University of Fribourg

About: University of Fribourg is a education organization based out in Fribourg, Freiburg, Switzerland. It is known for research contribution in the topics: Population & Glacier. The organization has 6040 authors who have published 14975 publications receiving 542500 citations. The organization is also known as: UNIFR & Universität Freiburg.

Rhythmic CLOCK-BMAL1 binding to multiple E-box motifs drives circadian Dbp transcription and chromatin transitions.

Abstract: Mammalian circadian rhythms are based on transcriptional and post-translational feedback loops. Essentially, the activity of the transcription factors BMAL1 (also known as MOP3) and CLOCK is rhythmically counterbalanced by Period (PER) and Cryptochrome (CRY) proteins to govern time of day-dependent gene expression. Here we show that circadian regulation of the mouse albumin D element-binding protein (Dbp) gene involves rhythmic binding of BMAL1 and CLOCK and marked daily chromatin transitions. Thus, the Dbp transcription cycle is paralleled by binding of BMAL1 and CLOCK to multiple extra- and intragenic E boxes, acetylation of Lys9 of histone H3, trimethylation of Lys4 of histone H3 and a reduction of histone density. In contrast, the antiphasic daily repression cycle is accompanied by dimethylation of Lys9 of histone H3, the binding of heterochromatin protein 1alpha and an increase in histone density. The rhythmic conversion of transcriptionally permissive chromatin to facultative heterochromatin relies on the presence of functional BMAL1-CLOCK binding sites.

A Unified Classification of Alien Species Based on the Magnitude of their Environmental Impacts

Abstract: Species moved by human activities beyond the limits of their native geographic ranges into areas in which they do not naturally occur (termed aliens) can cause a broad range of significant changes to recipient ecosystems; however, their impacts vary greatly across species and the ecosystems into which they are introduced. There is therefore a critical need for a standardised method to evaluate, compare, and eventually predict the magnitudes of these different impacts. Here, we propose a straightforward system for classifying alien species according to the magnitude of their environmental impacts, based on the mechanisms of impact used to code species in the International Union for Conservation of Nature (IUCN) Global Invasive Species Database, which are presented here for the first time. The classification system uses five semi-quantitative scenarios describing impacts under each mechanism to assign species to different levels of impact-ranging from Minimal to Massive-with assignment corresponding to the highest level of deleterious impact associated with any of the mechanisms. The scheme also includes categories for species that are Not Evaluated, have No Alien Population, or are Data Deficient, and a method for assigning uncertainty to all the classifications. We show how this classification system is applicable at different levels of ecological complexity and different spatial and temporal scales, and embraces existing impact metrics. In fact, the scheme is analogous to the already widely adopted and accepted Red List approach to categorising extinction risk, and so could conceivably be readily integrated with existing practices and policies in many regions.

The clock gene Per2 influences the glutamatergic system and modulates alcohol consumption.

Abstract: Period (Per) genes are involved in regulation of the circadian clock and are thought to modulate several brain functions. We demonstrate that Per2Brdm1 mutant mice, which have a deletion in the PAS domain of the Per2 protein, show alterations in the glutamatergic system. Lowered expression of the glutamate transporter Eaat1 is observed in these animals, leading to reduced uptake of glutamate by astrocytes. As a consequence, glutamate levels increase in the extracellular space of Per2Brdm1 mutant mouse brains. This is accompanied by increased alcohol intake in these animals. In humans, variations of the PER2 gene are associated with regulation of alcohol consumption. Acamprosate, a drug used to prevent craving and relapse in alcoholic patients is thought to act by dampening a hyper-glutamatergic state. This drug reduced augmented glutamate levels and normalized increased alcohol consumption in Per2Brdm1 mutant mice. Collectively, these data establish glutamate as a link between dysfunction of the circadian clock gene Per2 and enhanced alcohol intake.

The 2003 heat wave in Europe: A shape of things to come? An analysis based on Swiss climatological data and model simulations

Abstract: [1] The 2003 heat wave that affected much of Europe from June to September bears a close resemblance to what many regional climate models are projecting for summers in the latter part of the 21st century. Model results suggest that under enhanced atmospheric greenhouse-gas concentrations, summer temperatures are likely to increase by over 4°C on average, with a corresponding increase in the frequency of severe heat waves. Statistical features of the 2003 heat wave for the Swiss site of Basel are investigated and compared to both past, 20th century events and possible future extreme temperatures based on model simulations of climatic change. For many purposes, the 2003 event can be used as an analog of future summers in coming decades in climate impacts and policy studies.