Project description:Caloric restriction (CR) slows the ageing process in many orgamisms, including mice. Liver is an important metabolic organ with active RNA expression. CR reprogrammes hepatic metabolism as well as hepatic transcriptome. We sought to study CR-induced transcriptomic changes in mouse liver to investigate the anti-ageing mechanisms of CR.
Project description:The ability of chromatin to switch back and forth from open euchromatin to closed heterochromatin is vital for transcriptional regulation and genomic stability, and subject to disruption by exposure to environmental agents such as hexavalent chromium. Cr(VI) exposure can cause chromosomal disruption through formation of Cr-DNA adducts, free radical-induced DNA damage, and DNA-Cr-protein and DNA-Cr-DNA cross-links, all of which may disrupt chromatin remodeling mechanisms responsible for maintenance or controlled modification of epigenetic homeostasis. In addition, dose-response analyses have shown that acute exposures to high-concentrations of Cr(VI) and chronic exposures to low-concentrations of the same agent lead to significantly different transcriptomic and genomic stability outcomes. To investigate how transcriptional responses to chromium exposure might correlate to structural changes in chromatin, we have used whole genome Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) analysis coupled with deep sequencing to identify regions of the genome that switch from open to closed chromatin or vice versa in response to exposure to varying Cr(VI) concentrations. We find that the switch affects gene expression levels in the target areas that vary depending on Cr(VI) concentration. At either Cr(VI) concentration, chromatin domains surrounding binding sites for AP-1 transcription factors become significantly open, treatment whereas BACH2 and CTCF binding sites are open solely at the low and high concentrations, respectively. Our results suggest that FAIRE may be a useful technique to map chromatin elements targeted by DNA damaging agents for which there is no prior knowledge of their specificity, and to identify subsequent transcriptomic changes induced by those agents.
Project description:To provide a robust understanding of a transcriptomic change by short-term CR at body fat of mice, we applied three serial strengths of CR to mice including 15%, 30%, and 45% reduction of carbon source. Using Affymetrix mouse 1.0 ST array platform, we obtained and analyzed the transcriptome data for significantly changed genes in expression. Here, we identified 446 genes and categorized the genes based on their biological roles. We observed gradual down-regulation of several signaling pathways including insulin/insulin-like growth factor (IGF) 1, epidermal growth factor (EGF), transforming growth factor beta (TGF-β) and canonical Wingless-type mouse mammary tumor virus integration site (Wnt) signaling according to the CR strengths. Many genes related to structural feature including extracellular matrix (ECM), cell adhesion and cytoskeleton were also down-regulated with a strong correlation to the serial CR treatments. Furthermore, genes for cell cycle and adipogenesis were down-regulated. According to previous studies, these are target functions of the aforementioned four signaling pathways. On the other hand, the genes for specific metabolic features including tricarboxylic acid (TCA) cycle and electron transport chain (ETC) exhibited a transcriptional increase. In addition, adipose tissue expansion markers such as leptin, Mesoderm specific transcript (Mest) and Secreted frizzled-related sequence protein 5 (Sfrp5), and most genes for transport and immune response showed a down-regulation by CR. Comparing gene expression profiles to understand transcriptomic changes of adipose tissue by serial strength (15%, 30%, and 45%) of short-term (10 weeks) caloric restriction to young age (18 weeks) mice (n=3 in each group).