Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

International audienceOn 17 January 2002, Nyiragongo volcano erupted along a 20 km-long fracture network extending from the volcano to the city of Goma. The event was captured by InSAR data from the ERS-2 and RADARSAT-1 satellites. A combination of 3D numerical modeling and inversions is used to analyze these displacements. Using Akaike Information Criteria, we determine that a model with two subvertical dikes is the most likely explanation for the 2002 InSAR deformation signal. A first, shallow dike, 2 km high, is associated with the eruptive fissure, and a second, deeper dike, 6 km high and 40 km long, lies about 3 km below the city of Goma. As the deep dike extends laterally for 20 km beneath the gas-rich Lake Kivu, the interaction of magma and dissolved gas should be considered as a significant hazard for future eruptions. A likely scenario for the eruption is that the magma supply to a deep reservoir started ten months before the eruption, as indicated by LP events and tremor. Stress analysis indicates that the deep dike could have triggered the injection of magma from the lake and shallow reservoir into the eruptive dike. The deep dike induced the opening of the southern part of this shallow dike, to which it transmitted magma though a narrow dike. This model is consistent with the geochemical analysis, the lava rheology and the pre- and post-eruptive seismicity. We infer low overpressures (1-10 MPa) for the dikes. These values are consistent with lithostatic crustal stresses close to the dikes and low magma pressure. As a consequence, the dike direction is probably not controlled by stresses but rather by a reduced tensile strength, inherited from previous rift intrusions. The lithostatic stresses indicate that magmatic activity is intense enough to relax tensional stresses associated with the rift extension

Surface ruptures associated to the July-August 2007 Gelai volcano-tectonic event, North Tanzania

A seismic crisis with a series of moderate earthquakes started on July 12th 2007 in the Natron area in North Tanzania. According to the USGS-NEIC earthquake catalogue, it lasted up to the 8th of September and 80 teleseismic earthquakes were recorded, with the strongest one on July 17th (Mw 5.9). Soon after the main event of July 17th, the presence of open surface fissures was reported on the ground, on the southern flank of the recent (th event shows the presence of two surface fracture systems delimiting a NNE-trending narrow graben in the southern flank of the Gelai volcano. These features were subsequently mapped in relative detail in the field in October 2007 before the following rain season. They turn to be subvertical open fissures, arranged in en-échelon way and displaying horizontal dilation as well as vertical offset. They are interpreted to evolve at depth into 60-75° dipping normal fault systems. According to their calculated dip, these fault systems converge at depth where they should either merge or intersect. Assuming a 50 m high vertical portion for the open fracture, the depth and horizontal coordinates of the fault intersection point are calculated for a series of profiles drawn across the graben structure.It is suspected that the July-August moderate-magnitude earthquake swam crisis might correspond to a volcano-tectonic event during which a magmatic dyke was injected at depth under the southern flank of the Gelai volcano. In this scenario, the observed graben structure bounded by the open fracture network and the inferred normal faults at depth are similar to the volcano-extensional structures that commonly form in the upper crust above a thin subvertical dyke injection. The top of this inferred dyke should correspond approximately to the intersection of the lines prolonging the two normal faults (even if physically the faults did not join the top of dyke), with an average depth of 4000m under the topographic surface

Sexually dimorphic gene expression emerges with embryonic genome activation and is dynamic throughout development

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public DomainVKR is supported by grants from the Biotechnology and Biological Sciences Research Council, UK (BB/M012494/1), VKR and CG by (BB/G00711/X/1). MLH is supported by a Research Council UK Academic Fellowship. RL is supported by EU-FP7 BLUEPRINT

Transcriptional Profiling of Human Liver Identifies Sex-Biased Genes Associated with Polygenic Dyslipidemia and Coronary Artery Disease

Sex-differences in human liver gene expression were characterized on a genome-wide scale using a large liver sample collection, allowing for detection of small expression differences with high statistical power. 1,249 sex-biased genes were identified, 70% showing higher expression in females. Chromosomal bias was apparent, with female-biased genes enriched on chrX and male-biased genes enriched on chrY and chr19, where 11 male-biased zinc-finger KRAB-repressor domain genes are distributed in six clusters. Top biological functions and diseases significantly enriched in sex-biased genes include transcription, chromatin organization and modification, sexual reproduction, lipid metabolism and cardiovascular disease. Notably, sex-biased genes are enriched at loci associated with polygenic dyslipidemia and coronary artery disease in genome-wide association studies. Moreover, of the 8 sex-biased genes at these loci, 4 have been directly linked to monogenic disorders of lipid metabolism and show an expression profile in females (elevated expression of ABCA1, APOA5 and LDLR; reduced expression of LIPC) that is consistent with the lower female risk of coronary artery disease. Female-biased expression was also observed for CYP7A1, which is activated by drugs used to treat hypercholesterolemia. Several sex-biased drug-metabolizing enzyme genes were identified, including members of the CYP, UGT, GPX and ALDH families. Half of 879 mouse orthologs, including many genes of lipid metabolism and homeostasis, show growth hormone-regulated sex-biased expression in mouse liver, suggesting growth hormone might play a similar regulatory role in human liver. Finally, the evolutionary rate of protein coding regions for human-mouse orthologs, revealed by dN/dS ratio, is significantly higher for genes showing the same sex-bias in both species than for non-sex-biased genes. These findings establish that human hepatic sex differences are widespread and affect diverse cell metabolic processes, and may help explain sex differences in lipid profiles associated with sex differential risk of coronary artery disease

Sexually dimorphic characteristics of the small intestine and colon of prepubescent C57BL/6 mice

Background There is increasing appreciation for sexually dimorphic effects, but the molecular mechanisms underlying these effects are only partially understood. In the present study, we explored transcriptomics and epigenetic differences in the small intestine and colon of prepubescent male and female mice. In addition, the microbiota composition of the colonic luminal content has been examined. Methods At postnatal day 14, male and female C57BL/6 mice were sacrificed and the small intestine, colon and content of luminal colon were isolated. Gene expression of both segments of the intestine was analysed by microarray analysis. DNA methylation of the promoter regions of selected sexually dimorphic genes was examined by pyrosequencing. Composition of the microbiota was explored by deep sequencing. Results Sexually dimorphic genes were observed in both segments of the intestine of 2-week-old mouse pups, with a stronger effect in the small intestine. Amongst the total of 349 genes displaying a sexually dimorphic effect in the small intestine and/or colon, several candidates exhibited a previously established function in the intestine (i.e. Nts, Nucb2, Alox5ap and Retnlγ). In addition, differential expression of genes linked to intestinal bowel disease (i.e. Ccr3, Ccl11 and Tnfr) and colorectal cancer development (i.e. Wt1 and Mmp25) was observed between males and females. Amongst the genes displaying significant sexually dimorphic expression, nine genes were histone-modifying enzymes, suggesting that epigenetic mechanisms might be a potential underlying regulatory mechanism. However, our results reveal no significant changes in DNA methylation of analysed CpGs within the selected differentially expressed genes. With respect to the bacterial community composition in the colon, a dominant effect of litter origin was found but no significant sex effect was detected. However, a sex effect on the dominance of specific taxa was observed. Conclusions This study reveals molecular dissimilarities between males and females in the small intestine and colon of prepubescent mice, which might underlie differences in physiological functioning and in disease predisposition in the two sexes

Thermal, deformation, and degassing remote sensing time‐series (A.D. 2000‐2017) at the 47 most active volcanoes in Latin America: Implications for volcanic systems

Volcanoes are hazardous to local and global populations, but only a fraction are continuously monitored by ground‐based sensors. For example, in Latin America, more than 60% of Holocene volcanoes are unmonitored, meaning long‐term multi‐parameter datasets of volcanic activity are rare and sparse. We use satellite observations of degassing, thermal anomalies, and surface deformation spanning 17 years at 47 of the most active volcanoes in Latin America, and compare these datasets to ground‐based observations archived by the Global Volcanism Program (GVP). This first comparison of multi‐satellite time‐series on a regional scale provides information regarding volcanic behavior during, non‐, pre‐, syn‐ and post‐eruptive periods. For example, at Copahue volcano, deviations from background activity in all three types of satellite measurements were manifested months to years in advance of renewed eruptive activity in 2012. By quantifying the amount of degassing, thermal output, and deformation measured at each of these volcanoes, we test the classification of these volcanoes as open or closed volcanic systems. We find that ~28% of the volcanoes do not fall into either classification and the rest show elements of both, demonstrating a dynamic range of behavior that can change over time. Finally, we recommend how volcano monitoring could be improved through better coordination of available satellite‐based capabilities and new instruments

Regulation of the hepatitis C virus RNA replicase by endogenous lipid peroxidation

Although oxidative tissue injury often accompanies viral infection, there is little understanding of how it influences virus replication. We show that multiple hepatitis C virus (HCV) genotypes are exquisitely sensitive to oxidative membrane damage, a property distinguishing them from other pathogenic RNA viruses. Lipid peroxidation, regulated in part through sphingosine kinase 2, severely restricts HCV replication in Huh-7 cells and primary human hepatoblasts. Endogenous oxidative membrane damage lowers the 50% effective concentration of direct-acting antivirals, suggesting critical regulation of the conformation of the NS3/4A protease and NS5B polymerase, membrane-bound HCV replicase components. Resistance to lipid peroxidation maps genetically to trans-membrane and membrane-proximal residues within these proteins, and is essential for robust replication in cell culture, as exemplified by the atypical JFH1 strain. Thus, the typical, wild-type HCV replicase is uniquely regulated by lipid peroxidation, providing a novel mechanism for attenuating replication in stressed tissue and possibly facilitating long-term viral persistence

Identification of subsiding areas undergoing significant magmatic carbon dioxide degassing, along the northern shore of Lake Kivu, East African Rift

We processed InSAR time series of ENVISAT ASAR descending and ascending datasets and identified two new deforming areas on the northern shore of Lake Kivu, characterized by steady ground subsidence of up to ~1 cm/year over a time period of about seven years (December 2002/January 2003–March 2010). Two distinct areas can be identified: one centered on the Rumoka volcanic cone, which built up during the 1912 eruption of Nyamulagira volcano, and a broader one centered on the Bulengo area on the northern shoreline of Lake Kivu. Both areas include high density of diffuse magmatic degassing areas (“mazuku”), which are topographic depressions in which substantial amount of carbon dioxide accumulates. The steady deflation of at least two fluid reservoirs is consistent with geodetic data but the presence of weak, porous layers, possibly connected with hydrothermal and hydrogeological processes in aquifers and Lake Kivu, could also account for the observed subsidence. The subsidence could be due to pore pressure decrease in porous layers, which may also serve as preferential pathways for escaping gases percolating from the aquifers and Lake Kivu