Cre/+ mice. The G9a cKO mice showed hypoplastic tendon formation at 3 weeks of age. Bromodeoxyuridine labeling on embryonic day 16.5 (E16.5) revealed decreased cell proliferation in the tenocytes of G9a cKO mice. Immunohistochemical analysis revealed decreased expression levels of G9a and its substrate, H3K9me2, in the vertebral tendons of G9a cKO mice. The tendon tissue of the vertebrae and limbs of G9a cKO mice showed reduced expression of a tendon marker, tenomodulin (Tnmd), and col1a1 genes, suggesting that tenocyte differentiation was suppressed. Overexpression of G9a resulted in enhancement of Tnmd and col1a1 expression in tenocytes in vitro. These results suggest that G9a regulates the proliferation and differentiation of tendon progenitor cells during tendon development. Thus, our results suggest that G9a plays an essential role in tendon development.
Project description:Previous studies have shown that tri- or di-methylation of histone H3 at lysine 9 (H3K9me3/me2) on the promoter of the peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα) contribute to the repression of PPARγ and C/EBPα and inhibition of adipogenesis in 3T3-L1 preadipocytes. The balance of histone methylation is regulated by histone methyltransferases and demethylases. However, it is poorly understood which demethylases are responsible for removing H3K9me3/me2 on the promoter of PPARγ and C/EBPα. JMJD2B is a H3K9me3/me2 demethylase that was previously shown to activate adipogenesis by promoting mitotic clonal expansion. Nevertheless, it remains unclear whether JMJD2B plays a role in the regulation of adipogenesis by removing H3K9me3/me2 on the promoter of PPARγ and C/EBPα and subsequently activating PPARγ and C/EBPα expression. Here, we showed that JMJD2B decreased H3K9me3/me2 on the promoter of PPARγ and C/EBPα, which in turn stimulated the expression of PPARγ and C/EBPα. JMJD2B knockdown using siRNA in 3T3-L1 preadipocytes repressed the expression of PPARγ and C/EBPα, resulting in inhibition of adipogenesis. This was accompanied by increased enrichment of H3K9me3/me2 on the promoter of PPARγ and C/EBPα. In contrast, overexpression of JMJD2B increased the expression of PPARγ and C/EBPα, which was accompanied by decreased enrichment of H3K9me3/me2 on the promoter and activated adipogenesis. Together, these results indicate that JMJD2B regulates PPARγ and C/EBPα during adipogenesis.
Project description:Wnt/beta-catenin signaling inhibits adipogenesis. Genome-wide profiling studies have revealed the enrichment of histone H3K27 methyltransferase Ezh2 on Wnt genes. However, the functional significance of such a direct link between the two types of developmental regulators in mammalian cells, and the role of Ezh2 in adipogenesis, remain unclear. Here we show Ezh2 and its H3K27 methyltransferase activity are required for adipogenesis. Ezh2 directly represses Wnt1, -6, -10a, and -10b genes in preadipocytes and during adipogenesis. Deletion of Ezh2 eliminates H3K27me3 on Wnt promoters and derepresses Wnt expression, which leads to activation of Wnt/beta-catenin signaling and inhibition of adipogenesis. Ectopic expression of the wild-type (WT) Ezh2, but not the enzymatically inactive F667I mutant, prevents the loss of H3K27me3 and the defects in adipogenesis in Ezh2(-/-) preadipocytes. The adipogenesis defects in Ezh2(-/-) cells can be rescued by expression of adipogenic transcription factors PPARgamma, C/EBPalpha, or inhibitors of Wnt/beta-catenin signaling. Interestingly, Ezh2(-/-) cells show marked increase of H3K27 acetylation globally as well as on Wnt promoters. These results indicate that H3K27 methyltransferase Ezh2 directly represses Wnt genes to facilitate adipogenesis and suggest that acetylation and trimethylation on H3K27 play opposing roles in regulating Wnt expression.
Project description:The discovery of Suv39h1, the first SET domain-containing histone lysine methyltransferase (HKMT), was reported in 2000. Since then, research on histone methylation has progressed rapidly. Among the identified HKMTs in mammals, G9a and GLP are the primary enzymes for mono- and dimethylation at Lys 9 of histone H3 (H3K9me1 and H3K9me2), and exist predominantly as a G9a-GLP heteromeric complex that appears to be a functional H3K9 methyltransferase in vivo. Recently, many important studies have reported that G9a and GLP play critical roles in various biological processes. The physiological relevance of G9a/GLP-mediated epigenetic gene regulation is discussed.