The effect ofγ-irradiation on soil enzyme stability

Summary Arylsulphatase, -1,3 glucanase, phosphatase and urease responded differently to -irradiation (5–50 Mrad) in air-dried and moist soils. In all instances phosphatase was the most stable. The variability between enzymes may be due to inherent biochemical and stuctural characteristics or to their location within the soil microenvironment.Supported by a grant from the NERC.     

Loss-of-function mutations in TGFB2 cause a syndromic presentation of thoracic aortic aneurysm

Loeys-Dietz syndrome (LDS) associates with a tissue signature for high transforming growth factor (TGF)-β signaling but is often caused by heterozygous mutations in genes encoding positive effectors of TGF-β signaling, including either subunit of the TGF-β receptor or SMAD3, thereby engendering controversy regarding the mechanism of disease. Here, we report heterozygous mutations or deletions in the gene encoding the TGF-β2 ligand for a phenotype within the LDS spectrum and show upregulation of TGF-β signaling in aortic tissue from affected individuals. Furthermore, haploinsufficient Tgfb2(+/-) mice have aortic root aneurysm and biochemical evidence of increased canonical and noncanonical TGF-β signaling. Mice that harbor both a mutant Marfan syndrome (MFS) allele (Fbn1(C1039G/+)) and Tgfb2 haploinsufficiency show increased TGF-β signaling and phenotypic worsening in association with normalization of TGF-β2 expression and high expression of TGF-β1. Taken together, these data support the hypothesis that compensatory autocrine and/or paracrine events contribute to the pathogenesis of TGF-β-mediated vasculopathies.     

Differential modulation of endotoxin responsiveness by human caspase-12 polymorphisms

Caspases mediate essential key proteolytic events in inflammatory cascades and the apoptotic cell death pathway. Human caspases functionally segregate into two distinct subfamilies: those involved in cytokine maturation (caspase-1, -4 and -5) and those involved in cellular apoptosis (caspase-2, -3, -6, -7, -8, -9 and -10). Although caspase-12 is phylogenetically related to the cytokine maturation caspases, in mice it has been proposed as a mediator of apoptosis induced by endoplasmic reticulum stress including amyloid-beta cytotoxicity, suggesting that it might contribute to the pathogenesis of Alzheimer's disease. Here we show that a single nucleotide polymorphism in caspase-12 in humans results in the synthesis of either a truncated protein (Csp12-S) or a full-length caspase proenzyme (Csp12-L). The read-through single nucleotide polymorphism encoding Csp12-L is confined to populations of African descent and confers hypo-responsiveness to lipopolysaccharide-stimulated cytokine production in ex vivo whole blood, but has no significant effect on apoptotic sensitivity. In a preliminary study, we find that the frequency of the Csp12-L allele is increased in African American individuals with severe sepsis. Thus, Csp12-L attenuates the inflammatory and innate immune response to endotoxins and in doing so may constitute a risk factor for developing sepsis.     

Distribution of14C after topical application of14C-labeled 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in mice

Summary Following topical application of¹⁴C-labeled 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine) to the skin of mice radioactivity was found in all viscera and tissues examined. Exclusive of the gut, highest values were recorded for the liver, kidney and lung.Supported by Public Health Service, grant CA 14825, from the National Cancer Institute, National Institutes of Health, Department of Health, Education and Welfare.     

Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms--such as corals and some plankton--will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean-carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.     

Multiple apical plasma membrane constituents are associated with susceptibility to meconium ileus in individuals with cystic fibrosis

Variants associated with meconium ileus in cystic fibrosis were identified in 3,763 affected individuals by genome-wide association study (GWAS). Five SNPs at two loci near SLC6A14 at Xq23-24 (minimum P = 1.28 × 10(-12) at rs3788766) and SLC26A9 at 1q32.1 (minimum P = 9.88 × 10(-9) at rs4077468) accounted for ~5% of phenotypic variability and were replicated in an independent sample of affected individuals (n = 2,372; P = 0.001 and 0.0001, respectively). By incorporating the knowledge that disease-causing mutations in CFTR alter electrolyte and fluid flux across surface epithelium into a hypothesis-driven GWAS (GWAS-HD), we identified associations with the same SNPs in SLC6A14 and SLC26A9 and established evidence for the involvement of SNPs in a third solute carrier gene, SLC9A3. In addition, GWAS-HD provided evidence of association between meconium ileus and multiple genes encoding constituents of the apical plasma membrane where CFTR resides (P = 0.0002; testing of 155 apical membrane genes jointly and in replication, P = 0.022). These findings suggest that modulating activities of apical membrane constituents could complement current therapeutic paradigms for cystic fibrosis.     

Congenital heart disease in mice deficient for the DiGeorge syndrome region.

The heterozygous chromosome deletion within the band 22q11 (del22q11) is an important cause of congenital cardiovascular defects. It is the genetic basis of DiGeorge syndrome and causes the most common deletion syndrome in humans. Because the deleted region is largely conserved in the mouse, we were able to engineer a chromosome deletion (Df1) spanning a segment of the murine region homologous to the human deleted region. Here we describe heterozygously deleted (Df1/+) mice with cardiovascular abnormalities of the same type as those associated with del22q11; we have traced the embryological origin of these abnormalities to defective development of the fourth pharyngeal arch arteries. Genetic complementation of the deletion using a chromosome duplicated for the Df1 DNA segment corrects the heart defects, indicating that they are caused by reduced dosage of genes located within Df1. The Df1/+ mouse model reveals the pathogenic basis of the most clinically severe aspect of DiGeorge syndrome and uncovers a new mechanism leading to aortic arch abnormalities. These mutants represent a mouse model of a human deletion syndrome generated by chromosome engineering.     

OXI1 kinase is necessary for oxidative burst-mediated signalling in Arabidopsis

Active oxygen species (AOS) generated in response to stimuli and during development can function as signalling molecules in eukaryotes, leading to specific downstream responses. In plants these include such diverse processes as coping with stress (for example pathogen attack, wounding and oxygen deprivation), abscisic-acid-induced guard-cell closure, and cellular development (for example root hair growth). Despite the importance of signalling via AOS in eukaryotes, little is known about the protein components operating downstream of AOS that mediate any of these processes. Here we show that expression of an Arabidopsis thaliana gene (OXI1) encoding a serine/threonine kinase is induced in response to a wide range of H2O2-generating stimuli. OXI1 kinase activity is itself also induced by H2O2 in vivo. OXI1 is required for full activation of the mitogen-activated protein kinases (MAPKs) MPK3 and MPK6 after treatment with AOS or elicitor and is necessary for at least two very different AOS-mediated processes: basal resistance to Peronospora parasitica infection, and root hair growth. Thus, OXI1 is an essential part of the signal transduction pathway linking oxidative burst signals to diverse downstream responses.     

The genome of the social amoeba Dictyostelium discoideum

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.