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Research Containing: Animals

Coactivator-Dependent Oscillation of Chromatin Accessibility Dictates Circadian Gene Amplitude via REV-ERB Loading

by on 22 August 2016in Biology & Biotechnology No comment

A central mechanism for controlling circadian gene amplitude remains elusive. We present evidence for a "facilitated repression (FR)" model that functions as an amplitude rheostat for circadian gene oscillation. We demonstrate that ROR and/or BMAL1 promote global chromatin decondensation during the activation phase of the circadian cycle to actively facilitate REV-ERB loading for repression of circadian gene expression. Mechanistically, we found that SRC-2 dictates global circadian chromatin remodeling through spatial and temporal recruitment of PBAF members of the SWI/SNF complex to facilitate loading of REV-ERB in the hepatic genome. Mathematical modeling highlights how the FR model sustains proper circadian rhythm despite fluctuations of REV-ERB levels. Our study not only reveals a mechanism for active communication between the positive and negative limbs of the circadian transcriptional loop but also establishes the concept that clock transcription factor binding dynamics is perhaps a central tenet for fine-tuning circadian rhythm.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26611104

SRC-2 is an essential coactivator for orchestrating metabolism and circadian rhythm

by on 22 August 2016in Biology & Biotechnology No comment

Synchrony of the mammalian circadian clock is achieved by complex transcriptional and translational feedback loops centered on the BMAL1:CLOCK heterodimer. Modulation of circadian feedback loops is essential for maintaining rhythmicity, yet the role of transcriptional coactivators in driving BMAL1:CLOCK transcriptional networks is largely unexplored. Here, we show diurnal hepatic steroid receptor coactivator 2 (SRC-2) recruitment to the genome that extensively overlaps with the BMAL1 cistrome during the light phase, targeting genes that enrich for circadian and metabolic processes. Notably, SRC-2 ablation impairs wheel-running behavior, alters circadian gene expression in several peripheral tissues, alters the rhythmicity of the hepatic metabolome, and deregulates the synchronization of cell-autonomous metabolites. We identify SRC-2 as a potent coregulator of BMAL1:CLOCK and find that SRC-2 targets itself with BMAL1:CLOCK in a feedforward loop. Collectively, our data suggest that SRC-2 is a transcriptional coactivator of the BMAL1:CLOCK oscillators and establish SRC-2 as a critical positive regulator of the mammalian circadian clock.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/24529706

Space Environmental Factor Impacts upon Murine Colon Microbiota and Mucosal Homeostasis

by on 22 August 2016in Biology & Biotechnology No comment

Astronaut intestinal health may be impacted by microgravity, radiation, and diet. The aim of this study was to characterize how high and low linear energy transfer (LET) radiation, microgravity, and elevated dietary iron affect colon microbiota (determined by 16S rDNA pyrosequencing) and colon function. Three independent experiments were conducted to achieve these goals: 1) fractionated low LET gamma radiation (137Cs, 3 Gy, RAD), high Fe diet (IRON) (650 mg/kg diet), and a combination of low LET gamma radiation and high Fe diet (IRON+RAD) in male Sprague-Dawley rats; 2) high LET 38Si particle exposure (0.050 Gy), 1/6 G partial weight bearing (PWB), and a combination of high LET38Si particle exposure and PWB in female BalbC/ByJ mice; and 3) 13 d spaceflight in female C57BL/6 mice. Low LET radiation, IRON and spaceflight increased Bacteroidetes and decreased Firmicutes. RAD and IRON+RAD increased Lactobacillales and lowered Clostridiales compared to the control (CON) and IRON treatments. Low LET radiation, IRON, and spaceflight did not significantly affect diversity or richness, or elevate pathogenic genera. Spaceflight increased Clostridiales and decreased Lactobacillales, and similar trends were observed in the experiment using a ground-based model of microgravity, suggesting altered gravity may affect colonic microbiota. Although we noted no differences in colon epithelial injury or inflammation, spaceflight elevated TGFbeta gene expression. Microbiota and mucosal characterization in these models is a first step in understanding the impact of the space environment on intestinal health.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26083373

In vitro organogenesis from pluripotent stem cells

by on 22 August 2016in Biology & Biotechnology No comment

Pluripotent stem cells (PSCs) have the ability to spontaneously generate structured tissues in vitro reminiscent of embryonic tissue development. Recently, complex organoids such as cortical tissues, cerebral brain organoids, optical cups, intestinal tissues, and liver buds have been generated from PSCs derived from healthy individuals and patients with genetic diseases, providing powerful tools to understand morphogenesis and disease pathology. This article highlights recent advances in the state-of-art generation of organoids from PSCs, possible signaling pathways and mechanisms involved in organogenesis, and the understanding of extracellular microenvironment. Challenges involved in the organoid generation such as increasing organoid size, enhancing the tissue complexity, and improving functional maturation are also discussed.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/24762764

Effects of microgravity on the mouse triceps brachii muscle

by on 22 August 2016in Biology & Biotechnology No comment

INTRODUCTION: In this study we investigated the effects of microgravity on the fiber properties of the mouse triceps brachii, a forelimb muscle that has no antigravity function. METHODS: Mice (n = 7) were exposed to microgravity for 13 days on the space shuttle Atlantis (Space Transportation System-135). The fiber cross-sectional area (CSA) and succinate dehydrogenase (SDH) staining intensity of the triceps brachii muscle were compared with those of controls (n = 7). SDH activity in this muscle was also estimated. RESULTS: Microgravity did not affect the body weight, muscle weight, or fiber CSA, but there was reduced SDH staining intensity of all types of fibers, irrespective of the muscle region (P < 0.05). Microgravity also reduced muscle SDH activity (P < 0.05). CONCLUSIONS: Short-term exposure to microgravity induced a decrease in oxidative capacity, but not atrophy, in the triceps brachii muscle of mice. Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/25307981

SRC-2 orchestrates polygenic inputs for fine-tuning glucose homeostasis

by on 22 August 2016in Biology & Biotechnology No comment

Despite extensive efforts to understand the monogenic contributions to perturbed glucose homeostasis, the complexity of genetic events that fractionally contribute to the spectrum of this pathology remain poorly understood. Proper maintenance of glucose homeostasis is the central feature of a constellation of comorbidities that define the metabolic syndrome. The ability of the liver to balance carbohydrate uptake and release during the feeding-to-fasting transition is essential to the regulation of peripheral glucose availability. The liver coordinates the expression of gene programs that control glucose absorption, storage, and secretion. Herein, we demonstrate that Steroid Receptor Coactivator 2 (SRC-2) orchestrates a hierarchy of nutritionally responsive transcriptional complexes to precisely modulate plasma glucose availability. Using DNA pull-down technology coupled with mass spectrometry, we have identified SRC-2 as an indispensable integrator of transcriptional complexes that control the rate-limiting steps of hepatic glucose release and accretion. Collectively, these findings position SRC-2 as a major regulator of polygenic inputs to metabolic gene regulation and perhaps identify a previously unappreciated model that helps to explain the clinical spectrum of glucose dysregulation.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26487680

Spaceflight impairs antigen-specific tolerance induction in vivo and increases inflammatory cytokines

by on 22 August 2016in Biology & Biotechnology No comment

The health risks of a dysregulated immune response during spaceflight are important to understand as plans emerge for humans to embark on long-term space travel to Mars. In this first-of-its-kind study, we used adoptive transfer of T-cell receptor transgenic OT-II CD4 T cells to track an in vivo antigen-specific immune response that was induced during the course of spaceflight. Experimental mice destined for spaceflight and mice that remained on the ground received transferred OT-II cells and cognate peptide stimulation with ovalbumin (OVA) 323-339 plus the inflammatory adjuvant, monophosphoryl lipid A. Control mice in both flight and ground cohorts received monophosphoryl lipid A alone without additional OVA stimulation. Numbers of OT-II cells in flight mice treated with OVA were significantly increased by 2-fold compared with ground mice treated with OVA, suggesting that tolerance induction was impaired by spaceflight. Production of proinflammatory cytokines were significantly increased in flight compared with ground mice, including a 5-fold increase in IFN-gamma and a 10-fold increase in IL-17. This study is the first to show that immune tolerance may be impaired in spaceflight, leading to excessive inflammatory responses.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26085131

Effects of spaceflight and ground recovery on mesenteric artery and vein constrictor properties in mice

by on 22 August 2016in Biology & Biotechnology No comment

Following exposure to microgravity, there is a reduced ability of astronauts to augment peripheral vascular resistance, often resulting in orthostatic hypotension. The purpose of this study was to test the hypothesis that mesenteric arteries and veins will exhibit diminished vasoconstrictor responses after spaceflight. Mesenteric arteries and veins from female mice flown on the Space Transportation System (STS)-131 (n=11), STS-133 (n=6), and STS-135 (n=3) shuttle missions and respective ground-based control mice (n=30) were isolated for in vitro experimentation. Vasoconstrictor responses were evoked in arteries via norepinephrine (NE), potassium chloride (KCl), and caffeine, and in veins through NE across a range of intraluminal pressures (2-12 cmH(2)O). Vasoconstriction to NE was also determined in mesenteric arteries at 1, 5, and 7 d postlanding. In arteries, maximal constriction to NE, KCl, and caffeine were reduced immediately following spaceflight and 1 d postflight. Spaceflight also reduced arterial ryanodine receptor-3 mRNA levels. In mesenteric veins, there was diminished constriction to NE after flight. The results indicate that the impaired vasoconstriction following spaceflight occurs through the ryanodine receptor-mediated intracellular Ca(2+) release mechanism. Such vascular changes in astronauts could compromise the maintenance of arterial pressure during orthostatic stress.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/23099650

Mechanical unloading of bone in microgravity reduces mesenchymal and hematopoietic stem cell-mediated tissue regeneration

by on 22 August 2016in Biology & Biotechnology No comment

Mechanical loading of mammalian tissues is a potent promoter of tissue growth and regeneration, whilst unloading in microgravity can cause reduced tissue regeneration, possibly through effects on stem cell tissue progenitors. To test the specific hypothesis that mechanical unloading alters differentiation of bone marrow mesenchymal and hematopoietic stem cell lineages, we studied cellular and molecular aspects of how bone marrow in the mouse proximal femur responds to unloading in microgravity. Trabecular and cortical endosteal bone surfaces in the femoral head underwent significant bone resorption in microgravity, enlarging the marrow cavity. Cells isolated from the femoral head marrow compartment showed significant down-regulation of gene expression markers for early mesenchymal and hematopoietic differentiation, including FUT1(-6.72), CSF2(-3.30), CD90(-3.33), PTPRC(-2.79), and GDF15(-2.45), but not stem cell markers, such as SOX2. At the cellular level, in situ histological analysis revealed decreased megakaryocyte numbers whilst erythrocytes were increased 2.33 fold. Furthermore, erythrocytes displayed elevated fucosylation and clustering adjacent to sinuses forming the marrow-blood barrier, possibly providing a mechanistic basis for explaining spaceflight anemia. Culture of isolated bone marrow cells immediately after microgravity exposure increased the marrow progenitor’s potential for mesenchymal differentiation into in-vitro mineralized bone nodules, and hematopoietic differentiation into osteoclasts, suggesting an accumulation of undifferentiated progenitors during exposure to microgravity. These results support the idea that mechanical unloading of mammalian tissues in microgravity is a strong inhibitor of tissue growth and regeneration mechanisms, acting at the level of early mesenchymal and hematopoietic stem cell differentiation.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/25011075

Sniffing out cancer using the JPL electronic nose: A pilot study of a novel approach to detection and differentiation of brain cancer

by on 9 June 2015in Technology Development & Demonstration No comment

A proof-of-concept study was done to determine whether an electronic nose developed for air quality monitoring at the Jet Propulsion Laboratory (JPL) could be used to distinguish between the odors of organ and tumor tissues, with an eye to using such a device as one of several modes in multi-modal imaging and tumor differentiation during surgery. Hypothesis We hypothesized that the JPL electronic nose (ENose) would be able to distinguish between the odors of various organ and tumor tissues. Materials and methods The odor signatures, or array response, of two organs, chicken heart and chicken liver, and cultured glioblastoma and melanoma tumor cell lines were recorded using the JPL Electronic Nose. The overall array responses were compared to determine whether they were sufficiently different to allow the organs and cell lines to be identified by their array responses. Results The ENose was able to distinguish between the two types of organ tissue and between the two types of tumor cell lines. The variation in array response for the organ tissues was 19% and between the two types of cultured cell lines was 22%. Conclusion This study shows that it is possible to use an electronic nose to distinguish between two types of tumor cells and between two types of organ tissue. As we conducted the experiment with a sensor array built for air quality monitoring rather than for medical purposes, it may be possible to select an array that is optimized to distinguish between different types of cells and organ tissues. Further focused studies are needed to investigate the odor signatures of different cells as well as cellular proliferation, growth, differentiation and infiltration.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S105381190900370X