Warming and redistribution of nitrogen inputs drive an increase in terrestrial nitrous oxide emission factor.

Anthropogenic nitrogen inputs cause major negative environmental impacts, including emissions of the important greenhouse gas N2O. Despite their importance, shifts in terrestrial N loss pathways driven by global change are highly uncertain. Here we present a coupled soil-atmosphere isotope model (IsoTONE) to quantify terrestrial N losses and N2O emission factors from 1850-2020. We find that N inputs from atmospheric deposition caused 51% of anthropogenic N2O emissions from soils in 2020. The mean effective global emission factor for N2O was 4.3 ± 0.3% in 2020 (weighted by N inputs), much higher than the surface area-weighted mean (1.1 ± 0.1%). Climate change and spatial redistribution of fertilisation N inputs have driven an increase in global emission factor over the past century, which accounts for 18% of the anthropogenic soil flux in 2020. Predicted increases in fertilisation in emerging economies will accelerate N2O-driven climate warming in coming decades, unless targeted mitigation measures are introduced.

Detection and validation of copy number variation in X-linked mental retardation.

Studies to identify the genetic defects associated with X-linked mental retardation (XLMR) in males have revealed tens of genes important for normal brain development and cognitive functioning in men. Despite extensive efforts in breakpoint cloning of chromosomal rearrangements and mutation screening of candidate genes on the X chromosome, still many XLMR families and sporadic cases remain unsolved. It is now clear that submicroscopic copy number changes on the X chromosome can explain about 5% of these idiopathic cases. Interestingly, beside gene deletions, an increase in gene dosage due to genomic duplications seems to contribute to causality more often than expected. Since larger duplications on the X chromosome are tolerated compared to deletions, they often harbour more than one gene hampering the identification of the causal gene. In contrast to copy number variations (CNVs) on autosomes, most disease-associated CNVs on the X chromosome in males are inherited from their mothers who normally do not present with any clinical symptoms due to non-random X inactivation. Here, we review the different methods applied to study copy number alterations on the X chromosome in patients with cognitive impairment, discuss those CNVs that are associated with disease and elaborate on the genes and mechanisms involved. At the end, we will resume in vivo assays to study the relation of CNVs on the X chromosome and mental disability.