A transcriptional and regulatory map of mouse somite maturation

The mammalian body plan is shaped by rhythmic segmentation of mesoderm into somites, which are transient embryonic structures that form down each side of the neural tube. We have analyzed the genome-wide transcriptional and chromatin dynamics occurring within nascent somites, from early inception of somitogenesis to the latest stages of body plan establishment. We created matched gene expression and open chromatin maps for the three leading pairs of somites at six time points during mouse embryonic development. We show that the rate of somite differentiation accelerates as development progresses. We identified a conserved maturation program followed by all somites, but somites from more developed embryos concomitantly switch on differentiation programs from derivative cell lineages soon after segmentation. Integrated analysis of the somitic transcriptional and chromatin activities identified opposing regulatory modules controlling the onset of differentiation. Our results provide a powerful, high-resolution view of the molecular genetics underlying somitic development in mammals

Le développement du modèle intégré des hydrosystèmes Eau-dyssée : Rapport PIREN SEINE

L’étude des scénarios d’évolution de la ressource en eau (des points de vue qualitatif et quantitatif) selon les différentes contraintes climatiques, économiques ou technologiques passe de plus en plus par la modélisation intégrée des hydrosystèmes. Le projet Eau-dyssée vise au développement d’un tel outil, en s’appuyant sur des modèles disciplinaires et sur l’utilisation du coupleur externe Palm (Piacentini et al, 2003). On se base dans un premier temps sur 4 modèles disciplinaires qui sont en cours d’intégration : le modèle hydrologique MODCOU, le modèle agronomique Stics, le modèle d’offre agronomique AROPA-j, et le schéma de surface atmosphérique Surfex (précédemment ISBA). Ces différents modèles ont déjà fait l’objet de couplages partiels (AROPA-j Stics, ISBA-MODCOU, ISBAStics, Stics-MODCOU). Cependant, ces couplages étaient peu interactifs (il s’agissait bien souvent d’un simple forçage, sans rétroaction possible) et souvent peu évolutifs du fait des modifications insérées pour réaliser ces forçages. Eau-dyssée vise donc au développement d’un couplage interactif, évolutif et modulaire entre modèles experts. Une première phase dans la construction d’Eau-dyssée a consisté à restructurer MODCOU pour le rendre plus modulaire et lui permettre de gérer de multiples interactions (Habets et al., 2008). Une deuxième phase qui vient juste de commencer consiste à réaliser le couplage entre MODCOU et les 3 autres modèles experts au sein d’Eau-dyssée. Cela passe d’abord par la prise en main de ces modèles experts, et par des tests de sensibilités avant d’en arriver au couplage. Ce rapport fait donc le point sur l’état du développement d’Eau-dyssée, avec tout d’abord, les modifications introduites dans le modèle hydrologique MODCOU, puis, le point sur les couplages avec les autres modèles experts

Sentinel-2 Based Empirical Indicator of Cropland Net Annual CO2 Fluxes

International audienc

Combined effect of climate change and groundwater abstraction on multi-layer and alluvial aquifers in France

International audienceAlthough nowadays groundwater resources are mostly affected by increasing water abstraction, they will have toface the impact of climate change. Even in a temperate climate as the one in northern France these two driverswill have strong impact on the aquifers. Evolution of groundwater resource is most often studied based onevolution of the rainfall infiltration that is assumed to be the aquifer recharge, although river-aquifer and multilayeraquifer exchanges are also part of the recharge and can only be estimated using a hydrogeological model.Moreover, providing a change of the piezometric level is usually not found to be meaningful by stakeholder as a 1meter variation can have different impact depending on the hydrogeological context. Therefore, in this study, toprovide greater insight into the impact of groundwater, two new indicators are used: the evolution of the extensionof groundwater-fed wetlands and the frequency with which a crisis piezometric head is exceeded. The crisispiezometric levels are used locally by stakeholders and as soon as the observed piezometric heads fall below theselevels, actions are taken to preserve the water resource. For the present study, the local crisis piezometric heads were extended to the whole studied basins, the Seine andUpper Rhine Graben basins. The results show that the two basins under study are not affected in the same way by climate and groundwaterabstraction changes. The Seine multi-layer aquifers are projected to suffer from a substantial decrease in rainfall infiltration (about 20%), while the decrease is lower in the Upper Rhine Graben aquifer (about 6%).In 2050, the extension of groundwater-fed wetlands is expected to lose about 900m2/km2, while the crisispiezometric heads are expected to be exceeded about 40% and 26% of the time on average on the Seine and UpperRhine Graben aquifers, respectively. The reduction of the groundwater abstraction has a large impact locally but isnot efficient enough to overcome the impact of climate change, although the impact is more sensitive on the Upper Rhine Graben than on the Seine, and particularly on the extension of wetlands and low flow.Sensitivity to the parameters that drive the river-aquifer exchange was found to be second order compared to theuncertainty due to the climate model in the Upper Rhine Graben, although these parameters have a considerable impact on present-day estimation of the aquifer balance. The two indicators are found to be highly useful to discuss the impact of climate change on groundwater with stakeholders.In order to be able to extent such studies to the whole aquifers of France, and to have a survey of such impact as soon as new downscaled projections are available, the AquiFR project is bringing together hydrogeologicalapplications used by stakeholder in a common plateform that will be based at Météo-Franc

Impactos dos níveis fluviais na simulação e trocas rio–aquíferos sob o aquífero aluvial do Reno Superior (França/Alemanha)

International audienceThis study aims to assess the sensitivity of river level estimations to the stream-aquifer exchanges within a hydrogeological model of the Upper Rhine alluvial aquifer (France/Germany), characterized as a large shallow aquifer with numerous hydro-power dams. Two specific points are addressed: errors associated with digital elevation models (DEMs) and errors associated with the estimation of river level. The fine-resolution raw Shuttle Radar Topographic Mission dataset is used to assess the impact of the DEM uncertainties. Specific corrections are used to overcome these uncertainties: a simple moving average is applied to the topography along the rivers and additional data are used along the Rhine River to account for the numerous dams. Then, the impact of the river-level temporal variations is assessed through two different methods based on observed rating curves and on the Manning formula. Results are evaluated against observation data from 37 river-level points located over the aquifer, 190 piezometers, and a spatial database of wetlands. DEM uncertainties affect the spatial variability of the stream-aquifer exchanges by inducing strong noise and unrealistic peaks. The corrected DEM reduces the biases between observations and simulations by 22 and 51% for the river levels and the river discharges, respectively. It also improves the agreement between simulated groundwater overflows and observed wetlands. Introducing river-level time variability increases the stream-aquifer exchange range and reduces the piezometric head variability. These results confirm the need to better assess river levels in regional hydrogeological modeling, especially for applications in which stream-aquifer exchanges are important