Tgif1 is a transcriptional corepressor that limits TGF responsive gene expression. TGF signaling has antiproliferative effects in several cell types, generally resulting in a G1 arrest. Mouse embryo fibroblasts (MEFs) are primary cells with limited life-span, that senesce after several passages in culture.
Premature senescence and increased TGFβ signaling in the absence of Tgif1.
Specimen part
View SamplesGlis3 mutant mice (Glis3zf/zf) die within the first week after birth due to overt diabetes, evidenced by hyperglycemia and hypoinsulinemia. Histopathological analysis showed that Glis3zf/zf mice develop a pancreatic phenotype with a dramatic loss of beta- (insulin) and delta- (somatostatin) cells contrasting a smaller relative loss of alpha- (glucagon), PP- (pancreatic polypeptide), and epsilon- (ghrelin) cells. Glis3zf/zf mice develop ductal cysts with decreased number of primary cilia, while the acini are not significantly affected. Gene expression profiling by microarray analysis demonstrated that the expression of terminal hormonal genes and several transcription factors important in endocrine development were significantly deregulated in Glis3zf/zf mice. During pancreatic development, Glis3 mRNA expression is induced during the secondary transition, a stage of cell lineage specification and extensive patterning. Changes in pancreatic development of Glis3zf/zf mice are noted during and after this stage. The population of pancreatic progenitors appears not to be greatly affected in Glis3zf/zf mice; however, the number of neurogenin 3 (Ngn3) positive, endocrine progenitors is significantly reduced. Our study indicates that Glis3 plays a key role in cell lineage specification, particularly the development of mature pancreatic beta-cells. In addition, we identified evidence that Glis3 regulates insulin gene expression through two Glis-binding sites in its proximal promoter indicating that Glis3 is a regulator of insulin gene expression.
Transcription factor Glis3, a novel critical player in the regulation of pancreatic beta-cell development and insulin gene expression.
Specimen part
View SamplesGene expression of Ethanol-treated hepatocytes from WT and transglutaminase 2 knockout mice
Role of transglutaminase 2 in liver injury via cross-linking and silencing of transcription factor Sp1.
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View SamplesImbalances in glucose and energy homeostasis are at the core of the worldwide epidemic of obesity and diabetes. Here, we illustrate an important role of the TGF-beta/Smad3 signaling pathway in regulating glucose and energy homeostasis. Smad3 deficient mice are protected from diet-induced obesity and diabetes. Interestingly, the metabolic protection is accompanied by Smad3-/- white adipose tissue acquiring the bioenergetic and gene expression profile of brown fat/skeletal muscle. Smad3-/- adipocytes demonstrate a marked increase in mitochondrial biogenesis, with a corresponding increase in basal respiration, and Smad3 acts as a repressor of PGC-alpha1 expression. We observe significant correlation between TGF-beta1 levels and adiposity in rodents and humans. Further, systemic blockade of TGF-beta1 signaling protects mice from obesity, diabetes and hepatic steatosis. Together, these results demonstrate that TGF-beta signaling regulates glucose tolerance and energy homeostasis and suggest that modulation of TGF-beta1 activity might be an effective treatment strategy for obesity and diabetes.
Protection from obesity and diabetes by blockade of TGF-β/Smad3 signaling.
Treatment
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