Abiotic methane formation in oxic soils

Methane plays an important role as a radiatively and chemically active gas in our atmosphere. Until recently, sources of atmospheric methane in the biosphere have been attributed to strictly anaerobic microbial processes during degradation of organic matter. However, some potentially abiotic sources from the biosphere have been discovered in the past few years, starting with methane emissions from plants and plant litter up to the recent discovery of methane production in saprotrophic fungi.rnAlso methane fluxes from aerobic soils have been observed for decades but no alternative source to methanogenesis has been identified so far.rnThis work aims to provide evidence for non-microbial methane formation in soils under oxic conditions. It was found that soils release methane upon heating and other environmental factors like ultraviolet irradiation, and drying-rewetting cycles. The chemical formation of methane during degradation of soil organic matter represents an additional source in soil that helps to understand the methane cycle in aerobic soils. Although the emission fluxes are relatively low when compared to those from aerobic soil sources like wetlands, they may still be important in warm and wet regions subjected to ultraviolet radiation. Therefore this methane source might be highly sensitive to global climate change.rnMethan ist an vielen chemischen Prozessen in der Atmosphäre beteiligt und hat großen Einfluss auf ihren Strahlungshaushalt. Bis vor kurzem wurden als natürliche biologische Quellen ausschließlich mikrobielle Prozesse beim Abbau organischer Stoffe in Betracht gezogen. Allerdings sind in den letzten Jahren einige potentiell abiotische Quellen in der Biosphäre entdeckt worden, angefangen bei der Methanproduktion in Pflanzen und pflanzlichem Detritus bis hin zur Methanbildung in saprophytischen Pilzen.rnAuch aus aeroben Böden, die bislang allgemein als Methansenken gelten, werden seit Jahrzehnten immer wieder Methanemissionen beobachtet. Bislang wurde jedoch keine weitere Quelle als Alternative zur Methanogenese identifiziert.rnDiese Arbeit hat zum Ziel, einen Nachweis für nicht-mikrobielle Bildung von Methan in Böden unter oxischen Bedingungen zu erbringen. Es wurde festgestellt, dass Böden beim Erhitzen und durch andere Umweltfaktoren wie UV-Bestrahlung und Vernässung Methan emittieren. Eine Beteiligung von methanogenen Archaen konnte dabei durch verschiedene Verfahren ausgeschlossen werden. Die chemische Bildung von Methan beim Abbau organischer Substanz im Boden könnte eine weitere Quelle im Boden sein, die benötigt wird, um den Methan-Kreislauf in aeroben Böden vollständig zu erfassen. Obwohl die Emissionsraten aus den aeroben Böden relativ niedrig sind im Vergleich zu aeroben Quellen wie Feuchtgebieten, könnte die abiotische Methanbildung in feuchtwarmen Klimaten mit höherer UV-Einstrahlung eine wichtige Quelle sein. Deshalb ist auch zu erwarten, dass die Dimension dieser Quelle auch vom Klimawandel beeinflusst werden wird.r

The whole-genome landscape of medulloblastoma subtypes.

Current therapies for medulloblastoma, a highly malignant childhood brain tumour, impose debilitating effects on the developing child, and highlight the need for molecularly targeted treatments with reduced toxicity. Previous studies have been unable to identify the full spectrum of driver genes and molecular processes that operate in medulloblastoma subgroups. Here we analyse the somatic landscape across 491 sequenced medulloblastoma samples and the molecular heterogeneity among 1,256 epigenetically analysed cases, and identify subgroup-specific driver alterations that include previously undiscovered actionable targets. Driver mutations were confidently assigned to most patients belonging to Group 3 and Group 4 medulloblastoma subgroups, greatly enhancing previous knowledge. New molecular subtypes were differentially enriched for specific driver events, including hotspot in-frame insertions that target KBTBD4 and 'enhancer hijacking' events that activate PRDM6. Thus, the application of integrative genomics to an extensive cohort of clinical samples derived from a single childhood cancer entity revealed a series of cancer genes and biologically relevant subtype diversity that represent attractive therapeutic targets for the treatment of patients with medulloblastoma

The whole-genome landscape of medulloblastoma subtypes

Current therapies for medulloblastoma, a highly malignant childhood brain tumour, impose debilitating effects on the developing child, and highlight the need for molecularly targeted treatments with reduced toxicity. Previous studies have been unable to identify the full spectrum of driver genes and molecular processes that operate in medulloblastoma subgroups. Here we analyse the somatic landscape across 491 sequenced medulloblastoma samples and the molecular heterogeneity among 1,256 epigenetically analysed cases, and identify subgroup-specific driver alterations that include previously undiscovered actionable targets. Driver mutations were confidently assigned to most patients belonging to Group 3 and Group 4 medulloblastoma subgroups, greatly enhancing previous knowledge. New molecular subtypes were differentially enriched for specific driver events, including hotspot in-frame insertions that target KBTBD4 and 'enhancer hijacking' events that activate PRDM6. Thus, the application of integrative genomics to an extensive cohort of clinical samples derived from a single childhood cancer entity revealed a series of cancer genes and biologically relevant subtype diversity that represent attractive therapeutic targets for the treatment of patients with medulloblastom