Project description:Background: The in vivo gene response associated with hyperthermia and subsequent return to homeostasis or development of heat illness is poorly understood. Early activation of gene networks in the heat stress response is likely to lead to the systemic inflammation, multi-organ functional impairment, and other pathophysiological states characteristic of heat illness. Here, we perform an unbiased global characterization of the multi-organ gene response using an in vivo model of heat stress in the conscious rat. Results: Rats were subjected to elevated temperatures until implanted thermal probes indicated a maximal core temperature of 41.8 M-BM-0C (Tc,Max). Liver, lung, kidney, and heart were harvested at Tc,Max, 24 hours, and 48 hours after heat stress in groups of experimental animals and time-matched controls kept at ambient temperature. Clinical chemistries suggested abnormal function in liver, kidney, and lung at Tc,Max, and cardiac histopathology at 48 hours supported persistent cardiac damage in 3 out of 6 animals. Microarray analysis identified 78 differentially expressed genes common to all 4 organs at Tc,Max (i.e., the consensus heat stress response). Gene set enrichment analysis of gene ontology terms identified 25 biological processes in 4 general gene ontology categories: protein folding, regulation of apoptosis, response to cytokines, and transcriptional responses. Functional analysis clustering of the 78 differentially expressed genes in the consensus heat stress response also identified functional categories of protein folding and regulation of apoptosis. Self-organizing maps identified gene-specific signatures corresponding to protein folding disorders specific to only heat-stressed rats with histopathologic evidence of cardiac injury at 48 hours. Enrichment analysis of differentially expressed proteins in heat-injured hearts at 48 hours corroborated gene enrichment analysis results. Quantitative proteomics analysis by iTRAQ demonstrated that differential protein expression was not comparable to transcript expression at Tc,Max and 24 hours. However, the profile of differentially expressed proteins closely matched the transcriptomic profile in heat-injured animals at 48 hours. Pathway analysis at both the transcript and protein levels supported catastrophic deficits in energetics and cellular metabolism, chronic proteotoxic response, and activation of the unfolded protein response. Calculation of protein super-saturation scores demonstrated an increased propensity of proteins to aggregate in the hearts of heat-injured animals at 48 hours, consistent with accumulation of misfolded proteins. Conclusions: Global transcriptomic and proteomic analysis identified networks of genes and proteins initiating an unfolded protein response, metabolic dysfunction, and mitochondrial energy crisis in animals with histopathologic evidence of persistent heat injury, providing the basis for a systems-level physiological model of heat illness and recovery. To induce the pathophysiological effects of heat stress, conscious rats were placed in an incubator at 37M-BM-:C and their core temperature was monitored. Animals were sacrificed when their core temperature reached 41.8M-BM-:C (Tc,Max), or they were returned to their normal housing environment and were allowed to recover for up to 24 or 48 hours prior to sacrifice. Time-matched controls were euthanized at times corresponding to Tc,Max, 24 hours, and 48 hours. For each condition n=6 for a total of 36 animals. Four tissues (liver, lung, kidney and heart) were analyzed from each animal for a total of 144 arrays; however a few arrays did not pass QC therefore only 140 are reported here: 34 liver, 35 lung, 36 kidney, or 35 heart.

Project description:Aims/hypothesis: While lipid deposition in skeletal muscle is considered to be involved in obesity-associated insulin resistance, neutral intramyocellular lipid (IMCL) accumulation per se does not necessarily induce insulin resistance. We previously demonstrated that overexpression of the lipid droplet coat protein perilipin 2 augments intramyocellular lipid content while improving insulin sensitivity. Another member of the perilipin family, perilipin 5 (PLIN5), is predominantly expressed in oxidative tissues like skeletal muscle. Here we investigated the effects of PLIN5 overexpression M-bM-^@M-^S in comparison with effects of PLIN2 M-bM-^@M-^S on skeletal muscle lipid levels, gene expression profiles and insulin sensitivity. Methods: Gene electroporation was used to overexpress PLIN5 in tibialis anterior muscle of rats fed a high fat diet. Eight days after electroporation, insulin-mediated glucose uptake in skeletal muscle was measured by means of a hyperinsulinemic euglycemic clamp. Electron microscopy, fluorescence microscopy and lipid extractions were performed to investigate IMCL accumulation. Gene expression profiles were obtained using microarrays. Results: TAG storage and lipid droplet size increased upon PLIN5 overexpression. Despite the higher IMCL content, insulin sensitivity was not impaired and DAG and acylcarnitine levels were unaffected. In contrast to the effects of PLIN2 overexpression, microarray data analysis revealed a gene expression profile favoring FA oxidation and improved mitochondrial function. Conclusions/interpretation: Both PLIN2 and PLIN5 increase neutral IMCL content without impeding insulin-mediated glucose uptake. As opposed to the effects of PLIN2 overexpression, overexpression of PLIN5 in skeletal muscle promoted expression of a cluster of genes under control of PPARM-NM-1 and PGC1M-NM-1 involved in FA catabolism and mitochondrial oxidation. Rats received a high fat diet for 3 weeks; 2 weeks after start of the diet intervention Plin5 (OXPAT) or Plin2 (ADRP) were overexpressed in either the right or left tibialis anterior muscle. One week later pooled tibialis anterior muscle samples were analysed on microarrays.

Project description:Methylation is a repressive modification of DNA prevalent throughout mammalian genomes yet mostly absent at CG rich stretches referred to as CGI. Here we identify their building principles by parallel genomic targeting of sequence libraries. Iterative insertions generated over 3,000 variants of genome-derived and artificial sequences at the same genomic site. Single molecule profiling of the methylation status of this collection allowed modeling the contribution of CG content and DNA binding factors towards the unmethylated state. It made the surprising prediction that the majority of CGs within endogenous islands are susceptible to methylation changes modulated by the presence of transcription factors, which is indeed confirmed by genome-wide methylation dynamics during multiple cellular differentiations. Our model further predicts blocks of constitutively unmethylated CGs independent from TF binding, which have a median size of ~300bp but are only present in half of all islands. Their constitutively unmethylated state is a hallmark of untransformed cells but their increased methylation is a specific and predictive feature of cancer. This study quantifies the two principal mechanisms governing methylation patterns in mammalian genomes. It provides a framework to interpret methylation data across normal and cancer samples and refines the concept of CpG islands. Methylation is a repressive modification of DNA prevalent throughout mammalian genomes yet mostly absent at CG rich stretches referred to as CGI. Here we identify their building principles by parallel genomic targeting of sequence libraries. Iterative insertions generated over 3,000 variants of genome-derived and artificial sequences at the same genomic site. Single molecule profiling of the methylation status of this collection allowed modeling the contribution of CG content and DNA binding factors towards the unmethylated state. It made the surprising prediction that the majority of CGs within endogenous islands are susceptible to methylation changes modulated by the presence of transcription factors, which is indeed confirmed by genome-wide methylation dynamics during multiple cellular differentiations. Our model further predicts blocks of constitutively unmethylated CGs independent from TF binding, which have a median size of ~300bp but are only present in half of all islands. Their constitutively unmethylated state is a hallmark of untransformed cells but their increased methylation is a specific and predictive feature of cancer. This study quantifies the two principal mechanisms governing methylation patterns in mammalian genomes. It provides a framework to interpret methylation data across normal and cancer samples and refines the concept of CpG islands. Libraries of DNA sequences were constructed either by mouse genome (129S6) or E.coli genome (NC_010473.1) subrepresentation or custom synthesis. DNA fragments were inserted into the genome of mouse embryonic stem cells by recombination mediated casette exchange (RMCE) at the B-globin locus. Methylation status of the inserted DNA sequences was profiled by bisulfite sequencing using a pair of universal primers flanking the fragments.

Project description:Abstract; Background: Gene transfer by electroporation (electro gene transfer) to muscle results in high level long term transgenic expression, showing great promise for treatment of e.g. protein deficiency syndromes. However little is known about the effects of electro gene transfer on muscle fibres. We have therefore investigated transcriptional changes through gene expression profile analyses, as well as morphological changes evaluated by histological analysis. Electro gene transfer was obtained using a combination of a short high voltage pulse (HV, 1000 V/cm, 100 @s) followed by a long low voltage pulse (LV, 100 V/cm, 400 ms); a pulse combination optimised for efficient and safe gene transfer. Muscles were transfected with green fluorescent protein (GFP) and excised at 4 hours, 48 hours or 3 weeks after treatment. Results: Differentially expressed genes were investigated by microarray analysis, and descriptive statistics were performed to evaluate the effects of 1) electroporation, 2) DNA injection, and 3) time after treatment. The biological significance of the results was assessed by gene annotation and supervised cluster analysis. Generally, electroporation caused down-regulation of structural proteins e.g. sarcospan and catalytic en-zymes such as phosphoenolpuryvate carboxykinase. Injection of DNA induced down-regulation of intracellular transport proteins e.g. sentrin. The effects on muscle fibres were transient as the expression profiles 3 weeks after treatment were closely related with the control muscles. Most interestingly, no changes in the expression of proteins involved in inflammatory responses or muscle regeneration was detected, indicating limited muscle damage and regeneration. Histological analysis revealed structural changes with loss of cell integrity and striation pattern in some fibres after DNA+HV+LV treatment, while electroporation alone caused minor loss of striation pattern but preservation of cell integrity. Conclusion: The small and transient changes found in the gene expression profiles are of great importance, as this demonstrates that electro gene transfer is safe with minor effects on the muscle host cells. These findings are essential for introducing the electro gene transfer to muscle for clinical use. Indeed the HV+LV pulse combination used have been optimised to ensure highly efficient and safe electro gene transfer. Experiment Overall Design: The mice did recieve to their tibialis cranialis muscle either No tretment/control (CTRL), Electroporation only (EP), Plasmid injection only (DNA) or Plasmid DNA and in vivo Electro gene transfer (EP+DNA). Experiment Overall Design: Four hrs, 48 hrs and 3 weeks after treatment the mice were euthanized and the expression profile of the treated muscles were analysed. Experiment Overall Design: The following number of mice were included: Experiment Overall Design: CTRL, 3 mice, Experiment Overall Design: EP at 4 hrs, 1 mouse, Experiment Overall Design: EP at 48 hrs, 1 mouse, Experiment Overall Design: EP at 3 weeks, 1 mouse, Experiment Overall Design: DNA at 4 hrs, 1 mouse, Experiment Overall Design: DNA at 48 hrs, 1 mouse, Experiment Overall Design: DNA at 3 weeks, 1 mouse, Experiment Overall Design: EP+DNA at 4 hrs, 2 mice, Experiment Overall Design: EP+DNA at 48 hrs, 1 mouse, Experiment Overall Design: EP+DNA at 3 weeks, 1 mouse. Experiment Overall Design: A total number of mice 13.

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Overexpression of clock output factor DBP in skeletal muscle of a rat.

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